texts: What is the industrial yield of paracetamol?

texts:
Anyone know how I can find out the typical yield of paracetamol (acetaminophen) from the acetylation of 4-aminophenol?

Please provide the source if you happen to know!


texts: Mass Spec - What could a loss of 28amu as the first fragmentation be?

texts: I guess 28 could be CO, C2H4 or N2. However I can't work out a mechanism by which CO could be the first fragmentation of any common organic compound. It seems like a diazonium salt could lose N2 as the first fragmentation but I've reason to believe this is not the unknown compound I'm trying to work out.


texts: Which conductivity law should I use to calculate the conductivity of a solution with high/low concentration?

texts:
I have a set of NaCl solutions with concentrations ranging from 0.05 M to 0.1 M.
I have been trying to calculate the conductivity of these solutions and compare the obtained values with the experimental ones obtained with a conductometer.

For this, I used the Kohlrausch's Law. But I observe some deviation on the values. I realized that the law may not apply for high concentrated solutions such as 0.1M. I read that since NaCl is a strong electrolyte, this law should still apply.

Is there a specific law or method to use to calculate the conductivity of concentrated solutions?


texts: Does Friedel-Crafts reaction fail with benzoic acid?

texts:
I know that Friedel-Crafts reaction  (either alkylation or acylation) fails with phenol and aniline, due to formation of a coordinate bond between Lewis acid catalyst and the lone pair of the respective functional group.

But I have read that even benzoic acid fails to undergo this reaction. I couldn't think of a reason for this. Can anyone explain why is it so?


texts: Why is dinitrogen tetroxide a planar molecule?

texts: I was wondering why $\ce{N2O4}$ is a planar species in spite of having a σ-bond in between the two $\ce{N}$ atoms for free rotation. Does it not form a conformer?


texts:
Usually in chemistry, we deal with bonding interactions. That is, if I have the diatomic A-A molecule or A-B molecule, there's a favorable interaction (i.e., a bond) and a prototypical MO diagram like this:

As I'd say in a lecture, one orbital goes down in energy, one orbital goes up in energy. I can use Hückel theory to define the energies of the bonding and anti-bonding interactions:

$$e_{ab} = e_a + \frac{H_{ab}^2}{e_a - e_b}$$
$$e^*_{ab} = e_b + \frac{H_{ab}^2}{e_b - e_a}$$

Now, consider if $H_{ab}$ is imaginary.. we'd use the same equations to get a very unusual MO diagram:

How would you describe such an interaction? It's clearly not the traditional favorable bonding. It's not a non-bonding interaction. And it's not the traditional anti-bonding case like $\ce{He2}$, because if I put 2 electrons into this system, the anti-bonding orbital isn't filled.

I ask the question because in a survey we've performed using DFT, we find many such combinations.

I'm leaning towards calling it an imaginary bond, but if there are known discussions, I'd be curious to read references.


texts: Is it possible to prevent sacrificial anode contaminate the soil?

texts: I have a mild steel pipe (black pipe, NOT zinc plated) water well. My question: is it possible to somehow put a sacrificial anode in an electrolyte contained in a bucket instead of burying it in the ground, which allows zinc to eventually enter and contaminate ground water?


texts: Can anyone point me towards an experiment guideline of some sort regarding fermentation of citric acid from Aspergillus Niger? I haven't been able to find one by myself. I've found plenty of research papers, but none with any sort of guideline.


texts: Decomposition products of sodium acetate

texts: I heated some sodium acetate to a high temperature (about 500 degrees celsius). Upon doing so, I could smell an irritating smell reminiscent of vinegar. I stopped then, assuming they were acetic acid vapors. Are they really acetic acid vapours, and if so, what is the remaining solid?


texts: Why polycarbonate couldn't stand some chemicals i.e. acid and base? What reaction will occur if polycarbonate meets acid or base?


texts: Spectroscopic Determination of an Equilibrium Constant

texts:
I got values of $\pu{5.0E-4}$, $\pu{2.5E-4}$, and $183$ for the following problems. However, these seem to be inaccurate and I'm not sure what to do.

Here is the procedure:

  Obtain 6 disposable test tubes. Label the test tubes 1 through 6. To each of the $\pu{6 mm}$ test tubes, add $\pu{5.0 mL}$ of $\pu{2.0E–4 M}$ $\ce{KSCN}$. If you make a mistake, you must rinse out and thoroughly dry the test tube before starting over.

  To test tube 1, add $\pu{5.0 mL}$ of $\pu{0.20 M}\; \ce{Fe(NO3)3}$ and stir. The resulting solution is your standard solution of $\ce{FeSCN^2+}$.

  For the other test tubes, do the following: Measure $\pu{10.0 mL}$ of $\pu{0.20 M}$ $\ce{Fe(NO3)3}$ in a $\pu{25 mL}$ graduated cylinder, fill to $\pu{25.0 mL}$ with distilled water, and stir thoroughly to mix. Measure $\pu{5.0 mL}$ of the resulting $\pu{0.080 M}$ $\ce{Fe^3+}$ into test tube 2.

  Discard all but $\pu{10.0 mL}$ of the $\pu{0.080 M}$ $\ce{Fe^3+}$, refill the graduated cylinder with $\pu{10.0 mL}$ of the $\pu{0.080 M}$ $\ce{Fe^3+}$ solution to $\pu{25.0 mL}$ with distilled water, and stir thoroughly. Add $\pu{5.0 mL}$ of the resulting $\pu{0.032 M}$ $\ce{Fe^3+}$ to test tube 3.

  Again discard all but $\pu{10.0 mL}$ of the contents of the graduated cylinder, refill to $\pu{25.0 mL}$ with distilled water, stir, and add $\pu{5.0 mL}$ to test tube 4.

  Repeat above procedure with test tubes 5 and 6.

  Calculate the initial concentrations of $\ce{Fe^3+}$ and $\ce{SCN-}$ for the six solutions to be prepared in this experiment (i.e., the 6 solutions prepared in test tubes 1–6). These are the concentrations just after the two solutions are mixed in the large test tube (thereby diluting each other) but before any $\ce{FeSCN^2+}$ has formed. Assume that the volumes are additive and that the $\ce{Fe(NO3)3}$ and $\ce{KSCN}$ are each completely dissociated. What is the concentration of $\ce{Fe^3+}$ in test tube #5?

  $$
\begin{array}{c|cc}
\hline
\text{Test tube} & \text{Initial}~[\ce{Fe^3+}] & \text{Initial}~[\ce{SCN-}] \\
\hline
1 & & \\
2 & & \\
3 & & \\
4 & & \\
5 & & \\
6 & & \\
\hline
\end{array}
$$

  For the chart in question 1, what is the molar concentration of $\ce{SCN-}$ in tube #4?
  If the equilibrium $\ce{[FeSCN^2+]}$ in test tube 2 was determined to be $\pu{8.3E-5 M}$, calculate the equilibrium $\ce{[Fe^3+]}$.


texts: Balancing reaction between lead(II) sulfide and ozone

texts:
I came across a question, asking to check whether the reaction is correctly balanced or not and one of the options were
$$\ce{PbS + 2O3 -> PbSO4 + O2}.\tag{R1}$$
The reaction seems to be a balanced one (atoms-balanced and charge-balanced).
But my teacher told that it is not the correct balanced reaction.
The reason given to me was that ozone breaks into $\ce{O2}$ and $\ce{[O]}$ as:
$$
\begin{align}
\ce{O3 &-> O2 + [O]}\tag{R1.1}\\
\ce{PbS + [O] &-> PbSO4}\tag{R1.2}
\end{align}
$$
Hence, the correct one is
$$\ce{PbS + 4 O3 -> PbSO4 + 4 O2}.\tag{R2}$$
But both reactions seem to be balanced and should depend on the conditions.
Am I thinking right? Or the reaction always proceed in this way only? If so, then why?


texts: Controlling rate of endothermic reaction

texts:
In an experiment, I have two endothermic reactions taking place simultaneously:

$$
\begin{align}
\ce{A + B &-> C + D}\tag{1}\\
\ce{E + G &-> Z + F}\tag{2}
\end{align}
$$

$\ce{C}$ and $\ce{Z}$ also take place in a reaction to form the final product of the process $\ce{J}$. In my experiment, I have to use a single heating source, and cannot change the concentration of the chemicals in $\ce{A + B}$ and $\ce{E + G}$ such that the production of $\ce{J}$ is as fast as possible. How can I find the optimum temperature for this reaction, and will it be useful?

It is my theory that

$$\frac{\text{rate}_1 + \text{rate}_2}{2}$$

can be found when both reactions take place in water heated by a single source, and the activation energies are known. However, there is a need for another factor other than concentration and heat which needs to ensure that the products $\ce{C}$ and $\ce{Z}$ are produced at such rates (independently and at different rates) which will ensure an efficient process.


texts: What is the reaction between plain soda and sugar?

texts: Today I was having lunch and I ordered plain soda. And some amount of sugar was added, suddenly all the liquid fell of the glass. I thought there should have been a reaction between plain soda and sugar. What is it?


texts: How many electrons can each shell in an atom hold?

texts: I know that the first shell can hold up to 2, the second and third can hold up to 8, and the fourth 18. But what about after that?


texts: Identification: was this gallium or mercury from broken thermometer?

texts:
I had accidentally broken a thermometer against my computer screen, resulting in the splash of the silvery substance seen below:

I cannot remember whether the thermometer is a mercury-free thermometer, and was wondering if you could help with identification of the substance given the following information:

This picture was taken about 1-2 minutes after the initial spill
The temperature of the room was around 70 degrees F.. at most 80 degrees
The silvery substance clung to the screen as shown.
Small bits of the silvery substance seeped into the computer. However, it was fully functional in the few instances I have used it

Any suggestions or additional follow up questions would be much appreciated. Thanks!


texts: The reason behind the steep rise in pH in the acid base titration curve

texts: Most books refer to a steep rise in pH when a titration reaches the equivalence point. However, I do not understand why … I mean I am adding the same drops of acid to the alkali but just as I near the correct volume (i.e. the volume required to neutralize the alkali), the pH just suddenly increases quickly.


texts: The role of temperature in Nernst equation

texts:
When measuring a non-standard voltaic cell’s electrode potential, regardless the standard conditions, as long as the concentration of product and reactant the same, a non-standard cell’s potential will be exactly equal to a standard cell’s potential.

$E= E^\circ -\frac{RT}{nF} \ln(Q)$

Q = 1 if the concentration of product equals to the concentration of reactant:

$E= E^\circ -\frac{RT}{nF} \ln(1)$

$E=E^\circ - 0$

In another word, no matter how temperature varies, as long as the concentration of both solution the same, temperature will have no effect on the voltage.

Is the understanding above valid? If it is, then my experimental result contradicted the Nernst equation. When I increase the temperature while having two half cell with the exact same concentration, the voltage increased as well. What is a possible cause for such result? (Assuming my voltemeter is funcotional one)


texts: What chemicals are used in receipt paper?

texts:
Most "invisible inks" turn brown when heated and they take a while to transform.  I would like to make (or obtain) an "ink" that responds to the heat of an iron and permanently turns black or a similarly dark color - instantly.  Thermal receipt paper does this where the paper is white until it is heated with almost instant response times AND the "ink" has a permanence of sorts (e.g. sticking a receipt in a freezer won't revert the reaction).  What chemical combinations in what amounts will do an equivalent transformation?

Bonus question:  What chemical combinations would create similar effects for standard palette colors?  That is, transparent/hidden until heat from an iron is applied, whereupon it instantly appears.

My goal is to use such an ink with paintbrushes and fountain pens on canvas.  Black is probably sufficient, but knowing how to make standard colors would dramatically expand my options.  The ink ideally shouldn't be toxic to touch after drying nor emit toxic fumes when heating with an iron at a "Cotton" setting.  It can be semi-toxic while wet but nothing that will melt nitrile gloves, fingers, or human lungs.  I will, of course, wear sufficient protection at all times as I don't really need any chemicals leeching through my skin.  Having a drawing/painting appear instantly in front of an audience from a seemingly blank canvas would be very dramatic and painting with invisible ink will be an interesting adventure.


texts: Is 1,3 alkyl shift allowed in Cyclobutyldicyclopropylmethyl Cation?

texts:
While reading a post , i came across the following mechanism .(source : Which ring expansion in cyclobutyl(cyclopropyl)methanol is favourable?)

The rearrangement is a series of shifts.

The first ring expansion is 1,2 alkyl shift.
The second ring expansion is 1,3 aalkyl shift.
Third step is again 1,2 Hydride shift.

I am aware of 1,2 shift but not not 1,3 shift.So I researched from various sources which are tabulated below .

ORGANIC CHEMISTRY ( SECOND EDITION ) by Jonathan Clayden ,Nick Greeves, Stuart Warren .Quoting from page no. 942 "The methyl group can slide smoothly from one orbital to another—there are bonding interactions
all the way. The next step, migration of H, is just the same—except that the HOMO is now a C–H σ bond.

in all the above , 1,2 shifts are seen.

Advanced Organic Chemistry , FIFTH EDITION ,Part A: Structure and Mechanisms
by Francis A. Carey and Richard J. Sundberg.

Quoting from page no.446 it says

"The preferred alignment of orbitals for a 1,2-hydride or alkyl shift
involves  coplanarity of the p-orbital at the carbocation ion center and the
orbital   of the migrating group "

1,2 shift pathway is seen.

https://www.masterorganicchemistry.com/2012/08/15/rearrangement-reactions-1-hydride-shifts/

Quoting from the above link.

"Here are some examples of “allowed” rearrangement reactions. Notice how we’re always going from a less substituted carbocation to a more substituted carbocation. One exception is at the very bottom; the rearrangement is favorable because the new carbocation is resonance stabilized."

A rearrangement can occur to give the more stable tertiary carbocation.(involves 1,2 shift)

https://www.masterorganicchemistry.com/2012/08/22/rearrangement-reactions-2-alkyl-shifts/

Quoting from the above link.The Mechanism Of Alkyl Migration Reaction is a 1,2 shift in two examples below.

Ring-Expansion Reactions

From https://en.wikipedia.org/wiki/Sigmatropic_reaction .This talks about Thermal alkyl [1,3] shifts.This type of mechanism is not possible for the rearrangement mechanism i am researching .The structure involved is totally different.

Therefor ,the above sources have all talked about 1, 2 shifts only .

So my question is , is 1,3 alkyl shift as given in the post (Which ring expansion in cyclobutyl(cyclopropyl)methanol is favourable?)

  allowed ?


texts: What interesting things can be seen in spectra between 400-700nm?

texts:
The visible spectrum (400-700nm) tends to give a very blurry spectral picture, as it is not a wide band relative to the typical peak width of features you can find there. Further, the vibrational modes tend to fall below it in IR, and the electron transitions that get physicists excited tend to fall above it in UV.

What are some examples of interesting features that a sightseeing student could find with a visible-spectrum spectrometer? They are quite common in low-budget labs but tend to only get used for measuring concentration with Beer's law.


texts: What emits the least radiation when hot?

texts:
What element with a high vapor point the emits to least light or radiation when heated to its vapor pressure point in a vacuum?

Ideally I would like to know in 0 gravity and 0 pressure which elements can be get the hottest around the sun before the vapor pressure point is reached and/or emit the least black body radiation when hot.

https://space.stackexchange.com/questions/35486/shielding-capability-of-liquid-metals


texts:
I shall try to revive this!
A full FAQ post has been written on chemistry.meta.SE, explaining the premise of synthesis golf and the 'rules'. Please take a look at this before answering (if you haven't already).

TAK-457 is a drug (more accurately, an injectable prodrug of TAK-456) that displays antifungal activity:[1,2,3]

Some rules, as usual:

At most one chiral centre may be bought in your starting material(s). [Chiral catalysts, ligands, auxiliaries, etc. do not fall under this rule.]
Your synthesis must feature a method for construction of either the triazole or tetrazole ring (i.e. do not buy both).
The counterion doesn't matter.
Bonus points for synthesis that can be adapted to produce the other three stereoisomers of the drug (preferably via late stage diversification as opposed to, say, using a different enantiomer of starting material). These stereoisomers were of interest.[4]

References

Ichikawa, T.; Kitazaki, T.; Matsushita, Y.; Yamada, M.; Hayashi, R.; Yamaguchi, M.; Kiyota, Y.; Okonogi, K.; Itoh, K. Optically Active Antifungal Azoles. XII. Synthesis and Antifungal Activity of the Water-Soluble Prodrugs of 1-[(1R,2R)-2-(2,4-Difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl]-3-[4-(1H-1-tetrazolyl)phenyl]-2-imidazolidinone. Chem. Pharm. Bull. 2001, 49 (9), 1102–1109. DOI: 10.1248/cpb.49.1102.
Hayashi, R.; Kitamoto, N.; Iizawa, Y.; Ichikawa, T.; Itoh, K.; Kitazaki, T.; Okonogi, K. Efficacy of TAK-457, a novel intravenous triazole, against invasive pulmonary aspergillosis in neutropenic mice. Antimicrob. Agents Chemother. 2002, 46 (2), 283–287. DOI: 10.1128/AAC.46.2.283-287.2002.
Tsuchimori, N.; Hayashi, R.; Kitamoto, N.; Asai, K.; Kitazaki, T.; Iizawa, Y.; Itoh, K.; Okonogi, K. In Vitro and In Vivo Antifungal Activities of TAK-456, a Novel Oral Triazole with a Broad Antifungal Spectrum. Antimicrob. Agents Chemother. 2002, 46 (5), 1388-1393. DOI: 10.1128/AAC.46.5.1388-1393.2002.
Ichikawa, T.; Yamada, M.; Yamaguchi, M.; Kitazaki, T.; Matsushita, Y.; Higashikawa, K.; Itoh, K. Optically Active Antifungal Azoles. XIII. Synthesis of Stereoisomers and Metabolites of 1-[(1R,2R)-2-(2,4-difluorophenyl)-2-hydroxy-1-methyl-3-(1H-1,2,4-triazol-1-yl)propyl]-3-[4-(1H-1-tetrazolyl)phenyl]-2-imidazolidinone (TAK-456). Chem. Pharm. Bull. 2001, 49 (9), 1110–1119. DOI: 10.1248/cpb.49.1110.


texts: pKa values for protonated nitrogens in ketoconazole

texts:
Everywhere on the internet I see that the  two $\mathrm pK_\mathrm a$'s of ketoconazole are 6.4 and 2.3, but I don't think that is correct.

The $\mathrm pK_\mathrm a$ of imidazole is around 6.4 . But ketoconazole also has a piperazine ring and normally this $\mathrm pK_\mathrm a$ is around 9.8. There are electron acceptors but I still find 2.3 to be very low. Is this correct and which of the two nitrogens will be protonated?


texts: Why is potassium cation harder than copper?

texts: According to HSAB theory, the smaller radius and the less polarizable an acid is, the harder it is. According to Wikipedia, the ionic radii of $\ce{ K+}$ is much larger than $\ce{Cu+}$, which makes sense because d-electrons are poor shielders. Also, $\ce{Cu+}$ has larger electron density but it has a higher effective nuclear charge in comparison to potassium ion because of the poor shielding ability of d-electrons. Yet why is $\ce{K+}$  ion considered hard while $\ce{Cu+}$ ions are considered soft?


texts: Calculating the Activity Coefficient parameters form Henry's Law

texts:
Here is the question, I am stuck on part B:

Basically, this is my thought process so far, as $x_a \rightarrow 0$, the Henry's law line becomes tangential to the actual partial pressure curve..
 Henry's law states that:
$$
p_{\alpha} = Hx_{\alpha}
$$

Similarly, using the activity coefficient model:
$$
p_{\alpha} = \gamma_{\alpha}x_{\alpha}p^*_{\alpha}
$$

Where H is Henry's constant and $p^*_{\alpha}$ is the vapour pressure of the pure component. So at small $x_{\alpha}$ values one can assume:
$$
H = \gamma_{\alpha}p^*_{\alpha}
$$

From this I can get values for the $\gamma$ (I've been given values for pure component pressure). Then I can get values for $\ln \gamma_1, \ln \gamma_2$. My next step would be to substitute in values of $x_2$ and $x_1$ into the given correlations. So, for $\gamma_1$ to be correct, $x_1$ must be very small, assume it is zero therefore $x_2 \approx 1$, therefore:

$$
\ln \gamma_1 = \frac{A \times 1^2}{\bigg( (1-1)^2\frac{A}{B} + 1 \bigg)^2} \implies \ln \gamma_1 = A
$$

Clearly, this is wrong because if I run through the same process for $\ln \gamma_2$, I get a different A value. Can someone please advise, thanks.


texts: While calculating the effective nuclear charge, why don't we consider effect of outer electrons on inner ones?

texts: When calculating the effective nuclear charge for an electron, why do we only consider the repulsive effect of the inner electrons on the outer electrons? The outer electrons also repel the inner ones (towards the nucleus) and so, when determining the effective nuclear charge for inner electrons, don't we need to account for this effect as well?


texts: How to reverse damage done by nail polish remover without acetone to a laptop keyboard?

texts:
Today I was trying to clean my laptop with a nail polish remover (ingredients: ethyl acetate, peg-40, hydrogenated castor oil, panthenol, parfum, d-limonene, geraniol, ci 26100, ci 60725). Not only it didn't get clean, but some white thing remained on the keys.
I tried boiling water and a piece of cloth to make it warm and easier to remove without any success.
What can be done to reverse the damage?


texts: What is the actual reason for geometrical isomerism?

texts: My teacher explained it as restricted rotation between the double bonds. But I think there is more to it. After all, why is it considered to be a type of isomerism itself? Whether an alkene is cis or trans only depends on how you make the structure on paper. So what is the basic idea behind it?


texts: Why does nucleophilic aromatic substitution occur at C-2 and C-4 of pyridine?

texts:
In the following reaction of 2,3,4-tribromopyridine with sodium methoxide in methanol,[1] why are only the C-2 and C-4 bromines replaced with methoxy groups?

Why doesn't the bromine at C-3 also get substituted?

Gibson, K. J.; D'Alarcao, M.; Leonard, N. J. Rearrangements of azabiphenylenes. The impact of nitrogen number and position. J. Org. Chem. 1985, 50 (14), 2462–2468 DOI: 10.1021/jo00214a012.


texts: Why allene cannot be described with an allyl system?

texts:
Why is it impossible in allene to have two pi-bonds in the same orientation?
=> Why isn't allene planar? (4 $p$ electrons are in two 2x2 $p$-orbitals)

From my chemical intuition I would guess that there are 4 electrons in a $p$-system with three orbitals, but frankly I don't know how to allocate the lone pair electrons of $\ce{CS2}$ into the $sp$ and $p$ orbitals.
=> Why does $\ce{CS2}$ have another geometry than $\ce{H2CCCH2}$?

I've tried to rationalize this by allocating electrons to different hybrid orbitals (especially in $\ce{CS2}$ I was not sure how many electrons do we have in the 2x3 $p$-orbitals):


texts: Are ionic bonds stronger than covalent bonds?

texts:
A covalent bond involves overlapping of orbitals while an Ionic bond involves charge separation.

Why are bonds formed by the overlapping of orbitals weaker than charge separation; why is an ionic bond stronger than a covalent bond?


texts: Why doesn't separating the layers change the equilibrium point?

texts:
I'm following this tutorial for synthesizing esters. I don't understand why adding water to the separation funnel doesn't push the equilibrium reaction point back to the left, or why draining it doesn't push the reaction to the right, given the tutorial's explanation of Le Chatelier's Principle:

When the reaction reaches equilibrium there is still a large amount of reactants left in the mixture resulting in a poor yield of the ester.
The yield of ester can be improved by increasing the concentration of one of the reactants (either the alcohol or the carboxylic acid).
By Le Chatelier's Principle an excess of one reactant will drive the reaction to the right, increasing the production of ester, and therefore increasing the yield of ester.
In our experiment we are using an excess of carboxylic aicd (acetic acid which is also known as ethanoic acid).
From the balanced chemical equation, you will also appreciate that the presence of water in the reaction mixture will drive the equilibrium to the left, favouring the formation of reactants rather than ester.


texts: Would burning of around 200 kg of animal fat in a tunnel cause an explosion?

texts:
As shown in the movie Ironclad, they burnt a group of fat pigs together, under a tunnel, beneath the fort base and it resulted in a massive explosion.

From chemistry's perspective, and considering the tunnel environment — less oxygen, less space for energy to dissipate,  would this really cause an explosion so massive that it will dismantle the structure above the tunnel? Or would there  be no explosion, just burning?

Apologies for cruelty involved in the question.


texts: Where can I obtain research material on the synthesis of polypyrrole?

texts:
I'm studying Chemistry at A-level and a large part of the course is a researcher paper that takes most of the year.

Conductive polymers interest me. I'm struggling to find any surfeited researcher on the synthesis of polypyrrole. I not sure if I need to buy a paper or another course of action would be more suitable.


texts: Can you create a buffer with a strong acid?

texts:
So I was wading through several textbooks yesterday reviewing the concepts of buffers. I found them lot more challenging than I used to. One thing in particular disturbed me: The books and internet all said "Yeah, buffers work pretty great in as long as the  $\rm pH \approx pK_a\pm 1$." But I am not one to leave these things alone. I finally found the Quantitative explanation I was looking for over at buffer capacity on Wikipedia.

However, the graph inside the link says the buffering capacity becomes great when you solution becomes very acidic or very basic, as well. And, of course, looking at titration curves there seem to be a few "buffer" zones e.g. where the solution is highly acidic or highly basic, the $\rm pH$ doesn't change as much after a certain point:

So, obviously there is something wrong with my reasoning, since nobody calls those areas buffer zones. Is it because it is not useful to have such a highly acid/basic solution? Or is it just because technically, there is no buffering, just small $\rm pH$ changes? Or maybe something else entirely...


texts: So I already asked yesterday about canonical and localized orbitals together with Koopman's theorem where we came to the conclusion that for for example ionization potentials localized orbitals cannot be used. So I assume a ionization would be from the HOMO which leaves me with the question, whenever we say an electron is excited from the HOMO into the LUMO of a system, are we talking about the canonical forms then? Because before I knew about those two I always imagined that there is a local position somewhere in the molecule like a double bond where one electron is exited into an antibonding MO creating a single bond or 1.5 bond and that you can really tell from where to where the transition is. But canonical orbitals do not really look like we imagine orbitals they are distributed over the whole molecule.


texts: Why do branched hydrocarbons burn more efficiently (complete & clean combustion)?

texts:
Branched and cycled hydrocarbons usually a higher octane number than their straight chain counterparts. This is due to a more complete and clean (no residue) combustion. In addition, there is no probability of knocking or detonation.

What are the reasons behind this?


texts: How do you explain pKa to non-professional?

texts:
Let's say we have substance $\ce{A}$, which is mixed with substance $\ce{B}$ to improve shelf-life because $\mathrm{p}K_\mathrm{a}$ of the substance $\ce{A}$ is $7.9$ and in mix the $\mathrm{pH}$ is $5.2$.

Does this mean that in the solution with $\mathrm{pH}$ near $8$ the substance $\ce{A}$ has multiple molecules in neutral state and not dissociate, thus it forms precipitates?

Does $\mathrm{p}K_\mathrm{a}$ mean that most of the molecules of the substance $\ce{A}$ are in nondissociated state?
 Does lowering $\mathrm{pH}$ in this case causes substance $\ce{A}$ to dissociate?

Are bold parts right? Please explain in plain English without the use of external links.


texts: Can Le Chatelier's principle be derived?

texts:
Le Chatelier's principle says :

  If a constraint (such as a change in pressure, temperature, or concentration of a reactant) is applied to a system in equilibrium, the equilibrium will shift so as to tend to counteract the effect of the constraint.

This seems as an analogue of Newton's first law of motion where we talk of inertia resisting a change in the state of rest or motion of a body. Now in physics we have General Relativity whence we can derive Newton's laws. Is there a corresponding general theory in the domain of chemical kinetics too, based on sounder mathematical principles rather than just empirical observations, whence we can derive the Le Chatelier's principle as a special case?

Any suggestions are thankfully invited.


texts: Low-spin / high-spin arguments: why overlooking pairing energy?

texts:
There are many arguments in inorganic chemistry based on a transition from a high-spin to a low-spin configuration, for example:

$K_{f,3} > K_{f,2}$ for $\ce{Fe(bipy)3}$ complex, because of "a considerable increase in LFSE" as the complex becomes low-spin (from Shriver and Atkins)

However, as the complex becomes low-spin there is also an increase in the pairing energy (or a decrease in the number of Fermi holes), so I don't see why the assumption above that low-spin complexes are always more stable than high-spin is necessarily true (it can just reflect a subtle balance between $\Delta$ and P with not indication of the overall change in energy).

Based on my knowledge, successive bipy ligands would only further enhance the mixing of $\mathrm{t_{2g}}$ SALCs and that is where increasing stabilization is coming from. However, I would predict that this factor would get weaker with each ligand substitution, as the energy match of the occupied $\mathrm{t_{2g}}$ and the π* of an incoming bipy becomes worse.

Perhaps, there is some non-linear dependence of the way the pairing energy is reduced as the orbitals get "smeared" over larger space (i.e. over both the metal and π-acceptors) on the number of $\ce{bipy}$ ligands?


texts: About the use of pascal or atmosphere in chemistry

texts:
I was wondering if there are specific formulae in chemistry for which it is "compulsory" or convenient to use atmosphere (atm) rather than pascal (or even mmHg) as a unit of measurement.

Of course, we can convert one into the other, but the choice of using one of the two also conditions other units, such as in the case of volume.

Can someone provide me with a good picture of the relationship between these units and the others that we may need to use in the same context? (e.g. we use L  with atm; $\mathrm{m^3}$ with Pa).


texts: Strip away a small amount of aluminium with household chemicals

texts:
I'm trying to turn a 6″ diameter mirror (I have spares) into a two-way mirror. It shouldn't be too hard to remove the backing, but then I need to remove most, but not all of the Aluminium plating.

My current plan is to remove the backing with paint-stripper, then soak the mirror in citric acid. However, I'm not sure how long it needs to be left in the citric acid, or even if that will work at all.

Are there any household, or easily acquired, chemicals I can use that will react with Aluminium in a controlled fashion?

Any help or pointers in the right direction would be appreciated.


texts: Is probability of finding electron changing here?

texts:
We all know what is a wave function. There is a technique to convert non normalized wave function to normalized wave function.

In case of non normalized wave function integration of square of wave function with respect to 'dt' in a length 'dx' will be any constant other than 1. In case of normalized wave equation the probability of finding will be maximum i.e. 1.

The process of converting a non-normalized wave function to a normalized wave function is known as Normalization technique. In this technique we multiply the wave function with some constant and makes it equal to 1 (condition for a normalized wave function). That means after conversion the probability of finding electron is becoming maximum.

If we multiply a wave function with any constant it's nature doesn't change. So, my question is after normalization of the wave function, the nature of the wave doesn't changes and how come the probability of finding electron becomes maximum i.e. 1???


texts: How can a nonspontaneous reaction occur?

texts:
$$\frac{-\Delta G}{T}=\Delta S_{universe}$$

(This equation applies under isobaric and isothermal conditions.)

I understand that if $\Delta G$ is positive, the reaction is nonspontaneous, and adding that amount of energy to a system can drive that reaction to occur. However, if you’re increasing the Gibbs free energy of the system, then by that equation, the entropy of the universe would be decreasing, which would violate the Second Law of Thermodynamics. Can anyone explain this?


texts:
I was following a recipe for a seasoning containing rice vinegar. The directions noted that a metal saucepan should NOT be to used to heat the seasoning because it would react with the vinegar.

What would happen, chemically, if I used a metal (stainless steel) pan?

My thought is that the acetic acid and Iron could react to form Iron(III) acetate. Would this complex be in a concentration high enough to warrant the, "do not put in a metal pan," warning or would the reaction be something else?


texts:
What is the oxidation state of nitrogen the following amino acid:

I figured it must be -III:

Hydrogen is always +I
Both electrons of the N-C bond are near the nitrogen (higher electronegativity).

However, I've also heard that the N-C bond sometimes is seen as neutral (+0), which would make the oxidation state of Nitrogen -II. Which one is correct?

Do the zwitterions play a key role here (as the molecule could also be H3N-C-COO)?


texts: What are some notable results from the field of mathematical chemistry?

texts:
I recently found that there is actually a small field of research called mathematical chemistry. It seems that a lot of the research done in this field focuses on graph-theory as applied to chemistry, and topology as applied to defining the structure of molecules.

It's a bit disappointing to me that mathematical chemistry is not a larger field, but it also makes sense because for some reason chemistry does not seem to be as easily asbtracted into a mathematical framework as physics or biology. Note that I don't mean applying mathematical models to chemistry as we do this all the time. For instance, in mathematical physics, which is a very diverse field populated by people trained as both mathematicians and physicists, physical problems are reframed in a natural mathematical framework and solved accordingly. I think a lot of work on the Navier-Stokes equation would qualify as the type of work I mean.

So, is anybody aware of any notable results which have come from the field of mathematical chemistry? Furthermore, do any of these results indicate anything physical which we did not already know to be true? Also, an answer which addressed potential applications of some results of mathematical chemistry would be interesting.

I suppose I will say that I am looking for references as well as summaries so as to narrow the scope of the question.


texts: Why is osmotic pressure only for solvent

texts:
I believe that the definition of osmotic pressure means that it is only about solvent passing through a semipermeable structure.  But is there a such thing as a solute passing through a semipermeable structure because it is very small too?

This has been bothering me for a couple days.


texts:
I have been pondering the assignment for the 1H NMR peaks observed. I can't really make sense of the observations from what I know.
https://www.chemicalbook.com/SpectrumEN_104-93-8_1HNMR.htm

My question is the assignment of the signal between 6 and 7.5ppm. Unlike the way it is currently assigned, I would imagine Ha to be the most upshifted peak (near 7ppm) because methoxy group is slightly electron withdrawing and therefore de-shield the protons of Ha more than Hb (Hb is near methyl group which is slightly electron donating).

Any idea of how you would interpret the peak assignments?

Data retrieved from here: https://www.chemicalbook.com/SpectrumEN_104-93-8_1HNMR.htm


texts: Are these three molecules optical isomers?

texts:
In the structures below (2) vs (3) seem obvious optical isomers to me.

But what about (1)? Is that just a stuctural isomer (e.g. Butane vs Isobutane) or is there a more specific way to describe the relation of (1) vs (2) / (3)?

Alternative sketch of (2) & (3) based on the comment by @DGS below:


texts: How are the π bonds arranged in Osmium Tetroxide?

texts:
The structure of $\ce{OsO4}$ has puzzled me greatly for a while. I know that it has a tetrahedral geometry.

I am quite piqued at the thought of how the $π$ bonds were arranged in the molecule.

My knowledge is very limited, and I know that $π$ bonds are formed due to the sideways overlap of $p$ orbitals.

While, in a regular unhybridized atom, the 3 $p$ orbitals are arranged orthogonal to each other ($p_x$, $p_y$, $p_z$), I am unsure on how they are arranged in $\ce{OsO4}$. Is it something like this?

Or is it that some other orbitals may be involved?


texts: Pressure in Skoog Instrumental Analysis Problem 27-22b (gas chromatography)

texts:
Problem 27-22b in:

Skoog; Holler; Crouch. Principles of Instrumental Analysis. Thomson Brooks/Cole (publisher varies by country)

asks for corrected retention volumes.

A compressibility factor, $j$ is needed to compute them.

Answers that I find online all get $j = 0.915$, and a dead volume $V_M$ of $\pu{8.3 mL}$, which agrees with the solution in the back of the book.
However they seem to use a unit conversion factor of $\pu{5.17 torr psi-1}$, which is off by a factor of $10$.

In my analysis $\frac{P_i}P$ should be ($\frac{\pu{2.727 bar}  }{\pu{0.997 bar}}$), $j$ should be $0.500$, and $V_M$ should be $\pu{4.5 mL}$.

Am I wrong?

  27-22

  A GC column was operated under the following conditions: Column:
  1.10 m ✕ 2.0 mm, packed with Chromosorb P: weight of stationary liquid added, 1.40 g; density of liquid, 1.02 g/mL pressures: inlet, 26.1
  psi above room; room, 748 torr measured outlet flow rate: 25.3
  mL/min temperature: room, 21.2°C; column, 102.0°C retention
  times: air, 18.0 s; methyl acetate, 1.98 min; methyl propionate, 4.16
  min; methyl n-butyrate, 7.93 min peak widths of esters at base:
  0.19, 0.39, and 0.79, respectively

  Calculate (a) the average flow rate in the column. (b) the
  corrected retention volumes for air and the three esters. (c) the
  specific retention volumes for the three components. (d) the
  distribution constants for each of the esters. (e) a corrected
  retention volume and retention time for methyl n-hexanoate.


texts: Why does [18]annulene show only one peak in its proton NMR at $\pu{100^\circ C}$? Does any structural change happen such that all the hydrogens are alike?


texts: Difference between S and I in the context of magnetic resonance experiments

texts:
In the lecture our professor told us that nuclei with $S>1/2$ have a quadrupole and are therefore detected with NQR instead of NMR.
The majority of all elements have nuclei with $S>1/2$.

I wondered why he used $S$ (electron spin) instead of $I$ (nuclear spin) in the slides?


texts:
Is this Newman projection energy profile for 2,3-dihydroxypropanal correct?

Also, I was to identify R/S configuration for the initial Newman projection. I am pretty sure it is R, but I need help here as well.


texts: Safe way to extract hydrogen from water through electrolysis

texts:
I've done some research on google but most guides I've seen recommend adding salt to the mixture for better conductance which results in the release of chlorine.

Is there a way to perform electrolysis on water that releases hydrogen and at the same time does not release any gases that are harmful to humans?
By that I mean can I use another electrolyte that does not produce harmful side effects (so sulfuric acid is also out, and I do realize it's next to impossible to do electrolysis on distilled water.)

I'm looking for a way to show this experiment to kids in enclosed space without good ventilation.


texts: most frequently used organic (name) reactions

texts:
The situation: Beside the relevant inventory in the Merck index, organic-chemistry.org lists 243 name reactions (as counted on 08-Feb-2018), the compilation by Kurti and Czako includes "250 selections" (to quote K.C. Nicolaou's introduction), Li's general reference on the topic "covers over 320 classical as well as contemporary name reactions" yet he equally compiled name reactions relevant to heterocyclic compounds to mention a few possible sources.  There may be a significant overlap of content, though.  The discern of nucleophile and electrophile, as pointed out here, or sometimes anthromorphisms like

"What would you do if *you* were an electron"

(Grossmann book) to ease drawing mechanisms are ackowledged, too.

The question: But, isn't there a more condensed list consisting of maybe 50 to 100 organic name reactions most often used reliably in small molecule organic chemistry?  As one possibility for "reliable" I think of reactions potentially used on larger scale (kg-lab, or journals like Org. Process Res. Dev.) or the ones suggested by computers in the course of an automated retrosynthetic analysis.


texts: How is temperature constant in enthalpy change formula?

texts:
I have learnt that temperature sort of indicates the internal energy of a system, or at least this is my intuition. So if temperature is constant, then internal energy is constant as well.
But in the derivation of the following formula
$$\begin{align}{
{\Delta H = \Delta U + \Delta n_g RT}}
  \end{align} $$
T doesn't have a delta, which means it's treated like a constant value, but then wouldn't this make $\Delta U = 0$? In fact most questions in my textbook have the statement "at constant pressure and 298/300 K", but $\Delta U$ isn't 0 despite the temperature being constant.
Am I missing/neglecting something here?


texts: Why is a sodium chloride molecule stable?

texts:
The ionization energy of sodium is $\pu{5.139eV}$. This is the energy absorbed when a neutral sodium atom is stripped of its outermost electron. The electron affinity of chlorine is $\pu{3.62eV}$. This is the energy released when an electron is added to a neutral chlorine atom to form the chlorine anion.
Now suppose we have a system containing exactly one neutral sodium atom and exactly one neutral chlorine atom infinitely far apart so that the systems potential energy is zero. If we wish to make a $\ce{NaCl}$ molecule from our system, we need to put $\pu{45.139eV}$ of energy into the system to ionize the sodium atom. Afterwards, we place the electron we have just pulled off the sodium atom onto the chlorine atom upon which we get back only $\pu{3.62eV}$ of energy. So the total energy of the system has increased by $\Delta E =\pu{5.139eV -3.62eV= 1.519eV}$.
If the total energy of the system has increased after performing the previous supposition, then why does the $\ce{NaCl}$ ionic bond occur? Surely it is less stable than having the two neutral atoms separate from each other? My understanding up till now has been that molecules form when the total energy of the system is lower than the total energy of the sum of its constituents?
Is this all because an individual $\ce{NaCl}$ bond is not stable on its own but it is stable when its within a crystal lattice?
Any help on this issue would be most appreciated!


texts: is water a non-metallic oxide? and hence acidic in nature?

texts:
I just read about non-metallic oxides in my textbook which says that non-metallic oxides are a compound formed of an oxide ion and a non-metal. It also said that they are acidic in nature. It gave examples of carbon dioxide and sulfur dioxide.

But then wouldn't hydrogen oxide (water) also be a non-metallic oxide and hence, acidic in nature. But most textbooks say that water is neutral. So how's that possible?


texts: How are arsenic compounds removed from drinking water?

texts: I used to live near a volcano where the groundwater contains naturally occurring arsenic compound. Since $\ce{As2O3}$, $\ce{As2S3}$, and $\ce{As4S4}$ are predominantly occurring in drinking water, what are the processes for removing them?


texts: X-ray structure analysis mirrored coordinates?

texts:
How to ensure, that X-ray crystallography structure analysis was done right to provide correct, non-mirrored atomic coordinates?

Example: Following Wikipedia image,

is generated from data taken from the article Redetermination of (+)-methamphetamine hydrochloride at 90 K.

However, the structure presented by the CIF file represents (R)-methamphetamine, known to be levomethamphetamine, (–)-methamphetamine,

the enantiomer of “native” methamphetamine, dextromethamphetamine, (+)-methamphetamine, identified as (S)-methamphetamine.

Also, the article does not claim that the absolute configuration of (dextro)methamphetamine has been for so long mistaken and that they come with revolutionary discovery, rather are just focusing on some inter-atomic distances. (Also the “traditional absolute configuration” has been verified e.g. by synthesis from D-phenylalanine.)

As far as I have known, X-ray structure analysis was unable to provide absolute configuration info. But technology evolves. Can one determine from the experimental data, that it's supposed to be “absolute” or “relative” only (so that the coordinates presented can be mirrored)?

UPDATE: After some comments, I should emphasize that the example is just for an example (of case where the reported coordinates seem to be mirrored; I don’t know how rare or common it is), but can be used as an example in the answer as well, of course (e.g. CIF file analysis, e.g. explaining the Flack parameter value meaning, …)

And a subquestion: When hydrogen positions are provided, does it imply that the configuration is absolute? (I presume that the coordinates can still be mirrored even in such case; I mean “uncertain z-coordinate orientation”.)


texts: Why are many drugs in the hydrochloride form?

texts:
Possible Duplicate:
  Why are solid phase organics often conjugated to HCl?

I'm wondering why a lot of drugs are in this hydrochloride form.

E.g.,

Cetirizine hydrochloride
Methylphenidate hydrochloride
Tramadol hydrochloride

I'm really curious to know why this form is so common for the presentation of a drug.


texts: At equilibrium, the mass of reactants and products are equal. Does that mean the reaction stops?

texts:
This one is troubling me, and I even got it wrong in my exam:

  at equilibrium the mass of reactants and products are equal, does that mean the reaction stops?

Please explain this one.


texts: Does salt on the snow and ice covered roads and sidewalks make the nearby air temperature cooler?

texts:
I  noticed when it snows and salt is melting the snow on the roads in the city, that the air temperature feels a lot cooler than the temperature indicated on the thermometer.
A 40 degree fahrenheit temperature feels like 30 degrees. Is it the moisture from melting snow or rain that makes the air temp feel ten degrees cooler or is it the salt brine (melted snow or ice  and salt?  Is it similar to adding salt  to the ice in an Hand powered ice cream churn to make the cream container colder to make ice cream?


texts: Which are the radicals containing phosphorus in ATP?

texts: The ATP molecule contains 3 $\ce P$ atoms linked through esteric bonds. The IUPAC name of triphosphate adenosine is "[[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methoxy-hydroxyphosphoryl] phosphono hydrogen phosphate" as PubChem states. This name presents 3 groups containing phosphorus in the end: hidroxyphosphoryl, phosphono and hydrogen phosphate. I'm not sure about how are these groups placed in the molecule because I can't seem to find the hydroxyphosphoryl. To ilustrate what I mean, I've drawn it. This is how I found the other groups, but I'm unsure it's the right way to look at the end of the molecule. In blue: methoxy, In green: hydrogen phosphate, In red: phosphono. The other black part does not match the hydroxyphosphoryl group.


texts:
If electrons have a negative charge and protons have a positive charge
then how come neutrons have zero charge without consisting of protons and electrons?


texts: When simulating spectral line broadening, which convolution is preferred?

texts:
Many computational chemistry packages permit the calculation of vibrational and electronic spectra. These spectra are obtained as a set of discrete eigenvalues however they are often convolved with some distribution to give a continuous spectrum that is realistic for a finite temperature, rather than a sequence of impulse functions.

The ADF package allows the user to convolve the spectrum with either a Gaussian or Cauchy (Lorentzian) function. My understanding is that the latter affords a more realistic line broadening, however the Gaussian must be there for a reason.

Which spectral broadening scheme is preferred? Why the choice?


texts: Calculate the root-mean-squared speed of free electrons in the Sun's corona given pressure, temperature and mass of an electron

texts:
$m_\text{e}=9.1\times10^{-31}\ \mathrm{kg}$, $T=2\times10^{6}\ \mathrm{K}$ and $p=0.030\ \mathrm{Pa}$ the solution is given as: $5.4\times10^6\ \mathrm{ms^{-1}}$ but I got $9.5\times10^6\ \mathrm{ms^{-1}}$ using the following method (which does not use the value given for pressure. I simply plugged the numbers into the equation below:

$$v_\text{rms}=\sqrt{\frac{3K_\text{B}T}{m}}$$

Where have I gone wrong?


texts: Is it rigorous enough to change a DFT functional after geometry optimization to calculate excited state properties?

texts: I have done the geometry optimization with the B3LYP functional, however, there is a need to calculate the excited state energy, so the CAM-B3LYP functional should be better suited for that. Do I need to reoptimize the geometry to use CAM-B3LYP or are these functionals simillar enough so no reoptimization is needed?


texts: Hybrid orbitals forming molecular orbitals

texts:
My teacher showed me this diagram on how the hybrid orbitals of two atoms combine to form molecular orbitals. I was confused by this because I thought that VB and MO theories were two separate theories. In VB theory, atoms form hybrid orbitals that overlap, and the electrons are located in the overlap.

In MO theory, molecular orbitals are formed from the superposition of regular atomic orbitals (not hybrid orbitals), so most MO diagrams I see are drawn like this:

So are molecular orbitals formed from regular (s,p,d, etc.) atomic orbitals, or are they also formed from the hybrid orbitals? And if hybrid orbitals do combine to form molecular orbitals, are the electrons still in between the two bonded atoms or are they delocalized like in the MO theory?


texts: According to this equation for glycolysis, what is reduced and where do the electrons go?

texts:
I know that the glucose is oxidized into pyruvate but I don't understand what is reduced or where the electrons go....

Equation:
$\ce{Glucose + 2 ADP + 2 NAD^+ -> 2 Pyruvate + 2 ATP + 2 NADH}$


texts: Why do alkali metals have an exothermic electron affinity?

texts: Alkali metals should have positive electron gain enthalpy as they are electropositive elements and also there atomic size is big in their periods so they should be reluctant to take electrons but they show negative electron gain enthalpies. Why?


texts:
What does it mean to shift a chemical equilibrium? For example,

  the equilibrium shifts to the left …

I don't understand that.


texts: Is HDPE affected by long term exposure to methanol?

texts:
For at least several years I'be been storing various chloride solutions with methanol as a solute in Nalgene containers, which I believe are made from high density polyethylene (HDP).

But recently two of these containers had failed. On these containers the plastic seems to have hardened and cracked (see photographs below).

The other containers still seem to be pliable, in good shape. I thought that HDPE would be resilient to methanol and provide indefinite storage. Was I wrong? Or is it perhaps the methanol in combination with the particular salt that led to failure of the container? The failed containers had strontium and potassium chloride solution. Others like lithium, sodium and copper solutions are OK.


texts: Why is it ill advised to eat the solid aspirine formed from salicylic acid + acetic anhydride

texts:
In the laboratory notes it is indicated that it is ill advised to eat the solid formed from this experiment. An esterification reaction, in which salicylic acid is treated with acetic anhydride.

If it is for the acid added as catalyst either sulfuric acid or phosphoric acid. Why isn't it possible to neutralize it with a strong basic?

The addition of water should be enough to quench (destroy) any remaining acetic anhydride and turn it into acetic acid, and this latter one is more soluble than aspirin so it should be possible to crystallize aspirin without any acid.

The question appears in this lab notes http://www2.xula.edu/chemistry/crs-orgleclab/Organic_Lab_1_2230L_Web_Files/23_Aspirin_notes.pdf

I think it is self-evident that your basement shouldn't become a pharmacy. I think it has more to do with the acids used in the synthesis. Does the industrial process differ from the synthesis presented in the article with regards to this aspect (acid catalyst and their neutralization after the process)?


texts: Where can I find an extensive list of the preferred chemical nomenclature?

texts:
I'm writing text to speech software, and as it stands, I already have a method for reading out mathematical formulas accurately, which I have been using with chemicals as well. Thus, something like:

H2O would be read more or less as "Ayche, sub two, O".

and

CO2 would be read more or less as "Sea, O, sub two"

That is fine here and there, However in a lot of texts this becomes extremely tedious, for example:

  In tissue, cellular respiration produces carbon dioxide as a waste product; as one of the primary roles of the cardiovascular system, most of this CO2 is rapidly removed from the tissues by its hydration to bicarbonate ion. The bicarbonate ion present in the blood plasma is transported to the lungs, where it is dehydrated back into CO2 and released during exhalation. These hydration and dehydration conversions of CO2 and H2CO3

https://en.wikipedia.org/wiki/Bicarbonate_buffer_system

In this paragraph alone, you would hear: "Sea, O, sub two" three times. While I am not a chemist, I would assume that most listeners would prefer to hear would prefer to listen to a nomenclature that actually gave a name to the formula in cases like these, thus instead of hearing "Sea, O, sub two" and  "Ayche, sub two, O". -- you would hear the preferred chemical nomenclature,

Carbon Dioxide

and

Water

or

Oxidane

or

Dihydrogen monoxide

Is there a big table or list or resource available of the preferred nomenclature? And how often does this nomenclature depend on context, in the sense where the nomenclature would change depending on whether this was medicine or astronomy (etc...)?


texts: Dependence of steric hinderance on enol content

texts:
The following is extract from my book-

  To illustrate this, let us consider the enol contents of acetyacetone and $\alpha$ - methylacetylacetone. Although both the enols are stabilized by H bonding the enol form of $\alpha$ - methylacetylacetone is destabilized to some extend by steric repulsion due to the presence of $\alpha$ - methyl group.

What kind of H bonding (sorry I know i am being stupid, the figure in my book showed a bond connecting H and oxygen and dotted line connecting another oxygen and the previous hydrogen. How can hydrogen form two bonds?) is being talked about and what is steric repulsion? How does the steric repulsion destabilize the enol form?


texts:
I had an argument with an assistant in my lab, as he stated that in a hypothetical reaction two aniline molecules could react in a way, that one takes a proton off of the other one, thus creating a $\ce{R-NH3^+}$ and a $\ce{R-NH^- }$

However, the $\mathrm pK_\mathrm a$ of aniline is 27, which means, that it is, if at all, a very very poor acid, making it in my eyes impossible to deprotonate. Maybe it could be possible with n-BuLi, but that was not part of the reaction. The main topic was a nucleophilic aromatic substitution to 1-bromo-4-nitrobenzene, with aniline.

Is it even hypothetically possible for such a deprotonation in pure aniline to occur?


texts: What is the correct nomenclature for Glucuronyl C5-epimerase?

texts: I see people writing "Glucuronyl C5-epimerase", "Glucuronyl C-5-epimerase", "Glucuronyl-C-5-epimerase" and "Glucuronyl C5 epimerase", which one is correct? Is there a naming convention?


texts: Generation of singlet oxygen by irradiation

texts: What is the mechanism involved in the generation of singlet oxygen when ground state triplet oxygen is irradiated in the presence of rose bengal?


texts: Stability of transition and post-transition metal alkoxides

texts:
Many transition metal alkoxides are seen in chemistry, for instance those of $\ce{Ti, Sn}$ and $\ce{Al}$, and in particular one of those of aluminium has its own role in the MPV reduction reaction.

I was wondering: how stable these $\ce{M(OR)_n}$ structures are?

To simplify the question:

Are they susceptible to acid/basic attacks (which could possibly hydrolyze them, maybe)?
Being them metal-alkoxide compounds, do they present similar reactivity as alkali metal oxides (eg: use in Williamson's synthesis of ethers)?
Would it be possible to obtain an alkali metal alkoxide from a transition metal alkoxide, hence synthesizing those compounds without using alkali metals?
When used in a reaction as a catalyst (eg: MPV or Oppenauer reactions), a metal alkoxide can be recovered and reused?


texts: How is it possible to quantify the strength of a Lewis acid/base?

texts: When the $pK_a$ scale is not applicable - when there is no proton/charged species transfer - what should be used to quantify the strength of an acid?


texts: Reaction with ethyl chloroacetate and potassium carbonate

texts:
I am carrying out a reaction using ethyl chloroacetate, potassium carbonate in acetone for a compound containing $\ce{-NH}$ group. So, the substitution will be at $\ce{-NH}$ position.

I have tried stirring at room temperature, but no product obtained.
Refluxing has given a liquid product. Reported product should be white crystals.
Any suggestions for how to get the product?


texts: Does a weak acid undergo it's weak ionization upon the addition of any kind of base?

texts:
For an example let's assume we have a weak acid  HA . And we add either a strong or a weak base. Then what I want to know is whether  the weak ionization of the acid HA taken place?.

Weak ionization of acid HA. ==>


texts:
What dissolves cyan-salts (NaCN and KCN) without destroying them the way water does via hydrolysis?

I have to make my own cyan-salts, so they're somewhat precious to me.  Every time I have to separate them (from metal cyanides as well as carbon and oxide impurities) using water I lose some: I can precipitate some from an aqueous solution with alcohol, but the rest hydrolyses significantly before it can be desiccated with the "amateur"-grade gear I have (I've tried both freeze-drying and vacuum drying).

What solvents can separate the cyan-salts from the other substances without hydrolysing, oxidizing, or otherwise destroying them?  (Ideally a solvent that is relatively volatile at room temperature so I can readily evaporate it to recover the salts.)


texts: Structural isomerism in iso-butyl and tertiary butyl alcohol

texts:
What type of structural isomerism exists between iso butyl alcohol and tertiary butyl alcohol?

I think that there exists only positional isomerism between them but the source from where I am studying says that they are both positional and chain isomers.


texts: With optimal conditions can we supercool any compound or is it that just water and a certain set of others can be supercooled? If not, why?


texts: What is a chemical daily life experience that can be modelled by superior mathematics?

texts:
I'm searching for a chemical daily life experience that can be modelled by superior mathematics so that the origin of the equations involved can be easily explained to a beginner in chemistry.

By superior mathematics I mean things like partial and ordinary differential equation, Integral Calculus, group theory, differential geometry. But I want to understand how are the equations derived.

For example, in physics, I could model the trajectory of the rear wheel of a bicycle (a daily life experience) and I fully understand all the equations involved, without being a physicist. I want something similar to find in chemistry.


texts: Why do the first and second laws of thermodynamics not contradict each other?

texts:
We're learning about entropy right now in general chemistry, and I'm trying to understand something.

From the fact that entropy can be directly compared with enthalpy, free energy, electromotive force, etc., and its being measured in units of $\pu{J//mol*K}$ – including joules, the units of energy – it would seem that entropy is some form of energy. By the first law of thermodynamics, then, entropy can't be created nor destroyed, only transformed and transferred. From Gibbs' equation we see that entropy is being transformed out of the molecular potential energy, and from Clausius' equations we see that entropy can be transferred between a system and its surroundings, with $\Delta S_\mathrm{system}=-\Delta S_\mathrm{surroundings}$. Since $\Delta S_\mathrm{universe}=\Delta S_\mathrm{system}+\Delta S_\mathrm{surroundings}$, it follows that $\Delta S_\mathrm{universe}=0$ – as one would expect from the first law.

Yet the second law of thermodynamics states that $\Delta S_\mathrm{universe}>0$.

If entropy is a form of energy, then how can universal entropy tend to increase?
If entropy is not a form of energy, then how can it be compared with actual forms of energy and measured in energy units?


texts: Calculate ion concentrations in mixed buffers

texts:
I have to state that I'm not a chemist, nor a chemistry student, but an electrical engineer with some chemistry knowledge. However, for my work I have to deal with a problem, from which my question arose.

There is a buffer solution made by dissolving $\ce{Na2HPO4}$, citric acid and KCl for a certain measurement. I would like to calculate what the ion concenctrations are in the solution.

This is where i got.

[$\ce{K+}$], [$\ce{Na+}$] and [$\ce{Cl-}$] are quite obvious.
Denoting the hydrogen phosphate anion as $\ce{BH2-}$, I have written the equation for the phosphate: $\ce{BH^2- (aq) + H2O <=>[K_b] BH2^- (aq) + OH- (aq)}$ and [$\ce{BH^2-}$]+[$\ce{BH2^-}$]=$M_{\ce{Na2HPO4},init}$
Denoting citric acid simply as $\ce{AH3}$ I have also written the equations for its three hydrolisation steps, such as $\ce{AH3 (aq) + H2O <=>[K_{a1}] AH2- +H3O+}$ and so on two equations more, plus [$\ce{AH3}$]+[$\ce{AH2^-}$]+[$\ce{AH^2-}$]+[$\ce{A^3-}$]=$M_{citric~acid,init}$
I have written the water autohydrolysis equation $\ce{H2O <=>[K_W] 1/2 H3O+ + 1/2 OH-}$
I have so far have the 9 unknowns [$\ce{H2O}$], [$\ce{H3O+}$], [$\ce{OH-}$], [$\ce{BH2-}$], [$\ce{BH-}$] [$\ce{AH3}$], [$\ce{AH2^-}$], [$\ce{AH^2-}$], [$\ce{A^3-}$] but only 7 equations. I could do the approximation that the water concentration is constant, which would be more than enough for practical purposes, but still there are 8 unknkowns remain. I could make the approx. that the dissolved citric acid concentration is equal to the final undissociated citric acid contentration, since hardly any dissociates, leaving 7 unknowns. But this is the point where it gets interesting for me, because I don't know how I should proceed without making these approximations, since I don't see clearly the physical and chemical processes in the system. Can you help me what other equations are there which (maybe at the cost of introducing some more variables) finally result in an exactly solvable equation system?


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I am struggling to find a mechanism for the above reaction.

So far I have suggested that the proton adds to one of the reacting aromatic species leaving the resonance stabilized secondary cation. This then adds to the ortho position on the second reactant (since alkyl groups are activating). I then get a positively charged intermediate.

For a simpler reaction I would simply remove the proton but I wonder whether the reaction from this step to the product is concerted? I couldn't see an obvious step so I deprotonated and again could find no obvious way to continue apart from a rather elaborate proton transfer from a carbon that does not possess the most acidic proton.


texts: Why does not aqua regia burn filter paper?

texts: We were doing basic radical analysis in lab and we were asked to add aqua regia on the filtered PPT collected on the filter paper and collect the formed solution , my question is if aqua regia can dissolve even gold and platinum why didn't it burned the filter paper(or made holes in it )


texts: Is the density of solute same as the density of solution?

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This problem came up while solving some problems on mass percentage and mole concept.

Essentially, our teacher said that the $w/w\%$ and the $v/v\%$ for a given solution will be the same, because in order to obtain $v/v\%$ there will be a mutual division by density.

However, the density of solute is different from density of solution, right? For example, the problem we were solving involved $\ce{NaOH}$ dissolved in water. But $\ce{NaOH}$ as a compound has a characteristic density, different from the density of the solution. So $w/w$ and $v/v$ should have different values, right?

I'm not sure if I'm able to clarify what I'm thinking, but I need help with this nonetheless.


texts: Can R-3-methyl-4-heptanone be enantioselectively synthesised from 4-heptanone?

texts:
I wonder if it is possible to do the following reaction with its enantioselectivity:

I am trying to do it via enolate, but I don't know how to make only the R product or if it's even possible to distinguish between R or S simply using enolates.

There's another way?

Thanks!


texts: Farnesyl Diphosphate: Chemical commercial synthesis

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Are there any practiced commercial routes for the synthesis of "farnesyl diphosphate"? I'm especially interested in options that would scale to industrial scale processing.

To add some context, there's a bunch of secondary metabolites that branch out from FPP. Assuming one can immobilize the requisite enzyme the next question is whether the substrate FPP could be somehow manufactured at scale using a chemical synthetic route.


texts: Platt's Notation/Nomenclature for transitions

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How do you read Platt's Notation / Nomenclature? Where can I learn this?
Some examples where I've seen this mentioned:

In Platt's notation the transitions are designated as $\ce{A -> B}$ and $\ce{A -> C}$ transitions
The analysis reveals that the $L_a$ and $B_a$ states of the benzene fragments mix with CT configurations
The second $\pi\pi^*$ state has the largest oscillator strength and it is designated as $L_a$, using Platt's nomenclature

$\ce{A -> B}$ seems to refer to the $\ce{\pi -> \pi^*}$, while $\ce{A -> C}$ seems to refer to $n\ce{-> \pi^*}$, but I'm not sure how to read the notation.


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I knew two chemical reactions of alcohol with sulfuric acid

$\ce{CH3CH2OH + H2SO4 -> CH2CH2}$
Here product is having a double bond (ethene) and this reaction happens at 443 K temperature.
$\ce{CH3CH2OH + H2SO4 -> C2H5OC2H5}$
Here product is ether an happens at 413 K temperature.

But today I came across another reaction.

$\ce{C2H5OH + H2SO4 -> C2H5OSO2OH + H2O}$

Now my question is when will this third reaction happen? Any specific temperature?

The book from which I found this reaction doesn't describe anything. Just says: Alcohols react with inorganic acids (except halogen acids) to form inorganic esters.


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Molecular systems - are in a simple count systems made up of molecules. But almost every system, surrounding us are molecular than. Considering the molecular systems in terms of chemistry compels us, firstly, impose dimensional constraints on the molecular system (which?), molecular system could not be macroscopic (How big?), otherwise you'll have to talk about it as a solid body; secondly, energies for such systems are limited (<1 eV); in third place we will be interested in properties of such system as whole, but not as sum of its parts properties.

So the main question is raised: What is the range of sizes for molecular systems?


texts: When is an alkene formed in a Wurtz reaction?

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I have read that the Wurtz reaction could take place via either a radical or a nucleophilic substitution reaction. Due to steric hindrance, an alkene would generally be formed on treating a tertiary alkyl halide with Sodium in dry ether. But, what about secondary halides???

For example, what would be the major product(s) of the Wurtz reaction of    2-chlorobutane?

Would we get a mixture of 2-butene and butane, or would we just get 3,4-dimethylhexane(a symmetric alkane)?


texts: What would this unsaturated cyclic compound be called?

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I came across this compound recently, and havent been able to find out what it's name could possibly be:

My guess was maybe it's "cyclohexylene cyclohexane", but not quite sure. Can anyone tell me what this compound could be called?


texts: Cerium (CeO) behavior in Glass Polishing?

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I am basically working in semiconductor industry and I specifically taking care of CMP (Chemical Mechanical Polishing). We did polish glass (borosilicate type of glass) and we are using slurry (which is cerium-based) as the chemical compound. Our polishing time was quite long (~40 min) and without chilling the slurry, it could deteriorate the polishing pad, material removal etc. I have decided to chill the slurry (CeO) at temp ~20 °C prior supply to my polishing machine.

How does this Ce chemically and mechanically impact my CMP performance? What is the agglomeration index of this Ce with the changes of temperature?

Any good article to share?


texts: Calculating excited states using GAMESS CISD module

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I am trying to compare the energies of the excited states of $\ce{C12H9N}$ molecule using the CIS and CISD module implemented in the quantum chemistry package in GAMESS.
While I can easily obtain the results with the CIS module, the implementation of CISD module seems difficult and my program crashes every time. It will be really helpful if anyone can let me how to calculate the excited states with singles and doubles excitation.
An example would really help.


texts: Why is liquid germanium denser than solid germanium?

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Why are some elements like Ge and Si have liquids denser than their solids? In water it is explainable by H bonding, but no H bonds or such are there in Ge and Si.
Well, I want an explanation about the structure formed by Ge and Si in their solid state which makes them less dense than their liquids, and also the bonds formed


texts: Why is Na+ reduced instead of H+ in the electrolysis of dilute NaCl(aq) with Mercury cathode?

texts:
In a class of electrolysis, my instructor told me that Hg forms Na-Hg in the electrolysis of dilute NaCl aqueous solution. For this reason, sodium cations are reduced in the cathode instead of hydronium ions. However, he did not give me any reason for how creating an amalgam affects the reduction of the metal or, why Hg creates amalgam in the first place.
So, I would like to know why Hg creates amalgam whereas other metals like Pt don't form them ? And also how this affects the reduction of Na.


texts: I know that methane to methanol is a common practice, but is it possible to convert methanol back into methane, and would it be a relatively easy process to achieve?


texts: How to calculate the volume of oxygen in a reaction between hydrogen peroxide and bleach using this apparatus

texts: I know that the reaction between bleach and hydrogen peroxide produces oxygen but using this apparatus and information  I need to state how to calculate the volume of oxygen released. From my initial thoughts, I thought that the volume of oxygen will simply be the volume of the gas collected, however, the answer is said to be the total volume of gas collected subtract $20\ \mathrm{cm^3}$. I fail to understand this as I believe that the $20\ \mathrm{cm^3}$ of the hydrogen peroxide reacts with the bleach completely and even if not, will still nly produce oxygen and not any other gas, making the use of subtraction unnecessary and wrong for our answer.


texts: Does the translational part of internal energy mean the kinetic energy of the gas?

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Internal energy of an ideal gas consists of energy due to translational, rotational , vibrational etc.

This line from WP says:

  In thermodynamics, the internal energy of a system is the energy contained within the system, excluding the kinetic energy of motion of the system as a whole and the potential energy of the system as a whole due to external force fields

At the same time it says:

  The ideal gas is a gas of particles considered as point objects ... Such systems are approximated by the monatomicgases, helium and the other noble gases. Here the kinetic energy consists only of the translationalenergy of the individual atoms. Monatomic particles do not rotate or vibrate, and are not electronically excited to higher energies except at very high temperatures.
  Therefore, internal energy changes in an ideal gas may be described solely by changes in its kinetic energy. Kinetic energy is simply the internal energy of the perfect gas and depends entirely on its pressure, volume and thermodynamic temperature.

So my question is:

Does the translational internal energy of the diatomic or polyatomic molecules also refer to their kinetic energies?


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If this compound exists, what will be its name?

Can it be called bicyclo[9.2.2.2] hepta-decane ?


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In this hydrocarbon there can be two main chains: one with two double bonds and one with a double and a triple bond

Both main chains contain seven carbon atoms.
Which will be considered correct and why?


texts: Can enamines be formed from α,β-unsaturated ketones?

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This question was a result of discussion form here: α,β-unsaturated carbonyl compounds and alkyl addition

The reaction below (condensation of cyclohexenone with a secondary amine) does not yield any results on a literature search, even when I only search for the product by itself (unless my search was not good enough):

Can enamines actually be formed from α,β-unsaturated ketones? If not, what prevents it from being possible?


texts:
I'm actually digging in something that comes from Syria...
How does Chlorine cause metal to get rusted?
It's full of pictures of rockets (allegedly filled with chlorine gas) that are all rusted. In my mind i find it pretty obvious that a strong acid like HCl can cause rust, but what's actually the precise mechanism?
Does HCL even matters oj simple Cl(g) can cause rusting?

PS: consider all the reactions taking place in open air

REPHRASED:
Is it possible for Cl(g) to cause some metal to get rusted in a matter of minutes?
What are the chemical reactions that make it possible/impossible?


texts: Is cyclohexane‐1,3‐dicarboxylic acid a correct IUPAC name?

texts:
I did the numbering by taking all the functional groups in principal chain (scheme A), but my teacher did it differently and proposed the name cyclohexane‐1,3‐dicarboxylic acid (scheme B):

The principal chain in my teacher's answer is shorter. Also, he did not put any $\ce{-COOH}$ in the principal chain which he could have done.
Where am I wrong?


texts: Is it possible to supercool hydrated salts like magnesium nitrate hexahydrate supercool just like for sodium acetate trihydrate?

texts:
Recently I stumbled upon the phenomenon of supercooling. I know that you can do this with water as well as with some phase change materials, like sodium acetate trihydrate (from the wintersport handwarmers). Reading up on some literature I saw that phase change materials are experimented with for short term storage of electrical energy from solar panels. I thought if supercooling could be used, energy could be stored for a longer period of time. But it seems that the sodium acetate trihydrate has a melting temperature that is to low and other salt hydrates with a higher melting temperature do not have the ability to supercool that easily. Arriving at my burning question to you guys is,

Why are water and sodium acetate trihydrate able to supercool and other salt hydrates are not (like magnesium nitrate hexahydrate)?

Can we increase the melting point of a salt hydrate (like sodium acetate trihydrate) without losing the ability of supercooling?


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I am fairly new to report writing, and am currently writing an experimental section.

Obviously we are required to list measurements, but I was wondering whether or not we are supposed to list the corresponding errors with these?

E.g. 5 mL $\pm$ 0.01 mL sodium hydroxide was added to...

Or if not, why this isn't included?


texts: Cyclopentadienyl radical geometry and MO considerations

texts:
Does the cyclopentadienyl radical attain a regular pentagon geometry or is there a deviation caused by the Jahn–Teller effect?
Without the Jahn-Teller effect the MO diagram would look like this:

But I guess that a more stable state would be obtained by the Jahn-Teller effect: the orbital marked with number 2 would drop in energy while 3 would rise. What is the true picture?


texts:
I believe that most people know that CFCs deplete the ozone... as does free chlorine. I have read that pool chlorine is not a factor because, it is "rapidly converted to forms that dissolve in water and therefore are removed from the lower atmosphere." and/or "ends up as hydrochloric acid or sodium chloride."

So, the premise is that bleach simply won't react with carbon in the soil to produce ozone depleting chemicals (ODCs)? Or is the mind boggling complexity of chlorine in the environment sufficient to say that it must be gone?

I know that bleach (and/or chlorine gas) reacts with VOCs (like acetone, to make chloroform). Bleach will also release chlorine gas (Cl2) in conjunction with mild acids or even just carbon dioxide. And most importantly, chloramines (which evaporate from the pool) will react with ozone or UVs to produce more bleach.

So I'm wondering, is bleach (especially from swimming pools) really not that bad?


texts: How sure can we be about the structure of purine?

texts:
While answering the question Basicities of nitrogen atoms in purine, I noticed, that there might be a rapid interchange of the hydrogen bonded to the nitrogen atoms.
I have found a crystal structure in D. G. Watson, R. M. Sweet and R. E. Marsh, Acta Cryst. 1965, 19, 573-580. (DOI: 10.1107/S0365110X65003900, CCDCID: 1239746, 1239747), that resolves it as 1. However, at least in solution I would assume that there should be a distribution of structures according to the scheme below. In all cases the aromaticity is retained.

I am not an expert on crystal structures, and I don't know how to read the .cif file correctly. I remember from my course on crystallography, that the positions of hydrogen are notoriously hard to confirm.
Can we therefore really be sure about this structure? Is there evidence in the crystallography data for a large disordering?

To provide a bit more context, I am asking this, because it is likely to change part of the answer I have given to the linked question. If there exists an equilibrium between the above protomers, then that would certainly make it even harder to find the most basic nitrogen in purine.


texts:
I am trying to figure out the product for the following reaction:

Its a Prins Reaction. My proposed mechanism for it is:

In my second step, that particular carbocation is formed since $\ce{Ph}$ is an electron-withdrawing group.

Mechanism looks neat enough, but the reaction given in Wiley's Solomon and Fryhle (Page 379) is:

I'd like to know why my mechanism is "wrong"? I think there's problem in the carbocation generation step but isn't the carbocation that I have formed more stable?


texts: What does A485 mean? And what does the values on the y-axis expresses?

texts: This question is from past exam paper. I don't want an answer to the multiple choice question below, I just want to understand what A485 means in the context of the question.


texts: Is reduction of copper oxide a combustion reaction?

texts:
Is the following reaction a combustion reaction or just a single displacement? Could be both?
$$\ce{H2 + CuO -> Cu + H2O}$$

A friend of mine claims it is a combustion reaction because it is exothermic and a redox reaction.


texts: In what sense is the Inductive effect a permanent effect?

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Almost everywhere I checked, the Inductive effect is described as a permanent effect with almost no mention of what that actually means.

What exactly is permanent about the effect?
If the effect is permanent, does that mean that even if the attached electron
withdrawing/donating group is removed, the induced effect still continues to
exist?


texts: Why is the mass of 1 mole of an atom/molecule equal to its gram atomic/molecular mass?(proof)

texts: Why do we take the mass of 1 mole of an atom to be equal to its gram atomic mass and the mass of 1 molecule to be equal to its gram molecular mass? I want a mathematical rigorous proof. There are other questions on this site dealing with this question but none of them have the "proof".


texts: If I have a glass of water, and the vapor pressure is the point of equilibrium where the liquid molecules are becoming gases and the gas molecules are colliding and becoming liquid at the same rate, does that mean none of the liquid is lost? I feel as if I am misunderstanding this concept because when I leave my cup of water on the table and come back to it later on I usually notice that there's less water in the cup because it evaporated.


texts: What is the platinum doing in a Zippo hand warmer?

texts: My Zippo hand warmer requires lighter fluid, platinum catalytic burner, and a heat source to start the flameless catalytic process. What is the platinum doing in this reaction?


texts: How to calculate the half time of a unimolecular reaction given the Arrhenius coefficient and the activation energy?

texts:
Consider the following unimolecular reaction:
  $$\ce{H2O2 + M -> OH + OH + M}$$

  The high pressure limit unimolecular rate coefficient for this reaction is $k_\mathrm{uni} = A\cdot \mathrm{e}^{\frac{-E_\mathrm{a}}{R \cdot T}}$, where $A = \pu{3E14 1/s}$, and $E_\mathrm{a} = \pu{305 kJ/mol}$. Calculate the half-life of this reaction at $\pu{1 atm}$ and $\pu{1000 K}$.

Source: Question 14.1 from John W. Daily: Statistical Thermodynamics: An Engineering Approach. Cambridge University Press, 2018. ISBN: 1108244645, 9781108244640. DOI: 10.1017/9781108233194.

I started by getting that $k_\mathrm{uni}$ through the formula, got $\pu{0.03515 1/s}$ and then, since it's unimolecular:
 $$t_{\frac{1}{2}} = \frac{\ln(2)}{k_\mathrm{uni}}.$$
But I got it wrong, I don't have the solutions manual to this book to check what is wrong. I also tried using the Troe form, using the $k_\mathrm{uni}$ from the starting formula as the $k_{\inf}$ but still got it wrong.

Okay, I finally found the solutions manual. And saw that the answer on it is completely wrong, so there was no way that introducing what that math gave would work. The halftime is actually 19.7 s, but in the book it is 9 $\mu$s, which doesn't make sense.


texts: Why does a dough with margarine absorb more oil than one with butter?

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My family makes deep-fried cakes. Normally, we use butter in the dough and fry it in canola oil. Recently though, we tried using margarine instead of butter and the cakes absorbed much more of the cooking oil than ever before.

What could be the reason for this?

First I thought that, by having a relatively similar, more unsaturated, molecular structure, the margarine had a greater intermolecular attraction with the canola oil than the butter with it's more saturated structure. I tried to search the web to find something to prove or disprove this, but, unfortunately, I found nothing of the sort.


texts: Do all flames require the same minimum concentration of oxygen to sustain themsleves?

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Assume you have burned some substance A in an airtight container until the fire goes out due to insufficient oxygen. You then place some burning substance B in the container through an airlock. Are there substances A and B such that the substance B would continue to burn for a significant amount of time using the oxygen left behind after substance A burned out?

In other words, do all materials require the same concentration of oxygen to sustain a flame?


texts: Why copper sulphate is a catalyst in this reaction

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Recently, we learnt about catalyst is a substance can increase the rate of reaction without any without itself undergoing any permanent chemical change.The experiment we did was the reaction between zinc and hydrochloric acid as the equation below

$$\ce{Zn + 2HCl -> ZnCl_2 + H_2}$$

However the thing I don't understand is why copper sulphate is a catalyst when the copper ion is reduced to copper atom as the equation below

$$\ce{Cu^2+ + Zn -> Cu + Zn^2+}$$

I mean how could it call as a catalyst when it is reduced from ion to atom


texts: How does concentration of H3O effect the concentration of OH

texts: I know that [H+][OH-] will always equal 10^-14 in 25c water, however, I would like to know why that is, like if there is an extremely small amount of both H+ and OH- in the water how would increasing one effect the other. I just feel like the odds of an H+ molecule hitting an OH- molecule is extremely low and that increasing the amount of H+ wouldn't increase them all that much.


texts: How to account for the common ion effect on osmolarity quantitatively?

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In adjusting the osmolarity of a solution of Benzalknonium Cl, Disodium Editate, and Disodium borate/boric acid buffer to be isotonic (about 290 mOsm), the addition of NaCl showed unexpected behavior, possibly non-linear.

I strongly suggest that the common ion effect plays a role here, but how to account for it quantitatively? in other words how to calculate the amount of molecules of say benzalkonium Cl shifted to undissociated state after addtion of
 NaCl ?

Thanks


texts: Defining the Turbomole named BP86 functional in Gaussian

texts:
According to Turbomole, the BP86 density functional has the following definition:

$$
\mathrm{Exchange = LDA + B88\\
Correlation = LDA(VWN(V)) + P86}
$$

What is the equivalent definition in Gaussian using IOp keywords?


texts: How do I perform thin-layer chromatography to identify alkaloid content in fruits?

texts: Fruits and as well as other plant parts usually contain alkaloids, which are nitrogenous compounds. I'd like to know how the  Thin-Layer Chromatography method can be used to determine the alkaloid content in a fruit.


texts: Mechanism for Friedel-Crafts Acylation in Synthesis of Sertraline

texts: In the first step of the synthesis of Sertraline, aluminium chloride catalyst was used in a Friedel-Craft's reaction to give the following product. My question is how does the exact mechanism work? 1-napthol does not seem look like an electrophile to me, and I do not understand how AlCl3 is able to turn 1-napthol into an electrophile. The best guess I have is that the phenol tautomerise to give a ketone, and AlCl3 forms a complex with it. Yet again, I do not understand how the γ carbon is made electrophilic using AlCl3. Any help would be appreciated.


texts: I heard dichloromethane is soluble in water 1:50, but I also heard it is not because it can't form hydrogen bonds. I'm confused. Is there a way to extract it? Would putting the water to $40~\mathrm{^\circ C}$ make it evaporate trough water?


texts:
We start with compound M:

[Please imagine green bonds as dotted bonds going into the plane]
From compound M, we are told that the 3 membered ring is opened u using sodium azide yielding a mix of isomers N and O.
I drew the following:

and

[Again, please imagine the green bonds as dotted bonds and the blue
bonds as wedge bonds]
Given are the following two molecules:

Are my solutions the same as the ones given? If they aren't, where did I go wrong?
Many thanks!


texts: Nanocar racing competition and the race tracks used

texts:
In the Nanocar race competition the molecules are raced on a gold surface.
Is there a specific property of gold that it forms a good "racetrack"? On what criteria does it compare with other metal surfaces?


texts: Evolution of gas during chemical reaction

texts: Why is it that whenever hydrogen gas is produced in a reaction, it comes out in the form of tiny bubbles, but whenever Carbon dioxide is produced it comes out in the form of a brisk effervescence like lather?


texts: What makes a metal more inclined to bond covalently?

texts: Many metals form compounds with s-block elements that are essentially entirely ionic. However, elements like silver, copper, lithium and so on, can form bonds that are significantly covalent in character. What are the factors that govern whether a particular metal will bond with significant covalent character? Is this linked to hardness and softness?


texts: Boltzmann factor vs. graph of Maxwell–Boltzmann distribution

texts:
In discussions of the Arrhenius equation describing how rates change with temperature, there is often a reference to collision theory.

In the Arrhenius equation,

$$ k = A \exp\left(-\frac{E_\mathrm A}{RT}\right)$$

there is a Boltzmann factor interpreted as the fraction of collisions of sufficient energy to overcome the activation barrier. If you plot the Boltzmann factor $\mathrm e^{-E_\mathrm{A}/RT}$ against temperature, it looks like a simple exponential decay (all quantities in the exponent are positive). However, most textbooks use a graph of the Maxwell–Boltzmann distribution (i.e. distribution of speeds of gas molecules), which is not a simple exponential decay but has a maximum near the average speed.

So how is a graph of the Maxwell–Boltzmann distribution relevant to the Arrhenius equation?


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The chemical shift in benzene is around $\pu{7.27 ppm}$, which is lower than, for example, aldehydes. However, the magnetic field due to the pi electrons are in line with the applied magnetic field $B_0$, resulting in $B_{eff}>B_0$. Whereas in aldehydes, the hydrogen is simply "less shielded". So shouldn't the $\ce H$ atoms in benzene (or alkynes etc.) have even greater chemical shifts than species that are deshielded "normally" through electron withdrawing substituents?

Also, somewhat of a side question: What kind of chemical shift would we see for a proton ($\ce{H+}$) in a proton NMR, since it is completely deshielded? Could this theoretically be measured?

(Following the previous logic, shouldn't benzene have a higher chemical shift than a naked proton?)


texts:
So we were analyzing Polymers using DSC and calibrated the system using Indium. I expected it to be a single transition only as Indium only has 1 known crystal structure and as I never worked with DSC nor seen a real thermogram before I was quite surprised to a relatively large hysteresis between metling and recrystallizing. I expected it to be a big gap for polymers but for something as uniform as a metal with only one crystal structure it forms I thought the point of melting and crystallizing should be quite close together.

I remember the lecture on solid state chemistry about DSC's of crystals where Ehrenfest and displacive/reconstructive changes in for example quartz-phases had hysteresis and I think displacive ones didn't have any but it was never really explained what caused this gap. I always imagined that it takes more time to form a symmetry like going against entropy and this is why more energy has to be taken out of the system.

But is there a better explanation for pure metals? Does this gap tell me anything about the structure in the end? I imagine that structures which tend to me rather amorphous might have a smaller gap because it's not so much symmetry involved in the process which would then also imply why it is big (relatively, I haven't compared it to any other compound yet) for Indium.


texts:
I still distinctly remember reading about how Lewis acidity/basicity was characterized using kinetics. The reason given was that because formation constants are so large, these reactions are not equilibrium reactions and completion reactions. So we just characterize strength using the rate of reaction/formation. This at least makes partial sense; formation constants are huge:

http://bilbo.chm.uri.edu/CHM112/tables/Kftable.htm

EDIT: I have found what I read:

  Many reactions of nucleophiles are not reversible. A bond forms, a bond breaks, and that’s the end of the reaction. The problem with this from a measurement standpoint is that we often can’t determine an equilibrium constant for a reaction. And if we can’t do that, then we can’t develop a reactivity scale based on equilibria.

  If we can’t measure equilibria, then what do we do? Well, we use the next best measurement available: to measure reaction rates.

1) Does the quoted text make sense?

2) Am I interpreting it correctly or out of context?

3) Reference to previously answered question: Lewis base strength and the hydrogen proton


texts: Difference between any arene and an aromatic compound?

texts:
I can't seem to find what the difference between these two is. In my text book, it says that 'arenes are aromatic hydrocarbons containing one or more benzene rings' which to me suggests that arenes are a subgroup of aromatic hydrocarbons and aromatic hydrocarbons need not contain one or more benzene rings. However later on in my book it says that 'any compound with the benzene ring is classified as an aromatic compound', which to me is the exact same definition as that given for an arene. Is there a difference between arenes and aromatic compounds?

Thank you in advance :)


texts: How can it be certain that some bonds are 180 degrees?

texts:
Take acetylene, for example.

It is defined that the two outer bonds are at 180 degrees.

How is it possible to theoretically define all $\ce{C-H}$ bonds in acetylene as being 180 degrees?


texts: What is the maximum concentration of HNO3 (nitric acid) which may be handled outside of a hood?

texts:
Commercial stock solutions of HNO3 (nitric acid) are usually 70% w/w, and according to several MSDSs (e.g. here), it is dangerous to inhale it:

    Symptoms/effects after inhalation : Irritation of the respiratory tract. Dry/sore throat. Corrosion of the upper respiratory tract.
    Coughing. FOLLOWING SYMPTOMS MAY APPEAR LATER: Respiratory difficulties. Possible
    inflammation of the respiratory tract. Risk of lung edema. Blue/grey discolouration of the skin

What I want to know is what is the maximum concentration that 70% HNO3 can be diluted to, which may be safe to work outside of a hood? Are there guidelines/credible sources for such information?

Please note, this is not a medical question, it is a question of safety practice in a chemistry lab.


texts: What is the difference between a reaction of Lewis acids with Lewis bases and a redox reaction?

texts:
For example I came across this equation:
$\ce{2Al_{(s)} + 6HCl_{(aq)}} \longrightarrow \ce{2Al^{3+}_{(aq)} + 6Cl^{-}_{(aq)} + 3H_2_{(g)}}$
And thought this was a redox reaction but my book says it shows basic nature of aluminium?


texts: Why does vibrational frequency influence quantum tunneling of a proton?

texts:
Furthermore, consideration of the tunneling in the framework of the Wigner theory assumes that the tunneling factor is small. However, the $\ce{O-H}$ frequency is very high ($\gg k_\mathrm{B}T/h$), and the H atom tunneling under a potential energy barrier when proceeding either from a ground or from other excited vibration levels may be significant.

Source: German, E. D.; Sheintuch, M. Kinetics of Catalytic OH Dissociation on Metal Surfaces. J. Phys. Chem. C 2012, 116 (9), 5700–5709. DOI:10.1021/jp2106499.

Why does a higher frequency influence the quantum tunneling effect?


texts: Is it possible to save an insoluble snowflake?

texts:
In The Big Bang Theory Season 3 Episode 1 "The Electric Can Opener Fluctuation"

Leonard gives Penny a snowflake that will never melt. He said some type of chemical gas name when he try to explain, but I don't understand what he said exactly so I can't do any research about that. You can watch it on this YouTube video as well.

I used Google for some searches like doesn't melt snowflake and insoluble snowflake but results gave me nothing.

So, is this possible to save a snowflake preserved in glass with a chemical element, gas or something?


texts: Does an increase in pressure necessarily lead to an increase in temperature?

texts:
Ideal gas law says that $pV = nRT$. So with compression, one way to add pressure which makes the volume smaller, can you actually increase the temperature?

It does not make sense to me that you can increase temperature, that is, add to the kinetic energy of the molecules, simply by increasing pressure, pressure meaning the force exerted on the gas from its surroundings. Can someone please explain this contradiction?


texts: If chemical bonding is quantum mechanic, is saying they bend and vibrate like springs wrong?

texts: I don't know much about quantum mechanics, but I do know that it's quite far removed from the easily observable and that anything "quantum" involves things that are discreet. So, how close is the analogy between molecular bending and vibration with that of springs? Is there maybe a better way to think, maybe a better analogy, to describe molecular bonds?