texts: Dependence of carbocation stability with respect to the length of alkyl group

texts:
Which carbocation is more stable, the ethyl carbocation or n-propyl carbocation?
What is the effect of alkyl group length on the stability of a carbocation?


texts: N2 symmetry representation in higher symmetry groups (D3h...)

texts:
I'd like to describe the symmetry of the ground state of $N_2$ in the higher symmetry groups like $D_{3h}$ and $D_{\infty h}$.

In this answer the topic is covered very good, but only for $D_{2h}$ point group, where $N_2$ orbitals are described by the irreducible representations like this:

$$\begin{array}{cccc}
\hline
\mathrm{s}     & \mathrm{p}_x    & \mathrm{p}_y    & \mathrm{p}_z    \\
\hline
\mathrm{A_{g}} & \mathrm{B_{3u}} & \mathrm{B_{2u}} & \mathrm{B_{1u}} \\
\hline
\end{array}$$

But, when I have a look at character tables for $D_{3h}$ and $D_{\infty h}$, there are no irreducible representations with basis functions $x$ and $y$ as can be seen below.

So, how am I supposed to describe the symmetry of the $p_x$ and $p_y$ orbitals to be able to represent the symmetry of the whole system subsequently?

My attempt

I've tried to describe the symmetry of $p_x$ in $D_{3h}$ like this:

$$
\begin{array}{cccccc}
\hline
E & 2C_3(z) & 3C^{'}_{2} & \sigma_h(xy) & 2S_3 & 3\sigma_v\\ \hline
1 & 0 & -1 & 1 & 0 & 0\\
\hline
\end{array}
$$

Having this reducible representation, I've tried to identify needed irreducible representation using the reduction formula described here:

$$
a_i = \frac{1}{h}\sum_Q N\cdot \chi(R)_Q \cdot \chi_i(R)_Q
$$

For the first IR I'm getting the following result

$$
a_{A^{'}_1} = \frac{1}{12}\left[ 1\cdot1\cdot1 + 0 + 3\cdot(-1)\cdot1 + 1\cdot1\cdot1 + 0 + 0 \right] = -\frac{1}{12},
$$

which doesn't maky any sense, as it should be an integer, if I understand it well.

What am I doing wrong here? Is my reducible representation incorrect or does the formula not apply in this situation?


texts: Unexpected result (sodium hypochlorite & steel wool)

texts:
So I got myself a large Erlenmeyer flask, some steel wool and the bleach from the bathroom, mixing them under safe conditions in small quantities to see the sparky reaction I'd heard about. Trouble is, I didn't know the bleach we had was non-chlorine!

EDIT: My silly mind assumed that no reaction meant I had non-chlorine bleach, but staring me in the face is hypoCHLORITE. My apologies, I'd not meant to mislead. The brand was Shaw's at the time, or "Signature Selections" which is their store brand. I got no sparks and no visible fumes nor immediate discoloration.

Disappointed, I left the mixture alone and uhm.. forgot about it.

Going back to check on it, I found the steel wool dissolved into a powder at the bottom, and the rest of the fluid was purple.

Curious, I used a giant coffee filter and strained the rusty cake-mix residue out of the rest of it, which was now a lighter purple.

I didn't know what I'd made and thought it best to simply leave it be for a while again. I kept it in the basement, visible when the door was open and kept an eye on it. Slowly the purple went away and the fluid decreased leaving a white powder and bits of clear-quartz like appearing crystals. After several months the crystals were larger, and the white powder has climbed the entire container and spread down the sides. It's now been about 18 months since the initial experiment, and the white powder (which is similar to efflorescence in appearance) has climbed about halfway down the outside of the container, and the inside crystals have grown slightly.

What in the world have I made?


texts: Can a solvent be a solid? I do not think so. But is it possible for a solvent to be a solid?


texts: I read from a source that the aqueous solution of ferrous sulfate ($\ce{FeSO4}$) gives an unstable brown compound on treating with $\ce{NaNO2}$ and dilute $\ce{HCl}$. Well, it is quite understandable that it is the $\ce{HNO2}$ formed in situ that further causes the reaction. But what is the reaction and what is that unstable compound formed?


texts:
How would I know that a compound and its isomers are enantiomers? Considering the chiral carbons

Consider the compound is 2-bromo-2-chlorobutanedioic acid.


texts:
I've made aluminum powder in a ball mill a few times, but my last batch began to smoke and caught on fire soon after I poured it from the tumbler. Nothing unusual was afoot. It was poured into a paper plate. The ball mill aggregate had steel bearings and a few rounded rocks, same as I had used before.
The only difference was I didn't place any charcoal along with the aluminum during the milling? So why would there be spontaneous combustion?


texts: Why do biphasic systems of fluorous and organic solvents form?

texts:
It's possible to select a perfluorinated hydrocarbon that is immiscible in another organic solvent, forming a distinct phase boundary. Such systems may become miscible at elevated temperature which is exploited in the design of some catalytic processes1.

Why is it that many fluorous solvents are immiscible with organic solvents? Are their polarities sufficiently different or is there another reason?

(1) Housecroft, C.E.; Sharpe, A.G.; Inorganic Chemistry 2e; Pearson Prentice Hall; 2005, pp. 798-799


texts: Is ammonium hydroxide safe to be used for sanitizing food?

texts:
At least one big fast food chain uses ammonium hydroxide for making "pink slime" edible by killing off harmful micro organisms: https://en.wikipedia.org/wiki/Ammonium_hydroxide

Is this product from this process safe to consume?


texts: Can a compound with indirectly bonded carbon and silicon atoms within the same aromatic system be called organosilicon compound?

texts:
Wikipedia says that organosilicon compounds are organic compounds with carbon-silicon bonds.

Does the class of organosilicon compounds include compounds in which the carbon and silicon are only indirectly bonded, for example the (hypothetical) molecule 1,3,5-trihydroxy-4,6-dioxa-2-lambda3-oxa-3,5-disilacyclohex-1-ene(3+), in which the carbon and silicon atoms are not formally directly bonded but are part of the same aromatic (six π-electrons) ring, sharing the same aromatic bonding orbitals?

Here's what the molecule looks like (direct uploadd won't work for some reason...)


texts: Can carbon and titanium form an ionic bond?

texts: Can carbon and titanium form an ionic bond because they both have four valence electrons? If titanium transfers four electrons to carbon, we get $\ce{Ti^4+}$ and $\ce{C^4-}$ which both have noble gas configurations.


texts: Is lanthanum classified as lanthanoids? If yes, then can somebody explain in detail why La has 6s2 5d1 as its electron configuration and Ce has 6s2 4f1 5d1?


texts:
While studying ionic equilibrium, I came across the term "Isohydric Solutions" which is defined as:

Solutions of electrolyte are said to be isohydric if the concentration of the common ion present in them is the same and on mixing such solutions, there occurs no change in the degree of dissociation of either of the electrolyte.

But as I understand from reading the statement, in the isohydric solutions, we have two solutions with a common ion whose concentration is the same in both the solutions.
So, when we mix the two solutions, the concentration of the common ion in the reaction quotient should increase (to be more precise, it should double) and then according to Le-Chatelier's principle, both the reactions will go backward which I think can only happen when there is a change in the dissociation constant of the 2 reactions (as equilibrium constant is constant for constant temperature).
So what exactly does the definition of isohydric solution mean?


texts: For a school project, I am in a group tasked with calculating Avogadro's Number in multiple manners.  Other than the Millikan Oil Drop Experiment, we know of no ways to compute it.  A Google search yielded no methods that could be of use (either complex beyond the high school level, or through using a mole of materials, which defeats the point of deriving the number).  What methods can we (intelligent high schoolers on a limited budget) use to compute Avogadro's Number?


texts: Why weren't the electrons attracted to doubly charged Helium particles in the Rutherford experiment?

texts:
I have a chapter and in it there was a topic on the Rutherford experiment.

It is written that doubly charged helium particles or alpha particles were thrown towards a very thin gold foil and some of the alpha particles where bounced back because there were positive particles (protons) and positive and positive always repel each other.

If this was the reason for the bouncing back of the alpha particles, then why didn't the electrons, which are much smaller than protons, get attracted from alpha particles?
Especially when the alpha particles are doubly charged.


texts: Confused about writing out electron configurations

texts:
I watched the Crash Course chemistry video about the electron. In the video Hank showed an example configuration of iron as $\mathrm{(1s)^2 (2s)^2 (2p)^6 (3s)^2 (3p)^6 (4s)^2 (3d)^6}$ and explained that due to energy constraints, electrons go to the s orbital of the 4th shell before going into the d orbital of the 3rd shell and so they are written in this order.

I looked up iron in Wikipedia and there the configuration is given as $\mathrm{[Ar](3d)^6 (4s)^2}$. I understand how it's shortened with argon, but why in Wikipedia is the d orbital of the 3rd shell written before the s orbital of the 4th shell?

Which one is preferred?


texts: I was comparing boiling points of $\ce{CHCl_3}$ and $\ce{CH_3Cl}$. According to me B.P. of $\ce{CHCl_3}$ should be higher due to it's higher molecular mass than $\ce{CH_3Cl}$, but the answer is opposite ,ie. B.P. of $\ce{CH_3Cl}$ $\gt$ B.P. of $\ce{CHCl_3}$.Why?


texts: Why does the reaction of the primary alcohol cyclopentylmethanol with hydrogen bromide follow SN1 mechanism?

texts:
Example 2: Identify all the products formed in the following reaction and indicate the major product.

Solution: Three products will be formed in the given reaction as shown below:

In this reaction the primary alcohol undergoes SN1 mechanism by forming a carbocation and then undergoing ring expansion, but primary alcohols prefer SN2 mechanism. So why is this primary alcohol undergoing SN1 mechanism?


texts: Compare the ionization energies of C and Cl?

texts: I saw a test question today that basically boiled down to comparing the ionization energies of $\ce{C}$ and $\ce{Cl}$. I know that in the periodic table, ionization energy generally increases as we move right across a row (because nuclear charge increases), and decreases as we move down a column (because atomic radius increases, so valence electrons feel less attraction to the nucleus). Note that $\ce{Cl}$ is in the row below $\ce{C}$, but is also to the right of $\ce{C}$, so it is not obvious how to compare the two. So, without looking up the ionization energies and using only the periodic table, how can I answer this question?


texts:
In the structure of $\ce{H2SO3}$

there is a lone pair on sulfur.
Why can't sulfur make a bond with one of the hydrogen atoms and a double bond with oxygen to avoid having a lone pair?
Such as given below:

Because here there will be sp3 hybridisation..... no lone pair, 4 sigma and 2 pi bonds.


texts: Is this the true expression for isochoric enthalpy of non-ideal gases?

texts:
$\def\d{\mathrm{d}}$
$\def\D{\Delta}$

I recall seeing an equation in a thermodynamics lecture,

  $$\tag{non-ideal gas at constant $V$} \D H = n \int_{T_1}^{T_2}\! C_{P,\mathrm{m}}\ \d T$$

where $C_{P,\mathrm{m}}$ denotes molar heat capacity at constant pressure. There was not really a derivation of this, merely a statement whose mathematical equivalent is

  $$\underbrace{\D H = nC_{P,\mathrm{m}}\D T}_{\text{true for ideal gases}}\to\overbrace{\D H=n\int_{T_1}^{T_2}\! C_{P,\mathrm{m}}\ \d T}^{\text{the simplest generalisation}}.$$

I have to admit that the explanation made sense at the time. However, trying to justify the result from first principles$-$the $1^{\text{st}}$ law of thermodynamics$-$has proven unfruitful thus far.

$$\tag{$\D V=0, \text{def of}\ C_{V,\mathrm{m}}$} \d H=nC_{V,\mathrm{m}}\,\d T + V\,\d P$$
$$\tag{$C_{P}-C_{V}=\frac{\alpha^2TV}{\kappa_T}$}\d H=n\left(C_{P,\mathrm{m}}-\frac{\alpha^2TV}{n\kappa_T}\right)\,\d T+V\,\d P$$
Assuming the lecture formula holds, then

$$\tag{volume constant}\frac{1}{n}\int_{T_1}^{T_2}\!\frac{\alpha^2T}{\kappa_T}\,\d T=\D P.$$
Is this the case? Why?


texts: Taking volume contraction into account when mixing water with ethanol

texts:
To calculate the amount of purified water and the amount of ethanol (96% Vol.) which is needed for a desired/variable amount of a mixture - given a desired/variable percentage of ethanol - I use the following formula:

$$W = \left(\frac{T * P}{ 100}\right) \times \frac{1}{0.96}$$

and

$$E = T -  W$$

Where $T$ is the desired Total amount of product (in liters); $P$ is the desired Percentage of ethanol in the final product (in %Vol.); $W$ is the calculated amount of Water (in liters) and $E$ is the calculated amount of Ethanol (in liters containing 96 %Vol ethanol).

For example - using this formula - when I need $\pu{40 liters}$ product containing 50% vol. ethanol, the calculated amounts of water and ethanol for the mixture become $19.1667 : 20.833$.

The problem in the above calculation is that because of volume contraction the desired total amount of the final product will be less as given in the formula. To me, the problem became even more confusing after I learned that volume contraction depends on the mixing ratio of both components in a nonlinear way.

What changes should I made to the formula to take volume contraction into account?


texts: Why is copper(II) carbonate not selected as an unknown compound for back titration? (Whereas another unknown carbonate is used instead?)

texts:
Why is copper(II) carbonate not selected as an unknown compound for back titration? (Whereas another carbonate is used instead)

I know that the carbonate to be provided on the day (not Copper (II) obviously) will be reacting with excess HCl. The excess HCl will then react with NaOH to determine the concentration of HCl and eventually Molar Mass of the provided carbonate substance.
NOTE: phenolphthalein is the indicator being used


texts: Can an exothermic (endothermic) process increase (decrease) internal energy?

texts:
We classify exothermic and endothermic processes based on enthalpy change, $\Delta H < 0$ and $\Delta H > 0$ respectively.

I assume this translates to $\Delta U < 0$ and $\Delta U > 0$, respectively, for most processes. (where $\Delta H = \Delta U + \Delta (PV)$, in general).

But not all? In which case we might have processes where $\Delta H < 0$ (exothermic) but $\Delta U > 0$? Could you give an example?

Otherwise exo and endo could just be classified based on $\Delta U$ alone instead of $\Delta U + \Delta (PV)$.

Background: I'm just trying to find a motivation for using the concept of enthalpy. I know about the motivation due to additional $PV$ work needed for  a given process (hence $U$ not enough to account for all the energy involved). Just wondering if the exo/endo classification is another motivation for using enthalpy?

Side note: We know something like this for $\Delta H$ v $\Delta G$, for classifying spontaneous v non-spontaneous processes. In that case $\Delta H$ is not enough and we need $\Delta G$. Just wondering if a similar thing happens in case of $\Delta U$ v $\Delta H$ for exo/endothermic classification.


texts: Is there a standardized way to assign a label to the symbol of a chemical element (in a published work)?

texts:
When referring to a particular atom, both in text and when using a graphical representation, several conventions are being applied.

In the field of crystallography an arabic numeral either follows the element symbol without any space, e.g. $\mathrm{C}42$ for carbon atom number $42$ (usually assigned during solve/refine routine by SHELX), or is being placed in braces, e.g. $\mathrm{C}(42).$
Sometimes hydrogens attached to the same carbon atom inherit its number and receive an additional letter, e.g. $\mathrm{H42c}$ for the third hydrogen in  $\mathrm{C42}$ methyl group.

In NMR spectroscopy an element is normally labeled with a script-sized symbol (arabic number or lowercase letter) in the bottom right corner, e.g. $\ce{H_3}$ or $\ce{H_c}.$
Mestrelab Mnova places numerical labels underneath the element symbol, e.g. $\underset{3}{\ce{H}}$, or directly in place of the element if the symbol for the latter is hidden (carbon, in most cases): ${\scriptsize 3}.$

These labeling schemes used in both instrumental methods (which I cherry-picked solely for the illustrative purposes) seem to work OK in a sense that they are compatible with expanded AZE-notation required to depict any element and its attributes, such as chemical symbol $\ce{El},$ mass number $A,$ atomic number $Z,$ oxidation number O.N., charge $q$ and number of atoms of given kind $x$:

$$\Large\ce{\overset{\text{O.N.}}{^{$A$}_{$Z$}El^{$q$}_x}}$$

and won't cause any confusion (except for $\ce{H_3},$ maybe).
However, it would be nice to know whether there is a standardized way to attribute a label to an element that can be uniformly displayed and recognized (main text, titles, structures, illustrations etc.).
Does such robust labeling scheme exist?

P.S. If you are a software developer and read this, also feel free to comment or add an answer as to which labeling scheme you've came up with for calling out a particular atom.


texts: Does -M Effect increases rate of hydration of aldehyde and ketone?

texts:
I saw somewhere written, the rate of hydration of carbonyl compounds depends on:

-I group
Steric hindrance
Intramolecular H bonding

Can -M effect also increases rate of hydration?


texts: What chemical regularly transported by road in the UK would cause serious injury/loss of life if it escaped in a road accident?

texts:
I'm writing a story where a serious multi-vehicle pileup happens in the winter during foggy weather. I need the fallout from this to include the escape of a substance that will cause significant injury/loss of life to those immediately involved in the accident.

What chemical can I use that is regularly transported by road in the UK that could cause this to happen?


texts:
Which has greater dipole moment: cis-1,2-dichloroethylene or 1,1-dichloroethylene?

I know that dipole moment depends upon the strength of dipole and angle between the dipoles.

1,1-Dichloroethylene has two chlorine atoms with 120° angle between them because of $\mathrm{sp^2}$ hybridization of carbon atom.

cis-1,2-Dichloroethylene has the same with the angle between chlorine atoms as 60° (or else the dipole moment of trans form would not have been zero).

So, the dipole moment of cis should be greater than that of 1,1-dichloroethylene, but the answer says the opposite (μ(1,1-dichloroethylene) > μ(cis-1,2-dichloroethylene)). Can anyone help me?


texts: Regioselectivity in electrophilic aromatic substitution of benzofuran and indole

texts: Why does benzofuran react preferentially at position 2 when nitrated or formylated, while indole reacts preferentially at position 3 (source: Joule and Mills, Heterocyclic Chemistry 5th ed., p 371)?


texts: What substance would crawl out of a vessel?

texts:
I remember in my first chemistry lessons at high school my teacher told us about atomic properties of materials elastics and stiffness and what ever else. At one point he came up with an example of a (theoretical?) liquid that would even crawl out of its vessel to overcome differences in gravity, desiring to get to as close to the gravity well as possible and even overcoming obstacles by trying to achieve this. Back then the idea quite fascinated me, enough to think about it again every few years.
But today, myself being a hobby astro physician and having at least a layman understanding of how gravity works, I start questioning his statement. I can't really understand how a substance could gain that "information" to when it can get closer to the source of gravity by a ratio between energy required to overcome the obstacle to gain in range reduction to the gravity source.
So my question is, what was the substance he was refering to?
Does such a substance exist? And if so, how does it work?


texts: Resonance stabilization and size of ligand atoms

texts: I am told that for these two molecules, one of them is not as resonance stabilized as the other. Apparently it's the chlorine one, and it's because of the mismatch in the size of chlorine and carbon. This makes sense prima facie, but can someone confirm this is true? I can see how carbon and nitrogen have similarly sized p orbitals and thus have good overlap, and how chlorine and carbon might have poor p orbital overlap, like a BB pellet with a basketball.


texts:
Why are glues/adhesives made up of polymers?
Can monomers be used to make an adhesive.

What is is about the fact that the molecules are stuck together in a chain that make them better/more useful as an adhesive?

Is it like its harder to push people over that are linking arms with other people?


texts: How could we figure out the recipe of Coca Cola?

texts:
I know that the ingredients and the manufacturing process are both important, as discussed in this question. What would be a modern approach to figuring out the ingredients?

The ingredients listed on the website are: "Carbonated Water, High Fructose Corn Syrup, Caramel Color, Phosphoric Acid, Natural Flavors, Caffeine." My ideal answer would provide information about how to get more detail about the specific ingredients (not just 'natural flavors') and their proportions.


texts:
I would like to know what min and max values of densities are achievable with water solutions.
There are some conditions:
1. Normal or close to normal temperature;
2. Non-radioactive solutions/components;
3. Acids are good as long as they can be safely contained.

Thanks for your help!


texts: MgO as food supplement - solubility in water

texts:
A number of magnesium food / sports supplements contain it as MgO - which is practically unsoluble in water. The recommended quantity is somewhere around .3g / day, so not an insignificant amount.
How is that supposed to work? Does it rely on the pH shifts in the human gut? I've tried to check MgO solubility in water depending on pH, but the publication I've found is behind a paywall.
Edit: IvanNeretin has pointed out that MgO will react with stomach acid, not dissolve in it. I suppose that's what the manufacturers go for.


texts: Reason for same frequency of spectral line in infrared and visible region

texts:
I encountered this question while trying to understand the basics of spectroscopy and atomic structure.

Which electronic transition in Balmer series of hydrogen atom has same frequency as that of n=6 to n=4 transition in Helium positive ion?

I am aware that lines of Balmer series correspond to visible region of electromagnetic spectrum and that to Brackett series correspond to infrared region.
How is it that the frequency of a spectral line belonging to infrared region be same as that of line belonging to visible region knowing that frequency is characteristic property unique to an electromagnetic radiation?


texts: Why aren't all bonds in cyclobutadiene not equal?

texts:
Cyclobutadiene is like benzene in that it has alternating single and double bonds in a ring. However, it's bonds are not the same length, the double bonds being shorter than single bonds. The molecule is rectangular, not square.

How would this be explained?
I have one plausible explanation that I tried to give...that is as follows

Cyclobutadiene is anti aromatic with 4n = 4 pi electrons, moreover it has huge strain in the molecule. To avoid such strain the molecule goes out of plane to compensate, but thus loses its ability to resonate.

Thus resonance structures like ones in benzene cannot be drawn for cyclobutadiene.

Is this correct? Please correct me if I am wrong..and some more data about this would be appreciated


texts: Is is valid to compare reaction quotient to $K_p$ as well as $K_c$?

texts:
Can I use the reaction quotient compared to $K_p$ to answer the following question?

The solid $\ce{XY}$ decomposes into gaseous $\ce{X}$ and $\ce{Y}$: $\ce{XY(s) <=> X(g) + Y(g)}$ with a $K_p = 4.1$ at $\pu{0 ^\circ C}$. If the reaction is carried out in a $\pu{22.4 L}$ container which initial amounts of $\ce{X}$ and $\ce{Y}$ will result in the formation of solid $\ce{XY}$?

a. $\pu{5.0 mol}$ of $\ce{X}$, $\pu{0.5 mol}$ of $\ce{Y}$
b. $\pu{2.0 mol}$ of $\ce{X}$, $\pu{2.0 mol}$ of $\ce{Y}$
c. $\pu{1 mol}$ of $\ce{X}$, $\pu{1 mol}$ of $\ce{Y}$
d. none of the above
If I had been given $K_c$, I could put the different answer choices into the equilibrium expression and obtain $Q$. If $Q$ turned out to be smaller than $K_c$, then that would suggest that products would be favored. Contrariwise, if $Q$ was larger than $K_c$, then reactant(s) would be favored. So, I would simply see if any of the choices resulted in a $Q$ larger than $K_c$.
But, I was not given $K_c$. Must I convert $K_p$ to $K_c$ before making the comparison with $Q$?
I suspect the answer is "yes" (i.e. I must do the conversion) because (1) the respective values are very different and (2) I get different answers to the question depending on which value I use. This leads me to believe that I cannot compare $Q$ with $K_p$. Any additional insight into why this might be the case would be appreciated.


texts:
Apologies for the question which is far below the brilliance of the minds on this page. I have an A-Level in Organic Chemistry but I'm tying myself in knots with this one.

I'm a magician looking to create a Russian Roulette effect with water and acid (sort of!) the actual secret is that both solutions are water.

Is there a readily available metal; or substance that looks like metal, that would make the water behave like an acid to convince an onlooker that it is a potentially life threatening acid.

As a bonus question – is there a way to cheat the litmus test so that one solution (also water!) turns it red, the other reacting neutrally (that's the easy one!)?


texts:
How do we represent a molecule in text form?

A molecule, as a computer scientist I see it as a connected graph of atoms. A connected graph means that beginning at any atom, there is a path to any other atom in the graph.

The interesting question is, how do we represent these as text?

Specific questions are:

1) Is $\ce{H2O}$ different than $\ce{OH2}$? That is, does order matter, or what does order mean?

2) What does this mean $\ce{NH4NO3}$? Why do we write N two times? Is this the same thing $\ce{NNH4O3}$?


texts: Diastereomers, enantiomers, and meso compounds of molecules with lots of chiral centres

texts:
For a molecule with 2 chiral centres, there are four possible combinations, (R,R), (R,S), (S,R) and (S,S). For example, 3-bromo-2-butanol has four stereoisomers: (2R,3R)-3-bromo-2-butanol, (2R,3S)-3-bromo-2-butanol,
(2S,3R)-3-bromo-2-butanol and (2S,3S)-3-bromo-2-butanol.

Of these combinations, the following pairs are diastereomers:

S,R and S,S

S,R and R,R

R,S and S,S

R,S and R,R

I notice that only one chiral centre has been flipped to form these pairs.

The following pairs are either enantiomers or meso compounds (e.g. for (2R,3S)-tartaric acid):

S,R and R,S

S,S and R,R

I notice that both chiral centres have been flipped to form these pairs.

Could we  generalise that flipping an even number of chiral centres always gives either an enantiomer or the same molecule if it's a meso compound, and flipping an odd number of chiral centres always gives a diastereomer?


texts: What is the logic behind complex splitting?

texts: Like, on a superficial level I know that due to different coupling constant value complex splitting follows a different rule than when splitting involves same hydrogen neighbors. But I don’t understand why and how complex splitting occurs at a intuitive level. Like in complex splitting, is the magnetic moment from the two different neighboring hydrogen adding or subtracting together to affect nmr peak of one of the peak? Is that what’s happening?


texts: Activating effects of amino and hydroxyl groups in different pH

texts:
How do the activating effects of substituents on an aromatic ring depend on the medium? Explain using the two compounds shown below.

I know that different groups on benzene ring can either deactivate (e.g. $\ce{-NO2}$) or activate (e.g. $\ce{-OH}$) the benzene ring towards attack by electrophiles. How does this activating or deactivating effect change in acidic and basic media?


texts:
If a real gas is adiabatically expanded against constant pressure, then which of the following will definitely increase?
Compressibility factor (Z) or Entropy (S)
Correct answer: Entropy
My answer: Compressibility
My Reasoning :
$Z=\frac{PV}{nRT}$
In adiabatic $TV^{γ-1}=\text{constant}$
Therefore, $T$ ∝ $\frac{1}{V^{γ-1}}$
$γ-1$ is greater than zero always. So we can say is volume increases, temp decreases. Therefore Z should increase as its numerator increases and denominator decreases. Entropy for isobaric adiabatic has $\ln\frac{T_2}{T_1}$. Since $T_2$ is less than $T_1$, entropy decreases. What am I doing wrong ?


texts: Questions regarding the preparation and recrystallisation of methyl 3-nitrobenzoate

texts:
I have a procedure for the synthesis of methyl 3-nitrobenzoate (via nitration of methyl benzoate):

  Weigh 2.0 g of methyl benzoate into a dry 50 cm3 conical flask.
  Add 4 cm3 of concentrated sulfuric acid slowly to the methyl benzoate with swirling to ensure thorough mixing. Cool this mixture by partially immersing the flask in an ice-water bath.
  Carefully transfer 1.5 cm3 of concentrated nitric acid into a dry test tube. Cool the nitric acid by partially immersing it in an ice-water bath before slowly adding, with swirling, 1.5 cm3 of concentrated sulfuric acid.
  Allow this mixture to cool. This is the nitrating mixture.
  Using the glass dropping pipette, very slowly add the nitrating mixture (over about 15 min, 1 drop every 10 seconds) to the contents of the conical flask. Stir the reaction mixture as the addition is made. During the addition keep the temperature of the reaction mixture below 6 °C.
  Once addition is complete, allow the flask containing the reaction mixture to stand at room temperature for 15 min.
  Carefully pour the reaction mixture onto a small amount (approx. 20 g) of crushed ice held in a beaker.
  Stir the crushed ice throughout. Solid methyl 3-nitrobenzoate will form.
  Allow the ice to melt and filter under suction. Wash the crude product with a little ice-cold water.

I have two questions:

Firstly, why does the conical flask need to be in an ice bath when adding $\ce{H2SO4}$ to methyl benzoate?
Secondly, why is ethanol used for recrystallisation?

Can't we just heat the mixture of methyl 3-nitrobenzoate after the nitrating mixture has been added?


texts: How does pH level change the concentration of dissolved oxygen (DO) in sea water?

texts:
I am planning to investigate the relationship between $\mathrm{pH}$ and dissolved oxygen.

I would like to have a reason without taking in account the plants, animals and decomposer roles.

I want to know if $\mathrm{pH}$ affects the concentration of dissolved oxygen. For example:

If I added $\ce{HCl}$ to water, would the concentration of DO change?
In same way, if I add $\ce{NaOH}$, would the concentration of DO change?


texts:
Write an unbalanced equation for the following: Magnesium metal is added to dilute nitric acid.

My attempt: Nitric acid commonly oxidizes metals and gets itself reduced in the process - to $\ce{NO}$ if the solution is dilute, and to $\ce{NO2}$ if it is concentrated. Therefore, I thought that the reaction would proceed as follows: $\ce{Mg + HNO3 -> Mg^2+ + NO + H2O}.$

However, my book says that instead of being reduced to $\ce{NO},$ the nitric acid is actually reduced to ammonium in the following fashion: $\ce{Mg + HNO3 -> Mg^2+ + NH4^+ + H2O}$

Why is the reaction with dilute nitric acid different specifically for Magnesium (as compared to nitric acid reactions with other metals, such as copper) ?


texts: Measuring pH using pH paper makes solution change color

texts: I have an unknown substance dissolved in water, and it's milky white. When I put in a pH paper, the paper shows that it is slightly basic at pH ~8. However, after putting in the pH paper, the solution changed color from milky white to a very faint blue. What possible compound could this be?


texts: Is the decomposition reaction of nitrogen monoxide to dinitrogen and dioxygen possible?

texts: Is the reaction $\ce{2NO -> N2 + O2}$ possible? Of course with some kind of catalyst plus high temperature. How can I find the answer to such questions and where can I find more information about this reaction?


texts: How will citric acid be deprotonated by pyridine?

texts: Why do we deprotonate that specific hydrogen as opposed to any other one? What information does the table on the right give us? It seems unrelated to citric acid - where does the fluorine come from?


texts: SARS-CoV - relative size of the spike protein

texts: I am taking an online course in image analysis and have been asked to use the attached image to determine the size of the SARS-S protein of the SARS-CoV relative to the total of its proteins. However, I have been given no explanation of the image, and with a physics background, I simply do not understand it. Can someone please explain the image (specifically the SARS-CoV column).


texts: Ink / formulation chemistry: What lab requirements

texts:
Little open information can be found on the requirements of the manufacture, development and testing of gel and printing inks.
It seems that most ink manufacturers have their own specific lab configuration.

Would you know of a recource, or could you list me a possible lab setup for such an endeveavor? While I have found books on the topic, few of them are of very practical nature.

Of specific interest to me are

analytic methods
synthetic apparatus
testing procedures and protocols

Thank you very much!


texts: Succinic anhydride esterification won't go forward

texts:
I'm trying to react succinic anhydride with a decyl alcohol to produce mono-decyl succinate. Literature and Google searches suggest that the monoesterification should proceed without catalyst. However I'm failing to get the reactions going. Reactions were in reflux, $\pu{80-140 ^\circ C}$ at $\pu{1 atm}$.
Any suggestions if anhydride esterifications even needs a catalyst? Would a solvent help?


texts: Ambiguity in synthesis (crystallization)

texts:
A paper says the following,

  Dichloroglyoxime was prepared by chlorination of glyoxime in 10 % HCl at 0 deg C and crystallized from toluene.

When they say "crystallized from toluene" do they unambiguously mean recrystallized from boiling toluene at standard pressure? Thermally these compounds are unstable and instead of a white nice product I've ended up with a purple one much to my dismay and I'm not sure what actually causes the purple.

I've had problems with this synthesis because the $^1$H NMR always shows more than one oxime environment.


texts:
During the electrolysis of $\ce{Ni(NO3)2}$ using nickel electrodes, it's said that the molarity of the solution remains constant as nickel's active, and dissolves and deposits in equal measure.
But water has an oxidation potential of 0.828 V, as compared to nickel's 0.24. So while the cathodic deposition seems fine, shouldn't it be oxygen that's liberated at the anode?


texts: Can we use peaks in any chromatogram to identify a compound

texts: Does a compound give a specific chromatogram peak, using which we can identify it in a mixture?


texts: Computational chemistry software to generate files of cartesian coordinates and zmatrix of molecules

texts:
Is there any software that I can provide bond lengths, bond angles and torsion dihedrals of a molecule and generate an output file in the format of cartesian coordinates or zmatrix?
Example:
I would have input similar to the one below (which i provide all bond lengths, bond angles and torsion dihedrals of a molecule)
BOND LENGTHS
     2 1 Si O2 1.63
     3 1 Si O2 1.63
     ...
BOND ANGLES
     2 1 3 Si O2 Si 148,482
     1 2 4 O2 Si C3 107,426
     ...
TORSION ANGLES
     3 1 2 4 -161,552
     3 1 2 8 -41,721
     ...

And I would like to have an output like this:

My idea is to vary some of this information and generate several Gaussian software inputs to calculate energy points at specific bond lengths, for example, without having to manually edit the molecule structure in this software.
I know that Open Babel software can do something like that, but I don't know what type of input to use.


texts: Is there a difference between dipole and dipole moment?

texts: I’m confused as to whether both terms “dipole” and “dipole moment” are the same or different, does the moment have something to do with the molecular geometry? I know the vectors of the charges cancel out however carbon dioxide has no dipole moment because of 180 degrees, this makes it non polar, but it still has partial charges right? So isn’t it still polar?


texts: Why does calcium chloride cause a greater freezing point depression in water than magnesium chloride?

texts:
So I saw this equation for the freezing point depression, when you add a solute: $\Delta T= K_\mathrm fmi$

Where,

$\Delta T =$ The freezing point depression
$K_\mathrm f =$ The freezing point depression constant (Cryoscopic constant)
$m =$ Molality
$i =$ van't hoff factor.

I read online that $\ce{CaCl2}$ would be better than $\ce{MgCl2}$, but I cannot understand why in the terms of this formula since $i$ for both of them is the same and $K_\mathrm f$ seems to be independent of the solute since I saw values of $K_f$ of water online. (without any solute given)

So, could someone answer why this happens? Because it seems to me that the $K_\mathrm f$ could be the only factor that would explain this. Specifically I would like to know if the charge or the electronegativity of the dissolved ions would make a difference.


texts: Order of nucleophilicity of Nitrogen atoms in adenine

texts:
I recently stumbled upon a question that got me thinking. It goes something like this:

Find the major product of the following reaction:

There were 3 options given:

So it basically aims at finding out the most suitable $\ce{N}$ to attack the $\ce{CH3I}$.
i.e. The most nucleophilic $\ce{N}$ in adenine. At first, I felt that should be the $\mathrm{sp^3}$ hybridized amine group(7). But then I had to consider the delocalization of its lone pair in the ring. Then it struck me that I was forgetting about the base, which made me think about the possibility of the deprotonation of the $\ce{N}$(9) to make the 5-membered ring aromatic, which is in fact a very stabilizing phenomenon. Thus the electron density on it should be higher making it more nucleophilic. So I guessed the answer to be the first product given in this list.
I looked up in the internet for sources, but of no avail. I was just searching on this platform for further verification and I found a similar question regarding order of basicity of $\ce{N}$
in adenine.
where @DavePhD pointed out that the $\ce{N}$(1) is the most basic one followed by 3 and 7. Thus suggesting probably option 3 in the list. Though I do know that basicity and nucleophilicity aren't simply the same, but still I cant just rule out the chance of me being wrong here.
So my question is whether or not my deductions are correct and if not, then I would be very obliged to get a detailed know-how about all the possible factors influencing the formation of major product in this reaction.
Acknowledgement:
ChemDoodle 2D sketcher for helping me to draw the diagrams of organic compounds mentioned in this question.


texts: Is chromium (III) green or violet in solution? In terms of oxidation reactions between chromate and $\ce{Cr}$ (III) it forms a green color in solution, but when I searched online in different sources it seems to say that it is actually purple. Which is the right answer?


texts: What tools are used to predict the products of a chemical reaction?

texts:
I was wondering if there is a decent and non-complex way to predict the outcome of mixing two chemicals together.

I know that molecular dynamics is used in computational chemistry to understand some of these types of problems, but in many cases I have noticed that they seem to be restricted to classical physics and therefore cannot accurately predict any real reactions.

My point in asking is such that I can have a broader understanding of this; However, at the moment, I am interested in the difference between this reaction:

and the same reaction while replacing the triflic acid ($\ce{CF3SO3H}$) with chlorosulfonic acid.

Would there be any differences if these two superacids were switched?

The paper from which I obtained this reaction from is here:

Klumpp, Douglas A., Rendy Rendy, Yun Zhang, Alma Gomez, and Aaron McElrea. "Dicationic Intermediates Involving Protonated Amides: Dual Modes of Reactivity Including the Acylation of Arenes." Organic Letters 6, no. 11 (2004): 1789-1792.


texts: What is the lethal dose ( LD50 ) of coffee?

texts:
Of course, there are many types of coffee, so I would like a range of lethal dose amounts for the average human, from the mildest of lattes to the most hardcore of espressos.

Pure caffeine's lethal dose is easily calculable, but what about coffee?


texts: Do electric charges increase activation barriers?

texts:
The activation energy governs the rate of reaction, and is thought to be equal to the energy needed to break the bonds needed to initiate the reaction. But if we have a reaction like:

$$\ce{A +B -> C}$$

And another like:

$$\ce{A+ + B+ -> C^2+}$$

Would the former have a lower activation energy since there is no repulsion between the molecules? Assume the same bonds are being broken in each case.


texts: A numeric definition which determines volatile and non-volatile compounds?

texts:
Important conditions: stripping by air from water.
Hypothetical example: Let’s say if Henry’s constant is e.g. 0.005, everything below is non-volatile, everything above volatile.
The problem is I cannot find any study which determines which any constant that can tell me this compound is considered volatile, or not.

I am trying to determine which compounds during aeration of industrial wastewater will strip fast/as first.
I have tables of Henry's constant but I cannot determine which is the border of "normally volatile compounds".


texts:
What is the group number or name for elements between group 3 and 4 (F-block) on the periodic table?  I noticed when I look at a periodic table of elements, the elements of the F-block between group 3 and 4 doesn’t have a group number.  Are they just refer as Lanthanide,and Actinide or Inner Transition Elements,  But why doesn't they have a group number, it least it appear that way.

Link to a wide version of Periodic table of Elements so you can see what I am talking about.
http://en.wikipedia.org/wiki/Template:Periodic_table_%28wide_large%29


texts: Determining the half-reaction equations for extraordinary redox reaction?

texts:
I have the following question stated in the science  teacher exam:

  Write the half-reaction equations for  the following reaction  by using oxidation numbers:
  $$\ce{Na2SO3  +  Na2CrO4  -> Na2SO4 + Cr(OH)3 }$$

I am having some difficulty determining the half-reaction equations because the question doesn’t indicate either to the states of the species in the reaction nor to the medium of the reaction.

By determining oxidation numbers it is possible to see what is being oxidised and what is being reduced. I have indicated oxidation numbers below in parentheses:

$$
\ce{
\overset{\color{black}{(+1)}}{Na2}
\overset{\color{red}{(+4)}}{S}
\overset{\color{black}{(-2)}}{O_3}
+ \overset{\color{black}{(+1)}}{Na2}\overset{\color{green}{(+6)}}{Cr}\overset{\color{black}{(-2)}}{O_4}
->
\overset{\color{black}{(+1)}}{Na2}
\overset{\color{red}{(+6)}}{S}
\overset{\color{black}{(-2)}}{O4}   + \overset{\color{green}{(+3)}}{Cr}(\overset{\color{black}{(-2)}}{\ce{O}}\overset{\color{black}{(+1)}}{\ce{H}})3}
$$

By supposing the reaction takes place in an acidic medium, I failed to answer the question.

But, by supposing the reaction takes place in the basic medium, I conclude to following  two half-reactions:

Oxidation half-reaction:
$$\ce{2OH-  + Na2SO3  -> Na2SO4  + H2O + 2e-}$$
Reduction  half- reaction:
$$\ce{3e- + 4H2O  + Na2CrO4  -> Cr(OH)3 +2Na+  + 5OH-}$$
The  completely balanced equation:
$$\ce{5H2O  + 3Na2SO3  +2Na2CrO4 -> 3Na2SO4 + 2Cr(OH)3 + 4NaOH}$$

I am not sure about this solution. Are there, and where if there are, mistakes in the solution? What is the correct solution?


texts: Why does the melting point get lower going down the Alkali Metal Group with increase in atomic number?


texts: Electrochemical series - when not at standard conditions

texts:
Is there a reason why this question's answer is treating it as if it is at standard conditions? Isn't it using 0.2M aqueous solutions, so the electrochemical series won't be valid for this question? The answer seems to ignore this.

Thanks


texts:
I would like to ask if anyone has any information (schematic diagram)of vector correlations for CO2 molecule. (Is it bending in the excited state with μ in plane? How CO fragment can be ejected after the break?)

Thank you in advance


texts: how to derive equilibrium concentrations from initial conditions for mass action reactions?

texts:
I am reading a tutorial on biochemical reactions and mass action kinetics (https://www.math.utah.edu/~keener/books/control.pdf, pp. 1-2) and would like to derive an analytic solution to confirm simulation results. This is NOT a homework question, I am simply trying to understand things.
The tutorial considers a simple reaction where A and B combine, reversibly, to produce C:
$A + B \rightarrow^{f} B$
$C \rightarrow^{r} A + B$
where $f, r$ are the forward/reverse rate constants. It is clear that the change in [C] over time is:
(Eq. 1) $\displaystyle\frac{d[C]}{dt} = f[A][B] - r[C]$
It's simple to then show that the equilibrium constant $K_{eq}$ is:
(Eq. 2) $K_{eq} = \displaystyle\frac{r}{f} = \frac{[A]_{eq}[B]_{eq}}{[C]_{eq}}$.
The question: how can we use this to derive the equilibrium concentration of one of the species (like $[C]_{eq}$) as a function of the initial concentrations of A and B, $A_0, B_0$ and rate constants $f, r$? Simulation of Eq. 1 for $A_0 = 200, B_0 = 100, f = 0.0001, r = 0.001$ shows that $[C]_{eq}$ is around $90$. How can this be confirmed analytically?
Attempt at solution: try to rewrite Eq. 2 in terms of initial concentrations. We can use the fact that $[A]_{eq}$ and $[B]_{eq}$ can each be rewritten in terms of $A_0, B_0, [C]_{eq}$:
$[A]_{eq} = A_0 - [C]_{eq}$
$[B]_{eq} = B_0 - [C]_{eq}$
this is because the equilibrium concentration of "pure" A (A that wasn't used with B to make C) has to the total amount of A we started with, minus the amount of A that went into producing C. Same argument for B.
But it's not clear if this helps get a solution? Plugging these quantities into Eq. 2 we get:
$\displaystyle\frac{(A_0 - [C]_{eq})(B_0 - [C]_{eq})}{[C]_{eq}} = K_{eq}$
$\displaystyle\frac{(A_0 - [C]_{eq})(B_0 - [C]_{eq})}{[C]_{eq}} - K_{eq} = 0$
which seems too messy to be correct. I was expecting a simpler quadratic equation for such a simple problem. Guidance on solution or references to derivations will be great.


texts: Create combinatorial library of biologically plausible chemical compounds based on library of known compounds

texts:
I recently downloaded all the molecular structures (about 13,000) stored in Pherobase, an open library of insect pheromones. I would now like to create a derived, more extensive combinatorial library of compounds that would likely occur in nature, but right now don't happen to be included in the library (e.g., similar aliphatic compounds but with a different chain length or different positions of methyl branches etc).

I know I can create these semi-manually by specifying certain series using SmiLib, or using ChemAxon's Reactor. I was wondering though if there are any good cheminformatic methods to recognize biosynthetic series, which could, e.g., subsume lists of compounds in the library in  Markush notation, which could then later be expanded. Or what could be other good ways to expand the library to include other biologically plausible related compounds?

Could Chemaxon's Metabolizer perhaps help, maybe after specifying plausible biosynthetic/enzymatic reactions? Any other ideas?

Just looking in Pubchem for structurally related compounds I think wouldn't work as that would result in too many biologically implausible compounds ... (The reason I want to do this is in the context of making a large QSPR library with in-silico predicted retention indices, and later perhaps also predicted EI-spectra).


texts: How can I build the wyoming like montmorillonite unit cell in avogadro for a molecular dynamics simulation?

texts: I am trying to build a unit cell for Wyoming-like montmorillonite, using Avogadro software. I am not sure how can I get access to the atom coordination and how to generate the .xyz file at the end? Is there any file that I can use as guidance during this process? Actually, I would appreciate any suggestions in this regard? please do not hesitate to share your knowledge with me.


texts: Which is the correct definition for metamers (or metamerism)?

texts:
I have heard two definitions of metamers.

Compounds having the same molecular formula but different number of carbon atoms on either side of the functional group.
Compounds having the same molecular formula but different alkyl groups on either side of the functional group.

Which one of these is correct?

Are pentan-2-one and 3-methylbutan-2-one metamers?


texts: Why can mercury(I) exist, but not zinc(I)?

texts:
Mercury shows variable valency while zinc does not.
Its electronic configuration is $\ce{[Xe]\:4f^14 5d^10 6s^2}$. So it can donate the $\ce{6s^2}$ electrons and should only be able to form $\ce{Hg^2+}$, right?

How can it show $+1$ oxidation state?
Why does not $\ce{Zn}$ show $+1$ oxidation state?


texts:
I found a nucleophilicity order as

$\ce{HO-} > \ce{CH3-O-} > \ce{(CH3)2CH-O-} > \ce{(CH3)3C-O-}$

The reason was given that bulky groups reduce nucleophilicity. But why?

The order of the $+I$ effect is $\text{tertiary} > \text{secondary} > \text{primary}$. Due to the greater $+I$ effect, the electron on oxygen must experience greater repulsion and thus the order of neucleophilicity must be reversed. Also, according to the given order of nucleophilicity a tertiary alcohol is more acidic than a primary alcohol. But I have read that presence of more $-I$ effect increase acidity of alcohols like $\ce{Cl-CH2-OH}$ is more acidic than $\ce{CH3-OH}$. Similarly due to more $+I$ effect in $\ce{(CH3)3C-OH}$, it should be less acidic than $\ce{(CH3)2CH-OH}$ which should be less acidic than $\ce{CH3-CH2-OH}$.


texts: Why is nitric acid a stronger oxidising agent than sulfuric acid?

texts: We were taught that nitric acid can oxidize $\ce{Cl-}$ to $\ce{Cl2}$, but sulfuric acid cannot. Is this due to its smaller size, or structure, or what?


texts: Analogues of alcohols exist for all the heavier Group 16 elements, namely sulfur, selenium, and tellurium. Would polonium also be able to form a "polonol" like $\ce{CH3PoH}$?


texts: Why is phenol soluble in sodium carbonate but not in sodium bicarbonate?

texts:
The original question was basically to predict which of sodium carbonate or sodium bicarbonate can be used to distinguish between phenol and benzene.

I was sure that phenol neither reacts nor dissolves in $\ce{NaHCO3}$ but I was not sure about the $\ce{Na2CO3}$.  By searching on Google I found that phenol is soluble in sodium carbonate. I am curious to know why this is, even though phenol doesn't liberate $\ce{CO2}$.


texts: Will I get bromine by electrolysis of the brine from the Dead Sea?

texts:
I know that electrolysis of a saturated solution of sodium chloride with an inert anode (eg., graphite) is a handy way to obtain pure chlorine. I have a sample of saturated salt solution from the Dead Sea which is reported to have up to 5% bromine concentration, the domination anion being $\ce{Cl}^{-}$, of course.

Will I get bromine on the anode by electrolysis of Dead Sea water?
In general, if I have a mixture of chlorides and bromides, what determines the ratio of electrolytically produced pure $\ce{Cl}_2$ and $\ce{Br}_2$?


texts:
What are the orders of rates of oxidation with $\ce{HIO4}$ of the following diols? Explain with reasons.
(a) $\ce{Me2C(OH)C(OH)Me2}$
(b) $\ce{Me2C(OH)CH(OH)Me}$
(c) $\ce{CH2(OH)CH2(OH)}$
(d) $\ce{MeCH(OH)CH(OH)Me}$

I know that the reaction proceeds by forming a cyclic diester of periodic acid followed by cleavage of $\ce{C-C}$ bond and formation of $\ce{C=O}$ bond.  But how do we compare the rates of the given compounds?
My first thought was to think $\ce{C-C}$ cleavage as formation of a pseudo carbocation which would be stabilised by +I effect of the alkyl groups and also the hyperconjugation, but I don't think it is right.


texts: Rationalising an apparent inconsistency in the determination of reaction spontaneity

texts:
It is well-known that a reaction is spontaneous if $\Delta G < 0$. This requirement is derived from thermodynamic considerations, as done here. However, there seems to be two different ways of calculating $\Delta G$. As provided by Orthocresol in the answer here, $\Delta G$ is the rate of change of the Gibbs free energy of the reaction mixture with respect to the extent of reaction. This definition based on the rate of change cannot be disputed as a negative gradient of the graph would mean that as the forward reaction proceeds, Gibbs free energy is being minimised.

However, there appears to be another way in which $\Delta G$ is being calculated. In this approach, we take $\Delta G$ as the absolute change in Gibbs free energy going from reactants to products. One way of calculating this would be using $\Delta G = \Delta G_f [Products] - \Delta G_f [Reactants]$. Another would be $\Delta_rG = \Delta_rH - T \Delta_rS$. In this case, we are not calculating the gradient of the $G$ against extent of reaction curve but instead, we are simply calculating the absolute change in $G$ from all reactants to all products.

Clearly, the two approaches, one based on the gradient of the curve and one based on the absolute change of $G$ between reactants and products, are not the same. However, both approaches can be used to calculate $\Delta G$ in the determination of reaction spontaneity. The second approach clearly being more dubious than the first.

My attempt is rationalise this is as follows:

Both approaches are based on the idea of minimisation of the Gibbs free energy. However, they differ in their analysis of the reaction. The first approach of calculating \Delta G$ considers an ensemble of molecules going from reactants to products. It looks at small adjustments to the ratio of reactants to products in the reaction mixture as reaction progresses and subsequent changes to entropy of the mixture (due to mixing of reactants and products)

However, in the second approach, we are trying to look at the energetics in the one-step change from a reactant molecule to a product molecule and we are merely concerned with the question: does $G$ decrease when a reactant molecule changes into a product molecule? Clearly, this process does not occur in small steps but occurs at once, unlike the conversion of a mole of reactants to a mole of products. We make use of the $\Delta G_f$ values for the reactants and products to make an approximation for the conversion of one reactant to one product. This 2nd approach is certainly not exact but it is certainly still chemically correct.


texts:
According to Werner's theory, metal ions have two types of valency-primary and secondary, where the primary valency is said to be satisfied by negative ions only, and  the secondary valency can be satisfied by positive ligand, negative or neutral molecule.

My question here is:
While formation of complex compounds, which of these valencies is satisfied?

What I'm not able to interpret from this is whether there is a 'possibility' for both the valencies being satisfied or is it necessary that both are satisfied?

Also if the later is true how is it possible? Can it be explained taking some example as reference.

I think I'm not able to interpret it and understand its details.


texts:
I always thought that p-orbitals had a dumbbell shape as pictured below.

(image source)

However, I was reading an article (see Table 1, item 2) that says, "...the spherical $\mathrm{p_{1/2}}$ subshell..." (my emphasis). The implication being that the $\mathrm{p_{1/2}}$ orbital (subshell?) has a greater electron density near the nucleus than the $\mathrm{p_{3/2}}$ orbital (subshell?). Why is this and why do they call the $\mathrm{p_{1/2}}$ orbital spherical?


texts: Transition state search for rotational motion

texts:
This question is regarding Gaussian Computational software package.

I have a system where one product forms from one conformational arrangement of molecular intermediate (conformational minimum) and another product forms from a second conformational arrangement of the same molecular intermediate (another conformational minimum). These two arrangements can be interconverted via a rotation about a single bond. In order to investigate the subsequent TS from each pathway, I also need to find the pathway that interconverts the two conformers.

How can I use Gaussian to find the rotational transition state that converts these two conformations? I have tried QST2 method using both conformers as input but did not work; I also tried doing a scan along the rotation about the single bond and do a subsequent TS search from the scan maxima but to no avail. Any other methods that I can use to find rotational transition states? I imagine the PES to be very flat, how can I improve my input for tighter convergence?


texts:
The first step of preparation of glycerol
with propene involves the chlorination of of propene at 773 K. It results to form allyl chloride. However the halogenation of alkenes  generally give vicinal dihalides

$$\ce{CH3-CH=CH2 + Cl2 -> CH2Cl-CH=CH2}$$


texts:
Okay, I am getting real confused on how water flows from a hypotonic solution to a hypertonic solution through a semipermeable membrane. It is known that hypertonic solutions have higher osmotic pressure than hypotonic ones, so shouldn't it be the opposite?
Is osmosis even related to osmotic pressure or is it just because of difference in concentration?


texts: Correctness of writing H3C as opposed to CH3 in a carbon chain

texts:
I have been studying alkanes, alkenes & alkynes for a while, and I see in the examples that all the basic structural formulas start with $\ce{CH3}$, then $\ce{CH2}$, and the last carbon atom is $\ce{CH3}$, but the one that is attached to the single/double/triple bond is $\ce{CH}$. (Please correct me if I'm explaining it with the right terms.)

Anyways, there's a question about drawing the structural formula for compounds.

  Draw a structural formula for hex-3-ene.

What my answer is:

$$\ce{CH3CH2CH=CHCH2CH3}$$

I thought this was right, then I looked at the solutions and it was

$$\ce{H3CCH2CH=CHCH2CH3}$$

So now my question is, why does it start with $\ce{H3C}$ not $\ce{CH3}$ like some other examples?


texts:
So, I'm confused about something.  Rigid plastic extrusions for outdoor applications, such as twinwall greenhouse panels and the like, are most commonly polycarbonate.  They're next most common acrylic, although the consensus generally seems to be that they're not as good in most regards.  However, I find little to no evidence of rigid PET extrusions.  It seems to be used in either 1) PET film, or 2) molded PET... but nothing in-between.

Why is that?

PET seems like a far superior material to polycarbonate in these applications.  While its amorphous properties aren't impressive, when biaxially stressed (BoPET/Mylar - something that is achieved in extrusion), its tensile modulus is three times higher than polycarbonate, and its Young's modulus is nearly twice as high.  High strengths are not unusual among crystalline/oriented polymers, but what is unsual is that crystalline polymers are usually opaque; BoPET, given a proper heat treatment, retains excellent transparency and crystallinity by keeping the size of its crystals down to below the wavelength of visible light.  PET is cheaper than polycarbonate.  It's more UV stable than polycarbonate - one of the biggest problems of polycarbonate panels.  In all respects, it seems like it'd be a superior option.

So why isn't it used?  There must be something I'm missing...


texts: Is this model to explain children about oxidation and fire correct?

texts:
I am teaching two young boys (elementary school) some basics about chemistry, but I have to learn as I go myself.

Is this a viable model to explain oxidation and fire?
When we light up the fireplace, oxygen "steals" electrons from the wood, which is carbon. But carbon won't let oxygen just leave with its electron(s), so this theft results in them clinging together, and we call that Co2.

At the moment they cling together, their tight grip gives off heat. We call this an exothermic reaction. This word may not be easy to remember, but think of "exhaust pipe" (going out, so "exo") and "thermos" (it stores something hot). So when you hear exothermic reaction you know it's a reaction that gives off heat.

And how much energy is required to get oxygen and carbon to let go of their tight grip? Exactly the same amout of thermic energy they gave off when they first clung together!


texts: Can the human body withstand the heat from setting plaster?

texts:
There was an incident a couple of years ago where a teenage girl during an art lessen got her hands stuck in a bucket with plaster. As the plaster set, the heat from the chemical process caused her fingers to melt (it says in the article that the temperature reached 60 °C; I am not sure how this can melt your fingers, but this seems to be the case). As a result, she had to have all but two fingers amputated. The lesson we seem to learn is that sticking your hands into a bucket with plaster is a bad idea.

At the same time, plaster casting the human body is something that people do all the time, both in art and for medical purposes. Of course, the layers are thinner in this case. But in this video (which is erotic, sorry about that, but it was the only video example I could find), a woman puts her entire body into a bucket of plaster and seems to get away with it just fine.

So, what are these people doing differently than in that school incident? Could they be using a different kind of plaster that generates less heat?


texts:
A transition metal can be defined as an element that possesses an incomplete sub-level in one or more of its oxidization states. In the textbook I'm reading, it claims that zinc is not a transition metal because it has a full $d$-sub-level in all its oxidization states.

A quick google reveals that zinc has oxidization states $-2, 0, +1$, which means that zinc(with oxidization number $+1$) has an incomplete d-sub-level and is a  transition metal.

What's going on here? Is my textbook incorrect?


texts: Determining reaction order in equilibrium reactions

texts:
Am hoping that someone can help me with the below question, and that I am asking in the right place. Am new here, so please forgive any missteps.

Given a reaction like this:

$$\ce{A + B <=> C + D},$$

is the differential/initial rates method of determining a reaction order valid? That is, the method which determines $b$ in $r = k C_\ce{B}^b$ as the slope in a $\ln({\mathrm{d}C_\ce{C}}/{\mathrm{d}t})$ vs $\ln(C_\ce{B})$ plot.

Basically, I wonder about three points here:

I have only seen examples for this method on single forward reactions, so is it valid when there is a reverse reaction?
Am I correct in thinking that I can use measurements of $C$ for $\ln(\text{rate})$, even though I'm interested in the reaction order of $\ce{B}$, because the rate can be written in terms of any of the reactants or products?
How crucial is it that the concentration (rate) measurements must come from initial times? If the change in all concentrations is very small, is it then not valid to use even a later values?


texts: What is the product of ammonia reacting with silicone?

texts:
I used a soft silicone hose to carry ammonia at ~70 °C. I was surprised to later find the hose had hardened.
A quick materials compatibility search for silicone had given me a lot of info but an "I" (standing for "Insufficient Information") for ammonia. I wrongly assumed it would be OK.
What happened? What was produced? Can ammonia also react with or leach out elements from glassware? Should I throw the hose away? Will it become brittle?


texts: Electronic and geometric configuration of Fe(OH)₂

texts:
I'm having serious problems in the electron configuration of iron dioxide $\ce{Fe(OH)2}$ because all I could come up with was $\ce{Fe}$ double bonded with each oxygen and single bonded with each hydrogen.

Everything seems good except for the iron that's bonded with 5 atoms (which I think is weird). Could someone you give me the right electron configuration (or geometry)?


texts:
I was looking at a question which asked to predict the product of reductive ozonolysis of benzene using $\ce{Zn/O3/H2O2}$  and I predicted them correctly using the cleaving of the double bond shortcut but then I realized that benzene is losing its stable aromatic state to form not as stable products.

So I would like to know why benzene proceeds through this reaction even if it doesn't seem as favourable? Also in that case, why don't reactions like hydrohalogenation or hydroxylation occur on benzene? As I see it, they would involve loss of stability too so what's so special about ozonolysis?


texts: Why does this compound have two benzene rings?

texts: If we look at carbons 1 and 2, they have 5 electrons. 3 are directly involved in bonding, and 2 are involved in delocalisation to create the 2 benzene rings. This would mean that they had 5 valence electrons, which isn't possible, and thus there should be only one benzene ring.


texts:
I'm trying to calculate the pH of a 1M $\ce{NH_4CH_3COO}$. I know that I'll have these reactions:

$\ce{NH_4CH_3COO <=> NH_4^+ + CH_3COO^-}$
$\ce{NH_4^+ <=> NH_3 + H^+}$
$\ce{CH_3COOH <=> CH_3COO^- + H^+}$

I know the $K_a$s of the last two, so I'm able to calculate the $K$ of the first one (it's $\frac {K_{a1}}{K_{a2}}$), which gives me these equations:

$\frac {K_{a1}}{K_{a2}} = \frac {(x-y)(x-z)} {1 - x}$
${K_{a1}} = \frac {y(y+z)} {x-y}$
${K_{a2}} = \frac {z(y+z)} {x-z}$

But I have only 2 independent equations (the first one is just the ratio of the second and third) and three variables so I'm unable to solve for $[\ce{H^+}]$, which is $y+z$...

What do I do?


texts: Why is cyclopropylmethyl radical opening so fast?

texts:
Ring opening of the cyclopropylmethyl radical is reliable and fast, and so has been used as a radical trap and a radical clock.

Could someone please explain what exactly makes this reaction so fast, besides the ring strain? Why is the anionic ring opening slower?


texts: What type of material is this and how is it corroding?

texts:
So I was thinking about corrosion and I came across this structure(see image)

Do you think the inner metal/alloy that is corroding is steel?

Also, what do you think the outer layer (in white) is? perhaps the metal is just coated with paint to avoid corrosion?

Finally, what type of corrosion do you think its undergoing? General Corrosion, Galvanic corrosion, uniform corrosion and so on.


texts: In a mass spectrum, how can the sum of relative abundances be greater than 100?

texts:
I apologise if this seems a very simple question, and also if I am overlooking something that is very simple.

For part of my A Level course, we have to be able to interpret mass spectrometer readings for isotopes of elements. Further on in the course, it is extended to molecules. However, quite often it has come up where a question like this arrives:

Given that relative abundance implies that all values are relative to each other, how can all of the relative abundances sum to a number that is greater than 100?


texts: What is the (conceptual) difference between binding energy and adsorption energy?

texts: I know the equations, but I have some difficulty getting the difference between the two concepts of binding energy and adsorption energy.


texts: How to make a placebo drink taste convincing?

texts: I'm trying to make a placebo alcoholic drink - something strong (cognac, whiskey or vodka). Is it possible to make a drink containing absolutely no alcohol taste like it's got 30 or 40% alcohol? What can I add to give it that "kick"?


texts: Does turning propane or butane gas tank upside down help to use the remaining gas?

texts: Some think that when gas (propane-butane mixture for cooking) in a gas tank is almost used (only remainings are left inside and the flame is hardly noticeable) and you turn it upside down it will improve gas burning. Is it true?


texts: How many alkanes having a molecular weight of hundred, are chiral?

texts:
I successfully found 2, but the answer key says that there are 4 such compounds possible. I found:

3-methyl hexane
2,3-dimethyl pentane

We can't have a cyclic ring as the masses won't match. What else could be made folks?


texts: What happens when para-water ice is suddenly melted?

texts:
Background (hydrogen)

In the case of recently liquified hydrogen (which is quite cold of course) it must be re-equilibrated before loading on to a rocket as fuel to avoid a sudden exothermic equilibration of the ratio of the ortho- and para- forms. This is because the nuclear spin degree of freedom (singlet vs triplet) initially remains hot even when the other degrees of freedom of the molecule are cold.

The question What is the ortho/para issue with LH2 as a fuel? quotes Hydrogen Fundamentals on a hydrogen safety website:

  Liquid hydrogen (LH2) has the advantage of extreme cleanliness and the more economic type of storage, however, on the expense of a significant energy consumption of about one third of its heat of combustion. Another drawback is the unavoidable loss by boil off which is typical to maintain the cold temperature in the tank. The evaporation rate is even enhanced when ortho hydrogen is stored. The heat liberated during the ortho-para conversion at 20 K is huge with 670 kJ/kg compared to a figure of 446 kJ/kg for the latent heat of vaporization at the same temperature. This represents a safety issue requiring a design of the hydrogen loop which is able to remove the heat of conversion in a safe manner.

Water

If instead I started with extremely cold water ice (we've now switched from $\ce{H2}$  to $\ce{H2O}$) say at liquid helium temperature, and add a enough heat to quickly raise it to 0°C and just melt it to liquid, it would be mostly para- water. This will be out of equilibrium, and the nuclear spins will still want to warm up as well.

What would happen next? Would the water quickly refreeze in a fraction of a second? Or would it take hours or days to quietly re-equilibrate?


texts: CO2 is a lewis acid as it can accept electrons. But as the octets of all atoms of CO2 are complete why does it accept electrons? Shouldn't it donate electrons and be a lewis base?


texts: How do I make a dysprosium chloride solution from dysprosium oxide?

texts:
I know that dysprosium oxide is insoluble in water.

I was told that I need to add concentrated $\ce{HCl}$ to the compound and then evaporate the $\ce{HCl}$ off. From looking at the reaction equation, I can see that I will get dysprosium chloride and water as products.

Once I'm able to dissolve the $\ce{Dy2O3}$, how is it that I'm supposed to evaporate off the excess $\ce{HCl}$? Do I just let it sit, or do I need to gently heat the solution? How can I tell when all the excess $\ce{HCl}$ is gone and I can start adding water to obtain the concentration of dysprosium chloride that I need?


texts:
Recently, I have encountered two different accounts explaining the origins of the name "barbituric acid". Both accounts do mention that the name of this compound was given by the famous organic chemist Adolf von Baeyer. Li mentions that von Baeyer named the compound after his girlfriend at the time, with the name Barbara$^{1}$. Quin & Tyrell, on the other hand, informs that von Baeyer named the compound after the patron saint of artilleryman, St. Barbara$^{2}$. This is a seemingly trivial question but I'm genuinely just curious.

References

Li, J. J. Name Reactions, 3rd ed.; Springer: Heidelberg 2006; p. 15.
Quin L. D.; Tyrell, J. A.; Fundamentals of Heterocyclic Chemistry: Importance in Nature and in the Synthesis of Pharmaceuticals. John Wiley & Sons: Hoboken, New Jersey 2010; p. 119.


texts: How do I calculate the degree of dissociation in equilibrium?

texts:
In my textbook, for calculating the percentage dissociation of $\ce{HF}$ for the given equation:
$$\ce{HF + H2O <=> H3O+ + F-}$$

The solution is:

Initial Concentrations
$$[\ce{HF}] = 0.08~\mathrm{M}, \: \ce{[H3O+]} = 0, \:\ce{[F- ]}= 0$$
Equilibrium concentrations
$$[\ce{HF}] = 0.08~\mathrm{M} - x, \: \ce{[H3O+]} = x, \:\ce{[F- ]}= x$$

I am not able to undestand why $x$ is subtracted from 0.08 and not $cx$ [ where $x$ is the degree of dissociation]

I tried solving the same problem taking $cx$ but not able to get the solution, can anybody explain the difference to me? I have tried asking a similar question earlier too but it is really hard for me to get my head around this concept.


texts: Does deuterium exhibit hydrogen bonding?

texts: I searched for this on Google but I only got research articles in the SERP. I know of the concept of hydrogen bonds, that they are a special class of van der Waals forces between highly electronegative atoms ($\ce{F/O/N/Cl})$ and the hydrogen atom. I am asking if deuterium also exhibits the same hydrogen bonding, and how does its "$\ce{D}$ bond" compare to the hydrogen's original "$\ce{H}$ bond"?


texts: Why is only one proton transferred in the reaction between sulfuric acid and sodium chloride

texts:
$$\ce{NaCl + H2SO4 -> NaHSO4 + HCl}$$

The above reaction happens, but why doesn't the following happen? Or does it but only when one of the reactants is in excess?

$$\ce{2NaCl + H2SO4 -> Na2SO4 + 2HCl}$$

The second reaction seems plausible to me. How can I predict whether a similar type of reaction will be like the first equation or the second equation?


texts: Why is there no electron swapping after excitation?

texts:
If we have 2 electrons in the 1st energy level named X & Y, and one electron in the 2nd energy level named Z.

If the electron X was excited and transferred to the higher energy level, why didn't Z replace it in the 1st energy level?
Why don't we say that there is a type of nuclear gravity, and it increases when the atom becomes unstable and that gravitates Z electron towards the nucleus instead of the excited one?


texts: Grignard reaction on electron-poor benzyl bromides

texts:
I am trying to prepare a Grignard reagent from 4-nitrobenzyl bromide

but the reaction just doesn't work. My conditions are:

10 mL of THF (anhydrous);
7.04 mmol of 4-nitrobenzyl bromide;
7.04 mmol of Mg;
Argon atmosphere.

Water is not a problem since I left all my glassware in the oven overnight and flame-dried the round bottom flask + stir bar before adding Mg and the bromide. I also did everything under argon. I know the reaction is not proceeding because virtually all of the Mg turnings I added are still there and the solution is still clear. I tried adding two crystals of iodine but it didn't help either.

Is there something about this particular bromide that prevents/slows down the formation of the Grignard? I was wondering if the fact that the nitro group is electron withdrawing could make it more difficult to form the carbanion-like structure of the Grignard.


texts: Does standard electrode potential depend upon temperature?

texts:
Does standard reduction potential depend on temperature?

I am confused because my institute gives the definition for standard reduction potential as the potential that is measured at standard state which defines as measured in atmospheric pressure at $\pu{298 K}$, and when the concentration of all the substances is unity. But as far as my understanding goes standard states can be defined at any temperature and not just $\pu{298 K}$.

Also, as its directly related to $\Delta G^\circ = -nFE_\mathrm{cell} = \Delta H^\circ - T\Delta S^\circ$, this points toward it being dependent on temperature. Also, when someone says standard state, does that put restriction on temperature being $\pu{298 K}$??


texts: How is using Jones reagent different than Potassium dichromate in Sulfuric acid for the oxidation of alcohols?

texts:
I was taught at an institution I study in that using $\ce{K2Cr2O7}$ in the presence of $\operatorname{dil}.\ce{H2SO4}$ will oxidise $1^{\circ}$ alcohols to aldehydes, and $2^{\circ}$ alcohols to ketones. This is supported in here too.

At the same time, I came across Jones reagent ($\ce{Na2Cr2O7}$ in the presence of $\operatorname{dil}.\ce{H2SO4}$) on Khan Academy. But this says that it is an extremely strong oxidising agent and can oxidise Aldehydes to Carboxylic Acids too (thus giving acids on the oxidation of $1^{\circ}$ alcohols).

I do not understand how the above two reagents have different oxidising abilities. Is my premise itself wrong or is there any reason for it to have different oxidising abilities?


texts:
I want to create several mixtures of oxygen and nitrogen gas, such as 0% oxygen, 10% oxygen, 20% oxygen, 30% oxygen... 100% oxygen, but I know very little about working with gas cylinders and regulators. Is it as simple as connecting the two cylinders with a y-shaped hose and setting the flow rates to 10% oxygen and 90% nitrogen? Or will I need a more complicated setup?

This is for dissolving the gas mixture in water so I can test methods for determining dissolved oxygen levels. I'm not filling SCUBA tanks or anything dangerous, but I would still like the mixtures to be fairly accurate so I can get good data.


texts: Can substituted acetone undergo Cannizzaro reaction?

texts:
I know the Cannizzaro reaction takes place in carboxyl compounds without $\alpha$-H with the regular examples being formaldehyde and benzaldehyde.

But can this reaction take place with say diphenylmethanone or di ter-butyl ketone (2,2,4,4-tetramethylpentan-3-one) or 2,2-dimethylpropanal ?

I couldn't find any examples of these compounds showing the cannizzaro reaction.


texts: Why are square planar molecules drawn from the side plane as opposed to the top plane?

texts: Simply put, why can't you draw square planar molecules top down (so you don't have to use depth bonds)?


texts: How a molecule electron cloud interact with polarised light to show optical activity and why only asymetrical molecules only do so?

texts: I want to know how exactly light electrical component or anything else interact with e- cloud


texts: Is hydrolytic polymerisation the mechanism by which the precipitate forms from the neutral complex?

texts:
From basic coordination chemistry and acid-base equilibria we understand that a metal hexa-aqua ion can be deprotonated until it's positive charge is balanced by the negative charge of the hydroxides rendering a neutral complex. We then say that this complex precipitates.

Recently in my inorganic class we studied hydrolytic polymerisation where complexes with hydroxyl groups condense into $\ce{OH}$ bridged complexes, which can form polynuclear structures. These structures then release the hydroxide when the solubility limits are reached.

My question is:

Are these two ideas the same, and is hydrolytic polymerisation the mechanism by which the precipitate forms from the neutral complex? Another way of phrasing it would be, are these complex precipitates extended structures or are they bound via intermolecular forces?


texts:
I would have thought the answer to this question would be simple, but after searching this site I was unable to find any answers.

I know Brønsted-Lowry acids are defined in terms of proton donation, but what is it that makes the acids donate protons?

I guess the same would apply to Lewis acids, but in terms of electron pair acceptance.


texts: Which has the largest bond angle between water, oxygen difluoride and dichlorine oxide?

texts:
Which one out of $\ce{H2O}, \ce{Cl2O}, \&\ \ce{F2O}$ will have largest bond angle?

I think it should be $\ce{H2O}$ because oxygen is most electronegative in this case so electrons will be more towards oxygen hence increasing bond angle, but the answer is $\ce{Cl2O}$.  Why?


texts: What is the chemical composition of VOC's off-gassed from polyurethane?

texts:
I understand that all polyurethane (PU) materials off gas VOCs. I tried finding the % composition of the gases off-gassed by PU, but I am not able to get satisfactory answer. On the same note, why are these gases off-gassed?

Thanks!


texts: Classic/killer/easy application for the deuterium kinetic isotope effect?

texts:
I'm a physicist. While visiting someone's o-chem class I learned about the existence of the deuterium kinetic isotope effect. This seems like an extremely sweet example of zero-point energy, and I would like to use it as an example when teaching the basic quantum mechanics that we teach in freshman physics at a community college.

In this context, I would like to be able to give a good example where we actually care about the deuterium kinetic isotope effect. Ideally this would be an example that would be at least somewhat understandable to people who (like me) have no clue about organic chemistry. Something like:

Without the deuterium kinetic isotope effect, we wouldn't be able to synthesize x (where x is nail polish, fullerenes, methamphetamine, ...)
Historically, there was intense controversy about how this mysterious chemical process in x worked (where x is learning in slime molds, work-hardening of bronze, ...), but then they injected their (slime mold, ...) with deuterium and used the deuterium kinetic isotope effect to prove that ...

Related: Why is a C–D bond stronger than a C–H bond?


texts:
The course calendar for my university describes Chem 101 and 102 as "math intensive". However, it doesn't say what kind of math is involved.

What kind of math should I expect in first year chemistry?
Would it be helpful to have first year calculus under my belt first?


texts: Regioselectivity in radical chlorination of a carboxylic acid

texts:
From an online textbook, the first step in the preparation of an amino acid:

Can we be sure that the chlorine will connect exactly at that spot, in the alpha-position? Won't we get an acyl chloride instead? Or a molecule where Cl is connected in the beta-position, or further down the line?


texts: What is the physical origin of conjugation?

texts:
I had a question about the origins of conjugation in conjugated molecules. Take two ethylenes as compared to butadiene. Huckel seemed to argue that conjugation was the result of pi-pi stabilization interactions between the HOMO of the two ethylene molecules. More specifically, he argued that during the creation of Ψ1 and Ψ2, the former is lowered in energy more than the latter is raised in energy, leading to overall stability.

While this explanation satisfies me very much, I have also come across some literature (especially in organic chemistry) citing that π->π* hyperconjugation the main contributor to the stabilization of conjugated molecules. While I do understand this, I "feel" that Huckel's definition is more satisfactory. I am wondering if anyone could give some validity to the latter and if someone could point to the major factor for stabilization in conjugated molecules.


texts: How could chlorine dioxide be stabilized in aqueous solution?

texts:
There is a water-based mouthwash product which is advertised as having the ingredient "stabilized chlorine dioxide." The only other listed ingredients are trisodium phosphate and citric acid. I assume this is a buffering solution or something.

In the company's documentation, it says it contains

  a stabilized molecular form of chlorine dioxide.

But in another location, the company claims that

  the solution is naturally activated by the amino acids in saliva,
  creating a small and very safe amount of chlorine dioxide.

So that sounds to me like there's actually something else in the solution, and the that the $\ce{ClO_2}$ is being produced ("activated") during use.

I've done some reading, and I have learned that $\ce{ClO_2}$ can be produced in several ways, but all of these methods seem to involve unpleasant reagents like chlorine gas, HCl, or oxalic acid.

I'd like to know what actual compound might be referred to as "stabilized chlorine dioxide" and what reactions might be involved.

I'm not asking about the effectiveness of the product, or what value $\ce{ClO_2}$ might have as a disinfectant, I'm just curious as to whether the claims made about the ingredients are plausible, and if so, what reactions might account for this?


texts: What organic solvents are suitable to use with potassium permanganate?

texts: I'm attempting to oxidize a substance with potassium permanganate and I was wondering what organic solvents I have at my disposal. The compound is soluble in chloroform and ethanol, but obviously those would not do well with a powerful oxidizing agent. The phase-transfer catalyst I'm going to employ is tetra-n-butylammonium bromide.


texts: What is more reactive towards a cyanohydrin formation an aldehyde or an Ketone?

texts: Which is more reactive—aldehydes or ketones—towards the nucleophilic addition by cyanide to form cyanohydrins?


texts: What's the chemical reaction between NaOCl and Brilliant Blue dye?

texts: Based on my research NaOCl dissociates into Na+ and OCl-. Looking at the photo, how does the OCl- ion and the brilliant blue dye structure end up as the product? How does the OH attach itself to the carbon group and what happens to the Cl- afterwards? I'm pretty sure since the C group has a double bond it needs to be broken by an addition reaction but I'm not sure how.


texts: Confused Reading of Pressure on Vacuum Gauge

texts:
I have a gauge used to measure vacuum but I'm a bit confused as the measurements state "Hg" (I would have supposed inches of mercury except it goes to -30) and "Bar" going to minus 1.
I need the pressure in Torr, how can I properly convert my readings?
I made a google conversion but it gives me a negative result in Torr which cannot be right.


texts: Is a hydrogen bond considered to be a van der Waals force?

texts: Is a hydrogen bond considered to be a Van der Waals force?


texts: Is there an example of an opaque solution which can be made transparent by adding another solute, such that no chemical reaction occurs?

texts: I am further interested in knowing exactly what the requirements are for a liquid to be transparent.


texts: How to dissolve bronze at room temperature

texts:
Is there any way to dissolve about 10 kg of bronze at room temperature?

If yes, which substance would be the best to use and how would the reaction look like?


texts:
On factors that influence the stability of carbocations, I came across this peculiar one:

  Bulky groups attached to the positively charged $C$-atom (of the carbocation), stabilize it by B-strain, which prevents the C-atom for returning to the $sp^{3}$ state.

   Source: Pearson's Organic Chemistry (7e), Morrison and Boyd

The issue? I've never heard of "B-strain" before. I mean, it's possible that bulky groups stabilize the positive $C$-atom via inductive (and other) effects...but what's with "B-strain"?

I ran a cursory Google search, but I couldn't find any reliable Chemistry-literature that deals with this. In fact, it raised more questions than answers, most notably, the presence of another effect called the "F-strain".

So I must ask:

What is the "B-strain", and how does it contribute to stabilization of carbocations?

Additionally, is there such a thing as the "F-strain"? If so, what's it all about?


texts: Inorganic Chemistry: the order of MO diagram

texts:
I understand that to create a molecular orbital diagram, the following rules are supposed to be met:

number of A.Os = number of M.Os
Symmetry of the binding orbitals
Similarity in energy

They will eventually create bonding, anti-bonding, and maybe non-bonding orbitals. However, I am having trouble stacking them up in a correct order. For instance, if you refer to the attached diagram below, I don't know how it first starts with 4a1' and goes up to 5a1'. The only clear ones for me are the non-bonding orbitals, which have the same energy as the original group orbitals.

Could you please help me understand this? The coefficients that come in front of letters are also confusing me as well...

Thank you so much!


texts: How do I arrive at correct furanose structures when starting from a Fischer projection?

texts:
While numbering the furanose ring from the left are we supposed to place the atoms on right of the Fischer projection to the top? Isn't it just the opposite to what we do while numbering from the right?

In the image the atoms/groups lying on the right of the 2nd Fischer structure is present to the bottom of every furanose carbon of the 3rd image (chronologically). So aren't they supposed to be present at the bottom even if we start from the left (referring to structure A)? But I find Wikipedia says they are supposed to be at the top.


texts: Pyrotechnic colorants- reactions & safety concerns regarding making charcoal discs

texts:
I want to create my own charcoal disks/tablets which will be mainly used for incense and I want each of the charcoal disks to glow different colours (eg one disc glows blue, another glows red etc.). The product will be using charcoal and other ingredients including Arabic gum. I will need to add certain chemicals such as metallic salts and so forth to create the desired aesthetic effects such as the colours.

My main concern is the safety of the product, I would like to experiment to see if any of this will work but most of all, I want to know if the end product will not become a dangerous fire hazard and that it will be non-toxic.
I’ve looked up some of the chemicals online but I want to be sure.
I know that you can add metal salts to flames in bonfires to add a similar effect.

(Example here: http://tiny.cc/hqjv9y and in fireworks displays. Can I have that similar desired effect with the charcoal disks as well as the safety with it?

Below are some of the chemicals that I’ve found and would like to know if any of them are safe to add to creating my product:

For a blue flame, you want Copper Chloride or Calcium Chloride
For a light green flame, you want Borax
For a dark green flame, you want Copper Sulfate or Alum
For a strong, red flame, you want Strontium Chloride
For a purple flame, you want Potassium Chloride
For a pink flame, you want Lithium Chloride
For an orange flame, you want Sodium Chloride
For a white flame, you want Magnesium Sulfate

Some chemicals also make coloured sparks, instead of colouring the flame:

For gold sparks, you want Iron (fillings)
For silver sparks, you want (powdered) Aluminum

Source here: https://www.quora.com/What-chemicals-can-change-the-color-of-fire

Other sources: https://www.thoughtco.com/how-to-make-colored-fire-p2-602196

Pyrotechnic colorant: https://en.wikipedia.org/wiki/Pyrotechnic_colorant

https://www.thoughtco.com/how-to-make-colored-sparklers-3980637

https://www.buysparklers.com/product/14-inch-neon-party-sparklers/

I've read that magnesium can be explosive although I also I want to achieve a white hue for one of my discs. Are there any other alternatives for this?

I also would like to add that I may or may not be adding salt peter (potassium nitrate) to the mix. If I do decide to add potassium nitrate, how will each of the selected pyrotechnic colourants behave with it?

I am trying to create a product with as little additives as possible, that burns cleanly, with little to no scent, with hardly any smoke and as mentioned before, is safe and non-toxic.


texts: Where can we buy chlorinated paraffin for lab application?

texts:
Any idea where to buy chlorinated paraffin for lab application? We need very viscous analog of $\ce{CHCl_3}$.

Should we think about synthesizing it?

I found a lot of places where I could buy 5 tons:) But we need only few liters for the rest of our life.


texts: What is the triple point pressure for Gallium?

texts:
I have seen various discussions about the triple point of Gallium determined to a very precise value, so precise that it is used as a reference for NIST scales and measurements.

However, these reference related documents mean 'temperature' only when talking about triple point. Triple-point is defined as a (temperature, pressure) pair, so I fail to understand why despite so many discussions on the triple point of Ga, the pressure value is not easy to find.

I did find a value of $10^{-38} \mathrm{atm}$ (if I'm not wrong) sometime in the past but I can't find the source. However I have two questions related to this value:

Does it even makes sense to talk about such a minuscule value of pressure? Wouldn't this mean one particle every cubic light-year or something? (edit: More like one particle every cubic kilometer, depending on temperature, but still).
Is it safe to say that Gallium melts at absolute zero pressure (perfect vacuum), and never sublimates or desorbs (outgassing of Ga atoms/clusters from solid Ga surface)?

In general, are there other metals that have such a small triple-point pressure that they are guaranteed to never exhibit the process of sublimation/desorption, even in a perfect vacuum? (i.e., they will always melt first before evaporating or boiling).


texts: What is the difference between ideal stages and transfer units in a packed bed gas absorber?

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I am having a hard time grasping what these two concepts are supposed to mean and how they differ. What I know so far is:

In a counter-current gas absorber, if we set the inlet and outlet concentrations of solute in gas and liquid, and also have control on the ratio of gas to liquid flow rates, we can find the outlet concentrations by making a "step" like a staircase (with the number of steps equaling the number of stages) from the operating line to the equilibrium curve.

I understand where this comes from. When we draw a "step", we are equating the two outlet concentrations to be in equilibrium.

Now, for the number of transfer units, we usually find this out by using the integral formula:

$$\text{NTU} = \int_{y_1}^{y_2}{\frac{dy}{y-y*}}$$

where $y$ is the operating line solute concentration in gas phase for a given $x$, i.e. solute concentration in liquid phase, and $y*$ is the equilibrium curve solute concentration for the same $x$.

What I have noticed is that often, the NTU is not an integer, it can also be a fraction. And this fraction, multiplied by the height of transfer unit (HTU), gives the total height of the bed needed for such a transition.

I am confused. I dont understand what NTU is exactly, or better, what a transfer unit is. I would greatly appreciate some guidance.


texts: This is a step in a experiment I have carried out. Usually DDQ (dichlorodicyanoquinone) would be used here to oxidise the dihydropyridine. However in this case Nitric Acid is being used as the oxidising agent. I'm unsure as to how this would happen mechanistically, my initial guess that since the product is aromatic and Nitrogen can help expel the hydrogen atom from the 4 position this will happen quite fast in one step. What role will the Nitric Acid have in this reaction? Mechanistic detail would be helpful, I can't find an example of this in any textbook.


texts: Derivation of relationship betwee standard Gibbs energy of reaction and equilibrium constant?

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How does one derive $\Delta_\mathrm r G^\circ = -RT\ln(K)$? I don't see the connection mathematically or conceptually; how does Gibbs at all relate to the equilibrium constant of a reaction?

This was part one of a three part question which I've split into 3 individual questions as advised. I left this question as the one associated with the original title; the other one is here  and I will edit the third in when my post cooldown allows me to post it, if anyone wishes to visit those as well now.


texts: If the polarity of the solvent increases, will the Rf value increase or decrease?

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True or False: A sample of aspirin has an $R_f$ value of 0.20 when measured on a silica gel TLC plate with a certain solvent mixture. If the polarity of the solvent is increased, the $R_f$ value of the aspirin will become larger.

Would this be false? Because aspirin is polar (I believe would be considered polar because it dissolves in water despite some other sources saying that it is actually non-polar) and the silica in the TLC plates are also polar, aspirin would not be able to travel very far because it would interact with the silica. Thus, shorter distance over longer distance = lower $R_f$ value, with $R_f$ = distance spot moves/ distance solvent moves.


texts: I am not from chemistry background. Could you tell me in simple words what the activity of hydrogen $a_{\ce{H+}}$ is? It arises in the context that the negative logarithm of the activity of hydrogen gives the pH: $\text{pH} = -\log_{10} a_{\ce{H+}}$.


texts: What does Brightness/ intensity of spectral lines depend on?

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My book states that it depends upon "The number of photons of same frequency or wavelength ABSORBED or EMITTED"
From what I understood, if many hydrogen atoms within the discharge tube EMIT the same wavelength, then, on passing the radiation through a prism, these waves will overlap on the photographic plate (Because all of them will get deflected to the same extent by the prism). Hence increasing the intensity. Is my understanding correct?
Secondly, how can the number of photons of the same wavelength ABSORBED create any difference in the intensity of spectral lines? As far as I know, absorption only results in black lines on the bright background corresponding to the absorbed wavelengths.