texts: Finding the rate constant of a first order reaction

texts:
The reaction

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

  is 1st order with respect to A and zero order with respect to
  B. The reaction is begun with the initial concentration of both reactants at $0.100 \,\text{M}$. After $1.5$ hours the concentration of
  B has dropped to $0.060 \,\text{M}$. What is the approximate value of the specific rate (reaction rate) constant for this reaction?

  (A) $0.15$ hr$^{-1}$

  (B) $0.34$ hr$^{-1}$

  (C) $0.61$ hr$^{-1}$

  (D) the specific rate constant cannot be determined unless the
  mechanism of the reaction known.

My thoughts: As the reaction is first order with respect to A and 0th order with respect to B, we can write the rate law as $\frac{d[A]}{dt} = -k[A]\to [A] =[A_0]e^{-kt} = 0.1e^{-kt}.$ Now, because A and B are in a 1:1 mole ratio, the concentration of A after 1.5 hours is also $0.06 \,\text{M},$ thus, we solve for $k$ as follows:
$$0.06=0.1e^{-k\cdot 1.5}$$
$$\to \ln(0.6)=-k\cdot 1.5$$
$$\to k = -\ln(0.6)/1.5\approx 0.34$$
Thus, the answer I obtained is B. However, the correct answer given is C. Is there any error in my work, or is the answer key wrong?


texts: What is the highest possible expanded octet?

texts:
Often called "hypervalent", chemicals like phosphorous pentachloride and sulfur hexafluoride are possible due to the fact that their central atoms form covalent bonds with more than four other atoms, giving rise to uncommon arrangements.

In the case of $\ce{PCl5}$, the phosphorous atom forms 5 bonds, giving rise to trigonal bipyramidal shape according to the VSEPR model. With $\ce{SF6}$, the Sulfur atom forms 6 bonds, giving rise to octahedral shape.

My question is, which central atom can achieve the highest number of bonds through the use of an expanded octet, and what is its shape?

The greatest I can think of is iodine heptafluoride, whose shape is pentagonal bipyramidal due to its fluorine atom of 7 bonds.


texts:
The following compound is a carbocation.

Clearly, the given compound does not have any element of symmetry. The compound is non planar due to the presence of ethyl group. Thus it must be chiral. But my book says the compound is achiral. How is this possible? Please explain.


texts:
In Boyle's law ($p$ inversely proportional to $V$ for constant $n$ and $T$), $p$ refers to the applied (external) pressure on the gas.

However, in the ideal gas law, my textbook says that $p$ refers to the pressure of the gas, which I think refers to the pressure applied by the gas. How is this possible, since the ideal gas law is derived from Boyle's law (and Charles' and Avogadro's laws)?

Shouldn't the $p$ in the ideal gas law then refer to the applied (external) pressure like in Boyle's law, not the pressure of (i.e. applied by) the gas?


texts: Is there a site where I can input RGB values and the site will respond with a pH?

texts: I have a tool where I point it at something, and it gives me an RGB value. I want to add universal indicator to a liquid, measure the RGB value and input it into the site to find the pH. Does anyone have any ideas?


texts: How to determine an oxidation number of an atom in the compound, that has at least two elements, which are not hydrogen or oxygen?

texts:
Wiki says:

  [Oxidation state] is defined as the charge an atom might be imagined to have when electrons are counted according to an agreed-upon set of rules:

  The oxidation state of a free element (uncombined element) is zero
    for a simple (monoatomic) ion, the oxidation state is equal to the net charge on the ion.

  Hydrogen has an oxidation state of 1 and oxygen has an oxidation state of −2 when they are present in most compounds. (Exceptions to this are that hydrogen has an oxidation state of −1 in hydrides of active metals, e.g. LiH, and oxygen has an oxidation state of −1 in peroxides, e.g. H2O2
          the algebraic sum of oxidation states of all atoms in a neutral molecule must be zero, while in ions the algebraic sum of the oxidation states of the constituent atoms must be equal to the charge on the ion.

The same is written in my textbook. But how am I supposed to find the ox. number of an atom, which is in compound like $\ce{K2UO4}$?


texts:
There is a problem I found online for practice that I cannot solve:

Problem

  Methane, $\ce{CH4}$, emerges from a $1\ \mathrm{cm}$ diameter nozzle
  at a rate of $120\ \mathrm{cm^3/s}$ and a mole fraction of $0.04$, and burns as a turbulent flame. The laminar flame speed of methane is $45\ \mathrm{cm/s}$ and the turbulent intensity is measured as $v_\mathrm{rms}=2\ \mathrm{m/s}$. Given the correlation for the turbulent flame speed $$S_\mathrm t = 0.35 S_\mathrm L\left(\frac{v'_\mathrm{rms}}{S_\mathrm L}\right)^{0.7}$$
  estimate the length of the flame. Assume that the flame is conical in shape

What I've tried

Compute the turbulent flame speed $S_\mathrm t=4.47\ \mathrm{m/s}$
From mass conservation, the mass flow rate exiting the pipe equal to the mass flow rate going through the flame. But there are still two unknowns before we can compute the area of the cone: the density of unburnt mixture and of the flame.
Assume $p=1\ \mathrm{atm}$ and $T=300\ \mathrm K$, compute density at the pipe exit using the Ideal gas Law $\rho = 1.15\ \mathrm{kg/m^3}$
Compute the adiabatic flame temperature at those conditions $T_\mathrm{ad}\approx1050\ \mathrm K$ (using $C_p$ at $300\ \mathrm K$)
Compute the resulting density at the flame $\rho_\mathrm f=0.323\ \mathrm{kg/m^3}$.
Compute the area of the cone and then the height of the cone

This method yield to the computation of the negative square root. What am I doing wrong? Even if there is a better way to approach this problem, I feel like my method should still give good results.


texts: How to calculate the value of heat absorption/ heat release during water electrolysis?

texts:
The overall reactions with the enthalpies of water electrolysis at room temperature can be represented by the equation below:

$$\ce{2H2O + \pu{237.2 kJ mol-1} + \pu{48.6 kJ mol-1} → 2 H2 + O2}$$

Where $\pu{237.23 kJ mol-1}$ is the maximum electrical work can perform and should be calculated by:

$$
\begin{align}
\Delta H^\circ &= \pu{0 kJ mol-1} - (\pu{-285.83 kJ mol-1}) \\
  &= \pu{285.83 kJ mol-1}
\end{align}
$$

$$
\begin{align}
\Delta S^\circ &= 0.5 \times\pu{205 J mol-1 K-1} + \pu{130.6 J mol-1 K-1} - \pu{70 J mol-1 K-1} \\
  &= \pu{163.1 J mol-1 K-1}
\end{align}
$$

$$
\begin{align}
\Delta G^\circ &= \Delta H^\circ - T\Delta S^\circ \\
  &= \pu{285.83 kJ mol-1} - \pu{298 K}\times\pu{163 J mol-1 K-1} \\
  &= \pu{237.23 kJ mol-1}
\end{align}
$$

where $\pu{48.6 kJ mol-1}$ is the net value of heat absorption, and can be calculated as the following:

$$
\begin{align}
T\Delta S^\circ &= \pu{298 K}\times\pu{163.1 J mol-1 K-1} \\
  &= \pu{48.6 kJ mol-1}
\end{align}
$$

This is the overall heat absorption during water electrolysis. I still don't know the heat release/absorption for the anode and cathode electrochemical reaction separately.

For the anode electrochemical reaction:

$$\ce{2 H2O → O2 + 4 H+ + 4 e-}$$

I believe this is a heat absorption process.

For the cathode electrochemical reaction:

$$\ce{2 H+ + 2 e- → H2}$$

I believe this is a heat release process.

How to calculate the value of heat absorption at anode, and heat release at cathode separately?


texts: For what chemical purpose did soldiers in WW2 carry small ion exchange resin columns in their survival kits?

texts:
My textbook [Chemistry Live, Declan Kennedy] states that ''During WW2 small ion exchange resin columns were part of a soldier's survival kit.''. I can't find any further info about this online or elsewhere. The chapter is on water purification and hard/soft water.
My thoughts are to either 1) to aid purification of urine for consumption 2) to remove ions from water that has been poisoned 3) to purify water that may be polluted due to all the metal waste (bullets, shrapnel, etc.)
Can anyone confirm the actual reason that soldiers carried these kits ?


texts:
In calculating UV/VIS spectra with computational procedures (say, TD-DFT), it is commonly assumed that the geometry of the ground-state is still valid also for the excited state due to the short time scale (I more or less took this statement from here).

So I asked myself, are there good references on time scales for chemical processes?
Some phenomena may be obviously faster than others, but others (say, two molecular excitations) may be not that obvious to compare.

I am looking for something simple, like a table (or tables) with examples.


texts: I would think the crystalline, ionic solid would have the lower entropy, however, the tablature indicates otherwise. Why does $\ce{NaCl(s)}$ have a greater entropy than $\ce{Na(s)}$?


texts:
this was a question for my chem class- and for some reason the answer was the last option. Why isn't it $\ce{Mn}$ which has the most unpaired electrons?

Which of the following species would you expect to be most
paramagnetic?
1.  $\ce{Mn}$
2.  $\ce{Mn^2+}$
3.  $\ce{Fe^3+}$
4. Both $\ce{Mn^2+}$ and $\ce{Fe^3+}$ are the same
and more paramagnetic than $\ce{Mn}$
5.  All have the same paramagnetism.


texts: If there are multiple bases in solution and a strong acid is added, will both bases react?

texts:
For example, if there is one mole of carbonate ions ($\ce{CO3 ^2-}$) and sulfate ions ($\ce{SO4 ^2-}$) in a solution, and one mole of hydrochloric acid ($\ce{HCl}$) is added, will the one mole of hydrochloric acid react just with the sulfate ions as that is stronger, forming hydrogen sulfate ions?
Or will the acid react with both the ions forming hydrogen carbonate ions ($\ce{HCO3-}$) and hydrogen sulfate ions ($\ce{HSO4-}$)?


texts: Comparing the dipole moment of water and ethanol

texts:
Why is the dipole moment of water (1.85D) larger than ethanol (1.66D)?

I thought the inductive effect from ethyl would develop more delta - charge on oxygen.. hence increasing the charge and the dipole moment


texts:
I'm trying to devise a synthesis for the following question.

I am aware it involves retrosynthetic, Wittig, Grignard and diels alder reactions, but unfortunately I can't really grasp all concepts which make me stuck. If there's any help or further explanation would be great.
I have tried to do retrosynthetic for the alkyne compound, also the Wittig reaction. I think Grignard should be the last step where it will change the oxygen bond to $\ce{OH}$. But I can't get myself to there yet.


texts:
First off, please forgive me, I am a chemistry novice!

Overall Process

Fuel for the system is distilled water
Split water into Hydrogen and Oxygen (electrolysis or similar process)
Exhaust Oxygen
Burn Hydrogen to power a generator/engine
Generator/engine charges battery
Battery powers Step 2 as well as whatever else we want to power

Problems

Energy gained needs to be greater than the sum of lost energy in all steps, as well as the energy required to perform electrolysis
We could compress the exhaust oxygen and use that as an energy source?
Is there a danger of running out of hydrogen? (Forgive my naivety, but I've heard about a helium shortage...)


texts: How can metals like magnesium and sodium burn underwater?

texts:
Please answer with as much detail as possible. I can't find the answer anywhere else and I need it for an essay.

Any websites I have found have conflicting answers.

One said that they don't actually burn underwater, rather than separate hydrogen from oxygen and burn at the surface. Another actually said that they do burn underwater because they take the oxygen source from the water. I do not have a specific definition for "burn" (the question itself is my assignment- write an essay answering that question!), so I know about as much as you do concerning the wording of the assignment.

I do know that alkali and alkaline earth metals are generally very reactive with water, and usually result in exothermic reactions.


texts: Why should the temperature be maintained at 0–5 °C in a diazotisation?

texts: I know that in a diazotisation reaction, the temperature should be carefully maintained within the range of 0–5 °C by use of an ice bath. Why is this so? How does the temperature affect the stability of the aryl diazonium salt?


texts: Why does chlorine undergo disproportionation in alkaline media?

texts:
One reaction used to form sodium hypochlorite (A type of bleach) is as follows:

$\ce{2NaOH(aq) +Cl2(g)->NaOCl(aq) + NaCl(aq) + H2O(l)}$

Provided the sodium hydroxide is dissolved in some substance.

I know that the sodium hydroxide dissociates to form the $\ce{Na+}$ and $\ce{OH-}$ ions, but I do not know why the $\ce{Cl2}$ breaks down into 2 separate atoms instead of just staying the way it is. My questions are: what are the driving forces behind this reaction and why does the $\ce{Cl2}$ break down? I see how it happens, I just don't know why.


texts:
I'm about to try to make my own soap for the first time. In order to create my recipe, I'm using this calculator.
As I'm using a lye solution, I have to fill the box %w/w of the solution. The calculator says:

  If you are using a ready made lye solution, check the box above and
  enter the enter the strength of your solution. The solution strength
  needs to be measured as a percentage of lye weight to water weight (%
  w/w).

I'm a bit confused here, I would have thought the w/w ratio was the ratio of the mass of NaOH in the solution to the total mass of the solution (and not the water mass used to disolve NaOH). So my first question is: what is really that w/w ratio?

My second question is how to interpret what I read on the lye solution (1L) I've bought. It's written:

  Sodium hydroxyde - N°CAS: 1310-73-2: 30%

What does this 30% refer to? Is this a ratio of volumes? Of mass? Is this the w/w ratio I want to know?

Thanks for helping me clarify this!


texts: Is this online fluorophore database reliable?

texts:
I need fluorescence spectra for various fluorophores in certain dispersion media for some calculations. There is an online database of University of Arizona: http://www.spectra.arizona.edu/
Is using such online resources reliable (not for formal purposes)?
I'm sorry for not asking a technical chemistry question.


texts: Phosphonate reaction with oxides and their stability?

texts:
I have read some papers stating that $\ce{SiO2}$ surfaces can bind phosphonates, but in water they hydrolyse. However, for $\ce{Si}$ surfaces, they are  stable in water. In both cases, the reaction takes place through $\ce{OH}$ groups that are present on the surface.

What I think is that on $\ce{SiO2}$ surfaces, there could be some steric effects which make hydrolysis "more convenient".
Another answer which seems less reasonable is that maybe the phosphonate group is electron withdrawing, and as the Si in the oxide already lacks electron density, this makes $\ce{Si-O-P}$ less stable, which is not the case for pure Si.

Related to this, why is the $\ce{Al-O-P}$ bond more stable in water than $\ce{Si-O-P}$?


texts: Clemmensen reduction of α-, β-keto acids

texts:
The following is from Organic Chemistry-2 for JEE Advanced by KS Verma:

α- or β-keto acids do not undergo Clemmensen reduction.

My reasoning was that the double bonds are in conjugation which makes them reluctant to participate in such reactions. However, this doesn't seem to be the case with β-keto acids which makes me suspect that my line of reasoning might be incorrect.
What is the reason for this behavior?


texts: Transition state and intermediate very close to each other

texts:
I've been studying a particular reaction with DFT, where a transition state and the following intermediate are very close to each other. The change in geometry is rather small and therefore the electronic energies differ only by about ~ 1-2 millihartrees. Still, the TS has the higher electronic energy (everything else would be surprising?), but adding thermal corrections to both structures leaves the intermediate about 2 kJ/mol higher in energy.

Does that make sense? Or is there something I did not consider in my calculations?


texts:
Hybridisation for a molecule is given by:
$$\frac{1}{2}(V + H - C + A)$$
Where,

V = Number of valance electrons in central atom
H = Number of surrounding monovalent atoms
C = Cationic charge
A = Anionic charge

If this expression is 2 then its $sp$ hybridised, 3 then $sp^2$ hybridised and so on.

However, I am not able to understand why this works.


texts: At the beginning of a weak acid titration curve (when titrated with a strong base), there is a sharp increase of pH before it levels out more due to the buffer solution that will occur. But why is that sharp increase there at the beginning? Is it because since the weak acid is weak, it is easier to increase it's pH when adding a strong base?


texts: Why are only two bond structures considered for ozone and not three?

texts:
We were taught in chemistry that:

Formal charges can be determined by drawing the Lewis dot structure, then subtracting the nonbonding electrons and half of the bonding electrons from the number of electrons ordinarily in that atom's valence.
Molecules tend to be in the state with the lowest formal charge on the central atom; in the event that there are multiple such forms, it will take on an in-between state called a resonance hybrid.
Three-dimensionally there's VSEPR theory which determines molecular geometry. We haven't gotten to how to calculate more complex angles just yet.

Consider ozone. There are two resonance structures for it: $\ce{O-O=O}$ and $\ce{O=O-O}$, both of which have equivalent formal charges: $(1)$ on the central atom, and $(-1)$ and $(0)$ on the axial atoms. This makes a resonance hybrid of $\ce{O\bond{~-}O\bond{~-}O}$, with bond order $\frac32$ for each bond.

Why isn't a third structure accounted for? Consider ozone structured like a triangle, with a single bond attaching each oxygen to the other two, and four unbound electrons on each oxygen:

The formal charge for every oxygen would be $(0)$.
The bond order would be $1$ for every bond; if merged as a resonance structure with the above two, it would create a structure with a bond order of $\frac43$ between the top oxygen and each side oxygen, and a bond order of $\frac13$ between the bottom two oxygens.

Yet the empirical evidence supports a bond order of $\frac32$ as a bent molecule, not a bond order of $\frac43$ as a triangular molecule. Why not?


texts: NGP mechanism vs the simple carbocation mechanism

texts:
Question:

Predict the product of: ($\ce{C^*}$ is a $\ce{C^14}$ carbon)

My attempt:
I simply assumed the super-leaving group $\ce{-OTs^-}$ would leave, forming a primary ethylbenzene carbocation. That would rearrange via a hydride shift to form a secondary carbocation on $\ce{C^*}$ atom. The nucleophilic $\ce{-OH}$ group of the $\ce{-COOH}$ group will then attack and lose a proton to form 1-phenylethylethanoate (with the ester linkage at the $\ce{C^*}$ carbon):

However, my book has instead taken a different route. In the very first step, after $\ce{OTs-}$ leaves, they have taken the NGP mechanism and formed this transition state:

and said that now the $\ce{OAc-}$ will attack either of the two carbons (in that trigonal ring). Hence, according to their logic, both types of 1-phenylethylethanoate will be formed - one with the ester linkage at the $\ce{C^*}$ carbon, and the other at the $\ce{C}$ carbon.
My question:
I have confirmed from Clayden (Chapter 37 Rearrangements page 976) that the product ratio is indeed 50:50. So:

Why is the NGP mechanism being favored here over the other mechanism I described, even though the NGP mechanism involves a loss of aromaticity?
Are there other cases where the NGP mechanism dominates over the simple carbocation mechanisms, or is this the only such case?

Source: MS Chouhan; Advanced Problems In Organic Chemistry; 11th ed; Q16 in  Alkyl Halides (Substitution)


texts:
The addition of a catalyst is known to increase the rate constant of a reaction by providing an easier pathway for the reaction to occur, one with lesser activation energy.

My doubt is:

Is it possible that the addition of a catalyst, alters the order of a reaction?

I haven't come across any such reaction so far, so it'd be great if someone could provide an example as well; if the reaction order can be changed upon addition of catalyst

My thoughts:

Sometimes, catalysts participate in the reaction; but are regenerated in the end without change in mass and chemical composition.
The very fact that a catalyst can participate in a reaction, should mean that it can influence the reaction's order, right?


texts: When disqualifying trans fat, are we qualifying cis-fat as healthy?

texts:
I have a question about fats. This may sound cliché! Because we are in the era of "trans-fat" free, "unsaturated" food. Not to mention it's the period where people get sicker and die faster (oh may be, the statistics weren't obvious in the past...).

Fats are important part of our diet and major source of energy (the mighty omega-3 fatty acids). But, The trans-fat, it's a linear molecule, it tends to stick and stacks up, builds up bad cholesterol, so that's not good for our cardiovascular system...

Does it mean, the opposite configuration, cis-fat is healthy for our body?
If cis is what's naturally found, by default it's unsaturated fat isn't it?

PS:

It's that time of the year again, for a community project we (the people who are new to biology, organic, biochemistry education) need to explain that to kids of age 7 and 10. They are going to go for shopping with us and we have to pop our eye balls to make sure they don't buy the wrong stuff. Because everything they adore seems to contain trans-fat from breakfast cereals, syrups, chips to doughnuts...list goes on. Saying something isn't bad not going to convince them an atom! So we gotta explain why they should go for trans fat free, unsaturated food or in the worst case just choose a saturated food instead of a trans-fatty thing and prevent any "kids-melo-drama".
I am struggling with this explaination and I doubt it's going to be any easier for the kids.

The breakfast cereals reference.


texts: By what mechanism does HF proceed in dissolving glass? Why is it the only acid that has this capability? Is it because of the small size and high electronegativity of fluorine?


texts: Does melting HDPE plastic produce toxic fumes? (melting, not burning)

texts:
● The question isn't about burning HDPE but melting it at the proper temperature. (At 120 to 180°C depending on it's density, it becomes gooey. According to the source below the "extrusion" temperature range of HDPE is 176 to 260°C ― at 260°C, I guess it becomes a very viscous liquid).

Is it perfectly safe (eg: indoor melting, in a kitchen oven). Or does it produce toxic fumes ― before 180°C? Before 260°C? If so which one?

● And what about melting it canola oil? (This technic seems more energy efficient, and easier to control the temperature).
This experimenter tried with Canola oil, which has a smoke point of over 204 °C. He melted the HDPE in the oil at 176°C (the output needs to form a block and expresses the oil).

Is it safer to melt HDPE in oil ?

○ Bonus: does the Canola oil degrade the HDE? (The experimenter found out that the oil "gets really thick when cool" and he thinks it's because some HDPE dissolves on it. Someone comment "The canola oil probably acts like that because some of the HDPE is converted into paraffin wax which is soluble in canola oil. HDPE isn't lipid soluble".

Any information on the topic is welcome

It's not a duplicated:
This question has been asked about specifically melting empty silicone tubes (made of HDPE). It's off topic since not about HDPE only (it's a complex issue since there are many different types of silicone on the market)


texts: Why can't phosphorus trifluoride be used as a Lewis acid catalyst in electrophilic substitution of benzene?

texts:
Which of the following cannot be used as Lewis acid in the electrophilic substitution of benzene?

  $\ce{BF3}$
  $\ce{SbCl3}$
  $\ce{FeCl3}$
  $\ce{PF3}$

My Attempt:

$\ce{BF3}$ and $\ce{FeCl3}$ are Lewis acids.
$\ce{PF3}$ though it has a filled s and p orbitals it can accept electrons from donors and expand its coordinate number up to six due to vacant d orbitals. It acts as a mild Lewis acid.
$\ce{SbCl3}$ has a completely filled s,p,d orbitals so it can no longer accept electrons, hence doesn't act as a Lewis acid.

My answer is option (2) but the answer provided is (4), where am I going wrong?


texts: What concentration (M) of citric acid should I use in a titration with 0.02M LiOH?

texts: I am using an automatic titrator that records the amount of acid/base added and the pH of the solution in the form of a graph. I am trying to titrate citric acid to capture all 3 pKas in this graph. I will be titrating 40mL of a ???M citric acid solution made up in 0.01M LiNO3 as a background electrolyte. The software's titration schedule begins by adding increments of 0.1M HNO3 until the pH reaches 2.5, then it adds increments of 0.02M LiOH until the pH reaches 10. What concentration (M) of citric acid should I use in this titration in order to capture its pKas?


texts:
In preparation for the Birch reduction, I am trying to prepare an electride salt, $\ce{[Na(NH3)6]+, e-}.$ This salt should be brilliant blue, as far as I know, but I am getting a black sludge when adding sodium to the liquid anhydrous ammonia at −60 °C or so.
Is this because the salt is missing the electron?
How do I remedy this?


texts: Separation of solvent from residue of material.

texts:
I have a residue of 2kl in which 1.8kl is solvent (EDC) and rest material is residue. First i was thinking to go with normal distillation to recover our solvent. But i heared somewhere that there is some kind of RESIN by which if it got passes solvent will be pass only and residue will collect on another side of that resin. if there is any concept like this please help me.
or there is any other to do?


texts:
I'm in need for the exact mechanism of the above reaction. I attempted some tries(mentioned in the mechanism above) and I felt the yield quite unsatisfactory.
- the last step remains stuck in an equilibrium. Is the energy of the product sufficiently high to surpass the equilibrium created??
- the probability of the product formation (according to the mechanism I assumed) is too low as the pair of electron would hardly prefer an attack on the 5th carbon (as it doesn't possess any partial positive charge as the 6th carboxy carbon does)


texts: Do tertiary ethers tolerate oxidative workup of an ozonolysis reaction?

texts: I am attempting to cleave a double bond into a carboxylic acid and carbon dioxide using an ozonolysis reaction followed by an oxidative workup. I am concerned with the presence of a tertiary ether in my reactant, however. I am planning on using standard ozonolysis procedures as described in Vogel's Textbook of Practical Organic Chemistry on page 592 using an oxidative workup with either potassium permanganate or hydrogen peroxide. I am worried that the oxidative conditions will also affect the tertiary ether. I cannot find any literature detailing the compatibility of tertiary ethers with peroxide or permanganate. Is there another protocol that would be milder on my substrate, or does it seem as though this reaction would not affect other functional groups? Here is my scheme:


texts:
I'm studying chemical engineering at uni (Belgium), and this year (my 2nd) we have to develop and build a stirling engine. It has to be powered by a relatively safe exothermic reaction (not dangerous for bystanders, so no formation of toxic fumes,...) and the whole thing is electrically controlled but that's not important here,

I've come up with this so far:

Sodium acetate crystallization
Hydratation of anhydrous copper sulphate
calcium chloride and water
sodiumhypochlorite oxidizing sodiumsulfite

An 'open flame' reaction is not allowed sadly enough..
I'm hoping to at least reach 70-80 degrees Celsius (158-176° Fahrenheit)

Chances are quite big that there are better reactions but I really can't think of anything else..

Thanks A LOT in advance everyone!


texts:
I was learning about crystal field theory recently. I am quite confused about predicting the shape of $\ce{[Cr(NO)4]}$ complex because I am not able to conclude whether it will be square planar or tetrahedral.

How to predict the shape of $\ce{[Cr(NO)4]}$ using crystal field theory?

Will $\ce{NO}$ act as a 3-e- donor here?

Will all the four $\ce{NO}$ that are in coordination with $\ce{Cr}$ be of the type nitrosyl or will three of them be nitroso and one nitrosyl (because $\ce{Cr^3+}$ is one of the common oxidation state of $\ce{Cr})?$


texts: Is there a liquid mixture that will become a solid when exposed to air/oxygen. Preferably a spongy material that is difficult to tear.


texts: Ketone/aldehyde synthesis from N-acylazetidines or aziridines

texts:
A common principle in organic chemistry is to make sure the product is less reactive than the starting material, to prevent overreaction. So, for example, the treatment of an ester with a Grignard reagent will afford not the corresponding ketone, but the alcohol.

However there are some cases where the contrary is true. In particular, when the tetrahedral intermediate is stable, then the reaction can be worked up to 1) produce the desired ketone and 2) destroy any unreacted organometallic reagent, thus preventing overreaction. The classic example is a Weinreb amide, where the tetrahedral intermediate is stabilised by chelation, AFAIK.

Somewhat recently the synthesis of ketones from N-acylazetidines was described:1

and also the reduction of N-acylaziridines is known to produce aldehydes:2

Presumably the idea is the same: the tetrahedral intermediate is stable under the conditions used. Why is this so? Is it connected to the small size of the ring?

References

Liu, C.; Achtenhagen, M.; Szostak, M. Chemoselective Ketone Synthesis by the Addition of Organometallics to N-Acylazetidines. Org. Lett. 2016, 18 (10), 2375–2378. DOI: 10.1021/acs.orglett.6b00842.
Brown, H. C.; Tsukamoto, A. Selective Reductions. I. The Partial Reduction of Tertiary Amides with Lithium Aluminum Hydride. A New Aldehyde Synthesis via the 1-Acylaziridines. J. Am. Chem. Soc. 1961, 83 (22), 4549–4552. DOI: 10.1021/ja01483a013.


texts: What ratio of 73% calcium hypochlorite powder to water mimics the strength of sodium hypochlorite (bleach)?

texts: Calcium hypochlorite is sold as pool shock in varying strengths.  I've read that it can be dissolved in water to create a 'bleach' (typically sodium hydrochloric or sodium hydroxide) and is often used as such to treat drinking water in developing countries, but every source I've read prescribes a different ratio. Strictly looking at chlorine levels for water sanitation, cleaning, etc., how much powder (at 73% calcium hydrochlorite) would you need to dissolve into 1 gallon of water to match common household bleach?


texts: Why there will be only limited shells in a particular atom?

texts: What is the maximum possible principal quantum number for an atom(any atom not a specific one) ?


texts: Is a transition metal with 7 d electons ever diamagnetic?

texts: A transition metal with 7 d electrons forms a complex ion with cyanide. I know that cyanide is a high field ligand, which means the electrons will pair before moving to the next energy level, but wouldn't there still be one unpaired electron? And wouldn't that make it paramagnetic? I was told that my prediction was wrong and that it was in fact diamagnetic, but I don't understand why.


texts: How does one apply the knowledge of the direction of a molecular dipole moment?

texts:
I was watching Khan academy's video about molecular dipole moments, which explained what they are and how they can be calculated. I also read this article.

Both sources explain the concept similar to common organic chemistry textbooks, but they did not provide any information regarding the uses or applications of a molecular dipole's direction, nor did the google search I conducted later.

So far, two things are clear to me:

A dipole moment is a vector, and therefore has a quantity and a direction.
Larger dipole moment is associated with a more polar molecule. This a good enough reason to find out how large is the dipole moment.

My question is: What possible applications can knowing the direction of a molecular dipole moment have?


texts: Does the addition of base to 3-pentanone give the cis or trans enolate?

texts:
I've spent several hours searching the WWW with entries like "stereoselective enolate formation" and similar ones, but I find almost only entries for Li-amide bases (LDA, LMTP) and no other bases like t-BuO, NMe3, NaH, n-BuLi concerning the stereoselectivity.

I'd like to know if the addition of these four bases to 3-pentanone all results with preference in the cis or trans enolate (and if possible with an explanation why).

Related: Stereoselective enolate formation with different bases: Does the addition of a base NR3 to a ketone affords the cis or the trans enolate?


texts: Are the C-C bond lengths different in 2-methyl propene

texts: When we were first taught resonance it was with the example of benzene and I myself justified it by thinking that the double bond oscillates because no two carbon atoms are special and hence there is no reason there will be a double bond between any two and not any other two. I now know that's not true. But just to avoid any latent confusion, can you verify my reasoning is wrong by answering this question? By my method, all three bonds will have same length and bond order 4/3


texts: Coulomb force and potential energy in water vs vacuum

texts: If you have 2 ions of equal but opposite charge, will the force between them be larger in a vacuum and smaller in water? Would this be because the relative permittivity of water is greater than 1 (around 80)? Also, what does this mean for the interaction energy? Would an interaction be larger in vacuum? I am trying to figure out whether a reaction is more likely to take place in the two different media between the two ions...


texts: Transition Metals that react with Vanillin and their Complexes

texts:
My question is simply whether anyone knows what are the transition metals that the phenol group of the vanillin molecule could react with, and thereby produce discolorations.

This question is particularly relevant to the flavors and fragrances industries, where vanillin is a widely used flavor and fragrance ingredient. It is unfortunately prone to purple discoloration when it reacts with trace amounts of iron (according to chapter 4 of Chemistry and Technology of Flavours and Fragrances).

I am curious to know what is the full list of transition metals that vanillin could react with, and what complexes and their colors could be produced as such.

Thank you.


texts:
I am trying to obtain a potential energy surface (PES) for $\ce{N2 + N}$ combination using scan feature of Gaussian. I have tried different combinations of basis sets and methods but unfortunately at some point in the iteration, the convergence criteria is not met and I get an "Aborted Core dump" closure in the log file. The Gaussian code is:

# HF/6-31G test scan

NNN PES

0 2
N
N 1 R1
N 2 R2 1 120.

R1 0.5 80 0.1
R2 0.5 80 0.1

Where am I going wrong. More importantly, I would be really thankful if someone could suggest how to choose a method and basis set for a type of problem. I was thinking if I can get some answer using HF/6-31G, I could use this as an input for a higher order method like cassf. What that be a good idea?


texts: Use of Spiegeleisen in manufacture of steel

texts:
I recently read the following statements related to Manufacture of steel via Bessemer Process:

  When no more $\ce{CO}$ is produced (i.e. blue flame disappears) a calculated amount of Spiegeleisen (an alloy of $\ce{Fe, Mn, C}$) is added and distributed throughout the mass by blowing air for some time.

Why do we need to add Spiegeleisen at the end? Is it to reduce the oxides of iron (that might have been formed)? Or due to some other reasons, like, say $\ce{Mn}$ to make steel harder and increase its tensile strength? But latter doesn't convince me, since we could have added $\ce{Mn}$ directly on order to get the same results. Also what's the meaning of calculated amount, how do we calculate the amount to be added, and why?


texts: Does CF3COOH undergo decarboxylation ? Why or why not?

texts:
Does $\ce{CF3COOH}$ undergo decarboxylation ? Why or why not?

Attempt:

I feel it should decarboxylate because $\ce{CF3-}$ carbanion must be stable due to fluorine's -I (electron withdrawing) effect  , but I am not sure.


texts: Standard solution and extracted solution : same concentration?

texts:
Summary :
I am currently testing how a certain type of foam adsorbs HAP, PCB and OCP, and to this end I am depositing some on the foam, then extracting it. To know how much was extracted, I need to compare with a standard solution of HAP, PCB and OCP. The problem is that when I look at the chromatograms, the extracted solution's peaks' areas are about 10 times the standard solution's peaks' areas. I don't know where in the experiment I am doing something wrong.

Details :
I have a solution of HAP, PCB and OCP at 10 mg/L. I put 100 µL of this solution on the foam, so that the deposited mass is 1 µg.
The foam is ASE-extracted with acetonitrile, then the acetonitrile is rotary-evaporated. What is left in the round-bottom flask is then diluted in 1 mL acetonitrile. So at maximum I have 1 µg pollutants in 1 mL acetonitrile.
To this 1 mL I then add distilled water until I have a 20 mL solution. The concentration of this solution should at maximum be 50 µg/L, right ? (If all pollutants are extracted from the foam and none lost to evaporation.)

The standard solution is made by also taking 100 µL from the 10 mg/L solution (so 1 µg pollutants), and adding distilled water until I have a 20 mL solution. So this solution's concentration should also be 50 µg/L, right ?

But when I put the two solutions through GC-MSMS, the peaks' areas of the extracted solution are about ten times greater than those of the standard solution. (Not always ten, but it is usually the case.)

Have I made a mistake somewhere ? Are my calculations/manipulations wrong somewhere ?
The internal standard used is naphtalene d8, and in each 20 mL solution I added 10 µL of a 10 mg/L naphtalene d8 solution. (So its concentration is 5 µg/L : is it a problem that the standard is not at the same concentration as the pollutants ?)

The experiment was repeated several times, with different foam extracts and different standard solutions, and the results were the same. It is not a problem of contamination, as everything has been extensively washed with distilled water, detergent and acetone.

In case it is relevant : when a solution is done, I sample 4 mL that I extract with a SPME fiber, and then I inject into the GC-MSMS.

Thank you in advance, I am still testing and calculating, so any help is appreciated.

To tschoppi (since I don't have enough reputation to comment) : I haven't tried with another kind of foam, but it's a good idea (to see at which step the problem lies). I'll see what we have in the lab. I am also pretty sure the foam I used isn't contaminated, because it was given to us straight from the package, and I washed it three times with different solvents and analysed the wash-solvent (which was clean)(but I may check again to be sure).


texts: How to prepare cyclohexanone without starting with cyclohexanol?

texts:
What's an easy way to prepare cyclohexanone if I dont have direct access to cyclohexanol? I'm willing to synthesize cyclohexanol from more common materials, then make cyclohexanone from that. But most of the instructions for one cyclohexano- say to start with the other cyclohexano-.

I'm looking to start with common materials and synthesize cyclohexanone or cyclohexanol. If i have cyclohexanol, i can use bleach and acetic acid to make cyclohexanone.

Since I dont have access to lab deliveries at the current moment, what are the most common chemicals to start with to make this happen? AKA, stuff I can order legally online without a lab cert.


texts: How to perform IR spectroscopy on silica particles at various relative humidities when they are passed through a tube using pressurized air?

texts: Surface bonds of silica particles are susceptible to humidity and frequently change between silanol and siloxane with changing RH. I want to measure how these surface bonds change with the humidity using IR spectroscopy when the particles are flown using pressurized air through a tube.


texts: Is it possible for a reaction to have an entropy change of zero?

texts: If the question seems rather "unscientific", be kind to accept my apology. My textbook is being highly unclear about the topic and I need to know the answer to this question before I go on with my studying.


texts: Will (3R,4S,5R)-1,3,4,5,6-pentahydroxyhexan-2-one tautomerise in nitric acid?

texts:
The following question was sent to me .The question is " Which of the following is  A ?"
The given answer was a,b,c

Background
If both ends of an aldose chain are oxidized to carboxylic acids the product is called an aldaric acid.

source : https://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/carbhyd.htm#carb2
My thoughts

Options a and c are direct reactions.
Option b gives 2 and  it can only rotated in the plane it is drawn (2D) by 180 degrees (http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch07/ch7-7.html) to give 1.
How ever option d in acidic medium could tautomerise to give 3d , that on oxidation again gives 1.

Therefore answer should be a,b,c,d.
My answer hinges on tautomerisation of ketone is acidic medium. Would this compound (3R,4S,5R)-1,3,4,5,6-pentahydroxyhexan-2-one tautomerise in nitric acid ?
Any help in this regard is very much appreciated. Thankyou.
reference :
1 http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch07/ch7-7.html


texts: Can ammonia be detected by a 1D-1H-NOESY experiment?

texts:
I'm not detecting ammonia in my samples while using a NOESY pulse program for a 1H-NMR experiment.

Is it possible for ammonia to be detected by a 1D-1H-NOESY experiment?


texts: Determine # of molecules in an unknown sample

texts: How might one determine the # of molecules in an unknown sample? If the sample is a gas,  we might use $PV=nRT$ to estimate # of molecules. If the sample is a solid or liquid and the chemical formula is known, we simply need to measure the mass. But can we determine the # of molecules without first determining the chemical formula?


texts: What does thermal stability of compounds depend on?

texts:
Does it somehow depend upon the lattice energy of the compound?
My textbook says that Lithium carbonate is not so stable to heat and forms more stable $\ce{Li2O}$ and $\ce{CO2}$.
Could it depend on the electropositive character? Because my textbook further sates that the stability of carbonates increases down the group.


texts: A contradiction regarding the reaction coefficient expression in the Nernst equation

texts:
I came up with the following question in my NCERT textbook:

  Write the Nernst equation and the emf of the following cell at $\pu{298 K}$.

  $$\ce{Fe}|\ce{Fe^2+}(\pu{0.001 M})||\ce{H+}(\pu{1 M})|\ce{H2 (g)}(\pu{1 bar})|\ce{Pt (s)}$$

  Given: $E^\circ(\ce{Fe^2+}/\ce{Fe}) = \pu{-0.44 V}$.

As per my understanding, the data of activity coefficients must given because the reaction coefficient in terms of concentration is not dimensionless and its logarithm would be meaningless.
$$\ce{Fe + 2H+ -> Fe^2+ + H2}$$
$$Q=\ce{[Fe^2+]/[H+]^2}$$
Secondly, using a unit of concentration other than mol/litre would definitely yield a different value. So I decided to check its solution from a reference book. In the solution, they have used the above expression of molar concentrations.

So, my question is, is this expression correct?


texts:
It was given in a chemistry book that things like orthophosporic acid, acetanilide and sodium stannate stabilize hydrogen peroxide, while carbon, $\ce{MnO2}$ and $\ce{Pt}$ help decomposing it.
Why is this so?


texts: Distinguish 1-bromobutane and 2-bromobutane with IR

texts:
How can I distinguish 1-bromobutane and 2-bromobutane by their IR spectrums?

In the 1-bromobutane spectrum I think the $\ce{-CH3}$ peak is shorter, but I don't know if that is actually reasonable or just a fluke.

In the spectrum that I think is 2-bromobutane there is an additional peak at around $1290$. What might this be?

The only alkyl halide peaks we discussed in class was the $\ce{C-Br}$ stretch $600-750$. They both seem to have this (although they do look different). How can I distinguish?


texts: Why does oxygen not like to be a double anion?

texts:
The electron affinity of a neutral oxygen atom is −142 kJ (it releases this energy). The electron affinity for the now double anion $\ce{O^2-}$ is 710 kJ (work must be done on the atom).

My question is, why the large jump in electron affinity? We are taught that the electrons do not interact much with each other in the way of shielding. I think this to be incorrect, because otherwise, the effective nuclear charge on all of the valence electrons should be about the same, including the new ones added to ionize the atom. This would make the electron affinity about the same for each electron. Plus, doesn’t the oxygen atom want to complete its shell? So why is it putting up a fight?


texts: What's the van 't Hoff factor of dilute aqueous ferrous sulphate solution?

texts:
Is it more than one or less than one?

Here is what I think: since it is a dilute and aqueous solution, so $\ce{FeSO4}$ will be hydrated and new formula will be $\ce{FeSO4*7H2O}$.

Thus, the abnormal mass would be greater than the normal molar mass.

Therefore, van 't Hoff factor would be less than $1$. Is that correct?


texts: Calculating concentration and volume in acid metal reactions

texts:
In the reaction:
$$\ce{3 Zn + 2 H3PO4 -> Zn3(PO4)2 + 3H2}$$

I know the initial mass of $\ce{Zn}$ to be 13.08 g and the volume of phosphoric acid to be 0.5 $\mathrm{dm^3}$. How do I work out the final concentration of $\ce{Zn(PO4)2}$ and the volume of $\ce{H2}$ gas evolved?

Once I work out the moles of Zn, are the moles of $\ce{Zn(PO4)2}$ just $\ce{Zn}$ moles/3?


texts: How to determine sulfate ions in a solution by precipitation?

texts: For example I am given an unidentified solution and am told that it may or may not contain sulfate ions. How can I confirm or deny the presence of sulfate in this solution?


texts: Is there a chemical reaction which could give off enough heat underwater to cook something?

texts:
The mer-people demand cooked food. They don't want to go on land to make it.

Is there a chemical reaction they could use which would create enough heat to cook their food underwater in a safe manner?


texts: Suggestions for solvents capable of efficiently performing alpha-bromination and nucleophilic substitutions

texts:
We performed the one-pot preparation of bupropion in class where the bromination of the carbon adjacent to the carbonyl group was performed using DCM as solvent, and upon completion the solvent was switched to n-methyl-2-pyrrolidone and was then reacted with an amine. I know that the nucleophilic substitution won't occur in DCM, the reason for which was also explained here on this site, so what alternate solvent could be used that allow for both bromination and substitution to occur without a solvent switch, AND still allow this procedure to still be conducted within a single class session? I asked the professor, but he said that he would have to think about it and get back to me... yeah, I have a feeling I am being blown off.

I believe that water would work for the bromination as long as the mixture is kept acidic, but then that complicates things with the amine as it will need to be in its basic form, unless that doesn't matter because by the time you add the amine, the bromination has already taken place and you would just neutralize first. However, aren't these reactions very slow in aqueous conditions? I know that water lowers nucleophilicity, so would that explain the hindered reaction times?

What about acetonitrile? I know this can be used in bromination, as I have read procedures that claim increased selectivity for monobromination.

In the event that you are not familiar with the preparation I am referring to, I am providing a link to the ACS paper that we used as the basis of the experiment.
http://pubs.acs.org/doi/abs/10.1021/ed077p1479

EDIT: There is also a follow up question regarding the usage of more than an equivalent of the amine during the substitution step as an acid scavenger. What is up with that? Why isn't the acid being formed in the substitution step being neutralized with an appropriate base that won't hydrolyze the bromoketone first? This just seem rudimentary to me, but I lack the encompassing understanding at this time. Is there a procedure I could reference as an example of what I just proposed?


texts:
All halogen derivatives (except fluorine) of succinimide exist and are used in various chemical processes. What makes N-fluorosuccinimde difficult to prepare? Still chemists have not been able to figure out the preparation of N-fluorosuccinimde and don't even bother to synthesize it since electrophilic/radical fluorination is accomplished by  N-fluoro-o-benzenedisulfonimide (NFOBS), N-fluorobenzenesulfonimide (NFSI), and Selectfluor. Moreover, even if NFS is successfully synthesized, can it be used as a fluorinating agent in electrophilic/radical fluorination?

According to Wikipedia, NBS is made by reacting sodium hydroxide and bromine in an ice-water solution of succinimide. The NBS product precipitates and is collected by filtration. I am assuming that NCS and NIS are made in the similar fashion (using appropriate halogens). But, why NFS has still not been made through a similar way (using fluorine)? Is the reaction condition unsuitable for fluorine or is there any other reason?

I was reading a forum discussing the scope of NFS as a fluorinating agent. It says:

    Does anyone know why is N-fluorosuccinimide (201281-58-5) such
    uncommon reagent for fluorination? I checked some major suppliers and
    none of them sells it.

  In my knowledge, N-Halogenesuccinimide are obtained by reacting of Succinimide with the halogen itself. This is valid for Chlorine, Bromine, and Iodine. Fluorine is too reactive. For the fluorine derivative,  iodinesuccinimide is treated with silver fluoride to exchange the halogen.

  The other option is to treat N-Hydroxysuccinimide with Thionyl
  fluoride or Phosphorous trifluoride.

Is this true? I couldn't find any source confirming the above synthesis and I am skeptical about the preparation process. Can NFS be made through the above process?


texts:
This is a statement given in my book:

A strong electrolyte is completely ionised at all dilutions but not completely dissociated.

But the book also uses the terms "Ionisation" and "Dissociation" interchangeably in other places.
When I further tried to search about this topic I found out there is equation which governs dilution of strong electrolyte-
$\lambda_m = \lambda_o + a\sqrt C$
So is it right to say that it will only get completely dissociated at infinite dilution (which is not practically possible)?
Hence my final questions are:

Are ionisation and dissociation the same or different?

If they are not the same then why are they different?

Also the correct explanation of the above statement given in my book?

Will this change for a weak electrolyte?

Also please consider that I am in high school. So please try to explain in simple terms so that I am able to clear my confusion.
Please also tell whether I can assume both the terms to be same or not at my current high school level.


texts: Unique Solubility Expression for Sulfide Salts

texts:
While looking at aqeuous $\ce{K_{sp}}$ values in the back of my textbook, I noticed that there is a asterisk by all of the sulfide compounds (such as $\ce{HgS}$), and the asterisk says, "For a solubility equilibrium of the type $\ce{MS_{(s)} + H_2O_{(l)} <=> M^{2+}_{(aq)} + HS^{-}_{(aq)} + OH^{-}_{(aq)}}$." Now, why is it this expression, instead of the expected $\ce{MS_{(s)} <=> M^{2+}_{(aq)} + S^{2-}_{(aq)}}$?

Upon examination, I see that the given expression is just the expected expression and then tacking on the base equilibrium of the $\ce{S^{2-}}$ ion, which is $\ce{S^{2-}_{(aq)} + H_2O_{(l)} <=>HS^{-}_{(aq)} + OH^{-}_{(aq)}}$. But why do we involve the base equilibrium of $\ce{S^{2-}}$ when we don't involve other quite basic anions, such as $\ce{F^-}$ or $\ce{CO_3^{2-}}$?


texts: Temperature dependence of reaction enthalpy

texts:
Estimate $\Delta_\mathrm{c}H^\circ(500\mathrm{~K})$ for methane by using the data given on the temperature dependence of heat capacities.

  $$\ce{CH4(g) + 2 O2(g) -> CO2(g) + 2H2O(g)}$$

My working

First, heat capacities as functions of temperature.

$$\begin{align}
C_{p,m}(\ce{CO2}) &= 44.22 + 8.79\times10^{-3} T - \frac{8.62\times10^{5}}{T^2}\\
C_{p,m}(\ce{H2O}) &= 75.29 + 0 + 0 \\
C_{p,m}(\ce{O2}) &= 29.96 + 4.18\times10^{-3}T - \frac{1.67\times10^{5}}{T^2} \\
C_{p,m}(\ce{CH4}) &= 35.31
\end{align}$$

Note: a function of temperature dependence wasn't given in the data table for methane, this value is at $298 \mathrm{~K}$. I used this because I did not know what else to do.

Then, I used Kirchhoff's Law:

$$\Delta H(500\mathrm{~K}) = \Delta H(298 \mathrm{~K}) + \int\limits_{298\mathrm{~K}}^{500\mathrm{~K}}\Delta C_{p,m}\,\mathrm{d}T$$

I computed $$\Delta C_{p,m} = \sum_{\mathrm{products}}\nu C_{p,m}-\sum_{\mathrm{reactants}}\nu C_{p,m}$$ (here, I used the molar heat capacities values listed above, adding the functions after multiplying by the appropriate stoichiometric coefficients) and obtained:

$$\Delta C_{p,m} = 16.15 + 0.43\times10^{-3}T - \frac{5.28\times10^{5}}{T^2}$$

Therefore:

$$\begin{align}
&&\int\limits_{298\mathrm{~K}}^{500\mathrm{~K}}\Delta C_{p,m}\,\mathrm{d}T &= 2.581 \mathrm{~kJ~mol^{-1}} \\
&&\Delta H^\circ(298\mathrm{~K}) &= -890 \mathrm{~kJ~mol^{-1}} \\
&\Rightarrow & \Delta H^\circ(500\mathrm{~K}) &= -887.4 \mathrm{~kJ~mol^{-1}}
\end{align}$$

However, my result is incorrect. The correct result is $-803.07\mathrm{~kJ~mol^{-1}}$.

Could someone please help me out on this?

As a reference, the textbook is Physical Chemistry 10th ed by Atkins.


texts:
From Chemguide:

Is the measurement unit $\ce{kJ*mol^{-1}}$ correct here? Shouldn't it be measured simply in kJ, because the $-572$ figure is for the whole reaction, i.e. for 2 moles of the product?


texts: In the Haworth projections of D and L glucose, is the stereochemistry at every carbon except the anomeric carbon just inverted?

texts:
I'm having a bit of trouble grasping sugar stereochemistry.

Using glucose as an example, if you cyclize D and L glucose, is the stereochemistry at every carbon just inverted from the other form?

Like for example, on carbon 2 for D glucose, the hydroxyl is down. On carbon 2 for L glucose, the hydroxyl would be up.

Is this trend true for every hydroxyl or $\ce{CH2OH}$ group except the one on the anomeric carbon?


texts: Enthalpy change of gas expansion against constant external pressure

texts:
A certain mass of gas is expanded from $\pu{1 L}$ at $\pu{10 atm}$ to $\pu{4L}$ at $\pu{5 atm}$ against a constant external pressure of $\pu{1 atm}$. If initial temperature of gas is $\pu{300 K}$ and heat capacity at constant volume of preocess is $\pu{50 J °C-1}$, find enthalpy change of process.

Here are my thoughts:

$$∆H = nC_p\,\Delta T = nC_V\,\Delta T + p\,\Delta V$$

where $p$ is external pressure.

$$\Delta U = c\,\Delta T$$

with $T_1 = \pu{300 K}$ and $T_2 = \pu{600 K}$ (which I got from gas equation), so

$$\Delta U = \pu{50 J K-1} \times \pu{300 K} = \pu{1.5 kJ}$$

Still I am not getting the correct answer. I believe my methodology is right.


texts: What exactly is formed when K2Cr2O7 is reduced?

texts:
I read on Wikipedia and in many books that when $\ce{K2Cr2O7}$ is reduced, it forms $\ce{Cr^3+}$ and a change is noticed from orange color to green. I want to know in what exact complex/salt/compound $\ce{Cr^3+}$ exists that it shows green color.

I know $\ce{[CrCl3].3H2O}$ shows green color but in many of these reactions, there is no $\ce{Cl-}$ ion, so I guess that is not formed. Also, $\ce{Cr^3+}$ can exist as $\ce{[Cr(H2O)6]^3+}$ but since it is violet in color, that possibility is also ruled out. So basically, how does the solution becomes green in color?


texts: Selectivity in acetonide formation from a polyol

texts:
In my total synthesis lecture notes the above example is given in which a polyol is reacted under acetonide forming conditions.

The notes point out that this product is the only product, no other actinides are observed. That said there possibly are two other products, both containing two acetonides, so why should just this one di-acetonide form?

The conditions are not very clear, but I assume all steps are reversible so what is actually being observed is thermodynamic product.


texts: Why is the recipe of Coca Cola still a secret?

texts:
Why is the recipe for Coca-Cola still a secret?
I think that given the current state of technology, it should be proficient enough to find any of the secret ingredients in Coca Cola.

Any thoughts?
Can we make a 100% identical clone of Coca-Cola next week?


texts: Is soap forming micelles in water an exothermic reaction?

texts:
I have seen it described as soap molecules releasing energy when forming micelles. Is that correct? Is it an exothermic reaction?
I mean a bunch of molecules uniting to form a micelle.


texts: Application of the definition of enthalpy in a modified way

texts:
My book gave me this equation at constant temperature and constant volume:

$$\ce{2NH3(g) -> N2(g) + 3H2(g); \Delta U = 92.3 kJ}$$

And it says here enthalpy and internal energy are the same as volume is constant. But I have a thought that its pressure is not constant and hence enthalpy change will be different, because enthalpy by definition is
\begin{align}
\mathrm dH &= \mathrm dU + \mathrm d(pV) \\
\mathrm dH &= \mathrm dU + \mathrm d(nRT)
\end{align}

For this equation we will get:

$$\Delta H = 92.3\ \mathrm{kJ} + 2RT$$

Am I correct with my thinking? If not, why?


texts: In Sn2 nucleophilic substitution reactions,the attacking nucleophile or leaving group is eliminated. The weaker base is eliminated. Then how do acid chlorides form as OH- is a stronger base than Cl–.


texts: I have seen classification of Mg+2 or any other cation or anion for that matter as an acid or a base, but I have never seen an element labelled as an acid or a base. Isn't there a possibility of Mg+2 being the conjugate acid of Mg a base? If not,why so?


texts: Why does the pKa - pKb relationship hold when Kw holds for the autoionization of water?

texts:
The relationship is commonly expressed as:
$$pK_a + pK_b = pK_w = 14$$
or
$$K_a * K_b = 10^{-14}$$
This holds because
$$K_a = \frac{[H^+][A^-]}{[HA]}$$
$$K_b = \frac{[OH^-][HA]}{[A^-]}$$
$$K_aK_b = \frac{[H^+][A^-]}{[HA]}\frac{[OH^-][HA]}{[A^-]}=[H^+][OH^-]=K_w=10^{-14}$$
$K_w$ is the autoionization constant of water, or the equilibrium constant of water as it reacts with itself in equilibrium. This has the measured value of $10^{-14}$.
But isn't this value measured when water is all by itself, reacting with itself in autoionization? Why does the value hold when, say, acid is added into the water? Why are the concentrations of protons and hydronium ions ($OH^-$) still both equal to $10^-7$?


texts: Material that is flexible when cold but becomes brittle when hot

texts:
I'm looking for a material that I can use to make a mesh netting.  It should be flexible and have reasonable tensile strength when cold but brittle when hot (>$\pu{400^\circ F}$).  I want to use it to contain charcoal when cold but disintegrate when charcoal is burning and some force is applied to it.

Any ideas?


texts: Question on deflection of cathode rays in a magnetic field

texts:
My book states that :

  When only electric field is applied, the electrons deviate from their
  path and hit the cathode ray tube at point A. Similarly when only
  magnetic field is applied , the electron strikes the cathode ray tube
  at point C.

I tried to apply the Fleming's Left hand rule used to find the direction of force on a current carrying wire where the direction of current is taken opposite to the direction of flow of electrons.

The rule states that :

  Stretch the thumb, forefinger and middle finger of your left hand such
  that they are mutually perpendicular. If the first finger points in
  the direction of magnetic field and the second finger in the direction
  of current, then the thumb will point in the direction of motion or
  the force acting on the conductor.

Applying this rule I found that the electrons should hit the cathode ray tube at A in a magnetic field . But in the book it is given that they strike it at C.

Please explain me where I went wrong . Thank you.


texts: Procedures for Syringe Pump and organometallic solution

texts:
For dispensing a pyrophoric organometallic acid into a reactor under argon flow, is it permissible to place the loaded syringe (glass 10ml, 9ml solution) on the syringe pump, with a long needle (36" septum piercing) through a septum on the reaction vessel (500ml, 50% volume solvent and reactant) set at 1.5 ml/h?

I am asking because after a couple trial runs I suspect an indeterminate amount of acid is staying in the long needle after drawing from the sure seal bottle (two penetrations: 36" needle and the argon needle) and despite holding the syringe upright and pushing the excess into the headspace and drawing an inert "cushion" back into the syringe I am somehow still overdosing.

My epiphany came as I was looking into schlenk storage flasks that in order to utilize a syringe pump for proper dose rate with pyrophorics one would run a nitrogen filled syringe in the pump with a needle going into a pressurized schlenk flask with a cannula coming out from the bottom of the liquid level to the reactor vessel and as the syringe pump pushed the empty syringe the displacement would equate to the amount of acid being pushed through the cannula.

If this all seems obvious I apologize, but I have read many of the Sigma Aldrich technical bulletins regarding pyrophoric handling and they do not mention slowly dispersing from a syringe. So far, besides the overdosing problem, I also suspect the solution is not entirely insulated within the syringe and it may be less reactive once it gets to the reactor. I am considering a Teflon pusher for the glass syringe and going to a PTFE-lined vinyl tube with luer lock barbs.

If anyone can point me in the right direction in terms of syringe pumping to a reactor with pyrophoric acids that would be awesome.


texts:
Which hydrogen of 3-methylcyclohex-2-en-1-one is the least acidic?

According to me it should be 2, as on its removal there won't be any resonance stabilization as would happen in the other cases. In addition to that a negative charge residing on a carbon attached to a double bond would be highly unstable.
But the answer key says that it is 3.

A follow up question: Which is the most acidic hydrogen?

According to me it should be 4 as it leads to a greater number of resonance structures.


texts:
For the first time I'm doing TD-DFT calculations (wB97XD functional) in Gaussian 09 for an open-shell system and the results look like the hell of a mess for me. The molecule is rather big, so I started with just 10 excited states to see how it would work.

First off, the ground electronic state is $^2A_2$, orbital 453 is HOMO and 454 is SOMO. Now to the excited states. In the output I found, for example, the following piece that looks strange to my eyes

Excited State   3:  2.139-B2     0.9431 eV 1314.65 nm  f=0.0816 <S**2>=0.894
453B -> 454B       0.98895
453B <- 454B       0.17190

The first line is fine: it says that the third excited state is $^2B_2$ (taking spin contamination into account).
The second line is also fine: it tells that the determinant corresponding to excitation from HOMO to SOMO has the largest coefficients in the CI expansion.
But what is the meaning of the third line?


texts: Isn't 11-trans-retinal more stable than 11-cis-retinal?

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11-cis-retinal can be found as a part of rhodopsin and it is the non-excited form of retinal. By absorbing light, retinal goes to a higher energy state and converts to 11-trans-retinal. At least I understand it so.
If all above is correct, I just don't get one thing. Shouldn't the cis form be less stable than trans (due to steric hindrance)?


texts: Can Gay-Lussac's law be observed in the reverse direction?

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Gay-Lussac's law states that if you decrease the temperature of a gas at constant volume, the pressure decreases by a corresponding amount. This is easy to carry out experimentally. But in practice is it possible to perform this the other way round, i.e. decrease the pressure and thus cause the temperature to drop, while keeping volume constant?

It seems to me that in order to reduce the pressure, you would go about lowering the chamber's volume by removing air from it. However, this would also remove a proportional number of moles from the chamber, so the temperature would remain unchanged.


texts:
I have a quick question: how can I distinguish between terpenoids compounds and polyketides?
For example artemisinin (see image below): it present a continuous carbon chain alternated with $\ce{O2}$, but it is a polycyclic structure as in terpenoid compound.
Which is the main criterion I should consider here?


texts: Are viscoelastic materials to be considered solids or fluids?

texts:
I recently stumbled upon the concept of viscoelasticity. Not being a chemist, but being interested in the topic, I started to read the wikipedia article.

The main thing I extracted from it is:
Solids are elastic, fluids are viscous, viscoelastics materials are both viscous and elastic.

I didn't get it, maybe due to my poor background. Is viscoelasticity a state of matter or just a property of materials? In the latter case, can we talk about viscoelastic solid and viscoelastic fluids?
I know the state of matter isn't an element nor compound or material property but it changes as temeprature and pressure change. The strength of the bonds between atoms/molecules and the "value" of their kinetic/vibrational energy is what determines how we see them.

Anyway, I couldn't really fit viscoelastic material in my chemistry mental scheme, so I'm here in search of some clarifications.


texts:
Copper(I) iodide is usually made by the reduction of copper(II) salts. An example of using potassium iodide and copper(I) sulphate is shown below.

$$\ce{2CuSO4 + 4KI + 2Na2S2O3 -> 2CuI + 2K2SO4 + Na2S4O6 +2NaI}$$

I did another method of synthesising $\ce{CuI}$ by preparing it directly from its elements, with $\ce{NaI}$ as the solvent for solid $\ce{I2}$:
$$\ce{2Cu + I2 -> 2CuI}$$

May I know why the 2nd method (direct synthesis) is better than the 1st in terms of green chemistry?


texts: What is the most stable conformation (Newman Projection) of CF3CH3?

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Is a totally eclipsed Newman projection the most stable conformation for a 2 carbon compound, with one carbon bonded to more electronegative atoms (making them partially negative), and the other carbon with something less electronegative (making it partially positive)?

For example, let's imagine $\ce{CF3CH3}$. If they are eclipsed, the fluorine side is partially negative and the hydrogen side is partially positive, so wouldn't they attract?

Or do the electron clouds always repel each other, no matter what atom is used (making a staggered conformation the most stable, not eclipsed)?


texts:
I’m asking this question in the most technical perspective of identifying substances, so I’m not considering the use of chemical tests like Benedict’s solution, biuret solution, Sudan III stain, or indicator dichlorophenolindophenol, as valid answers since these methods rely on identifying the color by observation. The answers I’m really looking for are based less on physical and more on chemical properties without the need of human observation or intervention.

(At this point, if you have an answer please reply… the rest is clarification to my question)
With that being said spectroscopy, chromatography, electrophoresis, and biochemical analysis are more along the lines of the answers I’m expecting. However, I’m really asking which of these methods or others in connection with other techniques, are the most convenient, smallest in size (in terms of equipment), and cost-effective in identifying food sources.

So in attempt to sum up my question, here's a scenario: I have a yellow onion. I extract juice from the onion and I give it to a skilled chemist/engineer labeled unknown. Using an analytical technique, in about a few seconds, the chemist supplies a prediction based on the components found within the unknown food (amino acids, peptides, proteins, enzymes, lipids, phospholipids, carbohydrates, alcohols, fat-soluble vitamins, water-soluble vitamins, organic acids, organic bases, phenolic compounds, bittering substances, pigments, aroma compounds, and dietary fiber)

What is/are the analytical techniques used? Is there a device that does such a thing?


texts:
Every source I read mentions the potential difference building up at the glass membrane (according to the Nernst equation). But how is this difference actually measured? Sticking an electrode into a solution doesn't mean that I can measure the potential at a membrane which is some distance away. Hence, there must be some reaction at the electrode itself. Mainly Ag/AgCl electrodes are used, as far as I read. So what causes this reaction?

On the other hand, as I already noted, every source is talking about the ion selective glass membrane. It is selective regarding $\ce{H+}$ ions and doesn't let them pass through? But what does this have to do with the measured potential? The Nernst equation only mentions the different activities of the solutions.


texts: Participation of Pi-bonds and lone pairs in resonance

texts:
Below is a quote from Klein's Organic Chemistry 3rd edition:

  Here is the bottom line: Whenever an atom possesses both a π bond and a lone pair, they will not both participate in resonance

However, I am confused as a few pages prior it was shown how allylic lone pairs and pi-bonds participated in resonance:

  The first curved arrow goes from the lone pair to form a π
  bond, while the second curved arrow goes from the π bond to form a lone pair:

What have I understood wrongly?


texts: Has QTPIE ever been applied to 1D metals such as polyacetylene?

texts: QTPIE is a fluctuating charge model that substantially improves modeling of polarization and charge transfer. I was curious whether it has ever been applied to 1D metals such as polyacetylene to provide new perspectives on topics such as Peierls' condensation and phase solitons?


texts: Why do frozen whipped cream remain "frozen" when thawed?

texts:
I froze some pastry with whipped cream on the other day (by mistake, I placed it on my balcony and expected it to be a few degrees above zero, but it wasn't). When I unfroze it again I was expecting the whipped cream to become soft again (or, I was actually expecting it to "collapse", that is lose all the air whipped into it) but instead, even when it was at room temperature, the whipped creamed remained basically as firm as it was when it was -10°C. Leaving it for a few hours didn't change that.

Milk, "unwhipped" whipped cream, butter and so on all can be frozen and then thawed and the result is more or less its original texture and consistency (just a quick shake and your fine). Why does whipped cream behave so differently?

Edit: I can add that I have googled this and find a lot of articles that confirm freezing whipped cream is a bad idea but no one explains why.


texts: Why do only ketones exhibit keto-enol tautomerism?

texts: Why can't esters or acids or their derivatives exhibit tautomerism? I mean if they did, then there would be a conjugation between lone pair electrons of oxygen and pi electrons adding to their stability. Then why don't they exhibit similar tautomerism?


texts: What is the significance of using cold conc H2S04 followed by boiling water for hydration of alkenes?

texts:
I tried searching the internet but I failed to find a answer  satisfactory to my understanding.
I know if I react the alkene with cold conc. H2SO4 I get an alkyl hydrogensulfate which upon reaction with boiling water gives alcohol,but I can't understand the need for these conditions like what if we reverse them.
I think that since alkene is nonpolar we react it with sulphuric acid to make the carbocation instead of direct reaction with water,but I dont understand the formation of alkyl hydrogen sulphate.If a carbocation has been formed, water can attack it easily forming an alcohol (assuming that HSO4- is weaker nucleophile than water).So why don't we just add both sulphuric acid and water combined?


texts: What are the unique reactions of conjugated carbon containing carbonyl compounds?

texts: Various sources give different ideas about the reduction reaction of α,β-unsaturated carbonyl compounds which have conjugated carbon. Just like cinnamaldehyde do aliphatic α,β-unsaturated carbonyl compounds react with H2/Ni or    LiAlH4 to hydrogenate their C=C bond to give alcohols. Please Give me some explanation behind the regioselectivity of soft and hard nucleophiles.


texts: Why is a cationic trialkylammonium functional group inductively withdrawing in nature?

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The alkyl groups on the nitrogen ion should donate electrons (alkyl groups are electron donating in nature). So, irrespective of the nitrogen ion being a cation (which is an electrophile), the alkyl groups should compensate the electrophilicity of the nitrogen cation, and the ion as a whole should be electron donating in nature.

Then why is $\ce{R3N+}$ considered to be electron withdrawing?


texts: Suppose one could generate an enzyme with arbitrary conditions at the active site. What conditions would then be necessary to cause carbon from dissolved $\ce{CO2}$ in low $pH$ water to combine with the free hydrogen and make methane?


texts: Does 'Stoichiometry' refer to the mole ratio of atoms in compounds and the mole ratio of compounds involved in chemical reactions?

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For my intro to chemistry class, I was asked to answer whether 'stoichiometry' refers to the mole ratio of atoms in compounds and the mole ratio of compounds involved in chemical reactions?

To the best of my knowledge those ratios are an essential part of stoichiometry, but stoichiometry is a discipline, and not a ratio, so the answer would be false.

Is that correct?


texts: What could be causing a small uptick in FCS curve at approximately 10 microseconds

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I work as an RA in an academic lab. I've been working with FCS fitting for an experiment, and took FCS curves for fluorescein and calmodulin, displayed with residuals below:

]2

I fitted both to an autocorrelation function

$$G(\tau)=1+\frac{T}{(1-T)} \frac{\exp(-\tau/\tau_{trip})}{V_{eff}(c)(1+\tau/\tau_D)\sqrt{1+p^2(\tau/\tau_D)}} $$

As you can see, the fit isn't too bad for preliminary results, but there's a weird uptick at about 1E-5 seconds that isn't accounted for by the model. That it looks about the same for both molecules suggests to me that it may be a small instrumental artifact. I collected both curves at about 6 uW power, 1 nM sample, and averaged five curves for each sample after subtracting an afterpulsing correction found by taking an FCS curve of nanopure water on a slide. I am using a confocal microscope setup. Does anyone know what could be causing an uptick in that timeframe?


texts: how to calculate the gas volume per purge when I change the cylinder?

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I have some gas cylinders in a gas cabinet. Every time I change the cylinder, I use N2(100%v/v, 60L/min) to purge the residue gas in the pipe to a local scrubber. I want to know how many gases I should treat per purge?

follow is my customer give me the condition：
gas name                 flow rate         pressure(MPa)
F2(5%F2,
Blance Kr/Ne 95%)      max 4.4L/min         14.8
BCl3                    same↑                0.0627
WF6                     same↑                0.04
ClF3                    same↑                0.0588
N2                       60                   ─

Here is someone give me the solution：
100% gas volume (L/purge)= 0.07(L)*[pressure (pa)/98066.5(pa)]*1(cylinder/purge)*concentration%

How come?
In my thought, it use the formula P1V1=P2V2, where V2 is what we want to calculate. P1 is the gas pressure in the cylinder, P2= the pressure in the pipe.
But 0.7(L)? Why? And why P2 is not 1 atm = 101325 (pa) but use 98066.5(pa)=1kgf/cm^2

BTW, the pressure(MPa) value let me confused. Generally, how much pressure is the gas cylinder for each kind of gas above? The value is closed to the pressure of a new cylinder or to a used-up cylinder?


texts:
To express heating, we usually use $\Delta$ over reaction arrows like
\begin{align}
\ce{CaCO3 ->[\Delta] CaO +O2}.
\end{align}
Why do we use $\Delta$ to mean heating during chemical reactions? I thought up with one idea that $\Delta$ symbolizes fire. But actually I have no information about the origin of this usage. Does anybody know the origin or reason of this usage of $\Delta$?


texts: Can beta D-glucose be present hydrolysate after hydrolysis of cellulose and how can it be converted into alpha D-glucose?

texts: When we perform the hydrolysis of cellulose by acid, we already knew that it can convert cellulose into glucose. As we know, cellulose is composed of beta glucose units linked by beta 1,4-glucosidic bonds. So I would like to know, resulting glucose after hydrolysis is beta or alpha glucose? If beta glucose is present, how can it be converted to alpha?


texts:
I am asked to give the type of reaction (SN1, SN2 or acid-base reaction) for the following reactions. I know that both $\ce{MeOH}$ and $\ce{EtOH}$ polar protic solvents, so because the first is an SN2 reaction shouldn't the second reaction be that as well? It says that it is an acid-base reaction as $\ce{MeO-}$ reacts with the $\ce{EtOH}$ to from 1-bromopropane, $\ce{MeOH}$ and $\ce{EtO-}$ and then goes on to from a SN2 reaction.

I would appreciate if someone could explain why the second reaction would be an acid-base reaction at first instead of a SN2 reaction.


texts: How to measure saturated salinity and mineral levels for flaked sea salt?

texts:
I am a sea salt enthusiast looking to make the perfect flakey sea salt. I start with sea water and boil it down to a thick brine. Then with less heat I reduce the brine more slowly and inverted salt flake pyramids are made. I am looking for tools/instruments that will help me measure/understand the content of the brine (mineral content and salinity). Sometimes I get perfect flakey salt pyramids like the photo attached and sometimes I get I get more chunky results. The temperature of the brine is always the same but I get different results at times. This leads me to think that its the content of minerals in the saturated brine solution.

Are there chemistry tools/instruments I can use to understand the actual chemical/mineral makeup of the brine that is turning to salt.


texts: In a nearly finished bowl of oat cereal, why do the pieces of cereal stick together? I figure that since they are composed of starches it could be hydrogen bonding. Is this true or is there some other reason?


texts: Is there a difference between hand soap and body soap with killing viruses?

texts:
With the Coronavirus in full swing around the globe, I wanted an answer to this, particularly since my dad has just been diagnosed with Leukaemia.

We can't find hand wash anywhere but instead I just bought some Radox shower gel and put that in a hand soap bottle.

Is there a significant difference between hand soap and shower gel when it comes to killing off germs/viruses? Or is the case that both are detergents and it's all around marketing?


texts:
Why ammonium ion has very similar properties to the heavier alkali metals and is often considered a close relative?

Ammonium is expected to behave as a metal ($\ce{NH4+}$ ions in a sea of electrons) at very high pressures. Can anyone explain?


texts: Order of the subshells in an electron configuration

texts:
According to what my chemistry teacher said, the energy of a subshell is given by the sum of its principal quantum number (n) and its second quantum number (l).

e.g.:

1s = n+l = 1+0 = 1
2s = n+l = 2+0 = 2
2p = n+l = 2+1 = 3
3s = n+l = 3+0 = 3

However, when it comes to make a graphical representation of an electron configuration (which follows an order of increasing energy), she doesn't put the subshells having the same energy in the same level, like in the following picture:

Shouldn't the subshells 2p and 3s (which both have an energy equals to 3), as well as 4p and 3d, be put in the same level, since they have the same energy?


texts: I would just like some reputable textbooks and or publication companies that have extensive research on plastics, as, for example, dealing with life cycles of plastics, degradation factors, effect on life, polymer types, etc.


texts: Looking for a radio-transparent epoxy/resin

texts:
I have much hobby experience with 2-part resins, but this time I'm looking to
make a repair part for the inside of a microwave oven (everything I've tried so far heats up, but the original part does not).  I need the result to be hard enough (shore durometer D ~ 75) to rotate the glass turntable tray within the oven, withstand ~ 250 degrees Fahrenheit (it will not be in contact with food) and be radio-transparent at the frequency of 2.4 GHz.

I've reached out to over a dozen epoxy/resin manufacturers, but am having trouble finding such a product.  Thank you in advance.


texts: What acids will Sodium Lauroyl Methyl Isethionate yield after hydrolysis?

texts:
As far as I understand, after hydrolysis Sodium Lauroyl Methyl Isethionate will yield sodium, lauroyl and methyl alcohols, and isethionic acid. Meaning lauroyl is referring to the fatty acid alcohol rather than to the acid itsIf.

But I have read that this is compound is defined as "the sodium salt of the methyl lauric acid ester of isethionic acid", which sounds like it would actually yield lauric acid rather than the alcohol.

So which is it? Will it yield lauric acid after hydrolysis or lauroyl alcohol? And how can I tell based off the name?

I think I may be mixed up in my understanding of salts versus esters, since I definitely have more experience with the latter. Most of the information I have found on the nomenclature of salts is not comprehensive enough to discuss complex salts such as this one. If you are aware of such a reference, please share.


texts:
I was recently asked the question "Why are noble gases stable? with the expectation of providing an answer beyond the general explanation of "they have full valence layers" and I couldn't think of one.

I would love to hear a full description of the this stability, I have a solid background in quantum mechanics, so feel free to speak of wave functions or the like if necessary.


texts:
The correct IUPAC name of the following compound is:

  (A) 1,1-diformyl propanal
  (B) 3-formyl butanedial
  (C) 2-formyl butanedial
  (D) 1,1,3-ethane tricarbaldehyde

The structure of 1,1-diformyl propanal has been given. And the IUPAC name has been written. But I can't get the same IUPAC name because I'm a beginner. Also I don't know how to get structure here in the question, so I didn't do it.
Help me with the IUPAC naming of the compound with step-by-step explanation . Please.


texts: I'm trying to reduce a disulfide bond, I've tried 2-mercapto-ethanol, because I've seen in literature that using a thiol is the most common procedure. I carry out the reaction at 80o C but so far I have no positive results


texts:
I tried to find a way to synthesize Dimetinden (N,N-dimethyl-2-[3-(1-phenylethyl)-1H-inden-2-yl]ethan-1-amine) with an Indensynthesis

https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0030-1261196

First of all I would like to know if there is anything wrong with the whole synthesis and how about the yield?

Second question would be the mechanism of the inden synthesis, because it looks kind of wrong.


texts: Why are the three most simple alcohols completely miscible?

texts:
I want to know why the three most simple alcohols (methanol, ethanol and propanol) are completely miscible in water?

I want to know what happens at molecular level.

I think hydrogen bonding plays an important role.


texts: How to deal with the unit "Coulomb per equivalent"?

texts:
In a question that I came across they defined $1\,\pu{F}$ as 96500 coulomb per equivalent. Now as far as my knowledge is concerned $1\,\pu{F} = 96500\,\pu{C/mol}$. The question involved asks to calculate the current that needs to be passed (or may be a function of that) wherein I mistook the $n$ factor and the answer was just half of what it was supposed to be. However that taking $1\,\pu{F}$ as "coulomb per equivalent" would lead me to a antoher unit (equivalent per mole) in order to get the desired unit in the question.

In this context I would like to:

a)  Get an intuitive explanation into the number of equivalents (just like moles is Avogadro number of substances).

b)  Know what the unit "equivalents/mole" means (is it the same thing as $n$ factor?) How does the $n$ factor treat number of moles and equivalents so differently?


texts: Significant Figures: To expand or not to expand?


texts:
I am genuinely confused on the difference between a procedure/flow chart and the synthetic method for a lab report and what exactly a synthetic method includes, and I can't find any information online. I would really appreciate the help if anyone has knowledge about it.

This is what the directions say, but it almost sounds the same as what a procedure would cover.

Thank you very much!


texts: Are phospholipids capable of forming automatically circles or vesicles?

texts: Sometimes scientist think that life began with membrames made of a kind of phospholipids. There wasn't any DNA needed for because those molecules would automatically form vesicles like cells. But is this really possible and how do those molecules form circles and vesicles?


texts: Finding partial derivatives for an ideal gas and van der Waals gas

texts: How do I determine $\left({\partial P\over\partial V_\mathrm m}\right)_T$ for an ideal gas and also for a van der Waals gas? Note that $T$ is the only variable which is held constant, and that's my trouble. I've only derived these equations in cases where two variables are held constant. I don't know where to start.


texts: What is the justification for Ligand Close Packing Model?

texts: The LCP model predicts that nonbonded atom to atom distances remain approximately the same when the central atoms are changed. What is the theoretical justification for this? thanks


texts: Why is dimethylmercury more toxic (to animal life) than methylmercury or ethylmercury?

texts:
It's obviously a two step process to reduce dimethylmercury to the less harmful inorganic form.

Is neuronal uptake also enhanced due to lipophilicity? Is there some other mechanism of toxicity I'm overlooking?


texts: Major product of Crossed-Cannizzaro Reaction between benzaldehyde and formaldehyde

texts:
I came across a question:

Predict the major product when conc. $\ce{NaOH}$ is added to a mixture of $\ce{PhCHO}$ and $\ce{HCHO}$.

According to me, as $\ce{HCHO}$ is less hindered and $\ce{>C=O}$ of $\ce{HCHO}$ is more reactive, so the major products must be $\ce{CH3ONa}$ and $\ce{HCOONa}$. The hydride transfer should be from one Formaldehyde molecule to the other.
However, the answer was given as $\ce{HCOONa}$ and $\ce{PhCH2ONa}$. Is there a mistake on my part?


texts: Just wondering if you fitted a cold water tank overflow pipe into a car park at the height of a car exhaust , if the carbon monoxide fumes went back up the oveflow pipe into the tank would this contaminate the water?


texts: How to correctly write "7 apples" according to the international system of units (SI)

texts:
According to international system of units (SI), we can write "7 kg of apples" to refer to the mass of these apples.

However, if we want refer to the amount of apples, that is, the number of entities, the unit should be the mole. So, what's the correct way to denote "7 apples" in accordance with the SI convention?

Additionally, is it correct (according to SI) to say "7 atoms of hydrogen"? Or must we use mole?


texts: Are my intuitions about how batteries work right?

texts:
Being really fascinated by how electricity actually works, I started studying batteries.
I initilally understimated the complexity of this apparently-simple objects, and thorugh studies and researches I have understood how they are the result of complex chemical and physical discoveries, blendend together in a triumph of engineering.
Anyway there are  some things that I still have to figure out completely, I made some pictures that aim to clarify my doubts and the question objects.
This is the picture of a zinc-copper cell with a non-specificated electrolyte:

It represents essentially how I imagine a cell of this kind.
Zinc and Copper have both reached a dynamic equilibirum with the electrolyte, so charges leave electrodes at the same rate as charges enter.
This creates an electrode's electric field, and the elctrode potential at the same time.
The net electric field represents the net force driving the elctrons from the zinc to the copper, resulting from the superoposition of the elctrodes fields.
Given that this analysis is right ( If it's not, please help me understand where is flawed), I don't understand how this electric field ( and so the potential) changes as time passes.
If electrons are leaving zinc to reach copper (and eventually react with some positive ions in the electrolyte,right?), how the electric field is mantained so that the flow can go on?
As electrons leave, how the zinc electrode field is affected?
Are positive ions leaving the zinc at a faster rate in order to compensate for th electrons deficency? (That would explain the zinc corrosion)
Is there an electrode's size limit (corrosion limit) where the electrons  that make up the elctrode aren't enough to keep the same voltage(the chemistry's votlage)?
Is it at the point that we start to see a decrease in the voltage of the cell?
Of course, all the considerations presume the precence of a salt bridge capable of mantaing the elctrolyte charge stable.


texts:
What happens when phenol reacts with $\ce{D2SO4}$ in presence of $\ce{D2O}$?

How many hydrogens in total are replaced by deuterium?

Is the hydrogen of the hydroxyl group and three hydrogens ortho and para to the -OH group replaced by deuterium, and the remaining two unaffected?

OR are all hydrogens replaced by deuterium?

I'm not sure what really happens, but as far as I know - even though ortho and para positions are greatly activated, some small percentage of meta attack may also take place. In fact, if it does take place, the final compound will be totally deuterated, as bonds with deuterium are stronger than those with hydrogen, and backward reaction will not be thermodynamically favoured.

It'd be great if someone could explain what's going on, and if possible please quote sources supporting your answer. Thanks a lot.


texts: Does the size of a hole in a container affect the rate of effusion?

texts:
Graham's Law of Effusion states that the rate of effusion of a gas is inversely proportional to the square root of density of the gas.
If there were two containers both with the same gas but one of the containers had a larger hole than the other, would the rate of effusion be quicker for the gas in the container with the larger hole?


texts: Can the following molecules be called meso compounds (cyclic structures which usually exist in non-planar forms)?

texts:
In the planar form the following molecules have one plane of symmetry.However in
  the chair-form (the most stable form) for the first molecule and the non-planar form for the second molecule there is no plane of
  symmetry.Will the molecules still be called meso?

BTW I do not think the molecules ever attain completely planar form.

Just for quick reference I'm adding the non-planar forms of the two molecules.


texts:
The above is the correct $ ^{13}C $ NMR spectrum of butanone.

In the $ ^{13}C $ NMR spectrum of butanone, I figure that the peak locations of the first and third carbons should be switched (27.3, 35.2). Shouldn't the third carbon be shifted upfield by the terminal methyl group and therefore have a "smaller ppm" than the first carbon?


texts:
I know I should divide $\pu{g L-1}$ by the molar mass of the substance, but I don't seem to find the specific answer on Google. So just to be sure:
If I have $10^{-5}~\pu{g L-1}~\ce{Cu^2+}$ solution, do I have $1.57 \times 10^{-7}~\pu{mol L-1}$?
I think I'm missing something.


texts: How does cyclic voltammetry in a electrolytic cell measure the precise oxidation potential?

texts:
From what I understand, the potential necessary to induce a current to flow in an electrolytic cell depends on both reduction potentials of the anode and cathode reactions, where E(cell) is comprised of these two potentials and determines the spontaneity of the reaction, and hence the current flow. Thus, in cyclic voltammetry in an electrolytic setup, wouldn't the anodic redox potential thus depend on the cathodic redox potential?

As in, the position of a peak potential at a certain point in a cyclic voltammogram would change depending on what is reduced at the cathode in an electrolytic cell, because a change in the redox potential of the cathode changes the required voltage to induce spontaneous current flow from the anode to the cathode.


texts: How does the polarity of the eluent and sample affect the Rf value in thin layer chromatography?

texts:
A three-component mixture (X, Y, Z) was separated using normal phase TLC. Three eluents of varying polarity were used. Select the TLC plate that was developed using the least polar eluent (click on the corresponding TLC number 1, 2, or 3 on the bottom of the plate). On TLC plate 3, select the least polar compound (click on X, Y, or Z spot on plate 3).

Does normal phase TLC mean silica gel TLC? If this is the case then plate 3 has the least polar eluent because the compounds are at the top. For the same reason compound Z would be the least polar.

The term eluent means solvent doesn't it.


texts:
I have a mixture of $\ce{Et2O},$ $\ce{EtOH}$ and water, and I want to distill off the ether. I am using a water bath so not much water is distilled over, as the boiling water is 100 °C, and the solvent has like 20 °C lower temp than the water bath working temp, I believe.

So, my point is, is it safe and reasonable to make a bath with 95% ethyl alcohol to prevent much $\ce{EtOH}$ evaporation without needing to closely keep track of the temperature?


texts: Why does attraction always cause release of energy making the system more stable?

texts:
Suppose $\ce{Na^+}$ and $\ce{Cl^-}$ form an ionic bond. In doing so they will come closer by attraction. Now as they come closer their speed will increase and hence the kinetic energy increases. So basically the electrostatic potential energy will be controverted into kinetic energy.

  My question is why do these processes that involve attraction cause a release of energy from the system? And after this release why is the system said to be more stable?

My understanding is there might be two concepts involved.

First, as the ions approach each other their speed increase, but as soon as they touch each other they collide and reflect back. So the ions keep on oscillating. These oscillations are what we know as heat and the temperature of $\ce{NaCl}$ will be higher than its surroundings so it will release its energy in the form of heat.

Second, it might be because any accelerating charge releases electromagnetic waves, and so as long as the ions oscillate they'll keep releasing energy in the form of EM waves which may be trapped by other ions or may escape.

After the energy will be released from the system(NaCl ion here) our system must become more stable. Stable in the sense that NaCl crystal will not convert back into ionic form separated from other ions because for coming back to that state the system must be provided the lost energy back by some external agency. This is the way how I understand the term stabilty; I don't what does this term mean in chemistry. I also don't know why " every system in nature wants to be more stable" -- This is the phrasing that I heard in school days from chemistry teacher. This fact must be related to some thermodynamic fact of kind that every system wants to release energy, but why?


texts: Is 4-chlorotoluene also an IUPAC name for 1-chloro-4-methylbenzene?

texts: I think that toluene is a common name for 1-methylbenzene. And in IUPAC nomenclature, we must provide formal prefixes and suffixes along with correct numbering so the only correct option must be 1-chloro-4 methylbenzene.


texts: What determines the high degree of selectivity in free radical brominations?

texts:
In my organic chemistry class, we were asked what determines the relatively high degree of selectivity in the reaction of a bromine radical with primary, secondary, and tertiary C–H bonds.

I said it is the overall free energy of the reaction because according to Hammond's postulate, endothermic (endergonic) reactions have transition states closely resembling the product side, making the difference between primary, secondary, and tertiary radicals more important in the transition state.

Would this logic be wrong?


texts: Migratory aptitude in Baeyer–Villiger reaction

texts:
I found a reaction in which we have to find the product:

I tried and got to know that it is Baeyer–Villiger reaction but I got confused after seeing the answer, I thought there would be a shift of methyl group according to migratory aptitude, but it is not like that the product is:

Why?