texts: Selectivity in aldol condensation between pivaldehyde and acetone

texts:
In a crossed aldol condensation (condensation between aldehyde and a ketone), the primary products are such, that the carbonyl group of the ketone remains intact, and the $\alpha$-hydrogen of ketone participates, i.e. gets removed by the base to form the resonance stabilised nucleophilic enolate which later attacks the aldehyde. These are formed together with the self-condensation products, but the reverse products (aldehyde-derived enolate + ketone) are rarely formed.

I had a look at the mechanism, and also how a base catalyses condensation by favouring enolate formation.

  Why is the ketone involved in enolate formation and not aldehyde in
  crossed/mixed aldol-condensation reactions?


texts: Computational Chemistry Negative Lattice Vectors

texts:
This is a computational chemistry question.
I've recently been using the Materials Project API to get VASP input data, that I've been processing. The POSCAR format is as so, for those who do not know: POSCAR

Title
Scaling Factor
Lattice Vector A
Lattice Vector B
Lattice Vector C
etc (Not relevant to question)

On a few rare cases, i get Lattice vectors with negative values in them:

0.872808 2.468674 1.511748
-2.623232 -0.003400 4.543571
1.745616 -2.468674 0.000000

which displays fine using VESTA. Using pymatgen I converted it to a CIF file, which says:

_cell_length_a   3.02349597
_cell_length_b   5.24646459
_cell_length_c   3.02349568

and looks identical to the POSCAR file. However, I do not understand where these values come. For example, Lattice vector A:  0.872808+abs(-2.623232)+1.745616 != 3.02349597.

Seeing as VESTA displays it correctly, and pymatgen converts it correctly, I feel like it is just a concept that I do not understand. I tried googling but found nothing helpful. How do I convert from the given lattice vectors with negative values to absolute values as shown in the CIF format? What is the math behind this?

SOLVED:

Use Vector Magnitude/Pythagoras Theorem: sqrt(LatvA[0]^2 + LatvA1^2 + LatvA[2]^2) = 3.02349597


texts: Placement of Electrodes for Electrochemistry?

texts: I'm kind of curious as to the relationship between resistance and the yield of electrochemical methods. If I have my electrodes rather close together in a conductive solution the resistance will be smaller than if I had them further apart and more current can flow. Would there be any penalty for having the electrodes close together like this? Will I miss some ions in solution, or are they distributed equally in solution and so will always move towards the electrodes as some will be taken out of the solution as gases (such as electrolysis of (H2O -> 2H2 + O2))?


texts:
The methyl radical, $\ce{.CH3}$, is a strong oxidant and a strong reductant according to Wikipedia.

Why is this so? Any additional reasons to the ones below?

I know that an oxidant itself is reduced; an oxidant helps something else lose electrons, so the oxidant must be the one gaining electrons. Given that the methyl radical has an unpaired electron, it is quite reasonable that it would be amenable to having an extra electron to pair up with its lone electron.

I know that a reductant itself is oxidized; a reductant helps something else gain electrons. The carbon in the methyl radical has an oxidation state of -3, and I know that carbon can adopt a variety of higher oxidation states, such as +3 in acetic acid.


texts: Why is substitution of halogens to alkanes a chain reaction?

texts:
During the propagation step 2, the alkyl radical always react with the halogen molecule according to my textbook. However, isn't the alkyl radical react with the halogen radical formed in the initiation step much better since it lowers the potential energy?

If there is a chance that the 2 radicals combine, won't the chain reaction terminate rapidly as less and less halogen radical is formed?


texts: Nitrogen fertilisation expressed as nitrogen equivalent

texts:
In a plant pathology paper I found levels of fertilisation applied in the experiment expressed as nitrogen equivalent.
Reporting the exact phrase:

  Nitrogen fertilisation with 8.6 g of nitrogen equivalent …

I found that equivalent weight for an element would be its atomic weight divided by its valency so, if I'm not wrong, equivalent weight for N would be ~4.67 g

What does this mean?
How much fertiliser was applied e.g. using ammonium sulfate?


texts: Why does the pH of soft drinks get lower as they go flat?

texts:
I am doing an investigation about the chemistry of soft drinks and as part of this I observed the effect of time on the pH of soft drinks fully expecting the pH to increase as the carbonic acid, a weak acid, decomposed and CO2 escaped. Instead, time after time, the pH decreased, not by much though in fact it hardly made a difference to the acidity of the drinks but it the pH still decreased every time.

So I did a control experiment with soda water and found that the pH did increase when the CO2 escaped the drink. I originally did it with Coke and Pepsi, which aside from carbonic acid also have phosphoric acid (Pepsi has citric acid as well) so the increase in acidity probably has to do with an interaction between the the weak carbonic acid and the strong phosphoric/citric acid. Can anyone help me to explain this?


texts: Difference between a dimethyl and ethyl substituent groups

texts:
I'm teaching myself organic chemistry and am struggling with differentiating between dimethyl and ethyl substituent groups.
Example: tert-butyl (1,1-dimethylethyl)

This chapter follows the one on bond-line structures, and I realize one of the rules for making a valid bond-line structure for straight-chain alkanes involves zig-zagging carbon. But I am confused on how to represent the substituent groups - is the ethyl group the V, and the methyl groups are each of the branches from the middle carbon atom of the substituent group?


texts: What is the basic difference between accidental degeneracy and normal degeneracy?

texts: As definition suggests accidental degeneracy is defined by the degeneracy generated by two symmetry protected states. But how is it different from a non accidental degeneracy.


texts: How do I remove some of the glycerin when making soap?

texts:
In some older descriptions of soap making, I read that when the base is added to the fat the glycerin separates and collects at the top where it is drained off. Fine, but there are no details.
In modern recipes I have been using for soap, however, the instructions invariably say to constantly stir after adding the base. Of course, if I do this, then the glycerin gets mixed into the soap, making it too soft. If I don't mix, then there is the problem that the base might not react with all of the oil.
So, there is kind of a disconnect between theoretical descriptions of soap making and glycerin removal, and actual real modern recipes.
The basic question is: how do I get the glycerin out when making soap?


texts: An experiment in my lab was about the Belousov–Zhabotinsky reaction and we measured 2 times - the induction period, which was the amount of time it took for the solution to change color and back for the first time, and the oscillation period, which was the period of color change cycles after that. The lab manual says to the inverse of both those times as the rate constant K for this reaction, but I am not sure why. Please help?


texts:
I want to ask a question about the exchange integral $\ce{H_{AB}}$ -

If I consider an exchange integral $\ce{H_{AB}}$ the following exchange integral can be evaluated:

so $\ce{S_{AB}}$ is $0$ at $\ce{R = \infty}$

but in this presentation I was shown today, at large values of R, $\ce{H_{AB}}$ is preportional to the overap integral $\ce{S_{AB}}$.

Surely at large distances and towards infinity, as $\ce{S_{AB}}$ goes to zero, $\ce{H_{AB}}$ also goes to zero too.

Where does the preportionality

$$H_{AB} \propto S_{AB}$$

come from then using these approimations when R is large?


texts: Filtering conformation search: redundant elimination or clustering

texts:
In my project, I study reaction computationally. The initial step in my workflow involves a conformational search using a constraint to bring the two reactive parts on my molecule together (reaction forms ring).

This conformational searching generates many confirmations, and it can be difficult to tell which are different.

Previously I use redundant comformer search which narrows down before I pick which conformers to study by DFT  but today it was suggested to use a clustering method to group the conformers. In the suggestion i was told that the clustering would group into chair vs boat vs twist etc which would be useful. I tried this using maestros inbuilt algorithm but the results were not very good - all of the clusters contained multiple ring types.

Is there any better way of clustering in order to sort my results. Using external software for instance, or mathematically. I also wonder whether both are needed (redundant conformer elimination then clustering, or just cluster all results).


texts: Does deuterated water slow down the overall metabolism of a cell?

texts:
Would deuterated water, being heavier, slow down the metabolic rate of the cell and subsequently the aging process?

edit: lets say I wanted to observe a cellular event, like the formation of the blsatopore or ameboid motion, could I soak a cell in a solution with D2O without killing it or severely damaging it ?


texts: Is sugar in mead different from "regular sugar"?

texts: My understanding of the process of making mead is that you combine honey, yeast and water in an anaerobic environment. The yeast-bacteria ferments the sugar in the honey and produces ethanol (among other things?). If this is true, how come labels for mead still list e.g. 90g of sugars per litre? If I'm consuming mead, am I really consuming 90g of regular sugars as found in fruit, candy etc or is this some variant of sugar that is chemically different (sugar alcohol?) in a significant way such that traditional advise "eat less sugar" do not apply?


texts: Modeling Belousov-Zhabotinsky reaction using ordinary differential equations

texts:
Is it possible to model the BZ reaction using first order ODEs? If so what would these equations be?

Or, is there something about the reaction that needs higher orders?


texts: Derivation and visualization of cell potential dependency on temperature and entropy

texts:
Working from the thermodynamic identity
$$\Delta{S} = -\left(\frac{\partial{\Delta{G}}}{\partial{T}}\right)_p,$$
is it allowed to integrate both sides to obtain an expression derived from the Nernst equation
$$E_\mathrm{cell} = \frac{T\,\Delta S}{zF}?$$
Can one plot the results and obtain $\Delta S$ from the gradient, assuming $\Delta S$ is constant for the reaction and $E_\mathrm{cell}$ values at some temperatures are given?


texts: Why add NaBH4 slowly to 4-t-butylcyclohexanone in ether solution? [Lab Procedure]

texts: $\ce{NaBH4}$ is to be added slowly to 4-t-butylcyclcohexanone in ether solution according to laboratory procedures, but I am curious as to why that is? 4-t-butylcyclohexanone undergoes reduction with $\ce{NaBH4}$, so is the reason behind adding NaBH4 slowly to ensure maximum product formation, or is there some safety concern behind this?


texts: Why don't periodic acids convert alkenes to 1,2 diols?

texts:
Periodic acids cleave 1,2 diols by forming an periodate ester as an intermediate. Osmium tetroxide also forms an osmate ester with alkenes and yields syn diols after a hydrolysis step. Given that their structures are so similar, why doesn't periodic acid also succeed in forming diols with alkenes? (These in another step will be further cleaved to ketones). Instead in the Lemieux-Johnson oxidation, osmium tetroxide is taken in the first step - followed by periodic acid.
Osmium tetroxide does not cleave 1,2 diols - though I thought it might be in its being not such a strong oxidising agent as periodate - it may not suffice to cleave a C-C bond. Why doesn't though periodic acid carry out diol formation as well?


texts: Boiling point elevation with multiple solutes

texts:
I've encountered a problem where glucose and $\ce{NaCl}$ are mixed with water and $\Delta T$ is to be calculated.
I've calculated  $\Delta T$ for both glucose ($i = 1$) and $\ce{NaCl}$ ($i = 2$) separately and added them.
Is this procedure correct or should I have treated them as one solute and used $i = 3$ as the Van't Hoff factor?


texts: Solution to the rate law of first order reaction followed by second order reaction (consecutive)

texts:
I'm trying to derive the rate law of a first order followed by second order consecutive reaction:

$$ \frac{\mathrm{d}[\ce{A}]}{\mathrm{d}t}=-k_1[\ce{A}]$$
$$ \frac{\mathrm{d}[\ce{B}]}{\mathrm{d}t}=k_1[\ce{A}]-k_2{[\ce{B}]^2}$$
$$ [\ce{A}](0)=[\ce{A}]_0,\ce{[B]}(0)=0$$

The solution for A is trivial:
$$ \ce{[A]}=\ce{[A]}_0\exp(-k_1t)$$

The problem is B, whose rate law ODE is not linear:
$$ \frac{\mathrm{d}[\ce{B}]}{\mathrm{d}t}=k_1[\ce{A}]_0\exp(-k_1t)-k_2{[\ce{B}]^2}$$

This is a nonlinear first order ODE, but can be rewritten to a linear second order ODE by substituting [\ce{B}] with:
$$[\ce{B}]=\frac{\mathrm{d}y}{\mathrm{d}t}\frac{1}{k_2y}$$

Which gives:
$$ -\frac{\mathrm{d}^2y}{\mathrm{d}t^2}+k_1k_2[\ce{A}]_0\exp(-k_1t)y=0$$

The solution is quite complicate and contains bessel functions of both the first and the second kind:

$$ [B] = \frac{C_1\,{\mathrm{e}}^{-\frac{k_{1}\,t}{2}}\,J_1\left(\frac{2\,{\mathrm{e}}^{-\frac{k_{1}\,t}{2}}\,\sqrt{-\ce{A}_{0}\,k_{1}\,k_{2}}}{k_{1}}\right)\,\sqrt{-A_{0}\,k_{1}\,k_{2}}-\ce{C}_2\,{\mathrm{e}}^{-\frac{k_{1}\,t}{2}}\,Y_1\left(-\frac{2\,{\mathrm{e}}^{-\frac{k_{1}\,t}{2}}\,\sqrt{-A_{0}\,k_{1}\,k_{2}}}{k_{1}}\right)\,\sqrt{-A_{0}\,k_{1}\,k_{2}}}{k_{2}\,\left(C_1\,J_0\left(\frac{2\,{\mathrm{e}}^{-\frac{k_{1}\,t}{2}}\,\sqrt{-A_{0}\,k_{1}\,k_{2}}}{k_{1}}\right)+C_2\,Y_0\left(-\frac{2\,{\mathrm{e}}^{-\frac{k_{1}\,t}{2}}\,\sqrt{-A_{0}\,k_{1}\,k_{2}}}{k_{1}}\right)\right)}$$

There are two arbitrary constants but I only have one condition:
$$\ce{[B]}(0)=0$$

So my questions are:

Is my approach solving the rate law correct ?
If so, how do I get rid of both constants ?
Is there any approximated solution to this rate law ?

[update]:
The ode is solved numerically with Runge-Kutta method. The symbolic solution seems correct.


texts: What is the purpose of Gaussian, itself?

texts: I have been doing some research into computational chemistry, having never looked into the area before, and have read about a popular, paid-for software "Gaussian", and free alternatives such as "GAMESS". From what I understand they are both capable of employing methodologies such as PM3, but I am struggling to understand the point of the software itself; how is a Gaussian PM3 calculation any different to a GAMESS calculation? There must be a reason one would want to pay for it.


texts: Why do 4d and 5d metals have more orbital overlap than 3d because of size?

texts:
When considering the electrical conductivity of metal oxides, they will conduct better if the metals orbitals can reach each other to overlap. Whether this can happen is contributed to by a couple of things such as Z-eff charge (electronegativity), the anion, oxidation state etc.  We're told that one of those properties is that as you down a group, the size of the orbitals increases, and hence more overlap.
But isn't making the atoms bigger just going to mean that the distances between the atoms get bigger proportionally? So switching a 3d for a 4d, but keeping the same structure would just look like "zooming in", but not change any proportional overlap?
As I understand f orbitals are inside (having an electron density maximum closer to the nucleus), and so don't participate in bonding.


texts:
The following compound undergoes ring expansion and contraction simultaneously.
I am not able to figure out a clear mechanism for the same, and stuck for a lot of time to get this clear. Kindly help me out with the same by using appropriate mechanism or models.

My Approach: I could think of the following. A carbocation would be formed after the protonation of -OH group and after it leaves. Now carbocation would not be able to directly rearrange at the bridging carbon. So probably the bond between the bridgehead carbon and the adjacent carbon breaks and a new bond is formed (ring contraction) leaving behind a "3 degree" carbocation at the original bridgehead.

Now this is what I'm facing problem understanding:
i) Mechanism of ring expansion using the newly formed carbocation.
ii) What provides energy for the bond to break and the ring to contract based on the mechanism I suggested earlier (does carbocation stability provide enough energy?). Also is my proposed mechanism even correct ?


texts: Why is disodium acetylide considered as an organic compound?

texts: Even though disodium acetylide ($\ce{C2Na2}$) has carbon bonded with metal atoms and does not have a single carbon hydrogen bond in it, why is it considered as an organic compound? If this is an organic compound then why don't we call $\ce{CO2}$ an organic because it can also be produced from reacting organic compounds?


texts:
It turns out pineapple juice can dissolve a jello set, and turn a beef roast to paste.

It turns out this is caused by Bromelain, an enzyme sometimes used in meat tenderising.

I'm trying to work out how you can eat pineapple without dissolving on the spot.

My question is: How does the human body process Bromelain in pineapple? (A meat tenderising/dissolving enzyme)


texts:
i'm doing a chemistry assignment and cant find the difference between hexane and hexane fraction. i think it means there are impurities but not sure so it would be nice if someone could help. for the the fuels i am doing hexane fraction and 1-hexanol. if it means there are impurities that will impact the experiment.

when i search google "hexane fraction" i get stuff on hexane not hexane fraction.


texts: Hydrolysing large molecules to reveal amino acids

texts:
Consider Oxytocin:

I am asked to hydrolyze Oxytocin and reveal 5 amino acids which are the result of this hydrolysis.

I must admit I have no idea where to begin. I know that generally amino acids are on the form of $\ce{NH_2-CH(R)-COOH}$, so perhaps looking at these double bonds to oxygen may be a starting point, as I assume they will become the acid group? But I really don't know how to move forward from there!


texts: Internal Energy Definition, Why is dU zero when dT is zero?

texts:
According to my Equation sheet, $$\delta U=\left(\frac{\delta U}{\delta T}\right)_V\,\delta T+\left(\frac{\delta U}{\delta V}\right)_T\,\delta V=C_V\,\delta T-C_V\left(\frac{\delta T}{\delta V}\right)_U\,\delta V$$ Where $\delta U$ is change in internal energy.

So one of the homework solutions said that for a system with a constant Temperature, $\delta T=0$ $\Delta U=0$. And I remember one of the TAs saying that $\Delta U=C_V\,\delta T$ and since $\delta T=0$ the value goes to zero, which makes sense. But she didn't even include the second term: $-C_V\left(\frac{\delta T}{\delta V}\right)_U\,\delta V$.

I was trying to make sense of the derivative but I'm really having trouble with the second term. The small letter $U$ outside the parenthesis is supposed to mean constant $U$.

Why am I allowed to ignore the second term?

The equation for enthalpy is very similar, and I have the same problem:

$$\delta H=\left(\frac{\delta H}{\delta T}\right)_p\,\delta T+\left(\frac {\delta H}{\delta H}\right)_T\,\delta H=C_p\,\delta T-C_p\left(\frac{\delta T}{\delta p}\right)_H\,\delta p$$


texts: Stoichiometric reaction of hydrochloric acid, potassium nitrate, and copper

texts:
I have the following reaction involving these elements:

$\ce{HCl}$ (hydrochloric acid)
$\ce{KNO3}$ (potassium nitrate, a nitrate salt)
$\ce{Cu}$ (copper)

The reaction should produce nitrogen dioxide ($\ce{NO2}$).

The chemical equation should look like this:

$$
\ce{HCl + KNO3 + Cu -> NO2}
$$

But I'm clearly missing something. Can anybody help me equalize and complete this equation?


texts:
I was wondering if anyone can tell me how to number this molecule:

This molecule is derived from azulene by addition of two sulfurs and two oxygens at positions 2, 6, 1, and 5 respectively. I would like to learn the proper procedure of numbering. I tried googling around and reading papers but could not find the correct terminology for this process.


texts: Giving too much energy to an exothermic reaction

texts: What will happen in an exothermic reaction if more than required energy is given? I mean, will it produce even more energy which will be highly dangerous or nothing will happen according to Le Chatelier's principle (as we are trying to carry the reaction in an opposite direction)?


texts: Why do transition metals make colored compounds despite the remaining d orbitals being hybridized?

texts:
I know that transition metals make colored compounds when they forms a bond with a ligand, as the ligand increases the energy level of $\ce{d_{x^2-y^2}}$ and $\ce{d_{z^2}}$ orbital by repelling these orbitals with the lone pair electrons of the ligand. So, the electrons move to the lower energy orbitals and when they absorb energy, they again move to the higher orbitals and that absorbed energy creates color.

Now my question is, $\ce{d_{x^2-y^2}}$ and $\ce{d_{z^2}}$ orbital become hybridized while forming a bond with the ligands and those orbitals get filled up with the lone pair electrons of ligands. Then, how are the electrons excited from lower energy orbitals into the higher energy orbital where there is no place left for them?


texts: How do the differences in the number of protons result in such great differences in elemental properties?

texts: I understand(I think) the mass and density aspect, i.e. the more protons you have, the more the element weighs, also the denser the atom is. What about everything else(color, for example)? Elements are not just masses and densities.


texts: Why are there no cheap diamond equivalents?

texts:
We recently learned in school that diamonds sparkle as the are very optically dense, meaning that it takes longer for light to pass through them, thus meaning that the light totally internally reflects when you look at a diamond, whereas in glass it would pass through at that angle.

Why have we not been able to create a solid material that is so optically dense? Is it because such materials are rare, expensive or hard to produce, or because no-one has looked into it?


texts: no positive $+$ or $-$ or negative label for $\pi$ orbitals

texts:
I want to ask a question about the symmetry for $\pi$ orbitals.

We were learning today about the deduction of an MO diagram for a typical $\ce{M-M}$ system with $\ce{D_{\infty h}}$ and I was confused on the labelling of the $\pi$ orbitals.

When labelling the $\ce{dz^2}$ orbitals, the following checklist was produced:

  orbitals along the bond $\rightarrow$ $\sigma$

  symmetry change through $i$ $\rightarrow$ g

  no phase change for $\sigma_{v}$ $\rightarrow$ +

  overall symmetry $\sigma_{g}^+$

but when we were labelling the $\ce{d_{yz}}$ and $\ce{d_{xz}}$ orbitals, the following information was given, without further explanation:

  no $+$ or $-$ label for $\pi$ orbitals

I worked out that the $+$ or $-$ relates to how the phase changes after reflection in the $\sigma _{v}$ but still couldn't work out why I can't apply the signs to the $\pi$ MOs.

Why is there no $+$ or $-$ notation for these $\pi$ MO's?


texts: Earlier I thought that $\ce{SO3^{2-}}$ (sulfite) is an ion with -2 charge but today I read on internet $\ce{SO3}$ (sulfur trioxide) is a molecule with no charge. How can this be possible? Please explain knowing that I am only a student of 10th standard (use normal chemistry concepts as far as possible).


texts:
How many atoms of Lithium are there in 14.3 grams of Lithium Fluoride?
I can't seem to single out how many atoms of Lithium are in lithium fluoride.

I know that the first step is to convert 14.3 grams to moles, so 14.3 multiplied by the molar mass of LiF divided by 1 is 0.55 moles. But where do I go after this? Do I just multiply 0.55 by Avogadro's number?


texts: Finding order of acidic strength for given compounds

texts:
The decreasing order of acid strength of the following compounds:
The given compounds are
Water ($\ce{H2O}$)
Ammonia ($\ce{NH3}$)
Acetylene ($\ce{C2H2}$)
Triphenyl system ($\ce{Ph3CH}$)
a) $\ce{NH3}$ > $\ce{Ph3CH}$ > $\ce{C2H2}$ > $\ce{H2O}$
b) $\ce{H2O}$ > $\ce{C2H2}$ > $\ce{Ph3CH}$ > $\ce{NH3}$
c) $\ce{C2H2}$ > $\ce{H2O}$ > $\ce{Ph3CH}$  > $\ce{NH3}$
d) $\ce{Ph3CH}$ > $\ce{C2H2}$ > $\ce{H2O}$ > $\ce{NH3}$

I gave the answer to be $\ce{Ph3CH}$ > Acetylene > Water > $\ce{NH3}$. Here I have marked the triphenyl system as the most acidic because it has resonance stabilization involved and $\ce{NH3}$ as the least acidic because it has basic nature. Using these two facts I have marked the answer as above however it was wrong. What is the correct order and why?


texts: Is there a sixth type of d-orbitals with index 2z²-x²-y²?

texts:
There are 5 types of d-orbitals: $\mathrm{d}_{xy}$, $\mathrm{d}_{zx}$, $\mathrm{d}_{yz}$, $\mathrm{d}_{x^2-y^2}$, and $\mathrm{d}_{z^2}$.

I encountered a question which asked about the various d-orbitals, but I came across one that I'd never heard of before: $\mathrm{d}_{2z^2-x^2-y^2}$.
the answer key says that it is a d-orbital.

How is that possible? Is it sixth d-orbital?


texts:
Why is it that sometimes a polyatomic ion's Lewis structure is adjusted to remove the formal charge on the central ion, but sometimes it is not?

For example, in the $\ce{I3-}$ ion (triiodide), the Lewis structure is the following:

This gives a single formal negative charge to the central iodine. In my textbook, it says to remove formal charges from the central atom whenever possible, so couldn't we form a double bond with one iodine and therefore move the formal charge off of the central atom like this?

Comparatively, in $\ce{IO4-}$ (periodate), the Lewis structure is:

There, the single formal negative charge is on one of the oxygens instead of on the central ion, making it a resonance structure.

So basically what I'm asking is why is there a formal charge on the triiodide ion's central atom but not on other ions' central atoms? Like why is it okay that the triiodide ion has a formal charge on the central atom when it could be moved off to create a resonance structure, such as in $\ce{IO4-}$?


texts: How does cross-conjugation destabilizes a molecule?

texts:
Wikipedia article on ortho effect suggests that o-toluic acid is more acidic than benzoic acid. This fact is rationalized by suggesting that steric effect causes COOH group to "twist" out of the plane and which increases it's acidity as it inhibits "cross-conjugation"that it was previously taking part in.
My instructor told me that cross-conjugation is two parallel conjugated sets of atom both terminating on a common atom. He says this parallel character of such conjugation makes conjugation on common atom less effective.
My question is -

How accurate is it to point out cross conjugation as the reason for acidity of o-toluic acid ?

How correct is the explanation of cross conjugation by my instructor?

Edit #1
There are some valid concern raised by Alchimista. It seems like I have not made my question clear to understand. I would rephrase it a bit ->
I am not advocating the usage of cross conjugation to explain acidity of o-toulic acid. But merely seeking clarification for its usage to explain acidity of o-toluic acid by the wikipedia article(linked here for convenience -https://en.wikipedia.org/wiki/Ortho_effect#General_explanation_for_first_ortho_effect). To rephrase the question, Wikipedia article states that cross conjugation "destabilizes" conjugate base of benzoic acid but never justifies the statement.
My main concern is not the justification for acidity of o-toluic acid as there are plenty of answers here on that(Link->https://chemistry.stackexchange.com/questions/7683/ortho-effect-in-substituted-aromatic-acids-and-bases). What I want to know is, if cross conjugation destabilizes benzoic acid as mentioned in the article and if yes then how?


texts: Formation of (Gamma) Methylparaconic acid

texts:
I came across this question recently,

I tried to devise a mechanism but I'm struck here,
My try -

Moreover, I think my mechanism is somewhat inefficient because of formation of some byproducts, which we don't want.

In short in my mechanism,

First we convert succinic acid to its ester (by esterification using ethanol).

Then, we use this ester to react with acetaldehyde in basic medium (dilute NaOH), intramolecular magic occurs to yield an ESTER of the desired product.

Now, here's where i'm struck, how do I convert ester of the desired product into acid, Can I do Hydrolysis, but I think then the ring might get cleaved!

Moreover, I think during this reaction, some acetaldehyde may undergo self condensation to yield a byproduct, this may be true for ester of succinic acid.

Any help will be appreciated!


texts:
From what I understand:

*oxidation numbers: are the "act" of electrons moving

while

*charge: is what the atom "wants" to do with its electrons.

-

Can anyone please clear up the distinction between the two and when its appropriate to use one, the other, or both at the same time?

-

Is it that charge is only used for ions?


texts: How do I interpret GAMESS thermochemistry output?

texts:
In GAMESS's thermochemistry output, which numbers mean what?
The gaussian docs have a nice description of how to use thermochemistry data, but for gaussian's output. This appears to be different, eg, it mentions thermal corrections to energy, enthalpy, and Gibbs free energy, but GAMESS outputs only one, vibrational, thermal correction.

Example output:

 USING IDEAL GAS, RIGID ROTOR, HARMONIC NORMAL MODE APPROXIMATIONS.
 P=  1.01325E+05 PASCAL.
 ALL FREQUENCIES ARE SCALED BY   1.00000
 THE MOMENTS OF INERTIA ARE (IN AMU*BOHR**2)
              0.00000            35.04363            35.04363
 THE ROTATIONAL SYMMETRY NUMBER IS  2.0
 THE ROTATIONAL CONSTANTS ARE (IN GHZ)
      0.00000    51.45266    51.45266
      6 -      6 VIBRATIONAL MODES ARE USED IN THERMOCHEMISTRY.
 THE HARMONIC ZERO POINT ENERGY IS (SCALED BY   1.000)
        0.000110 HARTREE/MOLECULE       24.044128 CM**-1/MOLECULE
        0.068746 KCAL/MOL                0.287632 KJ/MOL

               Q               LN Q
 ELEC.     1.00000E+00       0.000000
 TRANS.    1.12480E+05      11.630533
 ROT.      6.03147E+01       4.099576
 VIB.      4.82855E+00       1.574546
 TOT.      3.27579E+07      17.304656

              E         H         G         CV        CP        S
           KJ/MOL    KJ/MOL    KJ/MOL   J/MOL-K   J/MOL-K   J/MOL-K
 ELEC.      0.000     0.000     0.000     0.000     0.000     0.000
 TRANS.     3.718     6.197   -28.831    12.472    20.786   117.487
 ROT.       2.479     2.479   -10.163     8.314     8.314    42.400
 VIB.       2.490     2.490    -3.616     8.277     8.277    20.478
 TOTAL      8.687    11.166   -42.610    29.063    37.378   180.365
 VIB. THERMAL CORRECTION E(T)-E(0) = H(T)-H(0) =      2202.424 J/MOL

              E         H         G         CV        CP        S
         KCAL/MOL  KCAL/MOL  KCAL/MOL CAL/MOL-K CAL/MOL-K CAL/MOL-K
 ELEC.      0.000     0.000     0.000     0.000     0.000     0.000
 TRANS.     0.889     1.481    -6.891     2.981     4.968    28.080
 ROT.       0.592     0.592    -2.429     1.987     1.987    10.134
 VIB.       0.595     0.595    -0.864     1.978     1.978     4.894
 TOTAL      2.076     2.669   -10.184     6.946     8.933    43.108
 VIB. THERMAL CORRECTION E(T)-E(0) = H(T)-H(0) =       526.392 CAL/MOL


texts: Question about null space balancing method

texts:
I'm trying to use the null space method to balance the following equation:
.
I obtained the following composition matrix:
$$\begin{bmatrix}
3 & 8 & 1 & 12 & 4 & 2 \\
1 & 0 & 0 & 1 & 0 & 0 \\
4 & 4 & 3 & 40 & 3 & 1 \\
0 & 2 & 1 & 3 & 1 & 0 \\
0 & 1 & 0 & 12 & 0 & 0
\end{bmatrix}$$
where rows are in order H P O N Mo. I take the rref of this matrix, and augment it with one row of zeroes except the last element is 1. Taking the inverse of that matrix, I get $$\begin{bmatrix}
\frac{1}{51} & \frac{4}{17} & \frac{35}{51} & -\frac{1}{51} & -\frac{56}{51} & 1\\
\end{bmatrix}.$$
After scaling the elements by 51 I would get the end result of coefficients: 1, 12, 35, 1, 56, 51 which does not at all balance the equation. A correct solution would be 1, 12, 21, 1, 21, 12.
I have used the exact same steps to balance other equations. What am I doing wrong?


texts:
I'm trying to find the R/S for the carbon marked with the asterisk. As I branched out to from the asterisk carbon to the red carbons, the methyl group has the 3rd priority (with the hidden hydrogen 4th). Here comes the confusion. In order to find the first point of difference for the two carbons, for one of the carbon, I can simply move outwards to the next green carbon (C, C, H). But for the other carbon, there are two paths I can take, one which gives (C, H, H) and the other (C, C, H). Now, which path should I take?

Assuming I take the path that gives me the (C, C, H) carbon. This gives me a tie. Again, I have two paths to take (indicated by the green arrow). Which path should I take? If I choose to go 'down', the two arrow clash at a single carbon.

I have consulted numerous textbooks but none of them seem to even surface this as an issue. In general, if there are multiply paths, which path should one take?

Extension of question: In a scenario that there are two carbon, C1 and C2 that 'ties', and it so happens that each of the two carbons has 'two paths' to take: C1 with path 1 and path 2, and C2 with path 3 and path 4. What happens if the priority of taking the different paths is not clear. Eg. Priority when taking path 1 is higher than the path taken by path 3, but path 2 has a lower priority then when taking path 4?


texts: What's the pKa (range) of a carbonyl functional group?

texts: Why is a $\mathrm pK_\mathrm a$ value for carbonyls never mentioned anywhere in textbooks I've use while other functional groups have these values?


texts: Fitting parameters of Lennard-Jones potential to properties of real materials

texts:
I'm using the Lennard-Jones potential for some (very simple) protein docking simulation* and couldn't find parameters for different materials (like $\ce{C}$, $\ce{N}$, $\ce{O}$, …). Does it even make sense to differentiate between different materials when using a crude approximation like the Lennard-Jones potential?

* the potential function for each configuration of the two molecules is the sum over all pairwise energies, for which I only consider the van der Waals term by using the LJ-potential


texts: Still taught to reverse oxidation half cells in electrochemistry?

texts:
In a question, Oxidation of metals/halogens by oxygen gas in acidic aqueous solution, there was a point made that reduction half-cells should not be reversed.

I was taught ($\approx 1970$) in the following manner. Given the reduction half cells:

  $$
\begin{align}
\ce{O2(g) + 4 H+(aq) + 4 e- &→ 2 H2O(l)} &\quad E^\circ &= \pu{+1.23 V} \\
\ce{Ag+ + e- &→ Ag(s)} &\quad E^\circ &= \pu{+0.799 V} \\
\ce{Br2(l) + 2 e- &→ 2 Br-(aq)} &\quad E^\circ &= \pu{+1.065 V}
\end{align}
$$

To get the the standard oxidation potentials you reverse the products and reactants and you must also flip the sign of the reaction. So:

  $$
\begin{align}
\ce{Ag(s) &→ Ag+ + e-  } &\quad E^\circ &= \pu{-0.799 V} \\
\ce{2 Br-(aq) &→ Br2(l) + 2 e- } &\quad E^\circ &= \pu{-1.065 V}
\end{align}
$$

Now you can write a balanced chemical reaction as such:

  $$
\begin{align}
\ce{O2(g) + 4 H+(aq) + 4 e- &→ 2 H2O(l)} &\quad E^\circ &= \pu{+1.23 V} \\
\ce{4Ag(s) &→ 4Ag+ + 4e-  } &\quad E^\circ &= \pu{-0.799 V} \\
\ce{O2(g) + 4 H+(aq) + 4 Ag(s)&→ 4Ag+ + 2 H2O(l)} &\quad E_\text{Total}^\circ &= \pu{+1.23 - 0.799 = +0.43 V}
\end{align}
$$

and to get the cell potential the two half cells are added, one being positive and the other negative. If the EMF is positive the forward reaction is spontaneous, if negative the reverse reaction is spontaneous.

Is flipping the reduction reaction not the standard method taught these days to balance redox reactions?


texts: CO2 IR extinction coefficients near the 15 micrometer band

texts:
I have searched multiple times for a spectrum or a table of the gaseous carbon dioxide Lambert-Beer extinction coefficients in the IR Earth thermal region.

All I found was absorption spectra.

Is this available anywhere with free access? I want it for illustrative/education purposes to make some Excel calculations.


texts: I can understand upto where the ideal gas equation is used to calculate volume of steam. But on trying to find out $ \Delta V$ , i saw that there are no gases on the reactant side so then $P\Delta V=(\Delta n)\times R\times T$ where $\Delta n$ would be $1.39$. Then $\Delta V$ is simply the volume of the steam i.e., $42.51$. But when calculating the work a value of $42.8$ has been used for $\mathrm dV$. Why is that done? Secondly, there seems to be two different values for $\Delta$H. First they have written it to be $\pu{12470.6 cal}$. and then while calculating $\Delta U$ they have used the value of $\pu{13500 calories}$. (That value seems to have come from the given data: If we multiply $9.72\times 10^3$ (molar $\Delta H_{vap}$) by $1.39$ (number of moles) we get something around $13500$). How did those two different values appear? I also want to tell here that this is not a hw question for me, as you can see this is a solved example, so you can consider it as my attempt to understand thermochemistry better


texts:
Recently the quack medicine folks online have been promoting the research of a certain Dr. Gerald Pollack who claims to have discovered a "forth phase of water", and who has recently published a book on the said topic.

Although it's clear that his research is being deliberately misinterpreted, it's not clear to me whether or not his own claims are valid in the first place. Although some papers on the topic were published in peer reviewed journals, it doesn't seem like anyone else in the scientific community has acknowledged or replicated his results.

So, is "EZ-water" a real breakthrough or just the brainchild of a deluded scientist?


texts: Why do not metals gain electrons and non-metals donate electrons?

texts:
My teacher said that metals lose electrons and non-metals gain electrons to complete the noble gas configuration because of stability as it consumes less energy but why are systems having high energy less stable as compared to systems having less energy.
Why do metals and non-metals lose and gain electrons respectively instead of gaining and losing them respectively?


texts: How to calculate the aqueous solubility of CO2 vs Pressure

texts:
I would like to make Na2CO3 react with HCl in a closed fixed volume vessel, and accordingly I'd like to understand how ensuing pressure will affect the equilibrium of my reaction (and to which extent my reaction will affect the level of pressure when equilibrium is reached).

I guess that the link between pressure and the reaction mostly has to do with CO2 retention into the solution, which leads me to want to understand how I can calculate CO2 solubility in water vs pressure.

Would anyone care to explain me how I could calculate CO2 solubility vs pressure? And tell me if there's anything big I am missing other than CO2 solubility?


texts: Why don't substances have a condensation point?

texts: All substances have a freezing point at which they transition from a liquid to a solid. They all also have a melting point at which they transition from a solid to a liquid. However, as far as I can tell a substance only has a boiling point at which it transitions from a liquid into a gas. There is no analogous concept of a "condensation point" at which a gas transitions into a liquid. Why not?


texts: What is the formally correct notation of t-Bu, i-Pr, p-NO2, n-Bu, a-HCl, etc.?

texts:
In chemical notation, can I safely assume that the notation of

a single lower-case latin character
followed by a hyphen
followed by an Element upper-case latin character (and possibly more characters)

should always be typeset as

italic lower-case character
hyphen  (i.e. never is a bond)
element following characters

This question is regarding the further improvement of mhchem.

I know that not all of them stand for the same concept, but I assume they share the same typographical representation. Beware, I am no chemist. And because I don't know the name of these notations, I could not find them in the colored IUPAC books.

The notation is quite rare. There were only 21 usages in 43k \ce calls extracted from chemistry.SE:

(p-NO2Ph)_2CO
t-BuO-
i-Pr
t-Bu
R=i-Pr
n-BuNH2
(c-Hex)2BCl

a-HCl  // should this be \alpha?

1s-H  // what is this?


texts: Entropy is a measure of unavailable energy?

texts:
I came across a statement in my text book which said that entropy is a measure of unavailable energy.

What does this statement signify?


texts: Why does basic peroxide react via conjugate addition rather than through direct addition?

texts:
The following reaction occurs:

The $\ce{HOO^{-}}$ ion reacts as a nucleophile at carbon number three and consequently the reaction is conjugate addition. However, Why would a peroxide not react through direct addition. I know that if the double bond wasn't there it would attack the carbonyl directly and then a rearrangement would occur (Baeyer-Villiger reaction: http://en.wikipedia.org/wiki/Baeyer%E2%80%93Villiger_oxidation). Why must it react at the alkene?


texts:
I got interested in Chemical Reaction Theory by studying the lecture notes of Feinberg and related papers for my bachelor thesis and want to dive deeper into that subject.

Are there any books you would recommend for doing so? I would really appreciate it. I'm looking for something which emphasizes the mathematical aspects but also gives good actual chemistry examples or references.

So far I found a book by Peter Érdi & Janos Tóth from 1989 called "Mathematical Models of Chemical Reactions: Theory and Applications of Deterministic and Stochastic Models", which does just that. However I fear it is a little outdated as it seems there has been quite some progress in that field recently. So maybe there isn't even a book out yet as the theory seems relatively fragmented.

Do you know more?


texts: How does addition of AgCl affect concentration of iodide in KI solution?

texts:
In a mixture of $\ce{AgCl(s)}$ and initial $\pu{0.10 M}$ $\ce{KI}$, what is the $[\ce{I-}]$ after the reaction proceeds?
Disclaimer: This is not a graded assignment, but rather a problem I'm trying to figure out for practice purposes from my textbook.


texts: What effect does the dye color have on the kinetics of a commercial lightstick?

texts:
According to thoughtco:

If fluorescent dyes weren't put in glow sticks, you wouldn't see any light at all. This is because the energy produced is usually invisible ultraviolet light. Fluorescent dyes may be added to light sticks to release colored light.

The dyes all have there own unique chemical structure, but how do these chemicals affect the amount of energy released in the chemical reaction? I am planning to do an investigation on the activation of energy of a lightstick, and I am wondering if the colors have anything to do with the reaction rate.


texts:
The hydrolysis of Group-15 tetrahalides gives us their hydroxides via a $\ce{S_{N^2}}$ mechanism:
$$\ce{PCl3 + 3H2O -> H3PO3 + 3HCl}$$
Nitrogen Trichloride, however, yields a different set of products, not forming the trihydroxide as expected.
$$\ce{NCl3 + 3H2O -> NH3 + 3HOCl}$$

A little bit of research led me to this exact same question (with 2 unsatisfactory answers) and this article, which claims that it exists, but I cannot read it. Why does $\ce{N(OH)3}$ not exist?

Another thought along similar lines is the existence of gem-diols in general, which are quite unstable, as well as $\ce{C(OH)4}$, which does not seem to exist as well. Is this an abnormal property of period 2 elements? All the other elements in group 14 and 15 form stable hydroxides whereas the first members do not seem to do so.


texts: What is the difference between an element and an atom?

texts:
First, I would like to quote sentences from a book introducing elements and atoms:

An element is a fundamental (pure) form of matter that cannot be broken down to a simpler form.
Elements are made up of particles called atoms. An atom is the smallest unit of any element [...]

The first quote states that element cannot be broken down to a simpler form, but the second quote says elements are formed by atoms, which means element can be split into a simpler form (atoms)?
The difference between atom and element confuses me.


texts: Do reverse reactions occur in combustion?

texts:
I am currently reading a textbook on combustion. They assume that all reactions go to completion, such that post combustion only unburned fuel/air and actual products remain.

Assuming that combustion is lean or perfect (no fuel left unburned) and not neglecting dissociation effects, can reverse reaction actually occur to reform fuel at equilibrium? In other words, is the equilibrium constant infinity in real life?


texts:
What is the dipole moment of p-dibromobenzene?

I know that p-dichlorobenzene has zero dipole moment, but my teacher said that this is not the case for bromine. I am still confused and feel its dipole moment as zero. My teacher said that it does have some dipole moment (supported through experimental data).


texts: Looking for a pressure phase diagram of selenium at large ranges of pressure and temperature

texts:
I'm doing undergraduate research and our group is having a lot of difficulty finding a comprehensive pressure phase diagram or phase table for selenium (including most known packing geometries that are known at extremely high pressures).

I figured I may ask here as we've spend a while searching and haven't turned up so much as a good lead for where this information may be documented. Furthermore, we'd like to know where to look from now on to find information like this (such as a similar chart for sulfur? Albeit we haven't spent as much time looking for this as it's not of our particular research interest).


texts:
Which is a stronger Lewis Acid $\ce{AlCl_3}$ or $\ce{SiCl_4}$?

I am confused as in $\ce{AlCl_3}$ , Al has an incomplete octet so it must be a stronger Lewis acid as compared to $\ce{SiCl_4}$, but the answer is just opposite.


texts:
I have already read Is adsorption exothermic, and if so, why?  but it didn't answered my query.

To illustrate, let's take a hypothetical vacuum space. In that space, there is a solid and a gas, the gas is getting adsorbed over the solid. In that case, if we'll use momentum conservation, we'll get that the net kinetic energy of system has increased due to positive work done by the internal forces, but heat exchanged from system to surrounding or vice-versa is zero( as there is no outside interaction present. Therefore, dU>0 as U is sum of kinetic and potential energy of system( note that I haven't made the internal force as due to a field with a assigned potential function). We know dH=dU+PdV for processes in which the pressure outside the system is constant( which we have assumed). Therefore, as dV=0( because I had taken a fixed volume of space), therefore dH>0. But in books it is written dH due to adsorption is negative. Also, if I had assigned a potential function for internal forces, what change would have taken place? Please help me out.


texts: Gallium makes aluminum soft like a wet tissue. Any other metals or alloys that are vulnerable to similar damage?

texts:
Gallium can make aluminum soft and brittle as long as it bypasses the aluminum oxide normally formed on the surface of the aluminum (for example by scratching the surface).

Mercury can weaken aluminum as well.

Are there any other metals or alloys that can be "weakened" by coming in contact with gallium, mercury or any other substance?


texts: Why is gunpowder urinated on in Blood Meridian?

texts:
An interesting section of Blood Meridian (1985) by Cormac McCarthy has the gang of "Indian fighters" surrounded and out of powder, so one of them manages to make it from scratch, making charcoal from wood, saltpeter from bat guano and finding sulfur in a volcanic area, but the final step has them urinating on the mixture and then drying it in the sun. I understand that urine can in fact be a source of nitrates but given that they already had saltpeter, I am puzzled. At the same time, I understand that gunpowder is made wet to form larger grains but this can be done with water (I think), which they had access to.

The gunpowder was first dry so urinating on it was not for safety; it may have been an old-fashioned idea about how to make gunpowder and an unnecessary step or at least water would work as well for "corning" – making granules from it.


texts:
I have a heated mixing reactor, as seen in the figure.
How to set up the energy balance of the heating jacket and the reactor?


texts:
Trying to figure out where peroxide gains 2 electrons and why it has a 2- charge? On the Lewis dot structure it shows each O has 6 electrons and that it has a single bond between the two Oxygen atoms.

To me, each O atom would have 4 electrons and have a double bond between them?


texts: How many ether metamers are possible for C4H10O?

texts:
How many ether metamers are possible for $\ce{C4H10O}?$

According to me, the answer should be 2 but it was given 3. I know 3 structures can be made:

$$\ce{CH3—O—CH2—CH2—CH3}\tag{1}$$

$$\ce{CH3—CH2—O—CH2—CH3}\tag{2}$$

$$\ce{CH3—O—CH(CH3)2}\tag{3}$$

Structure 2 and 3 are metamers, but 1st and 3rd structures are positional isomers(?), then how the answer can be 3?


texts: Reaction of nitrobenzene with potassium ferricyanide

texts:
I came across this question in an exercise book. Can anyone give detailed answer (mechanism) of this reaction?

I am unable to proceed. I thought there maybe some redox reaction involved where $$\ce{Fe^3+ -> Fe^2+}$$ maybe taking place but then nitrobenzene would have to be oxidised. Can someone please help ?


texts: Is there more than one equation for Delta T(reaction)?

texts:
So, I have to find the $\Delta T_{\mathrm{reaction}}$ of a solution for my lab report. Earlier in the lab, it gave the equation as

$\Delta T_{\mathrm{reaction}}=T_{\mathrm{mixture}}+\frac{1}{2}(T_{\mathrm{substance~1}}+T_{\mathrm{substance~2}})$

and all temperatures were at the exact time of mixing found from a linear equation of temperature points on a graph. Now, I have another mixture which is water and a substance and I am supposed to find the $\Delta T_{\mathrm{reaction}}$.

Here's the thing, we don't have the temperature of the substance, only the temp of the water and the solution it made, so how could I go about doing it? I thought about using room temperature since it was a solid substance but it doesn't say anything about that.

The substance is solid $\ce{NaOH}$.


texts: What is the origin of rotational energy barrier in ethane?

texts:
What is the origin of rotational barrier in ethane?
In most organic chemistry textbooks, we learned that it's originated from steric repulsion between two methyl groups. But recently I heard that there also exists other perspective which explains rotation barrier using hyperconjugation model.
So I searched and read many papers about the origin of rotational barrier in ethane and I notice that there are two competing models for explaining this rotation barrier.
But there are no significant conclusions and it still remains controversy "what is the primary energy term in rotation barrier?".
Because many authors suggested many calculations to prove what is mainly contributed to rotation barrier and there results for supporting there argument, but each calculation is based on different approximations and theories. (e.g. NBOs are not optimal --> hyperconjugation energy is overestimated)
So my question is that "Is there no conclusion? What factor mainly contributes to ethane rotation barrier?"


texts:
I have a very very general question:

In DFT functional selection , mostly people speak about the most recent ones. For example my professor always asks: " which DFT Functional did you select ? "  and if I say B3LYP, he says : " No ! that's too old ! " but if I answer: M06 , he says : " hmm ... sounds promising, that's a modern functional ".

I think it is too naive to select functionals just based on their chronologic sequence. I want to ask if there is any good and reliable criteria for functional selection. For example a criteria that says for an alkene with some specific characteristics, go for M06-L and for an alkane with other characteristics, use B97xxx family and so on..

Is there such a criteria ?   I hope this topic can become a good guideline for future reference. !


texts:
I saw that the hydroboration of Limonene (1-Methyl-4-(1-methylethenyl)-cyclohexene) does only happen on the methylethenyl group. Up to now, I wasn't able however to find out why. Generally speaking, a hydroboration can happen on any double bond, so why doesn't it react – at least a bit – with the cyclohexene?

I could argue, that the stereochemistry of the cyclohexene is not as favorable as the one of the methylethenyl group, but I don't see this being the case. On the cyclohexene the methyl group is in the way, where as on the methylethenyl group it is the cyclohexene.


texts: What material is an Inkjet transparent printing film (slide) made of?

texts: I don't mean photographic film/film base but rather the A4/Letter sheets of transparent film that were used in slide projectors during lectures. For example see this.


texts: Why is molality per mass solvent rather than per mass of solution?

texts:
Knowing the moles of substance per mass of solution would be useful. Pour some solution and you'd know how much substance you have. Why is molality defined not this way, but as moles of substance per mass solute instead? It seems like this unit was engineered to have a value similar to molarity rather than to be maximally useful.

Why was molality defined this way? Is there an advantage I'm missing? This measurement seems easy to prepare but more cumbersome to use, and I can't see why that would be an advantage.


texts:
I am a high-school student and I am currently taking a course on chemical kinetics. Towards, what seems, end of the course at highschool level, the Arrhenius equation came in. Now, I'm not sure if what I'm presented is just a general form of Arrhenius equation and there's more to it, or this is it. Well, anyways, one of the things I am being told to learn is the plot between graph of rate constant $k$ vs temperature $T$. $$k=A\mathrm e^{-E_\mathrm a/(RT)}$$
The graph is sort of looks like with increasing $T$, the value of $k$ is skyrocketing (kinda like $y=x^2$ in first quadrant) but if I'm not mistaken, the rate constant $k$ should equal $A$ as temperature tends to infinity. Now I believe there must be some other factor in the equation that is also a function of temperature and is causing the graph to be the way it is. Can someone help me understand the same?
(In case you didn't get, because I am unable to attach an image, the looks like $y=x^2$ instead of $x=y^2$, which basically interrupts my intuition of Temperature on $x$ axis ever approaching infinity. $k$ on $y$ and $T$ on $x$ axis.)


texts: How does polarity of a solvent increase conductance of electrolyte?

texts: My textbook says that electrolyte ionize more in polar solvents and greater is the polarity, larger is the conductance. But if polar solvents (lets take water) causes the formation of shells around electrolyte (say NaCl) then shouldn't effective size increase and hence conductance should decrease? What factor is more dominant? Size/Solvation or Polarity?


texts: IUPAC rules on omission of locants in carboxylic acid

texts:
I have been lately in debate with my teacher as to why did the IUPAC name the compound with the current official IUPAC name of 2-methylpropanoic acid. (CN: isobutyric acid)

My argument is that:

You can't attach a methyl in carbon 1 (because the bonds in carbon 1 will exceed 4)
You can't attach a methyl in carbon 3 (because it will become butanoic acid)
Placing the locant in a substituent with no other constitutional isomers will be useless when to be interpreted, will be a few more characters longer, and will be less pleasant for the eyes end ears (I mean, methylpropanoic acid a bit more pleasant to see and hear than 2-methylpropanoic acid, right?)

To verify my initial assumption, is the name of such compound 2-methylpropanoic acid? If it is, then we may proceed to the real question in the next paragraph.

So, where in the 2013 Blue Book or any updated IUPAC nomenclature guidelines with less complicated wordings in organic chemistry books (this has seniority over the former) can I see that you must not omit the locant in these cases (and why).

Additionally, how can I request to the Union to alter this notion to make it methylpropanoic acid because of the stated reasons? (It's a bit like ethan-1-ol and ethanol.)


texts: Does the structure of water change when a drop of color is added?

texts: If I add a drop of color to water, would it change its structure entirely?


texts: What (simple) household chemicals react with oxygen?

texts:
I'm interested in making a small "preservation chamber" that I can basically use to store objects without the presence of oxygen. I have a resealable stainless steel canister and the plan is pretty much just to put whatever object I want to be preserved inside, together with a chemical/object/thing that absorbs the oxygen from the air inside the can, protecting the other item. I don't have access to anything fancy, so I need something is/can be made from household materials that will react with/contain oxygen.

Here's the catch: It CANNOT be a candle. The container has a plexiglass cover that will melt if it's exposed to the heat of a flame. (I tried it before; it worked, but the plastic almost cracked. I don't dare to do it again.)


texts: Calculating the theoretical Density of a Lithium oxide

texts:
I am trying to calculate the theoretical density for lithium oxide using the following formula
$$\rho= \frac{n^{'}\sum M_c+\sum M_A}{V_c N_{AV}}$$
where

$n^{'}$ is the number of formula units in unit cell

$M_c$ is the sum of atomic weights of all cations in unit cell.

$M_A$ is the sum of atomic weights of all anions within unit cell.

$V_c$ is the unit cell volume

$N_{AV}$ Avogadro's number.

Here is what I have so far:
The structure for lithium oxide is similar to that of FCC so the number of oxygem atoms in this unit cell is $8/8+6/2=4$.

If the unit cell is to have an electrically neutral charge, it must have a total of $8$ lithium anions.
The radius of a oxygen ion with a coordination number of 8 is about $128$pm and for lithium with a coordination number of 4 is about $73$ pm

Since the crystal structure is cubic, the volume is $a^3$ but we need to write $a$ in terms of the radius of the lithium and oxygen ions.

From the structure we can deduce that $a=2\sqrt{2}(r+R)$ (since lithium and oxygen ions touch along the diagonal of a square).

The atomic weight for oxygen is $16$g/mol and the atomic mass for lithium is $6.491$g/mol

$$\rho = \frac{4\times 16+8\times 6.491}{16\sqrt{2}(73\times10^{-10}+128\times10^{-10})^3\ (6.022 \times 10^{23})}=1.05 \text{ g/cm}^3$$

The theoretical density however is closer to $2$ am I missing something?


texts: In a $\mathrm{S_N2}$ reaction, a good nucleophile is considered to be willing to donate electrons. So how do we generalize this fact across the periodic table? Does that mean the more electronegative an atom is, the better the nucleophile?


texts: Properties of the products of styrene chlorification

texts:
Background: When chlorinating styrene with an electrophile two products can be formed by substitution of the benzene ring. That is because the ethylene group is ortho and para directing, from the +M and the ± effect.

Questions: Which is the more stable product? Is the difference in stability related to the steric repulsion between the neighbouring groups in the ortho (1,2) product?

Also does the combination of the aromatic system and the vinyl group have any effect or interaction?


texts: Why are Bohr's formulae for radius and velocity still in use when Heisenberg's uncertainty principle predicts otherwise?

texts:
I learnt about Heisenberg's Uncertainty principle which states that it is not possible to determine the position and momentum of a small particle at the same time.

I was told that it is because in order to be able to see the atoms, we need to make use of radiations, and when we do that, the electrons get excited by those radiations and their position changes. No matter how sophisticated our instruments get, there will be some error. If we use radiation of wavelength
"D" to measure the position of electron, then minimum error in position will be "D"

I didn't really get how would we use radiations to make the atoms visible. Can you please explain that?
This principle clearly states that we cannot be certain about the position and velocity of an electron in an atom, and this must also be true for hydrogen like species. But we still use the formulae given by Bohr's model of atom to find out velocity of electron in nth orbit and its position for hydrogen like species. My teacher says that these formulae give satisfactory results for hydrogen like species. How could that be? Is it because the error is minimum in the case of hydrogen like species?

I am not able to intuitively arrive to an explanation to both these above question.


texts: What are lattice points exactly? For what purpose are they used in solid state chemistry?


texts: Eutectic Phase Diagram of Al-Si Analysis

texts:
Hello,
How can I know from this phase diagram:
1. The composition of the alloy Al-Si that allows precipitation to occure?
2. The range of temperatures where the Al-Si is soluble?
3. The range of temperatures in which precipitation can take place?

Regarding the 1st and 2nd question- I assume that 1.6%wt Si at 557 degrees Celsius is the max solubility limit of this alloy, and that you can't have precipitation if there are higher percentages of Si in the aluminium.
But what about precipitation temperatures? Which conditions allow having precipitation?


texts: Strongest B/L Acid Which Can Exist (Leveling Effect)

texts:
Got a few issues with this:

Here is the Lewis Structure:

As we can see, we have five lone pairs on which a hydrogen proton can land and form the solvent's conjugate acid. Let's consider them left to right.

1) Oxygen lone pair. Adding a hydrogen proton here would make the oxygen have a formal charge of +1. Not exactly ideal for an atom which is so electronegative (even more EN than nitrogen is).

2) sp3 nitrogen. This seems like a good site; it parallels that the ammonia molecule. However, we would be creating a +1 formal charge.

3) sp2 nitrogen. We again would be creating a +1 formal charge.

4) sp nitrogen. And finally, we would be creating a +1 formal charge.

I know that the more s-character, the more able is the hybridized atom able to stabilize negative charge. It isn't called electronegativity for nothing.

That being said, is electronegativity inversely related to electropositivity?

So should the sp nitrogen be least able to stabilize a positive formal charge?

From a Lewis acid/base consideration, we would say that each of these lone pair sites are pretty nucleophilic. So which is the most nucleophilic. We need the strongest electron donating tendency. And that appears to be the sp3 nitrogen because in an sp3 nitrogen, the electrons are further from the nucleus on a time-average basis than the electrons in an sp2 or sp nitrogen.


texts: Where is bifurcation situated on cyclohexane isomerisation PES?

texts:
I am wondering what does PES for cyclohexane isomerisation looks like.

I have two possibilities in mind but each has some kind of vagueness.

1) Starting from boat conformation minimum, followed by transition state, then bifurcation, after that two separate paths leading to halfchair transition states and then chair minima.

I am wondering what this first transition state would look like? I can't seem to imagine conformation that would be different from boat but leading to two further conformational possibilities.

2) Starting form boat conformation minimum, followed by bifurcation, after that two separate paths leading to halfchair transition states and then chair minima.

In this case I am wondering how can bifurcation occur without valley ridge inflection point, and I can't seem to imagine valley ridge inflection point coming from boat minimum.

Aditional question: Does bifurcation occur only when moving on PES from global minimum?

I don't know if I'm missing some major point here, but any help is welcome.

Also any suggestions for some book or article about this?


texts:
How do you melt magnesium without causing its combustion?

I own a foundry capable of reaching temperatures around 2000 °F, and I recently bought some magnesium for melting before doing my research. I cannot find any information on how this process works or if it is even possible.


texts: My daughter is working on a 5th grade science fair experiment.  She soaked white seashells in various drinkable liquids to test the effects of those liquids on teeth (teeth are represented by seashells). We were expecting to find loss of mass and discoloration of the seashells, but we were completely surprised by the reaction observed in the grape juice seashell.  The pictures attached are not great at showing what I mean, but besides the discoloration, the seashell shimmers!  There seem to be crystals all over it. It appears like it is covered in glitter.  Has anybody heard of such chemical reaction?  I researched this, but cannot seem to find anything to explain it to my daughter.  We don't know if the juice simply ate away at the outer protective layer of the seashell to expose the sparkly inside (not likely) or are we looking at a chemical reaction (more likely).


texts: What are the differences between D and L glucopyranose?

texts:
I have just studied the concept of cyclotron in carbohydrates. My reference book used Glucose as an example and began by saying we can find D-glucose or L-glucose:

Depending on what enantiomer we have, we will get opposite chair conformations at cyclisation:

After saying this, my book states that significant differences appear at cyclisation of these enantiomers, and there I just do not follow. The only difference I see is that one is the mirror image of the other. But visually, I see both structures identically equal.

Could someone explain to me what differences I should be observing in both chair conformations, and also, what consequences these have on the molecules' behaviors?


texts: In removing temporary hardness by boiling, $\ce{Mg(HCO3)}$ is converted to $\ce{Mg(OH)2}$ but not $\ce{Mg(CO3)}$. The answer that I found in our coursebook was that it has a higher solubility product, but if its solubility product is higher, then it should be more soluble than $\ce{Mg(CO3)}$. Can you tell me the correct reason?


texts:
I'm slightly confused about NMR.

I seem to remember at school that if a molecule is symmetrical in $\ce{^1H}$ NMR, that only one peak would be shown e.g. propane's terminal $\ce{-CH3}$.

Consider the two molecules shown below.

My professor remarked that both these isomers would show a doublet and triplet in their proton-decoupled $\ce{^31P}$ NMR and I was struggling to work out why.

Consider the molecule on the left as molecule A and the right as molecule B.

My train of logic was that the axial $\ce{Ph3P}$ group on molecule A would be split by each $\ce{P}$ atom that is equatorial, so using the expression $2nI + 1$ where $I = \frac{1}{2}$ so our singlet would be split into a triplet.

Likewise, the equatorial $\ce{Ph3P}$ groups would both only see one axial $\ce{Ph3P}$ group, hence only a singlet would be observed.

I used the same logic on molecule B.

Is this the correct reasoning for the doublet and triplets observed in both molecules?


texts: Kröger-Vink notation for defect reactions

texts:
In the Kröger-Vink notation the effective charge $c$ is marked as superscript while the site location $s$ is marked as subscript on the atom itself $\ce{A}$:

$$\ce{A^{c}_{s}}$$

As far as I have learned the effective charge is the charge difference from the perfect lattice situation. The Wikipedia definition agrees:

  $c$ corresponds to the electronic charge of the species relative to the site that it occupies

While neutral charge (no difference) is usually an $x$, I have always worked with a slash $/$ or similar for one negative charge and a dot $\bullet$ for one positive charge.

I have run across a notation in a teacher's lecture material that says:

$$\ce{Zn^{/}_{Zn}} \quad \text{ and } \quad \ce{Zn^{\bullet}_{Zn}}$$

As I understand it, adding a $\ce{Zn}$ to it's own natural position makes no charge change, so it should be $\ce{Zn^{x}_{Zn}}$. How is the above notation then possible? Does it imply that the $\ce{Zn}$ has lost or gained one electron, respectivily, and thus has a net charge?


texts: Are there any forbidden collisional electronic transitions?

texts:
There are spectroscopy selection rules marking some radiative electronic transitions as forbidden. For example, it is stated that single electron of H atom can not move from S2 to S1, or from P2 to S2 (and vice versa) with photon emission/absorption.

But is this true in the case of collisional (or, more generally, radiationless) transitions? Are there any selection rules and what they are if any?

I found the Wigner spin conservation rule. Are there any more rules?


texts: Hyperconjugation, stability of molecules, and heat of formation

texts:
I recently asked a question about why the heat of formation of organic radicals and positive ions decreases with their size and degree of branching at the radical or ionic site. The user "Buttonwood" made the comment that hyperconjugation is one of the forms stabilising cations and radicals.

This begs two questions:

What is the reasoning behind why hyperconjugation increases the stability of cations and radicals, and therefore decreases the heat of formation? Point 3. of this section of the Wikipedia article for hyperconjugation  says that "the heat of formation of molecules with hyperconjugation are greater than sum of their bond energies and the heats of hydrogenation per double bond are less than the heat of hydrogenation of ethylene."; does this not imply that hyperconjugation increases the heat of formation of molecules?
Why does an increase in stability imply a decrease in heat of formation? To a novice who is ignorant on this subject such as myself, it would intuitively seem that greater stability implies an increase in heat of formation, since the molecule is more "stable" in its current form and therefore it takes more energy to affect changes in its structure?

I would greatly appreciate it if people would please take the time to clarify these points.


texts: Could a magnet pull oxygen out of the air?

texts:
I read that the $\ce{O2}$ molecule is paramagnetic, so I'm wondering: could a strong magnet pull the $\ce{O2}$ to one part of a room – enough to cause breathing problems for the organisms in the room?

(I'm not a professional chemist, though I took some college chemistry.)


texts: The mole is used extensively in chemistry, why not elsewhere?

texts:
In chemistry, the unit "mole" is used in many places, and is an important tool when working with quantities.

I have not seen it used elsewhere--for example, we never count people or TVs with the unit.

What makes the mole so useful in chemistry, and why isn't it used elsewhere?


texts: Calculating collision diameter with viscosity, but not having the mass given

texts:
I've got a homework question i'm stumped on.

  The viscosity of the ethylene gas was measured at $99.8\times10^{-7}\ \mathrm{N\ s\ m^{-2}}$ at $288\ \mathrm K$. Calculate the collision diameter in $\overset{\circ}{\mathrm{A}}$ for this gas molecule.

I started with

$$\eta=\frac{m\overline v}{3\sqrt2\pi d^2} $$

then i said

$$\overline v=\sqrt{\frac{8RT}{\pi M}}$$

Molar mass $M=28.05\ \mathrm{g\ mol^{-1}}$

So my equation looks like

$$\eta=\frac{m}{3\sqrt2\pi d^2}\sqrt{\frac{8RT}{\pi M}} $$

but $m$ is still a variable. What should I do from here? Is there another substitution I can do?

So apparently my confusion about solving this problem, came from a lack of understanding what the $m$ variable was supposed to represent. I had thought that it was the total mass of the system, but it is actually the mass of one molecule.


texts:
O likes to be negative if charged at all. Most metal oxides are of the form $\ce{A^{x+} O^{2-}_{x/2}}$ (where $x$ is the magnitude of the positive charge and $\ce{A}$ is a metal.) Here, despite the $\ce{O}$ preferring covalent bonds it most often forms ionic bonds because of how metals behave and EN difference.

There are some compounds that have $\ce{O^+}$ in them. Hydronium is an example of that. When the O is positively charged the ions form a cation complex which itself is in a complex of ions and so on and so forth. This is why $\ce{H3O+}$ isn't really $\ce{H3O+}$ as individual ions but rather a complex formed from $\ce{H3O+}$ ions spreading the positive charge across all positively charged oxygen atoms.

Is the oxide anion despite being really reactive more stable than the $\ce{O^+}$ ion since in the oxide anion the $\ce{O}$ already has an octet and it is negatively charged which is what $\ce{O}$ prefers?


texts: Why does my sodium acetate look like metalic magma?

texts:
I tried to make sodium acetate.

Ingredients:

Store bought vinegar - 8% acetic acid, water, E150C  (caramel)
Baking soda - $\ce{NaHCO_3}$

Steps:

I first emptied sacks of baking soda to a container
I kept adding vinegar until the resulting fuming was mild
I started heating the solution slowly, I kept adding more vinegar as long as I could see bubbly reaction
I increased heat until all water evaporated. I was left with white-brown chunks of (presumably) sodium acetate and the impurities from vinegar
I kept heating this until it melted into opaque black liquid
I poured the hot molten stuff into ceramic bowl

This is my result:

I might upload better picture tomorrow, when there's more light available.

So, this does not really look as sodium acetate at all. It looks like a volcano. Clearly there's more volcano-ish experiments with vinegar than I thought.

How do I purify this? Is there even any sodium acetate? Could I burn (decompose) it or something?


texts: Why can Grignard's Reagent be stored in ether?

texts: Grignard's Reagent will generate a strong base and nucleophile, $\ce{R-}$. Can this not show nucleophilic substitution at the C atom attached to the O atom of the ether, causing $\ce{RO-}$ to depart as a leaving group? Since $\ce{RO-}$ is a better leaving group than $\ce{R-}$ this reaction should be feasible. Additonally, $\ce{R-}$ is a very good nucleophile.


texts:
To determine the order of one reactant at pseudo concentration of another reactant the plot of $\ln(A_t - A_∞)$ versus $t$ is used.
$A_t$ is absorbance of the intermediate at time $t$.
$A_∞$ is absorbance of intermediate at the end of the reaction (approximately after 24 hours).

Why $A_∞$ is important here?


texts: Which element has larger atomic radius -- beryllium or xenon?

texts:
I say that xenon radius is smaller comparing to beryllium, but my friend says otherwise.

What I think is that xenon is down in periodic table comparing to beryllium (3 periods down) and it's far toward the right (16 groups ahead). So, the nuclear pull dominate (16 by 3 which is very big) and therefore xenon's radius is smaller than beryllium's.

My friends said that xenon is down in periodic table compared to beryllium and hence it's bigger and the nuclear pull effect has only little effect.

So who is right ?


texts: Is there a broader nomenclature convention to explain why the ‘a’ in ‘chlorophyll a’ is italicized?

texts: By convention, the letter that specifies which side chain a chlorophyll molecule contains is italicized: for instance, chlorophyll a. Does this convention stem from any broader principle of chemical nomenclature, or is it more of a quirk unique to chlorophyll?


texts:
I read on the net that phenylalanine gives a negative result with xanthoproteic test and the reason that was given was that the benzene ring is deactivated and hence the extent of nitration is very less.

What I dont understand is that isn't the benzene ring in phenylalanine actually activated through hyperconjugation from the $\ce{CH2}$ group of $\beta$-carbon and hence shouldn't it give positive results with the xanthoproteic test?


texts: Why doesn't the SeO2 oxidation of ketones stop at the hydroxyketone stage?

texts:
When $\ce{SeO2}$ is used to oxidise aldehydes and ketones, $\ce{SeO2}$ becomes hydrated in water, and the active reagent is selenous acid $\ce{H2SeO3}$ which oxidizes aldehydes and ketones to furnish 1,2-dicarbonyl compounds such as 9 in the scheme below.1 The α-hydroxyketone 10 is not observed. Why is that so?

1 Sharpless, K. B.; Gordon, K. M. Selenium dioxide oxidation of ketones and aldehydes. Evidence for the intermediacy of .beta.-ketoseleninic acids. J. Am. Chem. Soc. 1976, 98 (1), 300–301. DOI:10.1021/ja00417a083


texts:
According to the fine structure formula for exact energies (Sommerfield formula)
$$E_{jn} = -m_\mathrm{e}c^2\left[1 - \left(1 + \left[\frac{\alpha}{n - j - \frac 1 2 + \sqrt{\left(j + \frac 1 2\right)^2 - \alpha^2}}\right]^2\right)^{-1/2}\right],$$
the energy depends only on $n$ and the absolute value of the total angular momentum $j.$ In the absence of magnetic field, there are two spectral lines for the sodium atom $\mathrm{D1}$ and $\mathrm{D2}.$ I am confused about the origin of the $\mathrm{D1}$ line since it corresponds to a transition $3P_{1/2}\rightarrow 3S_{1/2},$ both states have total angular momentum $j=1/2.$ However, these should be degenerate according to Dirac theory.
What am I missing here? Is the $\mathrm{D1}$ line purely due to electron-electron repulsion inside the sodium atom?


texts: Solubility of Gold in low concentrations

texts:
When preparing ICP-MS calibration standards for trace metal (~100 ppt) analysis, the values for Gold do not remain stable for more than a day. The standards are prepared using commercially available 10 ppm solutions in Nitric Acid with traces of HF.

A known amount of the Gold standard is added to 2 mL of 70% ultra pure Nitric Acid, an Indium Internal Standard and diluted to a pre-determined volume with ultra pure deionized water. The samples being analyzed are in 49% hydrofluoric acid to which has been added 2 mL of 70% ultra pure Nitric Acid, an Indium Internal Standard and diluted with an equal volume of ultra pure deionized water.

Would preparing matrix-matched calibration standards solve this problem?


texts: In a neutralization reaction between a strong acid and weak base, can I assume the weak base is totally ionized?

texts:
Here's a Chemistry question from the infamously terrible Nelson textbook.

  10.0 mL of $\ce{NH3(aq)}$, with a concentration of $\mathrm{5.70\dot\ 10^{-2}}$ mol/L, is titrated to the endpoint (by which I assume they mean equivalence point) with $\mathrm{2.85}$ mL of $\ce{HBr}$ solution. What is the concentration of the $\ce{HBr}$ solution?

The answer they give is $\mathrm{0.200}$ mol/L which assumes that all of the moles of $\ce{NH3}$ reacts with the acid. I am unsure of this because I thought weak bases only ionized partially, and the amount they ionize has to be gleaned from the $\mathrm{K_b}$ table.

Why, if it is at all, correct to assume all of the base reacts?


texts: Is puffing through high pressure release the only way to make puffed cereal from a starch based mix or are there food safe chemical approaches?

texts:
I'm attempting to make puffed cereal at home and I was wondering with a chemical approach if it is possible to achieve the same structure and expansion which for example a puffing gun would be needed. My understanding is that the gelatinization of the starch plays a vital roll in the texture of the final product. My idea was to incorporate air or gas into the cooked gel and then to dehydrate the mixture to achieve a similair result. But I haven't found any resources regarding the behaviour of starch based gels when trying to incorporate air or gas. I know that starch is hygroscopic and that gelatinization allows through the breaking of the hydrogen bonds and heating the incorporation of water into the areas of amylopectin. But how does this gel allow air or gas to be trapped or is it not possible? Is there even a chemical approach to this or can this only be solved by physical approaches (sudden pressure release)?
Edit: Any resources that could point me into the right direction or help me to better understand this topic would also be appreciated as well. I'm new to all of this.


texts: How to find the number of optically active and optically inactive isomers for a spiropentane derivative?

texts:
What will be the number of optically active and inactive isomers 1,2,4,5-tetramethylspiro[2.2]pentane?

The question asked for the difference between number of optically active and optically inactive isomers. When I drew them, I could find 6 optically active, and none optically inactive isomers. So, according to me answer should have been $6-0=6$. But the given answer is 5. Apparently, one optically inactive isomer is possible, but I don't see how.

I am assuming the answer given to be correct. Though, there is very slightest possibility of it being incorrect too, but I don't have any source to confirm, thefore asking on Chemistry SE. :)


texts: Calculating pH in titration of monoprotic weak acid with strong base

texts:
$25.0\:\mathrm{ml}$ of $0.10\:\mathrm{M}$ $\ce{CH3COOH}$ is titrated with $0.10\:\mathrm{M}$ $\ce{NaOH}$. What is the $\mathrm{pH}$ after the addition of $30.0\:\mathrm{ml}$ $\ce{NaOH}$?

In broad strokes, as I understand it, the sodium hydroxide in this case would completely consume the acetic acid, leaving a solution of acetate ions, $\ce{Na+}$ and $\ce{OH-}$.

What makes sense to me then is to figure that the $\mathrm{pH}$ is now dominated by the concentration of hydroxide ions, so the $\mathrm{pH}$ would be given by

$\mathrm{pH} = 14-(-\log([\ce{OH-}])= 11.96$

where $[\ce{OH-}] = \frac{[(30.0 - 25.0) \times 10^{-4}]\:\mathrm{mol}}{(30.0+25.0) \times 10^{-3}\:\mathrm{l}}$

i.e., the remaining moles of hydroxide ($0.0005$) per liter of total volume ($55\:\mathrm{ml}$)

but is this correct? Do I need to take into account the conjugate base’s contribution to deprotonation of water? If so, how is that done?

I’d like to be clever and use the lack of $K_\mathrm{a}$ or related constants in the problem to indicate that I’m on the right track, but that would be giving too much credit to my professor’s design of these questions (and the prior question in this series does give $\mathrm{p}K_\mathrm{a}$ for acetic acid)


texts: Determining the product which is not possible in the reaction

texts:
This is an objective type question I encountered in a objective test.

NBS (N-bromosuccinimide) is used for the allylic substitution of $\ce{Br}$ in a reaction. In this reaction, since the allylic carbon is the carbon adjacent to the carbon having double bonds, I thought that options B), C) and D) all can be the products but not A). However, the answer key gives the answer as D) and I can't understand why it should be?


texts: I understand that dissociation is when something dissolve. I heard this mostly only happen in liquids. But now I heard it can also happen in gases. Is this true? If so, when and why does this happen, and does it only happen to certain gases? I tried to do research but didn't find too much information. The only real information I found was on Wikipedia and it was confusing.


texts:
Recently I came across a question asking for the geometry of the aforementioned molecule.
The answer key claimed the shape as an irregular tetrahedron, but as per my knowledge, it should have been like a see-saw.

What am I missing here?


texts: I added citric acid in my dish washing liquid. It stopped foaming.  Iwant my liquid again to foam. because I prepared 4 litres of liquid. Please let me know how can i get back my liquid foam. please answer immediately.


texts: Calculating rate constant from equilibrium constant

texts:
I'm trying to determine the forward rate for the Haber Process, but can't find the rate constant.
I have the equilibrium constant, but to my knowledge this only gives me the ratio of the rate constnts for the forward and reverse reactions. Is there a way of determining the rate constant for the forward reaction with Kp, ΔG, temperature, pressure and concentrations?
Thank you.


texts: Why is naphthalene less stable than benzene according to per benzene ring?

texts:
Why is benzene more stable than naphthalene according to per benzene ring. Which results in a higher heat of hydrogenation (i.e. energy released on hydrogenation) of benzene than naphthalene according to per benzene ring, i.e. if we hydrogenate only one benzene ring in each. I think it should be opposite.

Both are aromatic in nature both have delocalised electrons but naphthalene has more resonance structures and more delocalisation so overall it must be more stable for a single ring.
May someone help?


texts: How can I go about obtaining the activation enthalpy of a reaction using the Arrhenius Equation experimentally?

texts:
I plan to do a string of experiments on the kinetics of the decomposition of hydrogen peroxide. I’m going to see the effect of catalyst concentration on rate and the effect of varying hydrogen peroxide concentration on rate, which will then allow me to formulate a rate equation for the reaction.

I would also like to calculate the activation enthalpy of the reaction specifically using the Arrhenius Equation $k=A\operatorname{e}^\tfrac{-E_\mathrm{a}}{RT}$. How would I do this? As far as I’m aware I should use varying temperatures in the reaction to get different values of the rate, but I’m not sure.

So what kind of experiment should I do (varying temperature to see the change in rate?)?

What should I do with my results?

Is the value of $E_\mathrm{a}$ obtained from analysing a specific graph that will be drawn up, and if so what graph would this be?


texts: Compact way to regulate 3000psi (200bar) down to 30psi (2bar)?

texts:
This was originally posted on the Lego page, and closed because it's not actually about Lego itself.  I thought I'd give them a chance first, in case someone had done this already and had some application-specific knowledge.  Then my next stop is here, since you guys are probably more familiar with the gear that I'm looking for.

I have this, that I want to power with a HPA, paintball, auxiliary SCUBA, or whatever-someone-decides-to-call-it tank:

I think a 6.1cm diameter, 0.22L or 0.35L tank will fit nicely in place of the 0.5L plastic water bottle.  I can redesign things and move some structure around if I have to, but the overall size is pretty well fixed.
The air inlet is a sports inflator needle pushed into the black hose in the front, with a bicycle pump currently attached to it.  The maximum pressure there is about 35psi (~2.3bar).
I can use a longer hose there if needed too, but that's about as short as it can be.  The straight section with a slight kink is the inflator needle.
So, is there a compact way to regulate the HPA tank from 3000psi (200bar) down to 30psi (2bar) with a schrader-valve type connection at the end?

I see that a fair number of HPA tanks (but not all) come with a factory-attached pre-regulator, that can apparently be adjusted by taking it apart and changing the spring.  But it seems like a stretch to me, to take something that is designed for 3000psi in / 800psi out, and get it all the way down to 30psi out instead.  Maybe it's possible, and if so, that's great!  But it seems like a bit much to me.
It seems more likely to me, to just barely get into the range that a shop air regulator can handle, and use that for the final delivery as well as a complete shutoff.  But there are still adapters to be found, and perhaps some creative folding to make it all fit in the available space.
I also found this, which says it takes 4000psi in and is fully adjustable from 4000psi out to 0psi out.  It looks a bit cumbersome at first glance, compared to the space that it would go in, but no real size reference except for the gauges.  Also, with such a wide range of adjustment, it might be difficult to have it "barely on" and stable at my required 30psi.  Not to mention a rube-goldberg chain of adapters, probably on both the inlet and the outlet sides of it.
Is there an elegant way to get the required 100x drop in pressure, with decent regulation (there's a throttle valve after the final regulator), in the space shown, and with the right connector at the end?  (imitation schrader valve)


texts: How is the bonding in the [Au6C(PPh3)6]2+ cluster explained?

texts: How can carbon form six bonds in such a compound as $\ce{[Au6C(PPh3)6]^2+}?$ I understand how carbon with five bonds can be formed $(\ce{CH5+},$ for instance), but it shouldn't have enough electrons to form six bonds.


texts: Why is polonium tetrafluoride non-existent?

texts:
I learnt that the group 16 elements can form halides, but with the exception that polonium cannot form a tetrahalide with fluorine.
However, I thought that it was possible. This is because the electronegativity difference between polonium and fluorine is very high since polonium is a metal and fluorine is a highly electronegative atom and so should be able to form a salt.
Why is this wrong?


texts:
I may know, but I would like an expert opinion and a possible solution?

I had an ethanol product from molasses, brown sugar and yeast which was clear. I then added (and feel all information is important):
1 vanilla bean
1 cinnamon stick
whole allspice berries
whole black peppercorns
1/2 star anise
1/8 tsp grated nutmeg
3, 2-inch pieces ginger
3-inch strips orange zest

I let that sit for 2 weeks and remained clear. I then poured that solution through a coffee filter into beaker and it remained clear.

Then I took tap water, boiled it and poured it into the bottle with the used spices and let that sit for a day. I then used that water to dilute the ethanol solution to a lower percentage. Again, running it through a coffee filter.

Final product, cloudy.

The only thing I can think of is my water. We get our water from a well so it could be high in mineral content.

Would water be the problem?
And solution to make it clear again?


texts: I recently did an experiment putting alcohol and acetic acid with conc. Sulfuric acid and heating it up, then i recondense the CH3COOC2H5. After that I put in some water and then NaCl solution I see some semi-transparent and red precipitate, can someone explain what it is


texts:
Electrons show wave-particle duality

Particle (atom) containing a wave (electron) on Quora

Atoms contain electrons. We consider atoms as particles but electrons which are inside the atom as waves (50% chances). When we talk about orbits and orbitals, outer electrons, inner electrons, I sub-consciously assume that we are talking
about the particle nature of electron. But this model is true only half of the time. The possibility of the electron being a wave at any time is also 50% . Particle nature and Wave nature are two different things because scientists came up with wave-particle duality. So we cannot talk about outer electrons, inner electrons, degenerate orbitals in the case of wave nature of electrons.Even if we can say inner part of the wave(close to nucleus) and outer part of the wave(away from the nucleus) ,what we are going to do in that case to solve energy, wavelength, position of the electron (in wave form) in an atom (a particle)?


texts: What makes R-MgX a more reactive Grignard reagent than R-Cu?

texts: What makes $\ce{R-MgX}$ a more reactive Grignard reagent than $\ce{R-Cu}$? Has it to do with solvation, bond enthalpy, electronegativity?


texts: Determine the velocity of the O fragment after the dissociation

texts:
A $\ce{SO3}$ molecule is radiated with light with a wavelength of $\pu{193 nm}$, which results in photodissociation.
$\ce{SO3} + \text{photon}(\lambda=\pu{193nm})\ce{-> SO2 + O}$
It is measured that the $\ce{SO2}$ fragment is in the electronic ground state, but in the vibrational excited state where bending is in $v=3$.

Calculate the velocity of the $\ce{O}$ fragment after the dissociation.

I know that:

The $\ce{SO3}$ molecule is at rest before the radiation, and we don't have to look at the rotation.

The dissociation energy is $\pu{5.0 eV}$

The normal vibration frequencies for $\ce{SO2}$ is $\omega_1= \pu{1151 cm^{-1}}$ (sym stretch), $\omega_2= \pu{518 cm^{-1}}$ (bending) and $\omega_3= \pu{1362 cm^{-1}}$ (asym stretch)

My first thought was to approach it like the photoelectric effect where you can determine the velocity of the ejected electron. But I can't seem to figure out how to do it using the dissociation energy and vibrational modes. I hope someone can help me with this?


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I have a clogged pipe in my bathroom so I went to the store to get something to unclog it. Basically there are two types that you can find in my area:

Sodium hydroxide pellets
"Liquid plumber" mixtures. The components for those are mainly surfactants, sodium hydroxide and sodium hypochlorite.

As far as I recall from the water treatment courses I took in college, hypochlorite's oxidizing activity is heavily dependent on pH, as the active form is hypochlorous acid, not the hypochlorite ion. At high pH values the oxidizing activity becomes really low whereas low pH will make it stronger.

Does it make sense to buy a product that mixes a strong base, such as sodium hydroxide, with sodium hypochlorite? Wouldn't it be a waste of money?


texts: C-H Bond Dissociation Energy varies with substitution

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What is the reason behind it?

"Among sp3 hybridized systems, methane has the strongest C-H bond. C-H bonds on primary carbons are stronger than those on secondary carbons, which are stronger than those on tertiary carbons."


texts: Using a calcium metal anode in aqueous solution?

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In school, I am doing an electrochemistry lab in which I need to create a galvanic cell battery with the highest voltage possible using two beakers, a salt bridge, and electrodes.

To maximize the voltage, I have decided to use calcium metal for the oxidation half-reaction and a sodium persulfate solution for the reduction half-reaction. I understand that for the reduction reaction in the cathode, I would merely dissolve the persulfate in water. However, calcium metal reacts with water, so how would I go about connecting the calcium to the salt bridge (which is a requirement in the lab)?

The salt bridge has an aqueous salt and my chemistry teacher said that the redox reaction that would result from letting the calcium touch the water would prevent it from being effective in the battery. Also, my class vaguely touched on the Nernst equation, but are there any other revisions I can make to the battery to increase the voltage, either by adding $\ce{OH-}$, $\ce{H+}$, or increasing/decreasing concentration of the persulfate solution?


texts: How does an atom's electronegativity change as it becomes more negatively charged?

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I had a question about the carbon atom specifically. Carbon has 4 valence electrons, with electronegativity 2.55 (approx). If I was to fire electrons at the carbon atom, each carbon will occupy up to 4 electrons (8 in total in outer shell) to complete the octet. Now, let's assume that this happens slowly such that we have time to observe each carbon atom as it changes its charge, from $\ce{C-, C^2-, C^3-, C^4-}$

My question is: how would the electronegativity of the carbon ions will vary from each other? Will it increase as electrons are added and becomes zero after obtaining full octet? What would happen upon taking away electrons from carbons through help of highly electronegative elements?


texts: Coefficient in front of molecules in a chemical equation

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In a chemical equation representing a chemical reaction what do the numbers in front of the molecules of compound and elements indicate? Do they signify number of molecules or moles or volume?

Example : $$\ce{ 2H_2 +O_2  -> 2H_2O}$$

Here does the "2" before $\ce{H2}$ and $\ce{H2O}$ indicate number of molecules or moles or volume?
In a particular chapter in my textbook it was written that they indicate number of molecules(atoms) but in a later chapter the numbers were being treated as if they are number of moles or volume.


texts: how can I predict the rate of water ions precipitation on a surface?

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Consider a titanium pot that contains 1kg water with the following ions:

$[Ca^{2+}]=22000$ ppm, $[Mg^{2+}]=1500$ ppm,$[Sr^{2+}]=791$ ppm,$[Na^{1+}]=48000$ ppm,$[Cl^{1-}]=120000$ ppm,$[SO_4^{2-}]=22000$ ppm

And predict the rate of component precipitation like CaSO4, CaCl2 and ... on the inside wall of the titanium surface at the 20 C, 30C, 50C.

Calculate the rate of component precipitation in water not only on the titanium wall.

After that, calculate the final steady-state ion contents that exists in the water.


texts: Salicylic acid - polarity and solubility

texts: Really confused about this, since there is carbon and two other types of atoms: should be polar, right? However, some people online say it is non-polar. Also, is it soluble in water?


texts: If a bucket of seawater is put into a centrifuge, would the spinning force be enough to move the salt in the solution toward the outer wall of that centrifuge?