texts: Strong or weak force between protons and neutrons?

texts:
I had learned that what keeps the protons and neutrons bound is the strong force and the weak force has to do with radioactive decay. but today I read an article from Science Daily that contradicts this. Here is the quote:
“Protons and neutrons are made of smaller particles called quarks that are bound together by the strong interaction, which is one of the four known forces of nature: strong force, electromagnetism, weak force and gravity. The weak force exists in the tiny distance within and between protons and neutrons; the strong interaction confines quarks in neutrons and protons.”
Can this be clarified by the community? Thanks!


texts: Why does entropy increase when the difference in temperatures is decreased?

texts:
From the Wikipedia article about Entropy (Source view via The Internet Archive):

In irreversible heat transfer, heat energy is irreversibly transferred from the higher temperature system to the lower temperature system, and the combined entropy of the systems increases.

If entropy were a measure of disorder, or randomness, or the amount of information needed to describe the microstates of a system, then it seems that when the difference in temperatures is high, entropy should be high. A temperature gradient in the systems is a form of ‘disorder’ hence should be a sign of higher entropy.
So why does entropy increase after the heat transfer, as the combined system approaches a uniform temperature? It seems to me like a state with less randomness or disorder.


texts: Stability of a carbocation, in part of camphor synthesis

texts:
Can someone explain to me why there is a rearrangement reaction of carbocation 1 to carbocation 2? To me the second carbocation appears to be less stable than the first because it is less substituted.

Thank you in advance


texts:
In a polystyrene cup calorimeter, $4.3\ \mathrm g$ of ammonium nitrate, $\ce{NH4NO}$, was added to $60.0\ \mathrm g$ of water and stirred to dissolve the solid completely. The initial temperature dropped from $22.0\ \mathrm{^\circ C}$ to a final temperature of $16.9\ \mathrm{^\circ C}$.
Calculate the enthalpy change in $\mathrm{kJ\ mol^{-1}}$ for this dissolution process, as represented by the chemical equation below:
$$\ce{NH4NO3(s) -> NH4NO3(aq)}$$
Assume that the calorimeter does not absorb any heat, that the density of the solution is the same as that of water $(1\ \mathrm{g\ ml^{-1}})$ and that the specific heat capacity of the solution is also the same as that of water $(4.18\ \mathrm{J\ g^{-1}\ K^{-1}})$.
$$M(\ce{NH4NO3})=80.05\ \mathrm{g\ mol^{-1}}$$

My attempt:
$$Q=mcT = 64.3\ \mathrm g \times 4.18\ \mathrm{J\ g^{-1}\ K^{-1}} \times -5.1\ \mathrm K = -1.37\ \mathrm{kJ}$$
But this doesn't seem right because I haven't used all the information given in the question, such as the molar mass of ammonium nitrate.


texts: Decarboxylation of 2‐cyano‐2‐cyclohexylideneacetic acid

texts:
2‐Cyano‐2‐cyclohexylideneacetic acid (1) is heated and $\ce{CO2}$ is lost:
[
Why is this not formed?

In other words, why do π-electrons move into the ring?


texts:
Oxygen is a small size atom known to make only two bonds (sigma bonds), it may also form coordination bonds {oxygen ion (2-) uses its outer shell in coordination (only s & p orbitals) that theoretically form a maximum of four bonds}.
In the decavanadate ion cluster (V10O28)6-, there are oxygen atoms with one bond, two bonds, three bonds and six bonds. Can anyone explain how oxygen can bridges 3 and 6 atoms in this structure


texts: Why does N-phenylhydroxylamine give Fehling's test?

texts:
I have studied that Fehling's test is given by aldehydes and alpha hydroxy ketones. I read in a book that it is also given by phenylhydroxylamine converting it to nitrosobenzene.
Does it gives the test as it has an alpha hydrogen or any other reason? Are there any more exceptions like this?


texts: Mathematical Expression for Limiting Molar Conductivity

texts:
I have been fiddling around with the theory of electrolytes, specifically molar conductivity, and ways of calculating limiting molar conductivity $\Lambda^0$.
I was able to come up with the following expression:
$$\Lambda^0 = \frac{\lambda}{mT}|z_+z_-|\, ,$$
where $m$ – mass of a single ion in solution (in $\pu{kg}$); $T$ – absolute temperature (in $\pu{K}$); $z_i$ – charge of a single ion (positive or negative); $\lambda$ is a constant given by
$$\lambda = \frac{N_\mathrm{A}he^2}{k_\mathrm{B}} = \frac{hF^2}{R} = \pu{7.42e-25 S kg m2 K mol-1}\, .$$
The above formula works for some chemical species, but fails for others.
Using my formula, $\Lambda^0$ for $\ce{HCl}$ at $\pu{298 K}$ ($m = \pu{6.06e-26 kg}$) is $\pu{0.0411 S m2 mol-1}$, which agrees well with the experimental value of $\pu{0.0426 S m2 mol-1}$.
Constants in the expression for $\lambda$ should be familiar to anyone who studies physical chemistry.
Have I found a new (easier!) approach of calculating $\Lambda^0$, or is my discovery just a coincidence (or, has this already been discovered)?
If it is indeed novel, any ideas on how to get a more accurate formula?
EDIT (in response to closed post): Theory suggests that the above equation should also depend on the (dimensionless) dielectric constant (relative permittivity) of water (when dealing with aqueous solutions) which is 78.4 at 298 K, and this is also expressed in the comments.


texts: What is the precipitate of aqueous copper (II) and polysulfides?

texts:
So if you heat up a piece of sodium engulfed in a large excess of sulfur, what you would get (from what I've read) is sodium polysulfide $\ce{NaS_n}$. But how large can $n$ get? If you left sodium polysulfide in molten sulfur, would you increase $n$?

If you tried to dissolve the sulfur-polysulfide mixture in water and filtered it, I assume you would get a basic aqueous hydrogen polysulfide solution. If you then poured in a solution of copper sulfate, besides $\ce{Cu(OH)2}$, would $\ce{CuS_n}$ also precipitate out with an arbitrarily large $n$, or would the larger polysulfides break up into elemental sulfur and lower polysulfides first and precipitate out $\ce{CuS_n}$ with a more discrete number $n$?

And if you acidified the polysulfide solution until you have only $\ce{HS-}$, $\ce{H2S}$ and suspended sulfur in the solution, from which you could get the precipitate $\ce{CuS}$, would you be able to calculate the initial mass of sodium used from the mass of copper sulfide?


texts:
I don't know why my solutions manual says these are enantiomers:

The Fisher projections I drew suggest that these are identical compounds.


texts: Disubstituted cyclic alcohols - looking for IUPAC rule

texts:
Given a simple cyclic alcohol:

We can name it cyclopentanol and using cyclopentan-1-ol wouldn't be correct. When more than one alcohol group is added:

we must use numbers and name it as cyclopentane‐1,1‐diol. However, what about situation like below?

In my understanding such compound should be named 1‐methylcyclopentan‐1‐ol and that's how I always named them. However I got into an argument with a person claiming the name of 1‐methylcyclopentan‐1‐ol is invalid and 1‐methylcyclopentanol must be used instead.

Does anyone maybe have a better google-fu and can locate a rule which specifies how such situation should be handled according to Gold Book or Blue Book?


texts: A compound contains both alpha,beta unsaturated carbonyl group and a normal carbonyl group. Is there any method to reduce the normal carbonyl group keeping the alpha,beta unsaturated carbonyl group intact?


texts: Why does the carboxylate ion show positive inductive effect?

texts:
While solving some problems on general organic chemistry, I came across this question that asked for the nature of inductive effects of $\ce{-CH_3}, \ce{-CO_2^-}, \ce{-Br}, \ce{-NH_3^+}$.
And in the solution to that problem, it says $\ce{-CO_2^-}$ shows $\ce{+I}$ effect.
How is it possible that the carboxylate ion with its two electronegative oxygen atoms shows a positive inductive effect instead of attracting a negative charge towards itself?
Please provide clarification on this.


texts: What gives variations in the color of cadmium sulfide paint pigment?

texts:
Oil paint manufacturers sometimes make several "shades" of a color, all of which list the exact same chemical ingredient.  For example, look at Gamblin's artist grade oils, in the yellow colors, linked here.

Two of those yellows, named Cadmium Yellow Medium, and Cadmium Yellow Deep, both list the pigment chemical as cadmium sulfide (CdS).

If they are the same chemical, then why are they different colors? I asked the paint company and they mentioned that it is the amount of sulfide, and the temperature and amount of time in the furnace.  I'm wondering, what does this translate to, in the chemistry?  Are there different crystal structures to CdS? Or is the furnace introducing some impurity like oxygen? Or is it something else?

I have similar questions about the cadmium red paints that are mixes of CdS and CdSe. But the yellow is the simpler case, so I ask about that first.


texts: Can carbon dioxide be reduced to carbon monoxide and oxygen to produce energy?

texts:
There are lots of questions about reducing or burning CO2 to carbon and oxygen to solve climate change, but of course that wouldn't work because it takes a lot of energy. But carbon monoxide is more stable than the dioxide, so could CO2 be split into CO and oxygen to create more heat? Of course this is a bad idea since it'd produce a toxic gas but is it at least theoretically possible?
Apologies if I'm misusing chemistry terms or concepts; please inform me in the comments section.


texts:
Does water have a chemical name?
If so, what is it?
P.S. I checked up the web and got all sorts of crazy answers like dihydrogenmonoxide, oxidane, hydrogendihydride etc. Please validate.


texts: Reactions in water radiolysis - producing hydroxyl radicals

texts:
There’s an excellent question on Stack Exchange regarding the radiolysis of water here but I have one simple outstanding question that perhaps someone might now; in radiobiology, a common DNA damaging free radial is caused by the radiolysis of water. This reaction is something like

$$\ce{H2O + $h\nu$ -> H2O+ + e- }$$

$$\ce{H2O+ + H2O ->  H3O+ + OH. }$$

which produces a hydroxyl radical which can prove fatal to cells. I follow the logic here, but given the massive energy of the ionizing radiation, how come a cleaving reaction like the following isn’t common?

$$\ce{H2O + $h\nu$ -> H. + OH. }$$

I’ve seen the energy quoted to break water this way at around $\pu{493.4 kJ/mol}$, which is way below the energy ($h\nu$) of an x-ray photon, even after compton scattering. Is there a reason why this reaction isn’t valid or common?


texts: How should we express concentrations and partial pressures in ΔG=-RTlnK?

texts:
I understand that $K$ will be dimensionless. Let's say an equilibrium involving $K_p$ and the reaction is $\ce{A -> B}$, $K_p$ will be dimensionless. If the reaction $\ce{A + B -> C}$, then based on the formula of $K_p$ will be:

$$ \frac{(\text{partial pressure of C})}{[(\text{partial pressure B})\times(\text{partial pressure of A})]}$$

Since partial pressure can be in $\mathrm{Pa}$, or $\mathrm{bar/atm}$, with the difference between them will be roughly 100000 times. So the $K_p$s will have 100000 difference. Putting the $K_p$ into $\Delta G=-RT\ln K$, there will be a huge difference of $\Delta G$. So what units of $K_p$ should we use in this case?


texts: Difference of dipole moments of dichloromethane and trichloromethane?

texts:
Why is the dipole moment of $\ce{CH2Cl2}$ ($1.60 ~\mathrm{D}$) greater than that of $\ce{CHCl3}$ ($1.08~\mathrm{D}$)?

Based on my knowledge of vectors, I feel it should be the other way around.


texts: Why does the energy level of a particle in a box decrease with length?

texts: I want to know the intuition of why L is in the denominator of the equation for the energy of a particle in a box. This helps explain why resonance is stabilizing without using molecular orbitals. Does it have to do with the Uncertainty Principle? As the length increases, uncertainty of position increases, so uncertainty of momentum decreases, consequently meaning that the kinetic energy is lower, lowering the overall energy of the orbital?


texts: Transmission, absorption, and reflection of light

texts:
My understanding is: when light hits an object, it can do one of three things: transmit through the object, be absorbed into the object, or reflect from the object.

However, I have also learned that when light hits atoms, it can excite electrons, leading to another emission of light as the electrons go back down to their ground states.

The first paragraph, while intuitive, does not seem to be logically explained by the second. Can someone please help me understand the first in terms of the concepts of the second?

Specifically, is absorption of light exciting an electron with more energy than necessary, and some energy remains in the atom, or is the entire energy of the photon absorbed?

Is reflection just hitting the atom with a photon that is just the right amount of energy to get it excited, so no net energy is gained?


texts: % coefficient of variation (%CV) for log-linear and log-log regression (calibrations)

texts:
I have a data set comprising the peak areas of an analyte measured in spiked calibration samples at 'known' and different concentrations levels. For each concentration level I have 5 replicates. My goal is to generate a calibration curve from this data and then, for each concentration level, determine the precision of the 'estimated concentration' expressed as percent coefficient of variation ($\%CV$).
If a linear relationship existed between the measured peak areas and 'known' concentrations, then for each concentration level I would simply calculate $\%CV$ as the standard deviation of the estimated concentration at a given 'known' concentration level and divide by the mean of the same estimated concentrations, before multiplying by 100. For my data set, however, I observe an inadequate linear (i.e. straight line) fit between measured peak areas and 'known' concentrations. Furthermore, there is heteroscedacity of the residuals when fitting a linear model.
To address the above, I've performed a $\log_{10}$ transformation of BOTH peak area and 'known' concentration. An adequate linear fit is observed. I would now like to calculate the precision (coefficient of variation, $\%CV$) of the estimated peak area based on this model.
According to the article cited below, the %CV for log-transformed data would be calculated as:
$$\%CV (\text{estimated concentration}) = 100\%  \cdot \sqrt{10^{\ln(10)\theta^2_{\log}} -1}$$
Where (if I understood correctly): $\theta^2_{\log}$ is the variance of the $\log$-transformed data.
So, I would specifically like to know: is the formula proposed by Canchola, et al. appropriate in the case where BOTH the response (i.e. peak area) and predictor (i.e. 'known' concentration) variable have been transformed?
In my mind, seeing as I would consider the variable of the estimated concentration on the $\log_{10}$-transformed scale, the formula outlined by Canchola, et al. should be fine.
Finally: if I had only $\log_{10}$-transformed the peak areas and then estimated the concentration (i.e. log-linear relationship), would I need to use the Canchola, et al. equation?
Referenced article: Jesse A. Canchola,  Shaowu Tang, Pari Hemyari, Ellen Paxinos, Ed Marins, "Correct use of percent coefficient of variation ($\%CV$) formula for $\log$-transformed data," MOJ Proteomics & Bioinformatics 2017, 6(4), 316-317 (DOI: 10.15406/mojpb.2017.06.00200).


texts:
[!well i thought that sterically least hindered compound will undergo sn2 most easily but in this case it the compound having benzene ring is undergoing sn2 more easily although it will repel the attacking nucleophile due to its electron dense nature.why isnt that happening here??][1]][1]

[1]: https://i.stack.imgur.com/28e4y.jpg


texts: Hydrogen peroxide / sodium or potassium permanganate: reaction type

texts:
I have some people on youtube stating the steam generating reaction of $$\ce{3H2O2 + 2KMnO4 → 3O2 + 2MnO2 + 2KOH + 2H2O}$$

is catalytic, from where I'm sitting it is purely stoichiometric. Can someone please enlighten me as to why some people would consider this reaction catalytic with the presence of the permanganate the catalyst?

If this reaction really is regarded as catalytic how is this so, it flies in the face of everything I've learnt about reaction types. I'm only an amateur, can someone who is proficient in their chemistry please clarify this.


texts: I am trying to find visual ways to demonstrate water contaminants. For example, chlorine reacts to N,N-diethyl-p-phenyldiamine (DPD), forming a magenta color. The chemical doesn't need to be accurate, as this is more of pass-fail test of the water. What reacts with fluoride to provide similar results?


texts: Calculating yield percentage of magnetite synthesis

texts:
I’ve made magnetite $\ce{Fe3O4}$ in the lab and now I need to calculate yield percentage. How can I do it? I have these data.

\begin{align}
\ce{FeSO4.7H2O(aq) &-> Fe^2+(aq) + SO4^2- (aq) + 7H2O(l)}\\
\ce{KOH(aq) &-> K+(aq) + OH- (aq)}\\
\ce{KNO3(aq) &-> K+(aq) + NO3- (aq)}\\
\ce{Fe^2+(aq) + 2OH- (aq) &-> Fe(OH)2(s)}\\
\ce{3Fe(OH)2(s) + NO3- (aq) &-> Fe3O4(s) + NO2- (aq) + 3H2O(l)}\\
\end{align}

\begin{align}
\ce{FeSO4.7H2O &->} 4.20~\mathrm{g}\\
\ce{KOH &->} 1.90~\mathrm{g}\\
\ce{KNO3 &->} 0.12~\mathrm{g}\\
\text{Magnetite}~\ce{&->} 0.36~\mathrm{g}\\
\end{align}

I know how to calculate the yield for simple reactions but I don’t know how to do it when there are many reactions involved.


texts: Finding Gibbs energy at different temperatures

texts: How can I find $∆G$ at a higher/lower temperature if I am given $∆G°$ and $∆H°$ $\pu{298 K}$, and a reaction equation (solubility)?


texts: Reaction of vinylacetylene (but-1-en-3-yne) with HCl

texts:
Vinylacetylene contains both a double bond and a triple bond. We know that alkenes are more reactive to electrophillic addition reactions, so I thought that the $\ce{H+}$ from $\ce{HCl}$ would get abstracted via the double bond.
However, the final answer says the product is 2-chloroprene, which is possible only if the triple bond abstracts it.

My teacher said that it was because of the carbocation stability and the abstraction of $\ce{H+}$ by triple bond forms a stabler carbocation and leads to conjugation and hence is favoured.

But then Wikipedia says that a 1,4 addition takes place and an allene rearrangement takes place.This means that the triple bond is the one that reacts first , but in a 1,4 fashion to form an allene which then rearranges. I was unable to find a mechanism for this allene rearrangement, why is this 1,4 addition favoured, and why it takes place. Also, what is the correct explanation: the first one or the second one?


texts: Milk digestion procedure for AAS analysis

texts:
I am working on a project of analyzing heavy metals in milk samples using flame AAS. So far I have only analyzed cadmium and the results of spiked and unspiked have large differences. I was wondering if something went wrong with my digestion procedure. The procedure is listed as followed:

2g of milk sample, add 5 ml of 68% HNO3 (spiked solution spiked with 1ml 100ppm of Cd stock solution)
solution heated at 70 °C for 2 hours with hot plate until solution clears up
3ml of H2O2 added to solution and heated to effervescence and cool solution
filter solution through filter paper
dilute solution with minimum HNO3
dilute with 5% HNO3 in 100ml volumetric flask
filter with 0.7 nm syringe filter
analyze with AAS

after the digestion of HNO3 and H2O2, there are some floating bits which I am not sure what are the compositions, which cannot be digested or dissolved even when I add extra acid. I suspect that filtering with the filter paper may have affected the metal content to be lower than expected. The spiked sample also do not show consistent readings. Glasswares have all been soaked in 5% HNO3 overnight.
I want to know is there anywhere I can improve my digestion procedure? Any relevant literature I can review? Thanks.


texts: High content of potassium reported by spectrometer in silverware items

texts:
We tried to analyze a few silver items (800/1000 fineness) using a hand-held  ED-XRF spectrometer, which is normally used for analyzing industrial alloys etc. The operating element range of the device was Mg-U.

The most surprising result of the experiment was a very high reported content of potassium, often higher than silver. For example, one of results (listing just elements with content >= 1%):

| element                           | content |
|-----------------------------------|---------|
| K                                 |   36.0% |
| Ag                                |   27.5% |
| (sum of elements lighter than Mg) |   24.7% |
| Cu                                |    5.0% |
| Sn                                |    4.5% |

Such high potassium content was pretty consistent across all our silver samples, but not present in others (like stainless steel)

Clearly it's not possible that the alloy could contain that much potassium. Where could this result come from? Can potassium be somehow bound to the molecules at the thin surface layer? Or is there some explanation for this phenomenon?


texts: Why is a tin can that appears like galvanised steel rusting?

texts:
I bought a canned pineapple and finished the content. The part of the can that is in contact with the liquid appears like galvanized steel (crystalline surface or spangles sort of appearance), while the part that are not looks pretty shiny like the outside of the can.

I then washed the can and added water to it, and heated the bottom of the can with a butane torch. After the water was heated up, I removed the torch and left it out for a while.

When I came back later, I emptied the water but noticed that the bottom rim of can had quite a bit of rusting. After inspecting it closely, I found that there are spots of (concentrated) rust on the cylindrical wall of the can as well. There are also light patches of rust on the inside bottom of the can. The seam on the cylindrical wall that is in contact with water is also badly rusted.

I thought galvanised steel only rusts when the layer of galvanisation wears out.
So, is the tin made with galvanised steel?
If yes, why are there concentrated spots of rust on the wall and other rusting?
If not, why does the inside of the can look like galvanised steel?
And BTW, why does the emptied and washed can smell "metallish"?


texts: Which has higher lattice energy: MgO or LiF?

texts:
Which has higher lattice energy: MgO or LiF ?

A compound has higher lattice energy if it's ions have smaller size and greater charge

Li cation is smaller than Mg cation => +1 for (LiF)
Fluoride anion is smaller than oxide anion => +1 for (LiF)
Mg cation has greater charge than Li cation => +1 for (MgO)
Oxide anion has greater charge than fluoride anion => +1 for (MgO)

Therefore, 'charge' factor favour MgO while 'size' factor favour LiF.

So, which one will have higher lattice energy?


texts: Determine Which has the higher density the pure liquids or solutions?

texts: What i know that it immensely depends on their individual density, but am not really sure since doing research they was no solid answer. i just want a conformation if what am suggesting is correct.


texts: Splitting of multiplets in ¹H NMR spectra?

texts:
I'm currently taking VCE (Victorian Certificate of Education) Chemistry classes, and we're currently studying the interpretation of spectra produced by Hydrogen NMR (Nuclear Magnetic Resonance) spectroscopy.

When studying the spectra of High Resolution 1H NMR, the peaks representing the different Hydrogen environments are split into multiplets based on the protons surrounding these environments. There has been a considerable amount of confusion in my classes over the actual principles / rules of thumb on how to calculate the multiplets for a particular environment of a known chemical (i.e.; known structue), based off the 'n + 1' rule.
(i.e.; an environment with n neighbours will be split into n+1 multiplets).

We are absolute on the principles that;

Peaks of a particular Hydrogen environment are not split by neighbouring protons in equivalent environments.
OH does not, and is not split by, it's neighbouring environments.

However, immense confusion arised over whether the following principle was correct.

Peaks of a particular Hydrogen environment will only be split by the protons in neighbouring environments once for each type of neighbouring environment.
e.g.  The middle "CH2" environment in "CH3–CH2–CH3" will only have 4 peaks;
Although it has 6 neighbouring protons, they are two lots of the same environment (CH3).

As a class, we found numerous examples from different text books and sources that provide examples of ¹H NMR spectra which did not clarify the matter; Some considered all neighbouring protons as neighbours, others discriminated on the repeated neighbouring environments. For example, the CH2 in CH3–CH2–CH3 was sometimes split into 4 peaks or 7 peaks, depending on the source.

Many Chemistry teachers contradicted each other on the matter.
There was repeated self corrections made by the teachers, such that now nobody really knows whether this principle is correct or not.

So, is there anybody that has the correct information on the matter?
Is there a reasonable explanation behind this strange lack of correlation,
or is there a common misconception about multiplet splitting?

Ultimately; How many multiplets should the CH2 in CH3–CH2–CH3 have?

(Note that if there is a complicated explanation that I am currently only at Year 12 VCE level, so links to resources I can pursue would be extremely helpful! It's been established that VCAA (an authority for the education system in Australia) ensures that the chemicals featured in the exams for NMR analysis will not be of a structure so as to allow the ambiguity above.)


texts:
I obtained measurements of temperature and pressure at various temperatures ($-10, 0, 20, \text{ and } 50^\circ \mathrm{C}$) and plotted them on a graph. Projecting backwards, the best-fit line predicts 0 pressure at significantly above $-273.15^\circ \mathrm{C}$(0 Kelvin). I am wondering why this is.

My understanding is that a true linear relation assumes "Ideal Gas Behavior", which is predicated on the false assumptions that molecules have no attraction for each other and that they take up no space. I know that at high/low temperatures and pressures the realities about volume and attraction begin to make a difference. But I don't understand how these account for my results.

The pressure for all measurements fell between $680$ and $820$ torr. My understanding is that that is not a significant amount of pressure. In terms of predicting pressures at lower temperatures, I understand that the less kinetic energy of the gas the more relevant the attractive forces are...but I would think that would lower the pressure which makes things worse--if the pressure actually falls faster and faster as temperature drops, then the predicted zero-pressure point would be even higher than the predicted values I got. I need it to be lower!

I am under the (possibly incorrect) impression that both the realities of volume and attraction are supposed to be causing my incorrect prediction...but I don't understand how either does...

Thanks for any help!


texts:
I've seen quite a few youtube videos about electrolysis for rust removal. The process seems to be effective. My question is: how does it work?

I get that the water is ionised so we have O- and OH+ ions. I get that O2 is liberated at the anode. But what is going on at the cathode to release the rust? Is the rust chemically changed or is the rust somehow chemically released from the parent metal?

I'm a (rusty - graduated 1981) physicist, so don't hold back on the answer.


texts: ATP chemical structure: phosphate groups with Oxygen anions or with OH groups?

texts:
I've googled repeatedly (with multiple search queries) to try and get an answer to this question but
nothing comes up.
Embarrassingly, I seem to be the only person who is confused by:

ATP with oxygen anions.

ATP with $\ce{OH}$ groups.

I looked at the $3$D view on PubChem  - when I click 'show oxygens' they are indeed  present as per image 2.

The chemical formula for ATP is $\ce{C10\underline{\mathrm H_{16}}N5O13P3}$: $16$ hydrogens, which means image $2$ fits the bill better than image $1$.
However, image 1 is more commonly found in tutorials about ATP.
Which representation is it best to go with?


texts: What do different forms of ice look like?

texts: Everyone is familiar with the very common, hexagonal ice. Bit there are many other forms of ice - what do they look like? If you had big blocks of ice in all the different known phases next to a block of hexagonal ice, what obvious differences would you notice?


texts: Does CH3CHNH exist, and what is it called?

texts:
I am drawing different Lewis Structures of small compounds containing nitrogen, hydrogen, and carbon. One permutation is $\ce{CH_3CHNH}$, but I have never heard of this compound. Initially, and falsely, I thought this compound was acetonitrile. It isn't coming up in Wolfram Alpha, Pubchem, or Wikipedia.

Does this compound exist? Also, what would this compound be called regardless of its existence value?


texts: How do I convert zwitterions to neutral form in Avogadro?

texts: I'd like to be able to convert zwitterions to neutral form in Avogadro if possible. How do I do this?


texts: Compare stability of the given carbocation

texts:
Give the order of stability of the given carbocations.

Usually stability is determined by studying effects taking place in the carbocation. All are resonating and there is no diff in inductive effect.So I want to know how the molecular weight might affect stability


texts: How can water be electrolysed if it's not ionic compound?

texts:
The electrodes have different charges. One is positive ( the cathode ) while one is negative (anode). They will attract the particles in the solution which are charged. Hydrogen to the cathode while oxygen will go to the anode.

I have been taught that water is a covalent bond. Also I have been taught that covalent bonds do no have a charge so how is it possible that this compound is charged if it's covalent?


texts: How to determine net charge of a polycation using Wade's rules?

texts:
In order to determine the net charge of polycations, which adopt a Wade-like structure (octahedral, trigonal bipyramidal, ...), Wade's rules can be used.

For example, the charge $x$ of the octahedral cluster $\ce{[Bi6]^x+}$ should be determined:

It is known that a Wade-cluster overall "needs" $2n+2$ electrons (to fill the $n+1$ energetically favoured, bonding MOs).
Bi atoms contain three valence p-electrons (the two s-electrons do not take part in the cluster-bonding). So in a $\ce{Bi_n}$ cluster, there are $3n$ electrons already available for bonding.
But only $2n+2$ electrons are needed: We need to remove $2n+2-3n=-n+2=-(n-2)$ electrons to obtain the favoured $2n+2$ electron count in the cluster.
So for example the $\ce{[Bi6]^x+}$ should have $-(6-2)=-4$ electrons "removed". We would arrive at a $\ce{[Bi6]^4+}$ net charge... ...but in reality, there is "only" a $\ce{[Bi6]^2+}$ - with two electrons more than determined according to the Wade's rules.

EDIT:  In contrast to that, the rules aboves apply to $\ce{[Bi5]^3+}$ (Thanks to @orthocresol).

Is there a misconception in my above thoughts? I can not find an illogical step - Maybe Wade's rules can not be applied to the polyatomic clusters (my textbooks suggests this nevertheless)? Or I should have take the s-electrons into account?


texts: SN1 reaction of ethanol at tertiary alkyl halide

texts:
I know this undergoes an $\ce{S_{N}1}$ reaction:

Ethanol is the solvent. Weak nucleophile. Neutral nucleophile. This points toward $\ce{S_{N}1/E1}$ (competing pathways).
The leaving group is on a tertiary carbon. This precludes backside attack, $\ce{S_{N}2}$.
The professor labeled this reaction as $\ce{S_{N}1}$.

My question: where's the substitution part of this reaction? I don't see any substitution. Is there supposed to be no reaction here? From what he wrote it looks like a bromine left as bromide ion and a hydrogen appeared out of nowhere.

My expected transition state is a tertiary carbocation, which will not rearrange, and then the nucleophilic oxygen part of the ethanol molecule attacks the carbocation. Bromide ion deprotonates the oxonium ion, and I get an ether.

Who's right?


texts: By what mechanisms can molecules with the same empirical formula be so different?

texts:
I understand the difference between empirical and chemical formula. But I always thought that compounds and molecules took their specific shape because it's the lowest energy configuration. How then, can fructose ($\ce{C6H12O6}$) and formaldehyde ($\ce{CH2O}$) both exist?
If for example formaldehyde had overall the smaller energy, why then wouldn't fructose just decompose in 6 $\ce{CH2O}$ molecules? What makes both of those molecules so stable?

I guess this is a very general question of what makes certain elements combine the way they do to form compounds.


texts: Why is copper a better conductor than iron?

texts:
Metals are good conductors as the electrons in their outer shell are loose and can plunge out of the atom with the application of the slightest force (voltage).

Silver is the best metallic conductor, then comes copper.

Why is one metal better at conduction than the other one?
What determines the difference in conduction between 2 metals?
Why is silver a better conductor than copper, and why is copper a better conductor than iron if all of them have loose electrons?


texts: Does the nomenclature of spiro compounds follow the same pattern as that for bicyclo compounds? That is, in absence of functional groups do we start form the largest chain to the smallest chain. What would be the case if there were functional groups?


texts: Optimization and DFT-D3 energy calculation in GamessFireFly version 8.1.1

texts:
My input was

$CONTRL SCFTYP=RHF DFTTYP=B2PLYP DFTD=.T. d5=.T. RUNTYP=OPTIMIZE $END
$DFTD VERSN=3 $END
$SYSTEM TIMLIM=3000 MEMORY=30000000 $END
$BASIS EXTFIL=.T.  GBASIS=acc-pvdz $END
$STATPT HSSEND=.T. NPRT=-2 $END
$FORCE NVIB=2 VIBSIZ=0.005 $END
$DATA
 H2O
C1
O  8.0                   -3.46278   2.54045   0.
H  1.0                  -2.50278   2.54045   0.
H  1.0                  -3.78324   3.44539   0.
 $END

I am getting the following error:
FATAL ERROR: DFTTYP = B2PLYP   DOES NOT YET HAVE GRADIENTS PROGRAMMED.

So is it not possible to perform optimization with this functional?


texts: How does electrolytic conductance depend on solvation?

texts:
My textbook says: If the ions are strongly solvated their effective size will increase and hence their conductance will decrease

P.s after reading my textbook, I don't think I'm sure what solvation means. If you could explain that, my understanding would be better.


texts: Can't aluminium chloride do electrophilic substitution as an electrophile?

texts:
In halogenation reaction of benzene, $\ce{AlCl3}$ is used as a catalyst in order to form electrophile $\ce{E^+}$.
So I was wondering that $\ce{AlCl3}$ is a Lewis acid (that fact being also used in mechanism) and so an electrophile. Why it can't just do electrophilic substitution reaction on the benzene itself? Isn't it strong enough or any other problem there doing that?


texts: Is a strontium-fluorine battery the highest voltage battery using pure elements?

texts:
Strontium has a very low standard electrode potential and fluorine has a very high one.

$$ E_{\ce{F2 + 2e^- -> 2F^-}} = 2.87\mathrm{V} $$
$$ E_{\ce{Sr -> Sr^+ + e^-}} = -4.10\mathrm{V} $$

In theory a strontium-fluorine battery would have a voltage of $6.97\mathrm{V}$ although there are many practical reasons such as danger and rarity of materials for such batteries not to be made.

Is a strontium-fluorine battery the theoretically highest voltage chemical battery using pure elements or is it possible to obtain a higher one?


texts: Pyridine synthesis by tin(II) chloride reduction of 5-nitronorbornene

texts:
What is the reaction mechanism here?
I guess the $\ce{SnCl2}$ reduces $\ce{NO2}$ to $\ce{NH2}$ but then what happens?


texts: U- or RO-method for Singlet-Triplet Gap?

texts:
When I want to compare the energy between two different spin states of the same molecule, i.e. singlet-triplet-gap, do I better use unrestricted or restricted open formalism to compare the energies between both?

Further on, do I need to calculate the singlet state also with restricted open/unrestricted method? At least within Gaussian I did not recognize any energy difference between all of them. (Which sounds logic for me, as if the ground state is a singlet, also the open shell version will find that best version would be to have the same orbitals in alpha and beta.)


texts:
What is the amount of baking soda that would be considered toxic for skin? I ask because there is a lot of misinformation online about using baking soda as a "natural" underarm deodorant, and how it is or is not harmful to use as such. Please clarify.

Thank you for your time in advance.


texts: What is the difference between moisture regain and water holding capacity?

texts: Water retention is how much water the fibre can retain. Water holding is function of hydrophilicity and construction of the fibre (fabric). What is the difference between those two? Because to retain is also to hold, in my knowledge.


texts:
I bought a box of A&H Washing Soda, the packaging of which implied that it was pure washing soda (sodium carbonate).

On dissolving it in osmotically-purified water, however, I found that the water took on a brown tinge, which would seem to indicate a contamination or adulteration of some type. Also, the washing soda tended to form hard chips or clumps, which I have not seen in previous experiments doing the same thing.

I suspect there may be some kind of organic compound being used to adulterate the washing soda.

How can I determine if there is an organic adulterant and remove it?


texts: How does the smell of a compound come about, and is it possible to define a smell?

texts:
Colour - and eyesight in general - arises because objects reflect/transmit certain wavelengths of colour, which is detected by our eyes.

On the other hand, what gives rise to smell? Is there a branch of chemistry associated with this? Is it possible to define the smell of any substance, using some parameters analogous to wavelength in the case of sight?

We know that $\ce{H2S}$ has a foul odor, but distilled $\ce{H2O}$ does not have any strong smell. Does $\ce{H2Se}$ have a similar foul smell?


texts:
$$\ce{CH3CH(CH3)CHCHCH2CH3 + HBr ->}$$
According to Markovnikov Rule, "the rich get richer". But, as we can see the 2 carbons have the same amount of $\ce{H}$. So, what's probably the answer?


texts:
I was reading about the various ways to optimise the geometry of the system, and found that none of the sources mention how the Hessian matrix is obtained.

How does one obtain the Hessian matrix? I’m thinking it’s either some analytical formula or just numerical differentiation.


texts: What kind of optical activity requires chirality?

texts:
From "Meso compound" in Wikipedia:

  A meso compound or meso isomer is a non-optically active member of a
  set of stereoisomers, at least two of which are optically active. This
  means that despite containing two or more stereogenic centers, the
  molecule is not chiral.

What is the meaning of "optical activity" in this context? In other words, what kind of photo activity requires chirality?


texts: Relationship between the partial pressure $p_J = x_J p$ and the perfect gas law $pV = nRT$

texts:
I am currently studying Atkins' Physical Chemistry, 11th edition, by Peter Atkins, Julio de Paula, and James Keeler. Chapter 1A.2 Equations of state says the following:

When dealing with gaseous mixtures, it is often necessary to know the contribution that each component makes to the total pressure of the sample. The partial pressure, $p_J$, of a gas $J$ in a mixture (any gas, not just a perfect gas), is defined
$$p_J = x_J p \tag{1A.6}$$
where $x_J$ is the mole fraction of the component $J$, the amount of $J$ expressed as a fraction of the total amount of molecules, $n$, in the sample:
$$x_J = \dfrac{n_J}{n} \ \ \ n = n_A + n_B + \dots \tag{1A.7}$$
When no $J$ molecules are present, $x_J = 0$; when only $J$ molecules are present, $x_J = 1$. It follows from the definition of $x_J$ that, whatever the composition of the mixture, $x_A + x_B + \dots = 1$ and therefore that the sum of the partial pressures is equal to the total pressure:
$$p_A + p_B + \dots = (x_A + x_B + \dots)p = p \tag{1A.8}$$
This relation is true for both real and perfect gases.

When all the gases are perfect, the partial pressure as defined in eqn 1A.6 is also the pressure that each gas would exert if it occupied the same container alone at the same temperature.

It is this last part that I am unsure about:

When all the gases are perfect, the partial pressure as defined in eqn 1A.6 is also the pressure that each gas would exert if it occupied the same container alone at the same temperature.

I don't understand why this is true. Furthermore, is this not in reference to the perfect gas law, $pV = nRT$? Then how does this relate to $pV = nRT$?
I would greatly appreciate it if people would please take the time to clarify this.


texts:
I could finally get a copy of the Red Book 2005 from a library. In the chapter dedicated to nomenclature of coordinate complexes, while explaining the κ-system of specifying donor atoms, the following two examples were given (among many others):

Can anyone explain how the naming is done for the two compounds (labelled 2 and 3 in the picture)? The problem that I am facing is with the closed rings. From where is the naming started?


texts: How do elemental halogens get their colour?

texts: I learnt that in halogens the colour is due to transfer of electrons from HOMO to LUMO during excitation but I have trouble understanding what that means. Also I don't understand how iodine is blackish in solid state while violet in gaseous state.


texts: Why does the mixture's temperature change while phase transition?

texts:
Consider a mixture made up of alcohol and water at room temperature. If I freeze this mixture, why does it change its temperature during the phase change?

I don't understand the difference between the case when you have a pure substance (only water or only alcohol) and that one. How could it be different (I mean, in molecular thinking...)?


texts: Wittig reaction in presence of carboxylic acids

texts:
The following reaction came in a recent test:

According to this reaction, the acidic hydrogen would protonate the ylide, and the standard wittig reaction would not take place. This source agrees with the same results.
However, according to El-Batta et al.1, the Wittig reaction in water can take place even in the presence of acidic groups, such as carboxylic acids and phenols:

It is also interesting that the Wittig reaction in water works well with substrates having acidic unprotected functional groups present; hence the presence of a carboxylic acid group (vide infra) or phenolic groups, such as p-hydroxybenzaldehyde, gives the corresponding cinnamate product 16 in 92% after heating the reaction for 1 h at 90 °C (entry 16). In sharp contrast, the same reaction in refluxing CH2Cl2(4 h) has been reported to provide only 8% of 16

Which one of these references is correct? Does the Wittig reaction really proceed in the presence of acidic groups? I'm looking for a good reference, along with an explanation on what occurs when a carboxylic acid group is present on the substrate.
References:

El-Batta, Amer, et al. “Wittig Reactions in Water Media Employing Stabilized Ylides with Aldehydes. Synthesis of α,β-Unsaturated Esters from Mixing Aldehydes, α-Bromoesters, and $\ce{Ph3P}$ in Aqueous $\ce{NaHCO3}$.” The Journal of Organic Chemistry, vol. 72, no. 14, July 2007, pp. 5244–59. doi:10.1021/jo070665k.


texts:
At Wikipedia a monomer is defined to be

  a molecule that may bind chemically to other molecules to form a
  polymer.

A polymer is defined to be

  a molecule composed of many monomers.

These definitions are obviously circular.

Are there non-circular definitions of monomers and polymers?


texts: Copper Sulfate Pentahydrate experiment, help please?

texts:
My science project specifies me to make seed crystals of copper sulfate. We must use the powder form to make seeds. There are two types of copper sulfate pentahydrate; one is granular form (small seeds), and the other one is powder form. We must produce crystal seeds from copper sulfate (powder form). We are not allowed to use the granular form, because it forms seeds on its own already.

Steps I have taken:

I saturated 50 ml of distilled water (room temperature) with copper sulfate pentahydrate (powder form).
I added about 15 ml of purified sulfuric acid to the mixture, so it prevents the hydrolysis with water.This purified sulfuric acid I got from boiling battery acid. I boiled about 50 ml of batter acid (sulfuric acid mixed with ionic water). I waited till it reached about 15 ml (water evaporation). The fumes were getting strong at that stage. I'm not sure if purified enough.
I then again mixed more copper sulfate to the mixture, and stirred it very well.
I put the china dish (mixture) on a hot plate, and waited for it to reach crystallization point, while stirring it very well.
5 I know the water has to evaporate for the mixture to produce seed crystals. I waited for the mixture to evaporate about to 20 ml.
I had no results.

I'm not sure what I'm doing wrong. I'm doing my project according to this video which I found on youtube. It is a very short video, and my main problem is the sulfuric acid part.

https://youtu.be/SAU-gptAFe0

Help.


texts: Why aren't lower aromatic organic compounds taught?

texts:
Why aren't aromatic compounds with 3, 4 or 5 carbon atoms taught at high school level chemistry? We are instead directly taught about aromatic compounds with 6 carbons/benzene rings. Why?

My core question is: is because the lower members are tough to understand? Do they have any strange properties?


texts: Does the mixture of a ligand exchange reaction contain all the complexes obtained in the part reactions?

texts:
A ligand exchange reaction involves many part reactions. So, does the mixture contain all the complexes from those part reactions?

Quoting an example from ChemGuide:

  This can be written as an equilibrium reaction to show the overall effect:

  $$\ce{[Cu(H2O)6]^2+ + 4NH3 <=> [Cu(NH3)4(H2O)2]^2+ + 4H2O}$$

  In fact, the water molecules get replaced one at a time, and so this is made up of a series of part-reactions:

  $$
\begin{align}
\ce{[Cu(H2O)6]^2+ + \color{blue}{NH3} &<=> [Cu\color{blue}{(NH3)}(H2O)5]^2+ + H2O}\\
\ce{[Cu\color{blue}{(NH3)}(H2O)5]^2+ + \color{blue}{NH3} &<=> [Cu\color{blue}{(NH3)2}(H2O)4]^2+ + H2O}\\
\ce{[Cu\color{blue}{(NH3)2}(H2O)4]^2+ + \color{blue}{NH3} &<=> [Cu\color{blue}{(NH3)3}(H2O)3]^2+ + H2O}\\
\ce{[Cu\color{blue}{(NH3)3}(H2O)3]^2+ + \color{blue}{NH3} &<=> [Cu\color{blue}{(NH3)4}(H2O)2]^2+ + H2O}\\
\end{align}$$

And if yes, then which complex has the highest concentration?


texts:
I physics graduate student, but I teach an interdisciplinary lab for the university which incorporates biology, physics, and chemistry.

We recently added a weak-acid titration lab to the course and I got a result which surprised me.

The procedure was to neutralize 100 mL of 0.010 M Phosphoric acid by adding 0.10 M NaOH.

We have 0.001 mole of phosphoric acid in solution, but this acid is triprotic which means that a maximum of 0.003 moles of hydronium can be released into the solution. My understanding of the equillibrium reactions was that as I lowered the ambient hydronium ion concentration more protons would be released by the acid.

So my expectation was that I would need to add 30 mL of the NaOH solution to reach a pH of 7. In practice it only took between 12-15 mL.

I talked this over with a Chemist I work with and she wasn't sure why this discrepancy happened either. One possiblity is that the person who prepared the acid screwed up, but we don't have more stock for me to test that theory.

So my question is do these results sound normal or did I have the right idea? If I didn't have the right idea then what am I missing theoretically speaking?


texts: When converting between a hydrated electrolyte amount in mass and in milliequivalents (meq), why are the water molecules taken into account?

texts:
A textbook I'm reading called "Ansel's Pharmaceutical Calculations, 13th edition" defines the milliequivalent (meq) thus (p. 187):

This unit of measure is related to the total number of ionic charges in solution,
and it takes note of the valence of the ions. In other words, it is a unit of measurement of the
amount of chemical activity of an electrolyte.

It then goes on to demonstrate how can one convert the amount of electrolyte by mass to the amount in meqs and vice versa, and it gives the following example (pasting as a picture to keep all the original formatting):

Now see the note below the exercise, highlighted in yellow. The text does not explain any further, and I'm a bit confused.
If the amount in milliequivalent represents the number of ionic charges in solution or "chemical activity", why do we need to use the atomic weight of the hydrated ionic compound? Do the water molecules contribute anything to the chemical activity of the solution? If one meq means essentially one charge, the amount of meqs obtained when using a molecular weight that includes the hydration molecules is not representative of the amount of ions in the solution (as given by molar amounts).
So what is the reason for including the weight of water molecules in the calculations?


texts: How can I filter dissolved PVA from water

texts:
I'm working with a 3D printer that uses PVA filament as a support material.  After a 3D printed part is made, it is put in water for some time to dissolve away the PVA supports.

I'm trying to speed up the process by using a heated magnetic stirring plate with a pump connected to a filter.  The filter is for removing the already dissolved PVA from the water solution so that the solution doesn't get saturated.

I plan on using a 2L container of water and heating it to about 60-80 degrees C.  There would be about 10-50 grams of PVA being dissolved at a time.

I have two main questions:

What kind of filter(s) could I use for PVA in a water solution?
Do I really need a filter?  I.e. would 50 g of PVA have issues dissolving in 2L of 80C water?


texts: How to calculate molecular volume from the wavefunction?

texts:
Very short question but maybe not a short answer !   As the probability of presence of electrons in a specific spatial position is defined as square of the wave function, I am wondering if there is a technique for molecular volume calculation based on the wavefunction.
Is there such a technique?

Update:  I could run the volume keyword in Gaussian.  This is the output for methane , but I can not find the volume in it !


texts: Substituted Diene Preparation from Aniline / Novel Cyclic Imine Preparation

texts:
I have recently been studying the following mechanism recommended by another user from the following DOI: https://doi.org/10.1016/j.tet.2004.06.026. In this paper, the following mechanism is proposed (I am only focusing on  the proposed mechanism in EtOH)

Please note that the author of the paper did not show the intermediate prior to keto-enol tautomerization. This provides a valuable insight into plausible reactions that can be derived from this mechanism. Below is the intermediate prior to keto-enol tautomerization (to restore aromaticity).

It is clear that the α-hydrogens next to the carbonyl are crucial in restoring aromaticity. If, however, these hydrogens were replaced with alkyl groups, the final product would be quite different, as outlined in the following reaction (DOI: https://doi.org/10.1002/ejoc.200701009):

While the author of the paper did not include all of the steps of the reaction, it is clear, that the alkyl groups are preventing the restoration of aromiticity via tautomerization. I drew out a new mechanism that could be applied to substances other than phloroglucinol in one of my previous questions. I have since confirmed this using SciFinder. Here is the general mechanism:

It is clear that the driving force behind this type of reaction is the lone pair on the oxygen atom which can allow not very powerful electrophiles to attack the aromatic ring in a concerted fashion in which all charged intermediates are prevented by the formation of the carbonyl. Now to my question. Does this mechanism seem applicable to deprotonated aniline? This would theoretically result in the formation of a primary imine in accordance to the following theoretical mechanism I have proposed:

I would have expected to find a reaction very similar to this on SciFinder; however, I did not come across anything involving substituted anilines and alkyl halides directly. I did, however, find a very similar reaction that involved substituted nitrosobenzene instead of aniline and Grignard reagents. A very similar product is also formed with the only difference being an oxime is formed instead of an imine. Here is the DOI: https://doi.org/10.1246/bcsj.48.3727. The reaction is shown below.

The paper does not go into much detail about the specific mechanism about this step in the reaction (mostly steps afterward). It does not seem to me, however, that this reaction is following the same mechanism as my proposed reaction. The Grignard reagent may help deprotonate the nitrosobenzene; however, in this case, there is no longer an electrophile, so so the mechanism is probably not the same. Is there any obvious reason why this newly proposed mechanism would not work (I do not think polymerization of the product will be an issue), as I would have expected this to already have been attempted, however, it has not.


texts: How is occupation number of lowest unoccupied natural orbital defined?

texts: I have run some calculations to analyse the occupation of natural orbitals. Since it is needed to run in triplet state, I get two orbitals with occupation number 1. Now, which orbital occupation number is to be taken as the occupation  number of lowest unoccupied natural orbital as it is needed to define the diradical character in the system ?


texts: Why does electronegativity increase as effective nuclear charge increases?

texts:
I know that electronegativity is the ability to attract shared electrons and that effective nuclear charge is the pull of the nucleus on outer electrons based on my notes.

But I'm not really sure how to explain the connection. Please help.


texts: Reaction between Iron (III) Oxide and CO?

texts:
I'm a science tutor and I came across a stoichiometry problem asking how much Iron is produced in a reaction between $\ce{Fe2O3}$ and $\ce{CO}$:

$$\ce{Fe2O3 + CO -> Fe + ?}$$

I know how to do the stoichiometry part, but I'm stumped about how to figure out the products. My guess is $\ce{Fe}$ and $\ce{CO2}$ since the $\ce{CO}$ would want to change to the more stable $\ce{CO2}$, thus deoxidizing the $\ce{Fe}$? All the student's problems so far have just been between simple ionic salts, and I never remember coming across one like this when I took AP Chen myself in highschool, since $\ce{CO}$ is covalent.


texts: Evaluation of a synthesis from aspirin to paracetamol from this Nile Red video

texts:
Recently the YouTube chemist Nile Red performed an interesting conversion from aspirin to paracetamol Aspirin to Acetaminophen - Part 1 of 6: Extracting Aspirin from Pills using the following steps:

He performed the following steps:

1) Extracting aspirin from pills (95%)

2) Hydrolysis of the ester (86%)

3) Decarboxylation (51%)

4) Nitration of phenol (6%)

5) Reduction of nitro group (58%)

6) Condensation reaction with acetic anhydride (18%)

Final yield: 0.26%

As you can see, the yield is quite discouraging, particularly the nitration of phenol. The synthesis that he planned was quite linear, first removing functional groups and then adding them. This unfortunately did not take full advantage of the functional groups present.

I feel that this is a good opportunity to reflect how we can carry out the reaction efficiently, and I will illustrate it with the picture below:

1) I feel that nitrating the aspirin directly would have been more effective.

Since the carboxylic acid is 3-directing and the ester 2,4-directing, this would lead to two nitration positions as shown by the asterisks. However, the site to the left would be more ideal as the site to the right is blocked by steric hindrance from the bulky ester group. The combined efforts of both functional groups would also increase the reaction yield quite considerably. Since this is done in the presence of concentrated nitric acid and sulfuric acid, it is not surprising that a hydrolysis can occur here when we add water, thus allowing us to do a one-pot reaction.

2) Now, decarboxylation should be carried out. Due to the powerful electron-withdrawing nature of the nitro group, the $\ce{C\bond{-}C}$ bond should be weaker than the original synthesis, giving us a better yield as well. This is important as the close proximity of the two groups allows for intramolecular hydrogen bonding, thus making decarboxylation more difficult than usual.

I am wondering how much the yield would be affected if it were synthesised in this method. Of course, it is impossible to theoretically come up with a value and can only be done experimentally, but it would be good if I can come up with some estimates. Let me know what you guys think. Thanks!


texts: Oxidation of sulfur dioxide to trioxide and its decomposition under same condition at higher temperature

texts:
I found that $\ce{SO2 + 1/2 O2 -> SO3}$ when catalysed by platinum and heated to $\pu{700 ^\circ C}$. On the other hand I found that $\ce{SO3 -> SO2 + 1/2 O2}$ with same catalysator and temperature about $\pu{800 ^\circ C}$. How depends these two cases in real reaction? What controls which reaction will happen?
I thought that one reaction is exothermic and other endotermic, and duration of reaction and temperature controls which reaction happens. But facts I found are different. Sorry for maybe too simple question. I would be pleased with some tips which chapters of chemistry to study to understand my problem more deeply.


texts:
Krapcho's decarboxylation is a reaction involving esters with a electron-withdrawing group $\beta$ to the carbonyl group and halide ions. It is typically conducted with $\ce {LiCl}$ and $\ce {DMSO}$ at high temperatures. However, in one of Krapcho's original papers, $\ce {NaCN}$ was also used alongside $\ce {DMSO}$.

What interests me is the first step of the reaction which involves the nucleophilic subsitution, likely by an $\ce {S_N2}$ pathway, of the alkyl group of the ester functionality. This is seemingly weird as the $\ce {C-O}$ bond usually does not break unless in acid catalysis. This is the case for the cleavage of ethers using $\ce {HX}$. I suppose the use of $\ce {LiCl}$ was to allow the $\ce {Li^+}$ to coordinate to the oxygen atom, allowing the $\ce {C-O}$ bond to cleave more easily. Why is it that $\ce {NaCN}$ can also do the job?


texts:
When I read about the different kinds of functional groups, they usually have formulas like $\ce{-NH2} $, $\ce{-COOH}$, $\ce {-OH}$, etc.

What does the bar represent? Any bond? Or can it only be a covalent one?


texts:
I would be really happy if someone would clarify the term "chemical activity" and its implications for me, and also how it is related to the concept of molar concentration. My textbook fails at explaining this clearly and, sadly, the Internet is filled with vague definitions and scientific verbiage that's too difficult for me to grasp. Also, why are activities included in various formulae, and what are their uses?

I never quite actually understood what are activities and how do they differ from molar concentrations, nor how are they used. In addition, when working with the Nernst equation, why are we allowed to compute the activities of the reactants and the equilibrium concentrations of the products? This is the stuff that really baffled me and I'd be highly appreciative if you could clarify it.


texts: How to determine the configuration of the attached chiral compound? It can be represented with two Lewis structures, in the one to the left, the =O substituent has the biggest priority, while in the right one, the -OMe substituent has the bigger priority. In the former case the configuration would be R, in the second S.


texts: Which will be major and minor alkene formed if E1 reaction occurs on 2-chloro-2,4,4-trimethylpentane?

texts:
More substituted alkene should be major product while the less substituted as minor product as it is E1 mechanism.
But in my answer sheet it is given reverse, i.e. major as less substituted and minor as more substituted by giving the reason that it is happening because of steric hindrance of tert-butyl group. But I am confused now that it should not be the case because there is no role of steric hindrance in E1 mechanism, and answer should be as usual.
Please help me in this question with other reason.


texts: Chemical structure of xenon heptafluoride anion

texts: When $\ce{XeF6}$ acts as a fluoride acceptor, $\ce{XeF7-}$ is formed. What is the hybridisation, geometry, and shape of $\ce{XeF7-}$?


texts:
Can you explain why phenitoin is weak acid even though nitrogen is base?
Does carbonyl group always make structure acid?
If this structure doesn't have carbonyl group, would it be base not acid?


texts: Estimating stability and mean life of anomalous tautomers

texts:
A pair of bases in the DNA, say, A-T, have a tautomerized form A*-T* (resulting from switching the sides of both protons along the hydrogen bridges).

I have studied how, by means of DFT computations, one can compute the energy difference between the normal and the anomalous forms. But, another point of interest is the stability of the tautomer.

I have read several times that those anomalous tautomers "decay" to the normal A-T form very quickly (much quicker than the time it lasts a round of DNA replication), which is interesting because it implies that tautomerization is not likely to be a source of spontaneous mutations.

What I would like to learn is how can one compute this expected life-time of the anomalous tautomer

I have an idea (which I don't know if it could be rigth or if maybe is completely worthless), which involves making a Born-Oppenheimer separation for the two protons (''after'' the DFT computation of the electronic ground state) and then study the non-adiabatic transitions between the different vibronic states of the couple of protons. I am happy to provide details, if someone whises so.

But perhaps "my method" is too messy, or naive (or both) and / or there are other standar approaches to compute approximately the expected mean life of anomalous tautomers such as the mentioned A*-T*.

I would be very grateful if someone could apport some insigth and/or references into how are these expected life-times calculated typically in computational chemistry!


texts: Why is the reaction quotient Q always equal to one at standard state?

texts:
I understand that at equilibrium, $Q$ is equal to $K$. This should not depend how I express concentrations (as amount of substance concentrations $c$ or as partial pressures $p$ or as molality $b$ or as mole fraction $x$) and which units I use (e.g. partial pressure in Pa or in atm) as long as I am consistent.

Various expressions rely on $Q$ being dimensionless (because we take its logarithm) and on being equal to one when all species are at standard state. For example, the equation for calculating the change in Gibbs free energy for a reaction should result in the standard Gibbs free energy for the standard state:

$$\Delta_r G = \Delta_r G^\circ + R T \ln Q = \Delta_r G^\circ \text{(for standard state)}$$

This requires that $Q = 1$ at standard state. The Nernst equation is another (related) example.

What I am wondering about is why $Q$ is always equal to one at standard state, no matter how I express concentrations when calculating reaction quotients.

For example, if I have a reaction like $\ce{A(g) + B(g) -> C(g)}$, doesn't the value of $Q$ change if I switch from concentration $c$ to partial pressure $p$, or use units of atm instead of Pa when measuring partial pressures? Come to think of it, doesn't the value of the equilibrium constant $K$ change as well when I change measures or units of concentration?


texts: How does 1 mole of a compound = the molecular weight of the compound?

texts:
I am reviewing moles, and came across this sentence in my book:

  One mole of a compound has a mass in grams equal the molecular weight of the compound expressed in amu and contains $6.022\times10^{23}$ molecules of that compound.

Now, I perfectly understand the second part of the sentence. 1 mole of compound has $6.022\times10^{23}$ molecules. But how do $6.022\times10^{23}$ molecules have a mass same as the molecular weight of compound?
Ex. Molecular weight of $\ce{SOCl2}$ is $119\ \mathrm{amu}$. That is the mass of 4 atoms. How do $6.022\times10^{23}$ molecules have the same mass?


texts: Crystal Field Splitting of d-Orbitals in Octahedral and Tetrahedral Ligand Fields

texts:
We're learning about the Crystal Field Theory (CFT, under coordination chemistry) at school now, and my teacher mentioned that the 5 d-orbitals split into orbital sets, namely the $\mathrm{t_{2g}}$ (triply degenerate-gerade) and the $\mathrm{e_{g}}$ (evenly degenerate-gerade) for an octahedral ligand field; whereas for the tetrahedral ligand field, the notation is the same except that the subscript 'g' is removed, indicating it is ungerade (That bit was my interpretation … I think I'm wrong though)

Now a lot of the books and sites I've looked up mention the same gerade notation for both octahedral and tetrahedral ligand fields.

So naturally my question would be "Which one's right and which one's wrong?" and a reason if possible.


texts: Normalising Kinetic Isotope Effect Per Deuterium Atom

texts:
I've synthesised a protic and deuterated version of a specific molecule where there are two deuterium atoms in the latter. I then go about and measure the kinetic isotope effect (KIE) for a reaction involving these two molecules. However, in many papers where there are multiple deuteriums per molecule it is common to quote a KIE per deuterium in addition to the observed KIE.
This is usually achieved by taking the nth root of the observed KIE where n= no. of deuteriums (see attachment for example: 10.1039/ b405075d).
My questions are:

Why the nth root? What is the basis for this? No paper explains why they chose the nth root.
Should one use the observed KIE or the KIE per deuterium when discussing a mechanistic proposal?


texts: Is this problem about acid-base titration wrong?

texts:
I wouldn't post mere 'problems' here normally, but I will hopefully be starting to give chemistry education to some 10-11-12th graders and I want to make sure that it is not I that has a problem but rather the problem in the book itself. Here is the problem:

$100~\mathrm{mL}$ of $\ce{H2SO4}$ solution is titrated with $5\cdot 10^{-2}\ \mathrm{M}$ solution of $\ce{NaOH}$. Here are the information that are given in the titration graph:
Total volume of $\ce{NaOH}$ solution added: $0$ | pH: $x$
Total volume of $\ce{NaOH}$ solution added: $400$ | pH: $7$
Total volume of $\ce{NaOH}$ solution added: $600$ | pH: $12$
According to what has been provided above, what is the $\mathrm{pH}$ of the initial $\ce{H2SO4}$ solution ($x$) ? (Assume that $\ce{H2SO4}$ fully dissociates in water to give $\ce{2H+}$ and $\ce{SO4^2-}$ ions)
A) 1
B) 2
C) 3
D) 4
E) 5

My answer: $-\log (2\cdot 10^{-1})$
My steps:

The $\ce{H+}$ ions in the acid solution have been neutralized by $400\ \mathrm{mL}$ of $5\cdot 10^{-2}\ \mathrm{M}\ \ce{NaOH}$ solution. That means that the amount of $\ce{OH-}$ ions in $400~\mathrm{mL}$ of that $\ce{NaOH}$ solution must equal the amount of $\ce{H+}$ ions in the acid solution.

The amount of $\ce{OH-}$ ions in $400~\mathrm{mL}$ of $5\cdot 10^{-2}~\mathrm{M}\ \ce{NaOH}$ solution can be found by taking the product of the liter of solution and the molarity of the solution. And that gives us $0.4\times 5\cdot 10^{-2} = 2\cdot 10^{-2}\ \mathrm{mol}\ \ce{OH-}$ ions. (Yes, I didn't use the units, I don't have to, I explained with words what I was going to do)

Since we used $2\cdot 10^{-2}\ \mathrm{mol}\ \ce{OH-}$ ions to neutralize the acid solution, that should mean that there were $2\cdot 10^{-2}\ \mathrm{mol}\ \ce{H+}$ in the acid solution.

To find the pH of the acid solution, we need to find the concentration of $\ce{H+}$ ions in that solution. The volume of the solution is known, $100~\mathrm{mL}$. And the amount of $ce{H+}$ ions too is known, $2\cdot 10^{-2}\ \mathrm{mol}$. The concentration of $\ce{H+}$ ions in the acid solution should therefore be $2\cdot 10^{-2} / 0.1 = 2\cdot 10^{-1}\ \mathrm{M}$.

$-\log[\ce{H+}] = -\log (2\cdot 10^{-1}) =$ none of the choices above.


texts: Hypothetical concerted process feasibility

texts:
How feasible is the following hypothetical reaction, where both C and D are awful leaving groups (so the reaction must happen in one step)?

I don't see a way how the orbitals could interact, so I think that such a transformation could only occur intermolecularly. I need a second opinion.


texts: Phenomenon where fumes can relight an extinguished flame

texts: I lit a mosquito coil and used it to melt down small down candle wax which had fallen on the floor. The coil then produced some dense fumes. I directed the fumes to the flame of a candle. As soon the fumes reached the candle, my coil caught fire again and started burning. I mean the flame actually traveled the path of the fumes and re lit my mosquito coil. I just wanted to know what this phenomenon is called? Why does this happen?


texts: How can the chlorophyll concentration of plants be measured?

texts: Is there a way to measure the chlorophyll content of plants (from e.g. leaves) with basic chemistry equipment (at home)?


texts:
I was going through a paper on organic LED chemistry [1]. I saw that the authors referred to "$1A_g$" and "$1B_u$" excitons (and also "$2A_g$" and "$2B_u$" excitons), terms which I don't really understand because I am from an engineering background. The terms are used on the 2nd-to-last paragraph of page 4 of the paper.

Can anyone help me understand this terminology?

[1] W. Barford, R. J. Bursill, and R. W. Smith, Phys. Rev. B 2002, 66, 115205


texts: Is the density of the solution significantly different from the density of the solvent?

texts:
I am working on a mathematical model for the dissolution of coffee in water. I need to know some precise details about the effects of dissolution on the density of the mixture of the substances (that is, the density of the solution). The system is isothermal and the pressure is constant. I just want to focus on mass, volume, density, and concentration as the relevant variables.

In the drawing (below), there is a graphical representation of the system in question (in the bottom image, I should have mentioned concentration of water and coffee instead of density). We have a container of water with a single coffee solid and I've drawn in 20 molecules for both the water and the coffee. The volumes are obviously not to scale (it looks like approximately 50% of the coffee has dissolved in the second pic, not 20%!).

Start

So at the beginning, $t = 0$, no coffee has dissolved so far and the solution liquid is simply the water. We have the following information for the density and the volume of the coffee, water, and the solution, respectively

$\rho_c = 1500$ kg m$^{-3}$

$\rho_w = 1000$ kg m$^{-3}$

$\rho_s = \rho_w = 1000$ kg m$^{-3}$

$V_c = 0.1$ m$^{-3}$

$V_w = 0.5$ m$^{-3}$

$V_s = V_w = 0.5$ m$^{-3}$

The solution is just the water at the start.

Finish

At, say, $t = 100$, 20% of the coffee has dissolved and has diffused out evenly into the solution and the system is in equilibrium.

Now the solution contains both water and coffee. I realise that the chemical reaction dissolution and interactions at a molecular level between the coffee and the water have an impact on the volume and density of the solution. I need information on the density of the solution to decide whether the compressible Navier-Stokes or the incompressible Navier-Stokes govern the flow in the solution.

What is the density  and volume of the solution? If experimental measurement is required for this can you instead give me an approximate answer.

I need to know how much of a change in solution density occurs from $t = 0$ to $t = 100$.


texts: How does amine inversion affect basicity?

texts:
What is amine inversion, and how does it affect basicity?

For instance, why is $\ce{Et3N}$ less basic than (2.2.2.)cyclohexyl-amine despite the +I from ethyl groups? The answer to the question is option 3.

  Compare the basic strengths of the compounds given:

  (i) > (ii) > (iii)
  (ii) > (i) > (iii)
  (ii) > (iii) > (i)
  (iii) > (ii) > (i)


texts: Why is molar mass of a substance and atomic mass number usually the same?

texts:
I recognize what atomic mass represent and what molar mass represents by why is it that a substances molar mass and it’s atomic mass are usually the same number

Ex: chlorine has an atomic mass of 35.453 u and a molar mass of 35.453 g/mol


texts: Can the number of intermediates for a reaction be more than the total number of transition states?

texts: I'm getting results from a transition state guess software, in which the number of intermediates are two and there's only one transition state for a reaction, is that possible?


texts: What is the molecular structure of xenon hexafluoride?

texts:
Xenon hexafluoride, $\ce{XeF6}$, can be obtained by reaction of xenon with excess fluorine gas.

What is the gas-phase structure of the molecule?

What experimental evidence is there to support it, and is there any theory which allows for an prediction of the structure?

[Note that solid $\ce{XeF6}$ has multiple polymeric forms, and is hence excluded from the scope of this question.]


texts:
I recently did the experiment where you drop a piece of iron in an aqueous solution of copper sulfate. After a while, the piece of iron gets coated with a fluffy coating of copper that can be dried and mashed into a powder. Apparently this happens because iron is more reactive than copper, according to the reactivity series.
Can I do the same thing by making an aqueous solution of aluminum sulfate, then dropping a piece of magnesium metal in? It should work because magnesium is above aluminum on the reactivity series, right?


texts: How do the three Miller indices (hkl) denote planes orthogonal to the reciprocal lattice vector?

texts:
The Wikipedia page for Miller indices defines Miller indices as follows:

There are two equivalent ways to define the meaning of the Miller indices: via a point in the reciprocal lattice, or as the inverse intercepts along the lattice vectors. Both definitions are given below. In either case, one needs to choose the three lattice vectors $\mathbf{a}_1$, $\mathbf{a}_2$, and $\mathbf{a}_3$ that define the unit cell (note that the conventional unit cell may be larger than the primitive cell of the Bravais lattice, as the examples below illustrate). Given these, the three primitive reciprocal lattice vectors are also determined (denoted $\mathbf{b}_1$, $\mathbf{b}_2$, and $\mathbf{b}_3$).
Then, given the three Miller indices $h, k, \ell, (hk\ell)$ denotes planes orthogonal to the reciprocal lattice vector:
$$\mathbf{g}_{hk\ell} = h \mathbf{b}_1 + k \mathbf{b}_2 + \ell \mathbf{b}_3.$$
That is, ($hk\ell$) simply indicates a normal to the planes in the basis of the primitive reciprocal lattice vectors. Because the coordinates are integers, this normal is itself always a reciprocal lattice vector. The requirement of lowest terms means that it is the shortest reciprocal lattice vector in the given direction.

This idea of the three Miller indices ($hk\ell$) denoting planes orthogonal to the reciprocal lattice vector is something that I'm not confident that I'm understanding. My understanding is that the real (real space) lattice vector is described by the Miller indices as $h{\mathbf  {a_{1}}}+k{\mathbf  {a_{2}}}+\ell {\mathbf  {a_{3}}}$, where the $\mathbf{a}_i$ are linearly independent basis vectors. However, if I am understanding this correctly, the Miller indices are actually not (directly) defined in terms of the real lattice vector, but are actually defined directly in terms of the reciprocal lattice vector $h{\mathbf  {b_{1}}}+k{\mathbf  {b_{2}}}+\ell {\mathbf  {b_{3}}}$, where ${\mathbf  {b_{i}}}$ are the basis of the reciprocal lattice vectors; specifically, the Miller indices are defined to denote the family of planes orthogonal to $h{\mathbf  {b_{1}}}+k{\mathbf  {b_{2}}}+\ell {\mathbf  {b_{3}}}$. This is evidenced by the fact that said orthogonal plane is not always orthogonal to the linear combination of real lattice vectors $h{\mathbf  {a_{1}}}+k{\mathbf  {a_{2}}}+\ell {\mathbf  {a_{3}}}$ (see image below), since the reciprocal lattice vectors need not be mutually orthogonal (that is, although the $\mathbf{b}_i$ are basis vectors, they are not necessarily linearly independent, which I think is mathematically correct (?)).

(By Felix King, and posted to https://en.wikipedia.org/wiki/Miller_index)
I would appreciate it if people would please take the time to review everything that I've written so far. Is my understanding correct? Am I misunderstanding anything?
The last point that I'm having a bit of trouble with is how a plane can be defined in such a way that it is orthogonal to three basis vectors? I suspect that this is possible if and only if the basis vectors are not all linearly independent, as I alluded to in my explanation above, but I'm not sure. I think this is more of a mathematical question, so I will instead post it to math.stackexchange for a more mathematics-focused answer, but I would also appreciate it if people could please review my understanding of this and provide clarification.


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

This third round of golf concerns the synthesis of chloramphenicol 2,2-dichloro-*N*-[(1*R*,2*R*)-1,3-dihydroxy-1-(4-nitrophenyl)propan-2-yl]acetamide, an antibiotic on the World Health Organisations list of essential medicines:

InChI=1S/C11H12Cl2N2O5/c12-10(13)11(18)14-8(5-16)9(17)6-1-3-7(4-2-6)15(19)20/h1-4,8-10,16-17H,5H2,(H,14,18)/t8-,9-/m1/s1

In addition to being a useful target, chloramphenicol was chosen as
during previous rounds of synthesis-golf, several people commented that they'd like to see targets amenable to biosynthetic transformations, and scaleable process routes. This target very much fits both of those criteria (the drug is manufactured on a huge scale, and several enzymatic routes have been developed).

The challenge is to propose a route to chloramphenicol, including a method for setting the absolute and relative stereochemistry of the 1,2-hydroxyamine functionality. You may start from anything commercially available in the Sigma Aldrich catalogue, but to keep things interesting, no starting material may contain more than 8 carbon atoms.


texts: My professor has had the reaction shown in DMSO and ethanol as solvents but made clear these are used for different circumstances. I did not understand what the difference in circumstances are. Does it have something to do with being polar and aprotic and what alkene is being reacted with the cyanide?


texts: What is the effect of oxygen in welding?

texts:
Welders use a shielding gas to avoid oxygen interact with the electrode. I supposed is might be because of ferric oxide formation as the electrode is steel-made. But fusion temperature of ferric oxide is quite the same than iron so I'm not sure what is the reason for the shielding gas (usually argon). I have gone through some works but found nothing about it.

Any idea what is the effect of oxygen? Is there any reaction involved which plays a role against a good welding or just physical issues?


texts: Effect of spontaneous transmutation of atom in crystal

texts:
What happens to a compound when one of its atoms changes via spontaneous nuclear reaction to an atom with very different bonding? For example, beryllium-7 turns into lithium-7 with a half-life of 53 days. After 53 days half the divalent Beryllium in a crystal of BeF2 would be monovalent Lithium ions. Half of the flourine atome formerly bonded to the former Beryllium atoms would be "floating free", not something Fluorine is wont to do. What would actually happen? Would there be a fluorine ion trapped in the crystal? A flourine atom? Some kind of radical?

Plainly energies available from  the nuclear reaction are orders of magnitude larger than anything that would ever be available in chemical bond energies, so even crazy unstable species have plenty of energy to form.


texts: Why does rotating a double bond break the bond?

texts: It is well known that double bonds are "stiff" and make particles less likely to rotate around the bond. But why? What makes it so that the bond has to be orientated a specific way?


texts: Using the quasi-steady assumption for reaction-diffusion equations

texts:
I have a question regarding an equation for changes in chemical concentration. The chemical concentration we are looking at changes due to diffusion, decay and production of the chemical. Since the diffusion happens so much faster than the other two, it is given that we can you a so-called quasi-steady assumption. This then gives the equation:

$$D \nabla^2c-a \cdot c+b\cdot c=0$$

where $a$ and $b$ are rates of decay and production, respectively. $c$ is the chemical concentration and D is the diffusion coefficient.

Is it correct that the reason we only have a derivative expression for the diffusion because it happens so fast relative to the other two, and therefore we can assume the chemical concentration for the two other processes to remain constant (using the quasi steady assumption), or is that not a correct reasoning for why the equation has the simple expression for decay and production, while we need a more complex expression for diffusion?


texts:
Can Grignards be chiral? I've seen them drawn as ionic structures in class. I've also seen little asterisks on certain positions of Grignards (a common designation of chirality). So this begs the question - are Grignards chiral?

From what I understand Grignards are best described as polar covalent rather than ionic, but that still leaves one more question: can ionic compounds be chiral?


texts: Why are substituted biphenyls optically active?

texts: Why are some substituted biphenyl compounds optically active and what kind of substituted biphenyls are optically active . I read this in a book but no satisfactory reasons were given and no examples were given thanks in advance .


texts: How does activated carbon bind the adsorbate?

texts:
I read some articles and journals about activated carbon and found a problem about how the adsorbate could bind to the activated carbon. Some said it is because of intramolecular forces (van der Waals) and some said it is because of chemisorption. If chemisorption plays a role, what would the bonding be?
And if the bonding is just caused by intramolecular forces, what is the active site of the activated carbon? An answer or illustration for better understanding is greatly appreciated.


texts: Why did phenol respond to Brady's reagent?

texts:
I was teaching a friend a few basic organic analysis experiments, during which I was showing him, how to get an alcohol, and took a sample of phenol.

The neutral $\ce{FeCl3}$ test went fine(which i mentioned, was only for phenols), with an ultra dark violet colouration, but just to show him a negative test, i added some of Brady's reagent, and surprisingly, it gave a yellowish colouration (something close, a mix of yellow and orange, couldn't trust my eyes, since i was kind of in disbelief). The samples in the lab are mostly pure, and not mixtures of different organic compounds. To satisfy him, i gave a possible explanation, saying that the phenol might've got oxidised to hydroquinone, and hence, might've given the test.

What probably would've happened there? Any chances my explanation was right?


texts: How to make sense of the 'Relaxation Method' for measuring reaction kinetics?

texts:
I get the concept that one can measure the rate of reaction by measuring the rate at which an equilibrium state reaches another equilibrium state after the system is perturbed (usually by heating). However, I do have an issue with it. Consider the reaction $$\ce{A <=> B}$$

My lecture handout suggests that the rate of change of $[\ce{A}]$ is given by:

$$\frac{\mathrm d[\ce{A}]}{\mathrm dt}=-k_\text{forward}[\ce{A}]+k_\text{reverse}[B]$$

However, surely it's just $\frac{\mathrm d[\ce{A}]}{\mathrm dt}=-k_\text{forward}[\ce{A}]$. The equation in the lecture handout would make sense at equilibrium because that is when $\frac{\mathrm d[\ce{A}]}{\mathrm dt}=0$ but I think it seems to insinuate that this is always valid (without explicitly saying so). Am I right or is that equation always valid? If it is: why?


texts: Calculating Equilibrium Constant from Cell Potential at Nonstandard Temperature

texts:
I'm currently working on a problem for a general chemistry class.
This is the voltaic cell given in the problem:
$$\ce{Sn^4+(aq) + Cu(s) -> Sn^2+(aq) + Cu^2+(aq)}$$
$$E^\circ_{cell} = \pu{-0.21 V}$$
What is the value of the equilibrium constant at $\pu{115 ^\circ C}$?

For this I'm using this equation $$-nFE^\circ_{cell}  = RT\log(K)$$ Plugging this into the equation:
$$ (\pu{2 mol e^-})(\pu{96500 C}/\pu{mol e^-})(\pu{-0.21 V}) = (\pu{8.314 J/molK})(\pu{388 K})\log(K)$$ I get a value of $$K = 3.49 \times 10^{-6}$$ However, my instructor's solution is using this equation $$- E^\circ_{cell} = (0.0592/n)\log(K)$$ and gets a value of $8.04276 \times 10^{-8}$.

I thought you could only use that equation if the temperature is $T = \pu{298 K}$ (standard state conditions). Not sure whether I'm right or wrong about this, any insight is appreciated.


texts: Is it true that human cells grow in levorotation?

texts:
I remember reading this in a popular science magazine, some 20 years ago: that in most of the living organisms, the proteins (in fact, the amino acid molecules that make the proteins) are levorotatory and very few such molecules are dextrorotatory.

Is that true, at least for humans?


texts:
I've been reading a lot of conflicting articles/threads pertaining to which lubricant is compatible with rubber/plastics and I'm stumped.

From what I've come across, the consensus is that silicone is safe to use on rubber and that petroleum based eats at it over time. But then I heard the opposite.

What I'm wondering is, if rubber is composed of some petroleum then why would a petroleum lubricant or grease have a negative effect on it? Also what about plastics and vinyl, do they get damaged as well?


texts: I have spent the last few years self-studying chemistry and I want to try doing practical experiments with chemistry in a safe manner. I don't plan on doing anything dangerous but would still like to keep precautionary measures. I allotted myself a medium-sized (8ft by 6ft) space in the garage to carry out any experiments. What equipment would you recommend me to keep for precautionary measures as well as carrying out chemistry experiments?


texts: Meaning of the Term "Heavy Metals" in CofA?

texts:
I've always wondered, what is the meaning of the following terms on a certificate of analysis:

"Heavy Metals"
"Heavy Metals (as Pb)"

What exactly is comprised in "heavy metals", "heavy metals (as Pb)" and what is excluded from each? What is the difference between the two variants? I tried to find a clear standard describing this to no avail.


texts: Propylene Glycol Degradation due to Sunlight

texts: I had a translucent container of propylene glycol exposed to sunlight.  When I went to use it, I noticed it has a strong "acetone" like odor.  Someone said it was a photo-oxidation reaction of the glycol into ketones or aldehydes.  What happened and will the odor get worse even though it is is now removed from sunlight?  Do I need to worry about these ketones or aldehydes in the glycol?


texts: Shouldn't the N pointed to by the red arrow also be a stereocenter? I am asking this because I think it's lone pair cannot take part in nitrogen inversion.


texts: Is plane of symmetry a necessary and sufficient condition for optical inactivity in coordination compounds?

texts:
In organic chemistry, we have to check for all three types of symmetry in a compound to check its chirality, ie, plane, alternate axis and centre of symmetry. But in coordination compounds, do we need to check all the symmetries to check its chirality? The ligands are supposed to be achiral. The difference between the two being that in coordination compounds only one "chiral" center is present but in organic compounds it can be more than one.
All the achiral coordination compounds of any coordination number which I have come across have a plane of symmetry. But for those which don't have, I have to check whether it's image coincides with itself or not. So, is plane of symmetry a necessary and sufficient condition for achirality of coordination compounds?
This thing is necessary for my purpose, as I have to solve problems in limited time, so I cannot use the orignal method always.


texts:
How does this compound even exist? Having such a massive ring strain.

Is it even conjugated? As it's resonance structure will have all double bonds.

Since it was reported to be found, there must be some stabilizing factor. I was wondering whether that might be aromaticity, since it does have 4n+2 electrons.


texts:
We know that the molecule of H₂O is V-shaped. This is what makes it a dipole.

But why is that? I mean, if the hydrogens have a partial positive charge, then they should try to get away from each other, until they are diametrically opposite to the oxygen molecule. But that doesn't happen. Why is this?


texts:
Recently I was watching a video on Valence Bond Theory, on the MIT Open-Course youtube channel. The teacher there said that

  For hybridization to occur, electron promotion from fully filled orbitals to empty ones is a must.

But here in a book it is specifically mentioned that

  Electron promotion, though common, but is not 'a must' for hybridization.

Also, it is clearly written that sometimes even the filled orbitals take part in hybridization.

I tried finding some examples of such a case on the web, but could not. It would be a great help if someone tells me even one example where the fully filled orbitals also take part in hybridization, with an explanation why it is so.

The link for the 41 min long video is here.


texts: Synthesis of para-chloroanisole using diazotisation followed by chlorination with aluminium chloride

texts:
Is this a legitimate reaction scheme to synthesise para-chloroanisole from benzene and methanol as the only organic reactants?

$$\ce{C6H6 -> HNO3/H2SO4 -> H2/Pd -> HONO/{Ethanol}\\ -> {Methoxide}/THF -> Cl2/AlCl3}$$

I think this would make ortho-chloroanisole (minor product) and para-chloroanisole (major product).

The methoxide would be generated by:
$$\ce{{Methanol} -> NaH -> {Methoxide}}$$


texts: I want to do a PES scan of a radical structure in Gaussian. However, I'm not completely sure how to prepare an input file. I've figured out that charge and multiplicity are 0 and 2. What I don't know is how to indicate where a radical is. Will Gaussian figure it out itself by bonds and electrons count or do I have to indicate it explicitly?


texts: Acetic acid or ethanoic acid - trivial names vs systematic names and correct formula representation

texts:
My teacher likes to use household materials to do experiments. Today, we did an experiment that showed the reaction of vinegar and eggshell.

When we were doing the analysis of the experiment, I realized that my teacher used the term acetic acid ($\ce{CH3COOH}$) instead of ethanoic acid. So, my questions are:

What is the accepted usage for the terms acetic acid and ethanoic acid?
Which formula is the accepted representation of acetic acid, $\ce{CH3COOH}$ or $\ce{C2H4O2}$?


texts: Finding the wavelength of maximum absorption of Tartrazine using Fieser-Kuhn

texts:
How would you use Fieser-Kuhn rules to calculate the wavelength of maximum absorption for tartrazine?

Fieser-Kuhn rules states that:
$\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$

What would $M$ be in this example? There aren't any alkyl substituents, but what I'm not sure about ring residues. Would this refer to the $SO_3Na$ and $COONa$?
Would $n$, the number of conjugated double bonds be equal to 12?

Does Pyrazole count as a ring for $R_{endo}$? So $R_{endo}=3$?

Or would Woodward-Fieser rules be more suitable to use in this scenario?


texts:
For comparing the stability of different compounds that undergo resonance, I was taught to first check for equivalent resonance, then the number of atoms on which the delocalization was taking place and so on(e.g phenolate ion vs acetate ion)

But comparing benzyl carbocation with $\ce{CH2=CH-CH2+}$, even though $\ce{CH2=CH-CH2+}$ has equivalent resonating structures(and hence a greater extent of delocalization of electrons), it is less stable than benzyl carbocation. Why?


texts: Has Crabtree's photochemically-activated mercury-catalysed hydrocarbon activation process ever been used commercially?

texts:
In the 1980s, while searching for new hydrocarbon activation catalysts, Crabtree's research group accidentally found that mercury vapour activated photochemically could perform some interesting and unusual alkane activation reactions yielding unusual products.

Some of the work is summarised in this Journal of Chemical Education paper from 1988. The reaction seems to be able to produce some unusual (and hard to get) dimers of hydrocarbons and is also tolerant of other functional groups (eg alcohols, amines) and can also generate cross coupled products (eg it will couple alcohols with hydrocarbons).

At the time it was thought to be an interesting curiosity but with some prospect of yielding easy routes to some hard-to-get targets.

Has it ever been used in a significant synthesis? Or for any industrial processes?


texts: How do I convert 4-(Methylthio)benzaldehyde to 4-(thioacetate)benzaldehyde?

texts: Sorry if I have the incorrect name of the final product. I'm trying to acylate the methyl mercaptan substituent to a thioester (thioacetate). I appreciate any help!


texts: Why must the rate law be experimentally determined?

texts:
I am familiar with the idea that rate law must be determined experimentally. I am also familiar with the idea that there is no formulated way for coming up with the rate law besides just experimentation.

My question is: why isn't the rate law of:

$$ aA + bB \rightarrow \mbox{something}$$

just:

$$r = k[A]^a[B]^b$$

?

I mean, the equilibrium constant expression involves something to that effect, and the equilibrium constant expression should be precisely talking about when the rates for each direction are equal. So if the rate law is not the above, then why does the equilibrium have that expression?

EDIT: A bit off topic, but how is it possible for something to be zeroth order?


texts:
If the standard hydrogen electrode (SHE) is set arbitrarily to have a potential that is equal to 0 V, and has an absolute real potential. Then, in electrochemistry, how are the electrode potentials of other electrodes are determined using it?

Our high school textbook states that we form a galvanic cell from the SHE and another half cell of the electrode that we want to determine its potential. Then using the voltmeter, the voltage of the cell should resemble the standard electrode potential of the electrode.

I really don’t get it, because the voltage should resemble the difference in potential between the electrodes.


texts: Deviation angle for 1st order diffraction

texts:
(i) A diffraction grating has 560 lines per mm. Calculate the grating spacing. If the total length of the grating is 2 cm, how many lines are there?

  (ii) Light of wavelength 500 nm is incident on the grating with this spacing. Calculate the deviation angle for 1st order diffraction.

I am having difficulty with the (ii) part. For my spacing I got 0.0018 mm. So, then I used

\begin{align}
n \lambda &= d \sin{\Theta} \\
\frac{n \lambda}{d} &= \sin{\Theta} \\
0.27 &= \sin{\Theta} \\
\Theta &= \sin^{-1}{(0.27)} = 15.7^\circ
\end{align}


texts: How can water catalyse a reaction between iodine and aluminium?

texts:
A few drops of water can initiate a reaction between iodine and aluminium.

https://www.youtube.com/watch?v=SKSU72-1ERc

How can this happen, since iodine is only slightly soluble in water?


texts: How many stereoisomers of 1-methylidene-2-(4,4,6-trimethylhepta-2,5-dien-1-yl)-1,2-dihydronaphthalene are there?

texts:
What is the total number of stereoisomer of this compound?

2
4
8
16

As there is only 1 chiral carbon, and 2 out of 4 C=C double bonds that contribute to geometric isomerism (cis/trans), I think there are 2^(1+2)=8 stereisomers. But the answer says 4. Can someone please explain the reasoning? Thanks!


texts: When succinic acid is treated with excess $\ce{NH3}$, what will the mechanism be? I feel both $\ce{COOH}$ groups should be converted to $\ce{CONH2}$, but this is not the product.