texts: Why is it not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons?

texts:
My textbook says the following about metallic bonding:

  The metal copper has one valence electron. The valence electrons of nearby copper atoms are shared in a similar way to covalently bonded solids, but it is not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons as occurs in a covalent bond. Instead, the electron sharing that occurs in metals is not as restricted as in the covalent solid.

The problem is that this section doesn't adequately (in sufficient detail) explain why it is not possible for seven close copper atoms to come together to gain a noble-gas configuration of valence electrons as occurs in a covalent bond.

I would greatly appreciate it if people could please take the time to clarify this in further detail.


texts: Is isobutyl chloride or ethyl chloride more reactive in an SN1 reaction?

texts:
Compare the rate of $\mathrm{S_N1}$ reaction in the following compounds:

We see that both compounds form primary carbocations. However, there is more hyperconjugation in the second compound as compared to the first one.
Also as the step in which the leaving group leaves is rate determining step (slowest step), which is before the rearrangement of the carbocation, I concluded that the second compound must have a greater rate of $\mathrm{S_N1}$ as compared to the first one.
But the answer says that the first has a greater reactivity than the second. Is the answer correct? If yes, then why?


texts: Role of Acetonitrile and Ammonium Acetate buffer in Leucomalachite Green stock solution?

texts:
I am trying to repeat an experiment conducted by FDA on Malachite Green (MG).
According to this paper,
Prepare a series of LC calibrants by aliquoting into individual 15 mL graduated
glass or disposable polypropylene centrifuge tubes, 50 µL, 100 µL, and 200 µL
of the 0.1 µg/mL MG2 solution and 50 µL and 100 µL of the 1.0 µg/mL MG1 solution.
Dilute each to 5.0mL with (1:1 vol) acetonitrile/ammonium acetate buffer
(mobile phase A), vortex mix or stopper and invert to mix thoroughly.
Based on a 5 g sample weight, these solutions will generate standards with
concentrations of 1, 2, 4, 10 and 20 ng/g of MG.

If I am not wrong, Malachite Green used in this paper is from the salt, Malachite Green Oxalate.

Is Acetonitrile used here as a pH buffer?
What is the role of Ammonium acetate?

If I plan on using Raman Spectroscopy to detect MG in my samples, shouldn't I be using the pure forms of MG as my reference signal? If so, wouldn't the addition of these two chemicals affect my readings?
References
The pdf document originally linked in this post (see edits) is no longer available.
The most similar reference identified (available here via the Internet Wayback Machine) is:

Wendy C. Andersen, José E. Roybal, Sherri B. Turnipseed. Determination of Malachite Green and Leucomalachite Green in Salmon with In-Situ Oxidation and Liquid Chromatography with Visible Detection. Laboratory Information Bulletin (LIB) 4334: Malachite Green and Leucomalachite Green in Salmon. Volume 20, No. 11, November 2004.


texts: Why isn't there a hydrogen bond present between the oxygen atom and hydrogen atom of adjacent alcohol groups?

texts:
*I know that there is inter-molecular hydrogen bonding between the molecules of glycerol.
*What makes the adjacent alcohol groups behave differently towards each other as compared to when they interact through separate molecules?
*(additional question) - How many Carbon-Carbon single bonds worth do hydrogen bonds persist?


texts: Visualizing atoms in XYZ file with colors representing partial charges

texts: I have a file containing the atomic coordinates (in XYZ format) of a structure, and I also have a list of the partial atomic charges for each atom. I'd like to create an image of the structure where the colors of the atoms correspond to the computed charges. What are some good ways for doing this?


texts: How to get the right formulas for combustion (rocket chamber) or where to find them?

texts:
I am a space enthusiast and am intrigued mostly by rockets.
I recently found a book HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES and have been fiddling around with rocket engine calculations and calculated a theoretical engine.
Now, this book/PDF has a lot of useful calculations and many other tips and tables in it. And the tables are what I want to know about.
In the document, there are calculated performances for many fuels at different pressures, mixture ratios, and many graphs of how the performance (or some "part" of it) is affected by other variables.
I also found many sites with this kind of graphs, like the site from Robert A. Braeunig and more precisely this site with these charts again.
So the question is: How can I calculate these graphs with my "totally" random variables or at least where could I find this knowledge. I'm basically interested just in the graphs shown on the  "more precise" link.
Thank you for your answers and for sharing your knowledge with me.

Disclaimer: I have no intention of building a real rocket engine as I do not have manufacturing knowledge nor tools to make it (so even if I wanted to I could literally).


texts: Reaction of alpha hydroxyketone with KOH

texts:
What happens when 2-hydroxycyclohexan-1-one (an alpha hydroxyketone) reacts with aqueous $\ce{KOH}$?

I tried something like Favorskii rearrangement, but it's wrong because OH isn't a good enough leaving group.


texts: Why do branched chain compounds have lower boiling points than the corresponding straight chain isomers?

texts:
The branched chain compounds have lower boiling points than the corresponding straight chain isomers. For example,

  $\ce{CH_3CH_2CH_2CH_2CH_3}$ -
  No branching-Pentane (n-pentane) ($\mathrm{b.p.}=309~\mathrm{K}$)
  $\ce{CH_3CH(CH_3)CH_2CH_3}$ -
  One branching-2-Methylbutane (Iso-pentane) ($\mathrm{b.p.}=301~\mathrm{K}$)
  $\ce{C(CH_3)_4}$ - Two branches-2,2-Dimethylpropane (Neo-pentane) ($\mathrm{b.p.}=282.5\mathrm{K~}$)

  This is due to the fact that branching of the chain makes the molecule more compact and thereby decreases the surface area. Therefore, the intermolecular attractive forces which depend upon the surface area, also become small in magnitude on account of branching. Consequently, the boiling points of the branched chain alkanes are less than the straight chain isomers.

The above extract from my book, mentions clearly that branching makes the molecule more compact and thereby decreases the surface area. Even for isomeric alkyl halides, the boiling points decrease with branching. The reason is said to be because of the decrease in surface area, same as explained before. How does decrease in the surface area make the intermolecular forces small in magnitude?


texts: Proving RTln($a_i$) equal to non PV work done by system,where $a_i$ is activity

texts:
We know that chemical potential is defined as ${\mu}_i={\mu}_i^{standard}+RT\ln(a_i)$. Here $a_i$ is the activity of $i^\text{th}$ component of solution. In case of gases instead of $a_i$ it is $f_i$ (fugacity). Activity is the activity coefficient multiplied by concentration or in case of fugacity it is the product of the fugacity coefficient multiplied by partial pressure of the gas.

But now this is not the only definition of Chemical potential. Chemical potential also means the partial molar Gibbs free energy when pressure and temperature of the system are constant. We know that change in Gibbs free energy of a system at constant temperature and pressure also represents Non-PV work done by system.

How can the term $RTln(a_i)$ can be correlated to Non-PV work done by system in order  for the two definitions to be equivalent?

NEW QUESTION AFTER READING YOUR ANSWER(S)

Philipp, Ok after reading all your answers I got now modified question that still remained.First of all we know K and Kc are related but kc can be modified by adding activity coefficients and standard concentrations to give equilibrium constant that should be equal to K.This requires the activity coefficients (That we used with Kc) to always follow relation with fugacity coefficients and RT terms which is not proved in answers there and that is what actually my question is asking.Sorry but I am reluctant here to write maths but I just say refer to the second equation from last in your This Answer

Actually earlier my question has title ways of expressing concentration in activity term


texts: Why is formyl chloride unstable? I know it is just a combination of CO and HCl. But why it is unstable whereas other acyl chlorides are stable, like acetyl chloride?


texts: What is the structure of trifluoromethanesulfonic acid in the gas phase?

texts:
During an interesting discussion in our group’s seminar, the question arose what actually causes trifluoroacetic acid to be a much better nucleophile than trifluoromethanesulfonic acid. Part of the discussion was whether the oxygens of trifluoromethanesulfonic acid were equal or not.

Traditionally, $\ce{TfOH}$ is drawn as shown in the structure below on the left. The structure would assume the molecule having point group $C_\mathrm{s}$ due to the non-equality of the oxygen atoms only one of which bears a hydrogen. The triflate anion $\ce{TfO-}$ in solution, on the other hand, has three homotopic oxygens as can be seen in the structure on the right, leading to the more symmetric point group $C_\mathrm{3v}$.

One of the opinions voiced in the discussion was that even the gas-phase molecule $\ce{TfOH}$ adopted a $C_\mathrm{3v}$ point group, the hydrogen being in the same axis as carbon and sulfur and somewhat centred between the three oxygens. This makes perfect sense when thinking about it. Therefore, my questions are:

Has the structure of trifluoromethanesulfonic acid or a structurally strongly related acid been studied in the gas phase? (Please provide a reference)
Does the experiment suggest equivalent or non-equivalent oxygens?
How well can that idea be extended? e.g. should one consider the structure of formic acid to be $C_\mathrm{2v}$ symmetric rather than $C_\mathrm{s}$?
Do (solid-state) crystal structures or other experiments exist that confirm a different structure for solid $\ce{TfOH}$?
If solid and gas phase structures differ substantially, what about the structure of the molecule in liquid phase/solution?


texts: Is there any software package for quantum chemistry that includes CAMB3LYP?

texts: I want to do calculations on systems with photoinduced electron transfer, and I've read that the Coloumb Attenuating Method is a modification of the functionals that makes calculations including long-range electron transfer more accurate. Unfortunately I can't seem to find CAM in Gaussian. Is there some other software I should look at?


texts: What factors contribute in making a solution more endothermic?

texts: For example, a solution between potassium nitrate and water is more endothermic than sodium nitrate in water. Can someone explain?


texts: How much hydrogen or oxygen will be produced in the electrolysis of water?

texts:
Is there a way to exactly calculate the quantity of hydrogen or oxygen in a water electrolysis? I am thinking of a plain and simple electrolysis like an anode and cathode in salted water separating oxygen and hydrogen.
I am looking for the relation between the amounts of hydrogen $n(\ce{H2})$ or oxygen $n(\ce{O2})$ and the amounts of water and salt, current, voltage and time of electrolysis.


texts: How to calculate concentrations in a diluted mixture of multiple solutions?

texts:
I have a homework problem as follows:

  A solution was prepared by mixing $25.0\ \mathrm{mL}$ of $0.208\ \mathrm{M}$ $\ce{Fe(NO3)3}$ and $4.50\ \mathrm{mL}$ of $0.00190\ \mathrm{M}$ $\ce{KSCN}$ and diluting to $50.00\ \mathrm{mL}$ with solvent, $0.10\ \mathrm{M}$ $\ce{HNO3}$. Calculate the initial concentrations of the thiocyanate ion and the iron(III) ion before any reaction takes place.

Now, how do I proceed with the question? At first I thought that it should just be the same concentration as the solutions, $0.208\ \mathrm{M}$ and $0.00190\ \mathrm{M}$, because there is only one thiocyanate and one iron(III) ion in the solutions. But the fact that we have an $\ce{HNO3}$ solution confuses me. Am I somehow supposed to use $M_1 V_1 = M_2 V_2$?


texts: Is NaCl crystal always going to have even number of atoms?

texts:
I just read:

  In $\ce{NaCl}$, atoms don't aggregate so as to form discrete molecules but they are held together in a network structure. The ratio of the $\ce{Na}$ to $\ce{Cl}$ atoms in a sodium chloride crystal is $1:1$.

Here I have a $\ce{NaCl}$ crystal. Assume that I can break this crystal in all possible ways. So that I have its two pieces every time with a different mass ratio. Would these pieces always contain even number of atoms of $\ce{Na}$ and $\ce{Cl}$. Or, is this ratio going to be same for all conditions?

Suppose I have a $\ce{NaCl}$ crystal of mass $a$. I break it into two pieces of masses $x$ and $y$ such that $x,y<a$ and $x+y=a$. $a$ is a constant by its definition whereas $x,y$ are variables. Then, is the following true?

$$R(x)=R(y)=1:1$$

Where $R(x)$ and $R(y)$ denotes the ratio of $\ce{Na}$ to $\ce{Cl}$ atoms for all values of $x$ and $y$ respectively.


texts: I will be given a binary mixture containing two unknown compounds(the mixture could be either liquid or solid- I don't know yet). The plan of the experiment is to identify the two compounds. So my primary concern is to separate the binary mixture and purify the individual compounds(then the subsequent classification tests/NMR/IR analysis should be straightforward).  I am thinking of doing an acid-base extraction but don't know how to since I don't know any physical properties of the compounds. Any suggestions would be appreciated.


texts: What causes straight fatty molecules to form a lattice (e.g. saturated fats)?

texts:
What causes multiple chains of saturated fats to pack together and form a solid? It is said that because the chains are straight, they form a lattice and line up more easily.

But if I had a bunch of straight sticks and drop them into a pile, they don't magically form a lattice where everything lines up. So is there something about the fatty chains that causes them to line up and pack closely together into a lattice?


texts: Is it possible to react two distinct carboxylic acids to form a dicarbonyl ester?

texts:
By a dicarbonyl ester I mean something like this:

where R1 and R2 are alkyl substituents and the reacting carboxylic acids are:


texts: Are wrinkles\folds in paper reversible by heat, pressure or something else?

texts:
I ran into this question on Lifehacks.SE, regarding how to remove wrinkles from a crumpled piece of paper. Suggestions included ironing the paper or placing it under some heavy books for a few days.

I am wondering about the chemistry of these processes and whether they are actually effective. This Reddit thread gives some general background about the molecular structure of paper and what happens when you fold paper with enough force to permanently create folds, i.e. to break bonds (as opposed to rolling it within the "elastic boundaries", as it says there). See also this excellent infographic from Compoundchem.

So, can ironing\applying pressure really straighten out a folded paper back to factory level? If not, is there any other way to unwrinkle a paper?

I'd appreciate explanations in the molecular level.


texts: Why is Libethenite (Cu2(OH)PO4) color green?

texts: It is not a complex compound and the copper atom is not oxidized so I'm wondering how does its color change. The book mentioned that at favorable conditions, adding water in Copper phosphate, which is blue, will result in the formation of Libethenite.


texts: The Reaction Between Nickel and Hydrochloric Acid

texts: Having conducted an investigation involving multiple metals, I have found that nickel refuses to react with concentrated hydrochloric acid. I have even left the reaction overnight and still have seen no mass change in the solid piece of nickel. Is the reaction simply extremely slow or does it not react despite being above hydrogen in the reactivity series?


texts:
In a reaction between an enol and an electrophile which will attack the electrophile, the oxygen of the $\ce{-OH}$ group or the pi electrons of the the double bond?

This is my attempt at a solution: Since, the oxygen atom has two lone pair of electrons it should be more electron rich than the double bond and therefore it should attack the eletrophile, Am i correct?


texts: Why is it a good idea to put some salt in the bread dough?

texts:
The salt that you can typically find in a kitchen is the $\ce{NaCl}$, isn't this salt supposed to act as an antiseptic?

I find a lot of recipes that suggest the addition of salt when preparing the mix for the leaven of the bread.

Isn't the salt supposed to act against the formation and the culture of bacteria that are carrying forward the leaven?


texts: Bromine Homolysis Using Handheld UV Lamp

texts:
I'm trying to investigate the homolysis of bromine for an IB Chemistry (high school) Internal Assessment. To do so, I need a UV lamp capable of splitting diatomic bromine into bromine radicals. Would a handheld UV flashlight off of Amazon (395 nm) or a 4W UV tube (265 nm) work to do this?

I'm trying to react bromine radicals with methane to produce other gases. I need to produce enough of these gases to create a noticeable change in mass of my bromine sample (0.05 g or more).


texts:
I am trying to estimate the redox potential of an excited state as described in this reference.

The paper says:

  The reduction potentials associated with the excited states
  cannot be directly measured and are typically calculated from
  known cyclic voltammetry (CV) and spectroscopic data. As
  an approximation, the excited-state potentials of a catalyst are
  related to its ground state potentials and its zero−zero excitation energy ($E_{0,0}$). $E_{0,0}$ can be estimated by the difference in
  energy between *PC $^3$MLCT$_1$ and PC $^1$A$_1$ and can be approximated by the maximum emission of the catalyst (Figure 2). As an example, the emission maximum for $\ce{Ru(bpy)3Cl2}$ in MeCN
  has been measured to be $\pu{615 nm}$ at room temperature and $\pu{582
nm}$ at $\pu{77 K}$ in a frozen MeOH/EtOH mixture. This corresponds
  to an $E_{0,0}$ value of $\pu{2.02 eV}$ at room temperature and $\pu{2.13 eV}$ at $\pu{77 K}$. Given the ground-state reduction potentials, the excited-state
  reduction potentials can be calculated as shown in Figure 4.

Then Figure 4 shows the calculation for the room temperature case:

$\ce{Ru(bpy)3^{3+} + e^- -> \text{*}Ru(bpy)3^{2+}}$

$E_{red} = \pu{1.26 V} - \pu{2.02 V} = \pu{-0.76 V}$

My question is: Why is it valid to use the $\pu{2.02 eV}$ from the spectroscopic measurement as $\pu{2.02 V}$ in the redox potential calculation?

From my understanding, $\pu{2.02 eV}$ is the energy between the ground state and the excited state, but these are units of energy, not potential, so I'm having a hard time seeing how can this calculation be done.


texts: Can hydrobromic acid perform substitution with propane?

texts: I am a student in the 11th grade, we recently had a chemistry exam, I lost marks because of a question that asks about the reaction between $\ce{HBr}$ and $\ce{C3H8}$. According to our teacher  $\ce{HBr + C3H8}$ is going to react and form $\ce{C3H7Br + H2}$. In my opinion I don’t think that a reaction is going to happen, because $\ce{HBr}$ is an acid and acids can't react with alkanes. Can you please state your opinion and justification?


texts:
Why does beryllium form carbide of formula $\ce{Be2C}$ and not $\ce{BeC2}$ as the other elements of its group?
I am not able to understand the change in formula of beryllium carbide.


texts: Why does this carbocation undergo further rearrangement?

texts:
I am trying to figure out the product of this reaction. I initially thought that a carbocation would be formed at where the chlorine leaves
from:

But according to the answer stated by the textbook, it should be this:

But why does this rearrangement have to occur? Isn't the carbocation quite stable already?
Any help would be appreciated.


texts: Is the hydrogenation of carbon dioxide to methane a solution or a problem?

texts:
The hydrogenation of $\ce{CO2}$ to $\ce{CH4}$ is thermodynamically a favored reaction at ambient to moderately high temperatures.
$$\ce{CO2 + 4H2 <=> CH4 + 2H2O (g)}\qquad G^\circ_{\pu{298K}}= \pu{-27 kcal/mol}$$
$\ce{CH4}$ (natural gas) is an excellent fuel for a variety of applications. It is also a good C1 feedstock for manufacturing other chemicals. This reaction can be used to recycle $\ce{CO2}$ and reduce its emission to the atmosphere.
So, why not use $\ce{H2}$ from photoelectrolysis of water to produce $\ce{CH4}$ and achieve multiple goals of storing solar energy, creating a useful feedstock and recycle atmospheric $\ce{CO2}$?

I said, $\ce{CH4}$ is 30 times worse than $\ce{CO2}$ to the atmosphere and also the photoelectrolysis of $\ce{H2}$ is still an expensive method that requires more time to achieve maturity.
Is it right? the other student on the panel said my answer was too vague.


texts: Role of acetone in the Finkelstein reaction

texts: What is the role  of acetone in the Finkelstein  reaction? It has something to do with Le Chatelier's principle but I am not able to understand why it will not proceed without acetone.


texts: What are some Qualitative test/s that you can use for benzophenone?

texts:
I have determined one of my unknowns to be benzophenone and in a lab setting (but that isn't possible because of COVID-19) I would conducted the 2,4 DNP test which should yield a positive result. However, I am a bit stuck on other tests that would make it very definitive that a ketone is present.

I know if I use the following test, I would get the following results:

The Tollen's test- it would be negative because an aldehyde isn't present
The iodoform test- would be negative because the ketone on benzophenone would be negative
The Chromic Acid test- would be negative because Aldehydes are oxidized by chromic acid, ketones are not.

But are there any other tests that can be used?

I have seen the previous post on this question dated back to 4 years ago and it didn't really help.


texts:
Compare the dipole moment of the following:

o-nitrophenol
o-dichlorobenzene
o-xylene

What I thought was:
o-dichlorobenzene should have the maximum, due to the acute angle and being more electronegative than the I- effect of $\ce{CH3}$ groups, and that o-nitrophenol would be the least since OH shows M+ and $\ce{NO2}$ is M- effect.

But the data from the internet says:
o-nitrophenol (3.01 D) > o-dichlorobenzene (2.67 D) > o-xylene (0.64 D)
How?


texts: How can nitrogen be quadruply bonded in tris(8-hydroxyquinoloinato)aluminum?

texts: Nitrogen typically has five outer valence electrons. So how does a triply-bonded nitrogen in 8-hydroxyquinoline end up quadruply bonded in tris(8-hydroxyquinolinato)aluminum?


texts: Temperature change and gas evolution for vinegar and baking soda experiment

texts:
This is sort of 2 questions in 1, but I think they are related.

Could someone please explain why this endothermic reaction doesn't further decrease the temperature when the amount of baking soda is increased?

The amount of vinegar is constant, varying amounts of sodium bicarbonate is independent.

Attempt 1: 100ml vinegar and 1 teaspoon baking soda, temperature went from 16 degrees Celsius to 12 degrees to Celsius in <10 seconds.

Attempt 2: 100ml vinegar and 2 teaspoon baking soda, temperature went from 16 degrees Celsius to 12 degrees to Celsius in <10 seconds.

Attempt 3: 100ml vinegar and 3 teaspoon baking soda, temperature went from 16 degrees Celsius to 12 degrees to Celsius in <10 seconds.

Also, the volume of the effervescing gas collected into a balloon was the same for 1-3 teaspoons of baking soda. once again vinegar is 100ml for all 3 attempts.

I expected a further decrease in temperature as more baking soda is used.
I expected more gas when more baking soda is used.

What happened?


texts: Can I use calcium chloride instead of sodium sulfate as drying agent?

texts:
In the synthesis of N-ethoxycarbonyl L-proline methyl ester from L-proline and ethyl chloroformate,
I dry the organic phase over sodium sulfate. Can I use calcium chloride instead of sodium sulfate?
I searched for information and I found that calcium chloride can contain basic impurities such as $\ce{Ca(OH)2}$ and $\ce{CaCl(OH)}$. Does someone know if it is actually the case?
If it would be correct I think that it cannot be used because the impurities can hydrolyse the ester.


texts:
In "advanced organic chemistry part A" book page:306&307 ,  the author uses the term 'solvent shell collapse' when talking about the reason for retention of conformation in tertiary benzyl systems (under hydrolysis reactions) where he states that some of the reason for this retention might be the collapse of solvent shell in the front side of ion pair, the difficulty in solvation from rear side due to bulky tertiary system and hydrogen bonding between anion and water molecule which facilitates the capture of water molecule from the front side of the ion pair.
Could you clarify more about the reasons? what is solvent shell collapse? and why does the bulky tertiary system affect the direction of nucleophilic attack on the planar carbocation as the nucleophile attacks from above or below the electrophile?


texts: Is sodium acetate a neutral or a basic salt?

texts: I read somewhere that salts which do not contain a replaceable hydrogen or hydroxyl group are classified as normal salts. But I also know that strong base-weak acid salts are basic in nature.


texts: Is it possible to calculate specific heat capacity of a compound based on its elements' heat capacities?

texts: What the question says. For example, if I knew the specific heat capacities of lithium and oxygen, could I work out the specific heat capacity of lithium oxide with no further information?


texts: Enthalpy change of dissolving air in water?

texts:
I'm looking for a value of the enthalpy change of dissolving air in water but can't find it. In other words, if I pull a vacuum over some water to remove all the air, per Henry's Law, how much energy change would I expect in the water as the normally-dissolved air evolved?

I tried searching for enthalpy of solvation of air in water and looking up N2(aq), etc., in standard thermodynamic  tables, but didn't get results for either one.


texts:
I'm about to teach concrete to some high school children. I'm not a chemist but as I understand it the limestone cycle is this:
$$
\begin{align}
\ce{CaCO3 &-> CaO + CO2}\tag{R1}\\
\ce{CaO + H2O &-> Ca(OH)2}\tag{R2}\\
\ce{Ca(OH)2 + CO2 &-> CaCO3 + H2O}\tag{R3}
\end{align}
$$
Two questions:

The water has to go somewhere or the concrete will stay wet. Air drying I could understand but how can concrete set underwater? And, assuming concrete dries from the outside in, wouldn't osmosis predict more water would be drawn into the concrete?

Making kilograms of calcium carbonate will take kilograms of calcium hydroxide and kilograms of carbon dioxide. How can such a large amount of carbon dioxide reach the concrete? There isn't a lot of it in water, is there? I could imagine some reaction might produce carbon dioxide in the concrete, but then wouldn't it end up frothy/honeycombed?


texts: Shouldn't this compound be called 2-methyl-5-(1,2-dimethylpropyl)nonane?

texts: The book says that the name should have dimethylpropyl methyl nonane in that order. Shouldn't the methyl group come first since methyl comes before methylpropyl (in the alphabetic order)? Our prof told us to ignore prefixes such as mono, di, tri when putting groups in alphabetic order.


texts:
The “real way” boric acid behaves as an acid in water is first by acting as a Lewis acid (bottom reaction, in black).  In fairness to the undergrads, I’d bet >25% of graduate students around the country would not be able to correctly explain the acidity of boric acid.

How are we supposed to know that boric acid heterolytically cleaves water as to leave a proton behind?

Is this something that is supposed to be immediately obvious? Or do we just have to read about experiments and then realize that this is how boric acid behaves as an acid - as exclusively a Lewis acid?

Other structurally analogous acids such as sulfuric acid also have a electrophilic center atom because of the electron-withdrawing oxygens, but these acids do not behave the way that boric acid does; these acids simply donate protons - they don't chop up water molecules to create protons.

Is a hint that $\ce{B(OH)_3}$ behaves this way found in the fact that boron can form either three or four bonds with elements? Should this clue us off to the possibility of $\ce{B(OH)_4^-}$?

Is another hint found in the fact that boric acid is trigonal planar with an unused p-orbital? Sulfuric acid on the other hand doesn't have any empty orbitals (well, it might have empty d-orbitals which may or may not be accessible).


texts: Why is Chlormephos highly toxic despite requiring metabolic activation?

texts: According to the book "The Chemistry of Organophosphorus Pesticides", the insecticide Chlormephos (S-(chloromethyl) O,O-diethyl phosphorodithioate) has an oral LD50 in rats of 7 mg/kg. For reference, the oral LD50 in rats for diisopropyl fluorophosphate is around 5 mg/kg. Why is chlormephos only slightly less toxic than DFP despite the fact that it would presumably require metabolic activation before being able to inhibit acetylcholinesterase due to the presence of a P=S bond? I would presume that the presence of a chloromethyl instead of methyl group contributes to the toxicity of chlormephos in some way, as the methyl analog is several times less toxic than chlormephos, but how? And why is chlormephos only slightly less toxic than DFP despite the fact that chlormephos would require metabolic activation before being able to inhibit AChE, while DFP would not?


texts: Comparing wt% to at% which is normalized to 100%

texts:
I have measured the element composition of a sample using ICP-OES, and reported my results in wt%. A study which has analyzed the same sample types, but with an electron microprobe, has reported their element concentrations in at%, which in addition are normalized to 100 %. I would like to compare my results to those in the article, but I am not sure how.

I am able to convert the atomic percentages to weight percentages, but I am not sure how to tackle the normalization of the data. When I add the wt% of my sample, I only get to about 50%. This loss is attributed to that I have not analyzed oxygen and carbon, which I suspect would make up a significant portion of the sample weight.

However, the study I want to cite has indeed analyzed both oxygen and carbon, and all the other elements I have measured. I do not suspect that they have a very large portion of at% unaccounted for. Therefore I believe their un-normalized data is quite similar to their normalized data.

So, how should I proceed with comparing my data to theirs? Should I just argue, like I have done here, that I think their data is "comparable enough"?

I would appreciate any insight on the subject!


texts: Potential energy of electron density at the nucleus

texts:
Consider the hydrogen atom for simplicity.

The electronic density at the nucleus is not null.

The attractive potential between a small volume of electronic density $\mathrm dV$ (at position $\vec r$) and the nucleus (at position $\vec R$) is:

$$\frac{-Z\rho(\vec r)}{|\vec R - \vec r|}\mathrm dV$$

How is the energy not going to (negative) infinity near the nucleus then? How is this accounted for to give the traditional $\pu{-0.5 Ha}$ energy value of the hydrogen atom?


texts: Can a charcoal generating process be a low carbon footprint incinerator?

texts:
Noting that cellulose, hydrocarbons and carbohydrates are mostly C, H and O, it occurred to me that one might take low grade recyclables no longer welcome, and trash in general, and convert them to energy and carbon using a sophisticated incinerator that uses advanced sensors and computer monitoring, air and heating controls to burn the waste with little carbon footprint.
Heat generated could be recycled to start future  batches, and excess heat could drive power generation.
An interesting side discussion would be how to use the carbon without releasing it to the atmosphere.  Carbon fiber, filtration?
Another aspect is what sorts of other pollution is a problem, like sulfur compounds, carbon monoxide?


texts: What is the role of ammonium chloride in the workup of a Grignard reaction?

texts: In the following Grignard reaction, why is aqueous ammonium chloride used to get to the products? I don't see how it participated in or modified the reaction from what is normally expected.


texts: Why does the transition state in both protonated and deuterated molecules have the same energy? My textbook assumes that during transitional state the isotopic bond is half-broken or on its way to break


texts: Difference between polarity and polarizability

texts:
How do the terms polarity and polarizability differ from each other?

In my opinion, polarity is the degree of ionic character in covalent compounds and polarizability implies towards degree of covalent character in ionic compounds. Am I correct?


texts:
Administration on my campus has become worried about the lack of a fume hood when using acetone in the 3D Print Club. I'm helping in the process of picking one out.

They do acetone vapor smoothing on their prints, but I know they have a box to do that in. Other than that, it's acetone in a bottle for dissolving support material and plastic residue.

Does there need to be a fume hood with acetone?
If I can get a ductless fume hood, what am I looking for to be sure that it can effectively take care of the acetone problem?

I need to prove to administration that the club is fixing the problem, and I frankly have no idea what to look for in fume hoods.


texts: Common ingredient between two disinfectants?

texts:
I find one of the most powerful associations to be odour, placing me very clearly in a time and place. Recently we were using Dettol in the house and I was reminded very clearly of a another disinfectant my grandmother used to use to clean greyhound kennels called Jeyes Fluid.

Is there a common ingredient between the two of them? If, so what is it; if not why do they smell similar (IMO)?


texts: Is the dimethylglyoximate anion ambidentate or not?

texts:
In class, my professor said that dimethylglyoximate is a special ambidemtate ligand that can donate lone pairs via both nitrogen (which it normally does), and oxygen (very rarely).

On googling whether it is ambidentate or not, I didn't find anything. Can anyone cite an example where dmgH is donating lone pairs of electrons via oxygen and not nitrogen?

If this doesn't exist, can someone confirm that dmgH is not ambidentate?


texts: Why do glucose, galactose and mannose differ in solubility in water?

texts: I don't understand why they would be so different, when the only structural difference is the orientation of hydroxyl groups.


texts: Which is the densest gas known to exist under normal "shirt sleeve" conditions: room temperature, one atmosphere, won't explode on contact with air, won't kill everyone in the building in trace amounts, etc.


texts:
So I was just exploring some ideas on my own and am having trouble analytically solving the following:

Let $D(n,m,T)$ be the time it takes to dissolve an n x n x n cube of concrete in m molar HcL at a temperature of T.  Find $D(n,m,T)$. Over the temperature range of $32 ^o < T < 273^o$ in fahrenheit.

Mathematically how does mechanism of dissolving work? Intuitively I understand the exchange of $\ce{H+}$ and $\ce{OH-}$ but still don't understand how to use this to generate said function.


texts: Could a strong acid become a strong base?

texts:
Is it technically possible for a strong acid to change into a strong base, through a chemical reaction?

Example: if an acid with pH 1 became a base with pH 12.


texts: How many products does this reaction yield?

texts: How many products can we get from the monochlorination of 2,4-dimethylpentane including stereoisomerism? I have seen someone say that it yields 3 structural isomers one of which has two enantiomers making them 4 products in total, but I couldn't find the chiral carbon he was talking about.


texts: Why aren't people pouring ethanol my unskinned chicken to remove excessive fat?

texts:
I see a lot of people putting cooked chicken thighs on paper towels to absorb the excessive fat. This gave me an idea: if you don't care about taste, why can't we rinse cooked chicken with ethanol and pour away the mixture?

The ethanol will quickly evaporate and the excessive grease from the chicken will be rinsed away.


texts: How do I find the ground state term symbol for transition metal complexes?

texts:
I have a problem where I'm trying to match metal complexes with the proper ground state term symbol.  I've tried doing a Google search and looking for a process, but haven't had any luck.  I decided to try the following for complexes that are octahedral ($O_\mathrm{h}$ symmetry):

Determine the d-electron count for the oxidation state of the metal atom
Look at the corresponding Tanabe-Sugano diagram to obtain the appropriate ground state term symbol

Is that considered even somewhat correct?

The other problem I'm having is that I there are certain configurations (e.g. $\ce{Cu^2+}$ has a $\mathrm{d^9}$ configuration) for which there are no Tanabe-Sugano diagrams (at least none that I can find) and so my process doesn't work.  Can someone please point me in the right direction?  Thank you!


texts: Hydrogen peroxide on damp clothes left out in the sun

texts:
Somebody told me that sunlight is a good bleach for clothes because leaving damp clothes outside in the sunlight will turn some of the water into hydrogen peroxide.
Is this true. If yes, then why can't we concentrate sunlight on water and produce hydrogen peroxide on mass scale? Also, a few references or books on this subject would be nice as I searched high and low on the internet and only found a few scientific articles (too advanced for me) on this subject and they mentioned a need for catalysts. What serves as the catalyst in the clothes drying example?


texts: Synthesis; effect of hydrogen gas and platinium

texts:
I'm pretty sure the last step in there is just something to throw us off. From what I understand, the first step will give us a Grignard, which will attack the carbonyl in formaldehyde to give us a primary alcohol, and the workup is just to neutralize any remaining Grignard and of course protonate the oxide ion that was just formed. I don't see any possibility of an intramolecular attack either ......

The H2/Pt step looks like a serious red herring from here; I know it doesn't touch the phenyl substituent. And there are no other pi bonds in this system for me to even consider. So is the last step just something to throw me off?


texts: Is water stream deflecting in an electric field really based on water's polarity?

texts:
A common highschool chemistry example for the polarity of water is the experiment where stream of water is deflected under the influence of a charge (electric field).

Now I have come across some condradicting claims, namely this Youtube video from Veritasium (from around 1:50) and more importantly a publication by Ziaei-Moayyed et. al..[1]

These sources suggest that this phenomenon is not based on the polarity of water but charged impurity ions in the water stream. They also claim that the electric field could also only re-orient the molecules, but not deflect them as the electric field also has an opposite effect on the other side of the dipole. This has been bothering me and it is hard to find concluding evidence either way. What are your thoughts?

References:

Ziaei-Moayyed, M.; Goodman, E.; Williams, P. Electrical Deflection of Polar Liquid Streams: A Misunderstood Demonstration. J. Chem. Educ. 2000, 77 (11), 1520. DOI: 10.1021/ed077p1520.


texts: Does the protective layer of Aluminum oxide form on the surface of aluminium alloys (such as Al-Zr) as well?

texts: Aluminum is an ideal element for usage in airports. Unlike Iron, when oxygenating, there is a protective layer formed that does not allow the rest of the Al metal to oxygenate.Does the protective layer $\ce{Al2O3}$ form on the surface of aluminum alloys (such as Al-Zr) as well as when it happens to Aluminum in its pure state?


texts: How to separate sodium carbonate from sodium hydroxide?

texts: I got a drain cleaner in dust form, which consists of $\ce{Na2CO3}$ and $\ce{NaOH}$. I wanted to extract the $\ce{NaOH}$ so I tried to heat the mixture in order to just melt the sodium hydroxide, but it didn't really work as expected. Is there any easy way to do it?


texts:
Arrange the following componds in the increasing order of bond angle.
  $$\ce{HOF,~OF2,~SF2}$$

I know that bond angle of $\ce{SF2}$ will be less than the bond angle of $\ce{OF2}$ because of larger size of sulfur atom.

How can I compare $\ce{HOF}$ with the other two? Since $\ce{H}$ is less electronegative than $\ce{O}$,  the bond pair of $\ce{O - H}$ bond will be more closer to $\ce{O}$. The opposite happens for $\ce{O - F}$ bond. In $\ce{SF2}$ both bond pairs are near $\ce{F}$ so the bonds can come closer to each other.


texts: Hydrazine vs 1,1-dimethylhydrazine for rocket fuel?

texts:
The question in my textbook is as follows:

  Hydrazine and 1,1-dimethylhydrazine both react spontaneously with O2
  and can be used as rocket fuels.

  $$\ce{ N2H4(l) + O2(g) -> N2(g) + 2H2O(g)}$$  $$\ce{N2H2(CH3)2(l) + 4O2(g) -> 2CO2(g) + 4H2O(g) + N2(g)}$$

  The molar enthalpy of formation of N2H4(l) is +50.6 kJ/mol, and that
  of N2H2(CH3)2(l) is +48.9kJ/mol. Use these values, with other $\Delta fH^{\circ}$ values , to decide whether the reaction of hydrazine or 1,1-dimethylhydrazine with oxygen provides more energy per gram.

My attempt at the solution:

Hydrazine reaction:

$\Delta fH^{\circ}\ \ce{N2H4(l)} = +50.6kJ/mol$

$\Delta fH^{\circ}\ \ce{H2O(g)} = -241.83kJ/mol$

By Hess's law of summation

$$\Delta rH^{\circ}=\sum\Delta fH^{\circ} products -\sum\Delta fH^{\circ} reactants  $$
$$ = [ 0 + 2(-241.83kJ)] - [(50.6) + 0] $$
$$ = -483.66 - 50.6 $$
$$ = -534.26 kJ/mol $$

1,1-dimethylhydrazine reaction:

$\Delta fH^{\circ}\ \ce{N2H2(CH3)2(l)} = +48.9kJ/mol$

$\Delta fH^{\circ}\ \ce{H2O(g)} = -241.83kJ/mol$

$\Delta fH^{\circ}\ \ce{CO2(g)} = --393.509kJ/mol$

By Hess's law of summation

$$\Delta rH^{\circ}=\sum\Delta fH^{\circ} products -\sum\Delta fH^{\circ} reactants  $$
$$ = [ 2(-393.509kJ/mol) + 4(-241.83kJ/mol) + 0] - [48.9kJ/mol + 0] $$
$$ = -483.66kJ/mol - 50.6kJ/mol $$
$$ = -1803.238 kJ/mol $$

Now, my first reaction is to say that the 1,1-dimethylhydrazine provides more energy, as it evolves 1803.238 kJ/mol of energy as heat for the reaction vs the 534.26kJ/mol evolved by the Hydrazine. I have a strong suspicion that this is wrong however based on the fact that a quick google search reveals that the Hydrazine is indeed used in rockets. The questions does say " energy per gram " so i also tried working out the number of moles in 1g of both Hydrazine and 1,1-dimethylhydrazine and then working out how much energy per mole equivalent to 1g but 1,1-dimethylhydrazine still evolves more energy when i do those calculations.

I unfortunately don't have an answer to this problem so i'd really appreciate any feedback. Thanks in advance!


texts: Are there attempts to investigate phase states at negative pressure?

texts:
Phase diagrams of various compounds and systems usually include only positive pressure. But I wonder whether it is possible to somehow investigate them under negative pressure?

Are there materials that change phase if mechanically stretched? For instance given that metallic form is sometimes achieved at high pressure, can a negative pressure applied to a metal produce a non-metalic form?

Or maybe the effect of negative pressure may be achieved by electrically uniformly charging the material?


texts: What is the name of "cis/trans" isomerism when all four groups are different?

texts:
How would you call a pair of isomers on the picture below?

They look a lot like regular cis/trans isomers, except all four groups are different. I can tell they are spacial isomers (stereoisomers) but is there a more specific name for this kind of isomerism?


texts: speeding up etching process of a copper board

texts:
Background:

I use Sodium persulfate to etch a copper board to manufacture home made Printed Circuit Board (PCB).

On the etching powder's plastic, it is written that:

  1.5-2dl of etch powder in 1 L of hot water or corresponding volumes

So I add 2 cup powder for 10 cup hot water. In the first time usage it works perfect and it etches the board (double layer 8x16 cm FP4 board) in 20-30 min. However, when I use it for the second time (in another day), the solution works tooo slow. The last time I waited 13 hours for board to be ready. As the board stayed too long on the enchant, the acid ate away many traces on the PCB.

I add extra sodium persulfate (around 2 cup again) when I use the solution second time.

I use microwave (900 W) to warm the enchant again. I have not measured the temperature of the acid but I guess it might be around 40-60 C and I don't have any temperature stabilization so that the solution get colds in 5-10 min again and I repeat the same procedure maybe 6-8 times per process.

Question

Why it takes too long to etch the copper when I use the solution second time although I add the same amount (2 cups) of sodium persulfate to the solution?

What can I do to speed up the etching process apart from mixing the solution?


texts: Why is a temporary name given to an element with an atomic number above 100?

texts:
All the elements with an atomic number more than 100 are given temporary names by IUPAC according to nomenclature rules. For example, element 101 was temporarily  named "Unnilunium" until they give it a permanent name (101 is now known as Mendelevium).

But why does the IUPAC give a temporary name to elements?


texts: Nitrosonium ion in the nitration of phenols

texts:
Peter Sykes mentions in the book Guidebook to Mechanism in Organic Chemistry (6th ed.) on p. 137 that:

  Highly reactive aromatic compounds, such as phenol, are found to undergo ready nitration even in dilute nitric acid, and at a far more rapid rate than can be explained on the basis of the concentration of $\ce{^⊕NO2}$ that is present in the mixture. This has been shown  to be due to the presence of nitrous acid in the system which nitrosates the reactive nucleus via the nitrosonium ion, $\ce{^⊕NO}$ […]

However, there was no mention as to why the nitration of more reactive aromatic compounds would result in there being nitrous acid in the system. I understand that the conventional explanation for why the nitration of activated benzene derivatives is more rapid is that there is a stronger attraction between the electrophile and the nucleophilic benzene ring due to the greater amount of electron density in the ring. This explanation using the presence of the nitrosonium ion seems interesting but I don't see how nitrous acid could be generated due to there being a more reactive aromatic compound being nitrated. Could someone enlighten me on this?


texts:
Carbon exists in more than one allotropic forms, and the allotropes have different physical properties due to different arrangement of atoms. I am going to compare their hardness for now.

Below is the structure of graphene:

Source: Wikipedia article on Graphene

From what I read, graphene is hard, but graphite is brittle.

If graphite is made up of many layers of graphene, then why is graphite not stronger than graphene?
I suppose when you say graphene (or diamond) is hard, it means that, for example, when you take a hammer to strike the layer of graphene, the layer is not easily broken, that is, the covalent bonds are hard to be broken by physical means.

By this reasoning, the layers in graphite are easily separated because they are held together by weak van der Waals forces, whereas it should be difficult for us to cut across the layers (in direction perpendicular to the plane of layers, cf: image below)

Does this mean that we can only cut the graphite in one dimension? I thought the graphite being brittle already implies that graphite can be cut in more than one dimension?

Original image source: Tirupati Graphite


texts: Does the added component (intended to disturb equilibrium) always ends up being more than the original amount, in the new equilibrium?

texts:
The title can be a little unclear. But what I am basically saying is say we add a reactant to a reaction to push the reaction forward toward the product side, that reactant which was increased in amount/ concentration will surely less. Part of it used to produce more products to gain new equilibrium. But will it always be more than the original amount in the equilibrium before?

Without knowing much of advanced math, I just experimented with some simple fractions; thus far I haven't seen anything that violate this rule.


texts: In an closed adiabatic container, if we carry out an exothermic process, what will happen to the temperature of the system

texts: I know that a closed adiabatic container acts as an isolated system, so I expect the internal energy of the system to be a constant as in an isolated system. But since it is an exothermic reaction, temperature will increase, and since internal energy is a function of temperature it should increase. This is a direct contradiction. Can anyone please help?


texts:
What are the advantages and disadvantages of the various types of condensers commonly found in the laboratory? Obviously more intricate pieces of glassware are more costly but assuming they are all available why would one use a Dimroth condenser vs. a Friedrichs when refluxing something? I've heard that Graham condensers are to be avoided when refluxing due to the possibility of clogging, and yet it is still very common - when is it appropriate to use one?

Illustration made with ChemDraw. Feel free to reference other designs but please attach a schematic for clarity.

Edit: This question was motivated by an organic preparation which involved the bromination of an alkene in boiling water. Bromine has a boiling point of 58.8 °C and on top of that the reaction was exothermic. It was difficult to avoid the loss of Br2 gas with your typical Allihn condenser, but the increased cooling capacity provided by a Friedrichs returned Br2 back to the flask as it was produced.

Also, while the Friedrichs forces vapors up a spiral path, the path itself is wide, and in my condenser at least, there was a bit of leeway for liquid to drop down the sides, helping to prevent blockages. I didn't try a Graham condenser but I imagine a much slower rate of addition would be supported by this condenser.


texts: Why does nitrous oxide have 300 times the global warming potential of CO2?

texts:
Both nitrous oxide and carbon dioxide have roughly the same atmospheric lifetime (nitrous oxide slightly longer), so I thought that it would have to do with the infrared absorbance associated with each of them. So I looked at their spectrum.

Perhaps this is misleading because it is my understanding that not much infrared light at around the 2300 $\pu{cm^{-1}}$ region exists. But even so, that means that the two peaks that matter are $\ce{CO2}$'s 700 peak, and $\ce{N2O}$'s 1300 peak. It is my understanding that the blackbody radiation of earth peaks at around 700, and though sizable, is much less at 1300. So, I don't see why nitrous oxide would have a greater global warming potential than carbon dioxide.


texts: Deriving an alternative expression for the Van der Waals equation using given parameters

texts:
The question is to find out an alternative expression for the Van der Waals equation of corresponding states for 1 mole of gas using the parameters given as $$A=\frac{P}{P_c},\quad B=\frac{V}{V_c},\quad C=\frac{T}{T_c} ,$$ where $P_c,T_c,V_c$ represent the critical pressure, temperature and volume respectively.

I am aware of the simple form of the Van der Waals equation which is $$\left(P+\frac{a}{V^2}\right)\left(V-b\right)=RT .$$ The values of $P_c , T_c \text{ and } V_c$ can also be written down in terms of the Van der Waals constants but I have no idea on how to proceed after this. I tried to substitute the known values but it made things complicated. Is there any other approach to this problem?


texts:
The ideal gas equation (or the van der Waals equation, for this matter) states that holding volume and temperature constant, increasing the number of moles of particles in the container will increase the total pressure exerted by the gas mixture.

That’s all well and good, but when it comes to looking at chemical reactions and their equilibria, Le Châtelier’s Principle states that when a gas mixture is pressurized, the equilibrium shifts to the side of the reaction that produces a lesser total number of moles. This would mean less particles, and therefore less pressure, as I see from the ideal gas equation.

What I do not understand is why the mass of each molecule does not affect the pressure exerted by the gas. If you have heavier molecules, they would each have more momentum, and would exert more force on the container’s walls—i.e. more pressure. So is this not a factor when considering Le Châtelier’s Principle? The equilibrium shifts toward the formation of more particles, but they are each lighter and exert less force. Why is this favorable over having less but heavier particles?


texts: What type of standard for HPLC capsaicin quantification?

texts:
I'm wondering which type of standard would be the most suitable for the quantitative analysis of capsaicin (8-Methyl-N-vanillyl-trans-6-nonenamide) containing products?

Sigma offers the following types:

analytical standard
United States Pharmacopeia reference standard
European Pharmacopoeia reference standard
Pharmaceutical secondary standard

While analytic standard entry gives a description (analytical standard for food analysis), assay (99.0+%) and HPLC suitability, no such data is displayed at the product pages of other type of standards.

Regarding my questions let's assume two separate situation here:

a) funds are unlimited
b) funds are limiteted


texts: Why is substituted amine a weaker activating group for electrophillic subsitution of benzene?

texts:
According to my text book the order of activating groups is as follows

Why is it so ? shouldn't substituted amine have more +i effect and therefore should be a more powerful donating group ? Where am i wrong in this reasoning ?


texts: What are the possible products in allylic bromination of 3-methylcyclopentene?

texts:
Bromination of an alkene by N-bromosuccinimide (NBS) in the presence of light or peroxide is a radical reaction and produces an allylic bromide. For the following bromination of 3-methylcyclopentene, which of the following allylic bromides would be products of the reaction?

In some other reactions such as elimination, there is a tendency to form the most substituted double bond, since it is the most stable. If that were the case, then the products should be A, E, F, and G, since these are all trisubstituted alkenes (the others are disubstituted). Is that a valid consideration here, or is there a different overriding rule?


texts:
I'm dealing with a common photoresist developer TMAH (tetramethylammonium hydroxide) and attempting to design a vapor sensor for a sealed chamber. Now I havent been able to confirm what exactly is evaporating from the solution causing it to smell.
I assumed that tetramethylammonium hydroxide would equilibrate with trimethylamine and methanol, and the liberated non-ionized species would evaporate before shifting back into their respective ions.
My question is whether those species as individual molecules would evaporate, or do droplets of the ionized solution evaporate together? And if droplets of water/TMAH solution evaporate, would water absorb energy, throwing off the reading made by a photoionization detector?


texts:
Melting point of manganese is lower than that of other 3d series except copper and zinc.

Melting point increases from scandium to chromium. The reason given in my book for this trend is the increase in number of unpaired d electrons which increases interatomic forces on account of covalent bonding.

But if thats the case, shouldnt manganeese have the highest melting point?


texts: Gaussian vs. Lorentz/Cauchy distributions for artificial broadening

texts:
When I am supposed to calculate an IR-, Raman-, or UV/Vis-spectrum, the calculations give me some x-y-values, e.g., Frequency-Intensity, or Energy-Oscillator Strength. Those values can either be printed as stick spectra or a sum of Gaussian-/Lorentz-distributions is being used to broaden the peaks to generate a more "natural" spectrum.

I've been asked a couple of times which broadening function to choose when, but actually never had a good answer/given explanation. The only thing that I wrote down quite some time ago, was that for IR- or Raman-spectra of solids a Gaussian broadening and for every other type of IR- or Raman-spectra a Lorentz broadening should be used.

Google searches for "gaussian or lorentz broadening" and "line broadening" did yield results that try to explain it, but I didn't find most of them really helpful.

So the question is: When do I choose the Gaussian or the Lorentz-functions for artificial broadening of IR-, Raman-, or UV-Vis stick spectra and why?


texts: Something about the idea of Molarity is confusing me

texts:
Okay, so molarity is defined as moles of solute per liter of solution. It is used to describe the concentration. So in the lab, when I see a bottle labeled something like $\mathrm{3.5~M}~\ce{H2SO4}$, is it saying that the only chemical in the bottle is this $\ce{H2SO4}$?

Because the way I think of it is "there are 3.5 moles of $\ce{H2SO4}$ per liter of solution". The word "solution" is kind of throwing me off because it makes me feel like they are saying that there is more than just $\ce{H2SO4}$ in the bottle. Correct me if I'm wrong, but don't you need at least 2 solutes to make a solution?

I don't know why I'm having such a hard time grasping this. But any help would be awesome!


texts: Predict the number of peaks in H-1 NMR of sesamolin

texts:
Would all of the Hs in an NMR of sesamolin (5-{(1S,3aR,4R,6aR)-4-[(2H-1,3-benzodioxol-5-yl)oxy]tetrahydro-1H,3H-furo[3,4-c]furan-1-yl}-2H-1,3-benzodioxole; shown above) be non-equivalent to each other? So even for the two Hs at A, they would be non-equivalent to each other.

Follow up question (about a different molecule that is similar): for sesamin (5,5'-[(1R,3aS,4R,6aS)-tetrahydro-1H,3H-furo[3,4-c]furan-1,4-diyl]bis(2H-1,3-benzodioxole); shown below), would there be 8 peaks in an H-1 NMR?


texts: Can an elimination reaction be visualised as the combination of the loss of a leaving group and proton transfer?

texts:
Specifically in the conversion of a haloalkane to an alkene, i believe this is the reaction mechanism.

Extrapolating on this, do all elimination reactions function as such, or is the term elimination reaction a reference to the ends rather than the means?


texts: What is the number of nodes in the molecular orbitals of cyclic H3?

texts:
A quick google search does reveal the molecular orbitals of this cyclic H3.

However, one source mentions there are are two nodes; while two of my professors said there's one node. Which is correct?

This seems to be a related question - I am not sure. There also is a question on linear H3+ - not cyclic.


texts:
I am currently trying to perform the Total Fatty Matter (TFM) test on soap and for some reason I am getting three phases instead of two.
The surfactant used is SLES and other reagents include hot water, HCl, petroleum ether.
I have no idea as to what could be causing the 3 phases and my knowledge in organic chemistry is very little. Any help would be greatly appreciated. Below is the procedure:
I dissolve soap in hot water and then I transfer the cooled solution to a decantation flask. I add concentrated HCl (37% stock solution) and then petroleum ether to increase extraction ratio.
I repeat this extraction two more times (and after this I am getting 3 phases) and then I purify the organic phase twice using hot water to eliminate any HCl.
I then heat the organic phase to vaporize ether and calculate TFM %.
The surfactant used in the soap is sodium laureth sulfate (SLES), and I think that it may relate to why I have 3 phases but I can't tell why. What is the reason for this?


texts: Is it possible to generalize whether an organic molecule is chiral or not?

texts: Can we generalize on the basis of number of chirality centers  if an organic molecule is chiral or not?


texts: How can I make a graphene supercapacitor?

texts: I have heard that a super capacitor can be made with a dvd burner. What materials do I need to to get and what software for my DVD burner do I need to make this amazing device?


texts: What causes the lowering of vapour pressure in volatile/nonvolatile solvent mixtures?

texts:
"Based on Figure 13.18, you might think that the reason volatile solvent molecules in a solution are less likely to escape to the gas phase, compared to the pure solvent, is that the solute molecules are physically blocking the solvent molecules from leaving at the surface. This is a common misconception. Design an experiment to test the hypothesis that solute blocking of solvent vaporization is not the reason that solutions have lower vapor pressures than pure solvents."

The explanation (in the main chapter, not as an answer to this question) given in Chemistry: The Central Science (13th Edition) by Brown, LeMay, and Bursten (abbreviated as CTCS) is: "A solution consisting of a volatile liquid solvent and a nonvolatile solute forms spontaneously because of the increase in entropy that accompanies their mixing. In effect, the solvent molecules are stabilized in their liquid state by this process and thus have a lower tendency to escape into the vapor state. Therefore, when a nonvolatile solute is present, the vapor pressure of the solvent is lower than the vapor pressure of the pure solvent, as illustrated in ▲ Figure 13.18."

However, this is, I believe, the only textbook which gives this explanation for lowering in vapour pressure on adding a non-volatile solute. The other (reputed) textbooks I've read, like Zumdahl and NCERT Grade XII Chemistry, all give the explanation that CTCS calls a "common misconception". So, which explanation is correct? If possible, please give an experiment also.


texts: Why are polysaccharides non-reducing sugars?

texts:
My book says that polysaccharides are non-reducing sugars, and they form of condensation of >6 molecules of monosaccharides. The condensation involves the carbonyl groups of the sugars, leaving only one free carbonyl group at the end of a big molecule.

My question is: since there is one free carbonyl group why aren't polysaccharides reducing sugars?!


texts: Lead-Acid Battery: Standard Electrode Potential

texts:
I'm making a lead-acid battery for an investigation. Since I only had sulfuric acid and lead electrodes, I decided to firstly run 2 lead electrodes through electrolysis in a sulfuric acid electrolyte. This would create the following half equations:
$$\ce{4H+ + 4e- -> 2H2}$$
$$\ce{Pb +2H2O->PbO2 +4H+ +4e-}$$
At this stage, I still need to perform some theoretical calculations of the required potential to run this electrolysis. Obviously, the standard reduction potential of the hydrogen ion is 0V. But I can't find the potential for the 2nd reaction. Could someone provide me with a source for it?


texts: Synthesis of indigo from anthranilic acid - reaction not taking place

texts:
I was trying to synthesise indigo via the Heumann indigo synthesis (II.), which involves heating antrhanilic acid and chloroacetic acid, both dissolved in isopropanol. After heating up, a hydroxide or another strong base is added to form indigo

I have slightly altered the synthesis process, added trichloroacetic acid instead of chloroacetic, and also added more reactants to tilt the equilibrium towards the product.

The problem is, that any signs of reaction have taken place after more than 3 hours

I have discussed the issue with my chemistry teacher, and he said that the trichloroacetic acid had been of poor quality (made 1990, majority of the original crystals dissolved, turned to brownish liquid). I also think could be simply stopped by the forming of salt (sodium trichloroacetate) and that being unable to interact with anthranilic acid.

I'm very desperate about this. Do you have any thoughts on how to get that reaction going?


texts: What is the mechanism for reduction of alkylmercuric compounds by hydrides?

texts: What is the mechanism of the reductive elimination of mercury metal using hydrides that is carried out after oxymercuration of the alkene? I have come across a free radical mechanism, but that suggests loss of the stereospecificity of the product, while the reaction is stereospecific in reality. Also, why isn't an acid sufficient to remove the mercury as it is with alkynes? Why is a reducing agent necessary at all?


texts: Evaluate indicator choice (phenolphthalein)

texts:
A student wishes to find the concentration of a $\pu{50 mL}$ solution of acetic acid $(K_\mathrm{a} = \pu{1.8e-5}).$ He performs a titration using a solution of $\pu{0.2 M}$ sodium hydroxide. The student selects phenolphthalein as his indicator choice which has a $K_\mathrm{a} = \pu{3.98e-10}.$ Justify the student’s choice of indicator.

My attempt: I found the $\mathrm{p}K_\mathrm{a}$ of the indicator to be $9.4$ and the fact that the titration was weak acid + strong base meant the $\mathrm{pH}$ at equivalence would be around that too, so the indicator was justified. In saying this, my justification isn’t very mathematical.


texts: Does direction matter in breaking a bond?

texts: Im not sure if this question belongs here or in another community. I was wondering if the direction that we apply a force in order to break a bond matters and how it affects strength. Say  we have one compound e.g NaCl. Compared to breaking the bond between the Na ion and Cl ion in a tensile manner, would it require a different force to "tear" it in a shearing manner.


texts:
There is an R an organic group connected to either Oxygen or Nitrogen. R is such a group which has almost zero electronic effects (Resonance effect and inductive effect). I want to ask if N or O are to donate a lone pair then which one will have higher donating capacity?

According to my opinion  it should be Oxygen as it is more electronegative than Nitrogen but I'm still not confident and want some proof considering other factors also and neither do I have an answer.


texts: how are the frequencies at a local maximum of PES like?

texts:
On the potential energy surface, if you find a local maximum and calculate its frequencies in Gaussian or something like that, will you get all negative frequencies or all positive frequencies?
I know that at a local minimum the frequencies are all positive and that at a saddle point there are both negative and positive frequencies, but what about a maximum point?


texts:
Can the R group of a Grignard reagent (RMgX) be an alkene?

Also what groups can't R be?


texts: Is using oxidized aluminium baking forms safe?

texts:
My apologies in advance if this is not the best forum for this kind of question.
Recently, I've bought a few non-anodized aluminium bread-baking forms, such as this one:

As you can see, there is already some discoloration on them when they come from the shop. My knowledge of chemistry is rudimentary but I presume it is an oxidized aluminum layer (do correct me if I am wrong here).
Now, my wife decided it is a good idea to wash these forms in a dishwasher. The forms became even darker, becoming rather gray over their entire area. There are a lof of posts on various forums and blogs telling you to not put aluminium cookware in dishwashers, and most of them go on about how to remove the oxidized layer.
For my purposes, I do not care how it looks. I would like to know whether it is safe to bake bread in those (post-dishwasher and without removing the oxide layer). There is very little information about this, as the online discussions revolve mostly about removing the gray layer. I've read someone saying that the oxide layer can even be beneficial as it might prevent aluminium leaking into food. This does make sense, presuming that the oxide itself is not harmful and does not leak. Could someone comment on this please? Any reference to scientific literature would be a bonus.
As a backstory, the reason I bought these forms is because they are traditionally used for making specific sorts of rye sourdoughs in the Baltic region. So I'd like to give them a go before buying more modern (and more boring) stainless steel forms.
Thanks in advance!


texts:
Suppose you have this spectrum and the molecular formula of $\ce{C10H12O}$

The structure is

My problem is with the peak at ~7 which is an H-Benzene signal, with quartet splitting and a relative area of 4.

Surely this means that:

The benzene would have only one Hydrogen environment
with 4 Hydrogens in that environment
and 3 hydrogens on the adjacent carbon atoms

But the answer has 2 H-Benzene environments.

How come this goes against normal? Please can answers be not too technical as I am a pre-university student


texts: For what reason does Calcium Phosphate dissolute at low pH? What makes it pH dependent? This question arised after reading about the calcium phosphate bridges in casein micelles and how they 'break apart' at a pH below 6, such that the micelle destabilises and essentially falls apart.


texts: Theoretical basis behind orbital correlation diagram for pericyclic reactions

texts:
When discussing pericyclic reactions, the Woodward-Hoffman rules allow one to predict whether a reaction will be thermally/photochemically allowed. This has been discussed in many questions on chem.SE, but essentially boils down to the following statement:

  A ground-state pericyclic change is symmetry allowed when the total number of $(4q+2)_\mathrm{s}$ and $(4r)_\mathrm{a}$ components is odd.

What the Woodward-Hoffman rules fail to explain however is why the reaction is allowed. Several explanations exist, such as the Huckel aromaticity of the transition states, however by far the most 'powerful' explanation is supposedly given by a well drawn orbital correlation diagram. Fleming devotes an entire section in his book on the topic of how to draw these diagrams:

"Correlation diagrams provide a compelling explanation, at least for those reactions that have well-defined elements of symmetry preserved throughout the reaction. The idea is to identify the symmetry elements maintained throughout the reaction, classify the orbitals undergoing change with respect to those symmetry elements, and then see how the orbitals of the starting materials connect with those of the product. The assumption is that an orbital in the starting material must feed into an orbital of the same symmetry in the product, preserving the symmetry throughout the reaction. Substituents, whether they technically break the symmetry or not, are treated as insignificant perturbations on the orbitals actually undergoing change."

Fig 1: Fleming, Molecular Orbitals and Organic Chemical Reactions- Reference Edition, 2010, Wiley

As far as I can find, and from recollection, Longuet-Higgins at Cambridge was the first person to use correlation diagrams to explain pericyclic processes (as per figure 2 below), but again, there's no explanation as to why this works.

Fig 2: Early (beautiful) example of a correlation diagram as applied to an electrocyclic reaction. J. Am. Chem. Soc. 1965, 87, 2045. (DOI)

To make an analogy to molecular orbital theory, clearly, correlation diagrams are simply 'mixing' things of the same symmetry (in this case A or S relative to some axis rather than the more expanded set of symmetry labels from group theory), but there seems to be little / no care in correlation diagrams as for the relative energies of the things being mixed. Is anyone able to explain the why of a correlation diagram?


texts: What atom would be protonated first in a strongly acidic solution?

texts: The answer is A. I thought it would be D since the ester group has the highest pka and the more basic functional group would be more prone to protonation. Also, I don't really get how to rank C in terms of atoms that would be protonated first as I don't know the pka of the ether group.


texts: Why does NaOH catalyze H2O2 decomposition?

texts:
I had a lab practice in which I had to test the effectiveness of different catalysts for the decomposition of $\ce{H2O2}$. Among them, there was: $\ce{KI(aq)}$, $\ce{FeCl3(aq)}$, $\ce{MnO(s)}$, $\ce{NaOH(aq)}$, $\ce{HCl(aq)}$ and $\ce{I2(s)}$.

In different test tubes, I added some $\ce{H2O2}$ and some catalyst. After a while, I added $\ce{NaOH}$ as well. I observed an increase in the effervescence for $\ce{KI}$, $\ce{FeCl3}$, $\ce{I2}$ and $\ce{MnO}$. However, when the mixture was only $\ce{H2O2}$ + $\ce{NaOH}$, nothing happened. I've made some research, but can't find an explanation for this...

I believe $\ce{NaOH}$ increases the rate of the reaction of the other catalysts, but why?


texts: Dissolution of lead chloride because of the formation of- Na2PbO2 or [Pb(OH)4]-2?

texts:
I read that $\ce{NaOH}$ precipitates lead hydroxide which dissolves with excess hydroxide.

In some sources, I read that lead chloride dissolves due to the formation of complex $\ce{[Pb(OH)4]^2-}$ but my teacher taught that it is because of the formation of $\ce{Na2PbO2}$

I don't think that both are same. I cannot find much information about $\ce{Na2PbO2}$ either.

Which of these two is actually formed?


texts: Deriving a relation between entropy, volume and particles through the chemical potential

texts:
I'm a teaching assistant on a first year course on Introduction to Thermodynamics based on the book "Molecular Driving Forces" by Dill & Bromberg.

There's a question which asks the students to derive the following relation between S, V and N:

$S(V,N) = Nkln(V)$

A simple solution that is hinted is to use the differential form of the fundamental entropy equation and realizing the following identities (assuming an ideal gas):

$\frac{P}{T} = (\frac{\partial S}{\partial V})_{U,N}=\frac{Nk}{V}$

$ds = Nk\int \frac{dV}{V} \rightarrow \Delta S = Nkln(\frac{V_2}{V_1})$

Now, I've meditated about and have been asked by several students the following question: could we arrive to the same (or equivalent) expression through a chemical potential route? After all, we need an expression that relates S both to N and V. Unfortunately, I have not been able to give a satisfactory answer.

Here's what I've tried, arriving to some ugly looking equation that intuitively looks incorrect to me:

Use the definition:
$\frac{\mu_j}{T}=-(\frac{\partial S}{\partial N_j})_{U,V,N_{j\neq i}}$, which also stems from the fundamental differential entropy equation.

Now I make the assumption that the chemical potential is equal to the density of molecules in the ideal gas. This is what I'm most dubious about, although I couldn't think of another way in which to have a relation to it. If that holds, I can then write the following identities:

$\mu = \frac{n}{V}$ then $P=\mu kT$

$\frac{-P}{T^2k} = \frac{\mu}{T} = (\frac{\partial S}{\partial N_j})_{U,V,N_{j\neq i}}$

Now because $P = \frac{nkT}{V}$,

$\frac{-P}{T^2k} = \frac{-nkT}{VT^2k}=\frac{-n}{VT}=(\frac{\partial S}{\partial N_j})_{U,V,N_{j\neq i}}$

Which I think can be solved:

$\int dS = \int \frac{-n}{VT}dn \rightarrow \Delta S = -\frac{\Delta n^2}{2VT}$

This result doesn't really make much sense to me (a negative entropy (?)). I'm a bit confused, because the first 'route' seems so simple but this second attempt looks fairly involved.

So, what I wrong in my logic? Apologies beforehand if I'm doing something egregiously wrong, it's been awhile since I've had to solve these 'pen and paper' problems.


texts: How does NMR spectrometer determine area under each peak?

texts: I am confused about exactly how does NMR machine figure our area under each peak, which then tells us how much protons present in the molecule. Does it have to do something with radio waves being emiitted after proton relaxes? Thanks.


texts: Mechanism of alkene dihydroxylation with potassium permanganate

texts:
I have scavenged the internet for different mechanisms for permanganate-mediated alkene oxidation and have found satisfactory mechanisms for oxidative cleavage and dihydroxylation under basic conditions.

However,I found out that $\ce{KMnO4}$ can still dihydroxylate alkenes under acidic conditions, when it is cold and dilute. I am aware that it is not efficient as it is prone to further oxidation, but the mechanism still makes me curious. I know the overall formula:

$$\ce{5alkene + 2MnO4- + 2H2O + 6H+ -> 5diol/glycol + Mn^2+}$$

I can't really understand this, does the manganese oxidise 5 alkenes at the same time? Does it get oxidised 5 times, with a different byproduct for each one? I think that the manganese-bearing compound is $\ce{MnO2}$ at first, then $\ce{Mn^2+}$, but I'm not really sure. If anyone can shed some light on the mechanism, it'll be a great help.

I link below my best attempt at the mechanism. The byproducts are incorrect as it's supposed to be $\ce{MnO2}$ or $\ce{Mn^2+}$

Here are some papers I've found that helped me, maybe someone can get more use out of them than me:

https://www.semanticscholar.org/paper/Oxidation-by-permanganate%3A-synthetic-and-aspects-Dash-Patel/fe91f5161ca1ab481ae111f1abc82d37d336f021
https://www.researchgate.net/publication/271107223_Permanganate_Oxidation_mechanisms_of_Alkylarenes


texts: Whats the Balanced chemical equation for heating sodium chloride and what type of a reaction is it?

texts: For my chemistry lab we had to heat sodium chloride and there was a colour change and a sizzling sound. Is it a decomposition or synthesis reaction, and what is the balanced chemical equation for it?


texts: I am working on building a robot to detect and pickup dog poop.  I have looked at the concentrations of the various components and simple chemical/electrical ways to detect them.  The best component to detect seems to be methanethiol but I could not find a simple sensor to detect it.  I found this sensor http://www.aliexpress.com/item/Free-shipping-4CH3SH-10-sensor-methanethiol-sensor-electrochemical-gas-sensor/32381228085.html and I was wondering if it could work for this purpose, I could not find much information on the sensor.  I was also thinking something like an alcohol sensor could work.


texts: Why is the Infrared spectrum usually drawn using transmittance rather than absorbance?

texts: Infrared radiation can be used to identify compounds but I noticed that the spectra are usually drawn using percentage transmittance rather than percentage absorbance . Why is that ?


texts: How to understand the (non-)degeneracy of states of singlet Σ and Δ terms for a ππ configuration of two nonequivalent electrons?

texts:
As instructed in Levine's Quantum Chemistry 7th edition, Chapter 13.8, page 377, for a $\pi \pi$ configuration of two nonequivalent electrons, four functions $\pi_{+1}(1) \pi_{-1}^{\prime}(2)$, $\pi_{+1}(2) \pi_{-1}^{\prime}(1)$, $\pi_{-1}(1) \pi^{\prime}_{+1}(2)$, $\pi_{-1}(2) \pi^{\prime}_{+1}(1)$
 are used to construct the wave functions of the singlet $\Sigma$ terms
$$
\begin{array}{ll}{^{1} \Sigma^{+}:} & {\pi_{+1}(1) \pi_{-1}^{\prime}(2)+\pi_{+1}(2) \pi_{-1}^{\prime}(1)+\pi_{-1}(1) \pi_{+1}^{\prime}(2)+\pi_{-1}(2) \pi_{+1}^{\prime}(1)} \\ {^{1} \Sigma^{-}:} & {\pi_{+1}(1) \pi_{-1}^{\prime}(2)+\pi_{+1}(2) \pi_{-1}^{\prime}(1)-\pi_{-1}(1) \pi_{+1}^{\prime}(2)-\pi_{-1}(2) \pi_{+1}^{\prime}(1)}\end{array}
$$

The text following these equations says "Clearly, these two spatial functions have different energies." Could you suggest how to understand this point ?

The discussion further below suggests that when four functions $\pi_{+1}(1) \pi_{+1}^{\prime}(2)$, $\pi_{+1}(2) \pi_{+1}^{\prime}(1)$, $\pi_{-1}(1) \pi^{\prime}_{-1}(2)$, $\pi_{-1}(2) \pi^{\prime}_{-1}(1)$
 are used to construct the ${}^1 \Delta^{+}$ and ${}^1 \Delta^{-}$ wave functions of the singlet $\Delta$ terms, "Since they have the same energy, there is no
point in using the $+$ and $-$ superscripts". Could you suggest how to understand this point and the reason of the difference from the above point ?

Many thanks for your suggestions !


texts: What topics to review before starting organic chemistry?

texts:
It's been over a semester since my most recent chemistry class, (general chemistry 2) because I could not take organic at my community college. It is only considered a sophomore level class unless taken in-residence at the university I am transferring to (which is understandable.)

I was curious if I could narrow down what topics I could begin reviewing before the start of the semester that would help me in organic chemistry.


texts: Proper use of vacuum pump during vacuum distillation

texts:
I am preparing to do a vacuum distillation and am unsure exactly how to manage the vacuum. The vacuum pump I have is a two-stage rotary vane pump which is capable of 250 microns or lower. It has a triple inlet, one 1/4", 3/8" and 1/2".

My glassware is typical distillation glassware including a Graham condenser and a vacuum takeoff joint that connects between the condenser and the receiver.

My concern is that if I apply too much vacuum that it will cause a glass implosion. Is this not a concern and I can just operate the vacuum pump freely, or do I need to take special steps to limit the degree of vacuum?

I watched a YouTube video of a guy doing a vacuum distillation and I noticed that he did not use a capillary bubbler. Under what circumstances can the bubbler be dispensed with?

Another concern is the need for a manometer. I have read that I need to use a closed-end manometer (very expensive) to measure the pressure in a vacuum distillation. Why can't I use a normal vacuum gauge? Also, if I am doing an azeotropic separation such as a water-ethanol separation, is it critical I monitor the pressure? I am assuming it is.


texts: What does the 129Xe NMR spectrum of XeOF4 look like?

texts:
What will the $\ce{^129Xe}$ NMR spectrum of $\ce{XeOF4}$ look like?

I know that its electron pair geometry is octahedral, and the molecular pair geometry is square pyramidal.

I believe that the lone pair on $\ce{Xe}$ will take the equatorial position (less sterically crowded), alongside the oxygen and 2 other equatorial fluorines in the same plane, to minimize electron pair repulsion.

So there will be 2 equatorial $\ce{F}$ and 2 axial $\ce{F}$. Therefore, am I right to say that the $\ce{^129Xe}$ NMR will be a triplet of triplets?


texts: Best ingredients for a homemade desinfectant

texts:
I am trying to determine the best recipe/ingredients for a homemade desinfectant/germ killer. I've been researching these as of now:

Isopropanol (or even Ethanol)
White vinegar
Borax
H2O2
Specific Essential oils (that are supposed to kill germs)

What I want is something liquid, that you can either spray on your hands or on a toilet seat for example, and kills the most germs possible while being easy to make/mix. It should not be corrosive/toxic etc.

Which of these products can be mixed together? Is there any other products I didn't research? Will mixing any of these cancel the effects of the other?

Thank you!


texts:
How would you confirm that a colorless liquid given to you is pure water?
A very easy solution is to take a sample of colourless liquid and put on stove if it starts boiling exactly at 100 ºC then it is pure water. Any other colourless liquid such as vinegar always have different boiling point. Also observe carefully that after some time whole liquid will convert into vapour without leaving any residue.
Now are there any other ways to understand?


texts: Why is a theoretical titration curve higher than a practical one?

texts:
I'm currently in high school and I did two titrations. The first one is a titration of $10.0~\mathrm{mL}$ $0.1~\mathrm{M}$ $\ce{HCl}$ with $x~\mathrm{mL}$ $\ce{NaOH}$. I obtained the following titration curve:

The blue curve is what I measured and the red curve is what the curve would look like in theory, with these data.

The second titration is a titration of $10.0~\mathrm{mL}$ $0.2~\mathrm{M}$ $\ce{CH3COOH}$ with $x~\mathrm{mL}$ $\ce{NaOH}$. I obtained the following titration curve:

Again, my measurements are in blue and the red curve is the theoretical model. I noticed that (looking at the second curve in specific) the measured pH value is most of the time lower than in the theoretical model, and close to the equivalence point, the graph is not as steep. Why is this? Not a valid reason would be that the pH sensor does not measure the right value instantly, because near the equivalence point, only one drop of $\ce{NaOH}$ was added about every two seconds. Do you have a more reasonable explanation?


texts: Is the following molecule aromatic or antiaromatic?

texts:
This molecule has the same chemical formula $\ce{C20H10}$ as corannulene (which also is non-planar) and corannulene is aromatic, so I'm pretty sure that this molecule should be aromatic too.

I tried to analyse it using the MoCubed app on my phone (on my previous posts, I wrote "WebMo" instead of "MoCubed" because I have both on my phone and sometimes get confused) but it keeps adding unnecessary hydrogen atoms and I can't rotate the molecule to remove all of them so I have to ask here.

P.S. I do know Hückel's rules, but they don't apply to pericyclic rings.


texts: Dependence of change in entropy on temperature

texts:
The thermodynamic definition of entropy is expressed as
$$dS = \frac{dq_{rev}}{T}$$
I understand that it depends on amount of heat transferred because heat transfer can be understood as the degree of dispersion of energy but what does the temperature dependence actually mean?


texts:
I came across a question in which the following reaction was taking place:
$$
\ce{Mg4C3 + H2O -> CH3CH \bond{#} CH}
$$
Each $\ce{Mg}$ atom must be present in a +2 oxidation state, thus the total charge of the cation is +8. We thus have a $\ce{C3^{8-}}$ anion. The only structure of this $\ce{C3^{8-}}$ anion I could come up with was three carbons attached to each other in a linear fashion, with the terminal carbons each bearing a -3 charge and the central carbon bearing a -2 charge.
From this anion I would have assumed that the product formed upon hydrolysis is propane, but the product formed in the above reaction is propyne, just like when $\ce{Mg2C3}$ undergoes hydrolysis.
I'm guessing that the explanation for propyne being formed is the actual lattice structure of $\ce{Mg4C3}$, but I couldn't find any literature referencing this reaction or the structure of $\ce{Mg4C3}$.
The question is taken from:

V.K. Jaiswal, s-block elements, Problems in Inorganic Chemistry, Thirteenth Edition, Page 331, question 36


texts:
Which ring of anthracene is reduced during Birch Reduction? What will the final product look like? Why?

My teacher said that the more electron deficient ring should undergo the reduction but I couldn't figure it out still. Any ideas?


texts:
It's a well-known fact that the dissociation of $\text{NaCl}$ can be represented by the series of equations $$ \begin{eqnarray*} \text{Na} &\rightarrow& \text{Na}^+ + \text{e}^- \qquad \Delta H = 495 \, \text{kJ} \\ \text{e}^- + \text{Cl} &\rightarrow& \text{Cl}^- \qquad \qquad \Delta H = -348 \, \text{kJ} \end {eqnarray*} $$

Adding gives $ \text{Na} + \text {Cl} \rightarrow \text{Na}^+ + \text{Cl}^- $ with $ \Delta H = 147 \, \text{kJ} $, which is positive so it is not spontaneous. What explains this?


texts: Vapor Pressure, Equillibrium, and Increasing Pressure

texts:
I'm trying to make sure my understanding of vapor pressure and transients is correct.

Let's assume I have a thermally-controlled sealed environment which started out as the regular air (i.e. atmospheric gasses and their respective ratios) with no gaseous water or ethanol at 101.325 kPa, 30 C. This container will maintain a temperature of 30 C after the start of this experiment.

Inside this environment there are two containers which can be remotely opened.

When I open the first container, exposing the pure water inside with a saturation vapor pressure (First question: is that the right term?) of 4.2455 kPa (from Wikipedia) and wait until it reaches equilibrium (100% humidity), does this mean this is the new state of the container?

Pressure: 101.325 + 4.2455 = 105.5705 kPa
Partial-Pressure of H2O: 4.2455 kPa

Then I open the second container, exposing pure isopropyl alcohol inside with a saturation vapor pressure of 10.555 kPa (from WolframAlpha) and wait until it reaches equilibrium again, does this mean this is the new state of the container?

Pressure: 101.325 + 4.2455 + 10.555 = 116.1255 kPa
Partial-Pressure of H2O: 4.2455 kPa
Partial-Pressure of Ethanol: 10.555 kPa

So, in the end, the pressure of the vessel increased each time a new liquid was introduced.

In this hypothetically-ideal environment, would the pressures simply rise until it reached that perfectly equilibrium? If so, I expect in a real environment the pressure would rise but there would always be a cold spot somewhere which caused the vapor pressure (in that specific area) to drop, leading to water condensing, leading to the partial pressure being lower as the air mixes, leading to more evaporation; is this correct?

Some notes:

Assume that there is enough of each liquid to reach equilibrium without running out of liquid.
The sealed environment effectively adds energy to counteract the heat of vaporization of each liquid, and also prevents the gasses from releasing/absorbing energy into/from the external environment or from changing due to pressure changes. It is essentially a magic make-everything-this-one-temperature machine.


texts:
Answer key says that A is the most basic site but I don’t understand the concept behind that.

To assess the basic site, I’d normally look at the molecule as is and assess the current stability of the atom in question. The least stable would be my strongest base.

Looking at this question both the atoms properties are the same (C with lone pair) so resonance is the next thing I would look at. Both of these rings have resonance which moves (delocalizes) the negative charge around. So I would think since the volume of resonance is greater in the bigger ring, A is more stable thus making B the stronger base.

What am I misunderstanding or what concept am I not considering?


texts: Why do chalcogens (Group VI) stink so badly?

texts:
For more fun with Dr. Derek Lowe, see this for a primer: Things I Won't Work With - Carbon Diselenide. The short of it is that we carbon-based life forms generally like oxygen. However, move just one row down in the group, to sulfur, and things start going horribly wrong. Sulfur, and the thiol/mercaptan analogs of otherwise relatively benign hydrocarbons and alcohols, gives us the thrilling eaudeur of rotten eggs, burning tires, skunks, farts, etc.

Move one row further, to selenium, and abandon all hope ye who enter here; the tamest common example of selenium in our daily lives is garlic, an instantly recognizable scent, especially when your body starts excreting the selenium-containing essential oil back out of your pores. It's supposed to be the last word in mosquito repellent; down here in Texas the little biters apparently have a taste for Italian. Selenium analogs of thiols often defy chemists' descriptions of their olfactory power; one of Dr. Lowe's other selenium-based posts, on selenophenol (the selenium analog of thiophenol, which is bad enough), puts it thusly: "Imagine 6 skunks wrapped in rubber innertubes and the whole thing is set ablaze; that might approach the metaphysical stench of this material".

This poses the rather interesting question; why do things change so suddenly with this group? I'm willing to believe that all of them have similar chemical properties, and we as humans and other oxygen-respiring life forms differentiate oxygen from the rest of the group because oxygen's good for us while the others are bad. But, that borders on the simplistic, and poses more questions, like why we work so much better on oxygen than sulfur (there are a few bacterial species hanging out near deep-sea vents that just can't get enough of those sulfur gases, so obviously there's sulfur-based "organic" metabolism just as there is oxygen-based). I guess what I'm looking for is an explanation of why two chalcogens, both obeying the octet rule as Periods 2 and 3 tend to, are treated so differently by our sensibilities.


texts: Molecular orbital (MO) diagram for N2 and N2^-

texts:
I have been taught that the MO diagram is different for molecules with 14 or less electrons than the one used for molecules with 15 or more electrons.

For $\ce{N2}$ the orbitals in increasing energy are:

$$\sigma_\mathrm{1s} < \sigma^*_\mathrm{1s} < \sigma_\mathrm{2s} < \sigma^*_\mathrm{2s} < \pi_{\mathrm{2p}_x}, \pi_{\mathrm{2p}_y} < \sigma_{\mathrm{2p}_z} < \pi^*_{\mathrm{2p}_x}, \pi^*_{\mathrm{2p}_y} < \sigma^*_{\mathrm{2p}_z}$$

because it has 14 electrons.

For $\ce{N2-}$ there are 15 electrons. Will the MO diagram be the same as that of $\ce{N2}$ or not? Why?

And because this is a good chance to ask, why is there this difference in orbital energies anyway?


texts: How does sugammadex (a modified cyclodextrin) draw rocuronium into its lipophilic cavity?

texts:
Sugammadex is a modified cyclodextrin: 8 member sugar ring with carboxyl thioether extensions. Rocuronium is an aminosteroid, 4 steroid rings and one protonated amine group.

Sugammadex binds rocuronium really tightly. The reason for this is straightforward - lipophilic interactions with the inner cavity of the cyclodextrin, which is the perfect size because of the thioether extensions. The negatively charged carboxylate groups lock into place with the protonated amine.

But the question asks how the rocuronium is initially drawn into the cavity, which makes less sense. I've only found one reference to this in the literature, in a figure caption that says the carboxylate groups interact with the four steroid rings.

But how? The rings are not aromatic, so there is no anion-pi interaction. One would think the positively charged amine would interact with the carboxylate groups far more often, leading to the wrong orientation. If anything, the hydrophobic rings should be repulsed by the negative charge?

Figure 6: Encapsulation process: Sugammadex carboxyl groups interact with steroidal rings A, B, C, and D, drawing the aminosteroidal NMBA molecule into the cavity where additional non-covalent attractions hold the molecule securely in place.

Reference:NCBI


texts:
I am not sure I completely understand the bonding in coordination compounds formed by donation of pi electron cloud by the ligands to the central atom.

For example, consider Ziese's salt:

I came across a question which asked the total number of sigma bonds in the salt. I expected the bond between ethene and platinum to be a sigma bond too because it appears as if it is formed by overlap of the orbitals along the axis and hence my answer was 9. But the answer given was 8 and the answer key didn't consider that bond as a sigma bond.

So is the bond between platinum and ethene a $\pi$ bond? If yes, then how?

What orbitals are actually involved in that bond?


texts: Why are weak acids not considered good leaving groups?

texts: So today in my first year lecture my professor said that weak bases are good leaving groups. I understand why they are good leaving groups in comparison to unstable strong bases but why are weak acids not included? Acids are electron pair acceptors, shouldn't they be better able to take on the donated electron pair? Furthermore, when we say weak bases, weak in comparison to what? To be substrate the solvent or to other potential leaving groups?


texts: length of bond, bond angle and p character in bond

texts:
My reference data: http://www.rsc.org/suppdata/ra/c4/c4ra06781a/c4ra06781a1.pdf

Consider these five chemicals:

A: $\ce{CH4}$ (methane)
B: $\ce{CH3Cl}$ (chloromethane)
C: $\ce{CH2Cl2}$ (dichloromethane)
D: $\ce{CHCl3}$ (trichloromethane/chloroform)
E: $\ce{CCl4}$ (tetrachloromethane/carbon tetrachloride)

From what I know, an orbital is longer and has higher energy as its p character increases.

From A to E, both $\ce{C-H}$ bond and $\ce{C-Cl}$ bonds get shorter, and $\ce{Cl-C-Cl}$ bond angle in D is smaller than that in C.

Nothing makes sense, first one implies more p character in $\ce{C-Cl}$ bond i.e. D < C < B and second order implies the opposite. I assumed equal x for every C's orbital taking part in $\ce{C-Cl}$ bond by symmetry.

The angle between two orbitals with $sp^x$ hybridisation is $\cos^{-1} \left( - \frac 1 x \right)$.

Also, from A to E, the electronegativity of central atom C increases, so C-Cl bond should become longer as the difference between EN decreases.

So my question is the p character and hybridization logic only working for 2nd-period elements exclusively?

Maybe relevant: It is a widespread opinion that bond energy in sigma bond p-p>s-p>s-s but sigma bond energies of $\mathrm{sp>sp^2>sp^3}$. The rationalization for the first order is more overlapping is possible due to directional and long nature of p orbital and rationalization for 2nd order is that energy of p is more than s, so the order of energies of molecular orbitals is more for more p character.

EDIT: In compounds containing $\ce{H,\ C,\ N,\ O,\ F}$ only I can predict bond lengths and bond angles almost every time using relative properties of hybrid orbitals and their relation with p character in a respective bond otherwise known as Bent's rule. But, once $\ce{Cl}$ enters the picture, there is no simple trend in any scenario, bond angle could be rationalized due to steric reasons but the cos and x relation should be valid if it follows simple hybridisation which should allow me to compare bond lengths by comparing lengths of participating orbitals (more p in carbon's hybrid orbital towards $\ce{Cl}$, longer orbital, and $\ce{Cl}$ has 3p in every case), but it seems it doesn't follow simple hybridisation. As an example, as bond angle increases, bond length must decrease, which is not the case for $\ce{CCl3}$, $\ce{CH2Cl2}$ etc