texts: What are the common products of the reaction: 2-bromobutane and NaOH

texts:
I am self-studying organic chemistry to better my understanding, I cannot formally enroll at a university due to being active duty.

From my understanding there are 2 possible mechanisms when 2-bromobutane reacts with NaOH or any strong hydroxyl base: The E2 and SN2. The carbon attached to bromine is secondary. In the E2 reaction, the oxygen from the hydroxide attacks the "beta" hydrogen, deprotinating it and allowing the electron to travel and form a double bond. Bromide is a leaving group. We get 2-butene as well as water and the bromide ion.

But we have two products from this reaction: trans-2-butene and cis-2-butene.

We also have (2,S)-butanol.

My question is which of these are more favored and why? I know that cis-2-butene would not be favored due to sterics. If possible, I would also like to know when E2 reactions are favored over SN2.


texts: If Gibbs energy of activation is positive, how is the change to the transition state possible?

texts: The Gibbs energy increases from the reactants to the transition state, but according to the Second Law of Thermodynamics, entropy of the universe can only increase. Why is the transition state possible then?


texts:
I have done part a and part b but I keep getting a negative concentration for part c.

For part a I got $\pu{2 \mu M}$
For part b I got $\pu{5.051 \mu M}$

For part c, I get  $2=3.2 + \text{[bound ligand]}$, but obviously that is wrong as you cannot have negative concentration for the bound ligand.


texts: Find the volume of the carbon dioxide product

texts:
Below you can see the chemical reaction I'm working with:

$$\ce{CH_3CH_2OH(l) + 3O_2(g) -> 2CO_2 (g) + 3H_2O(g)}$$

I've got so far:

How can I calculate the volume of the product of carbon dioxide gas (the pressure is 1 bar, and the temperature is 20 deg Celsius).


texts: Can you meassure a negative pH value with a pH meter?

texts:
I was checking the $\mathrm{pH}$ of $\pu{1 M}$ chromic acid solution, and I got its $\mathrm{pH}$ around -1.7. Yet, $\mathrm{pH}$ of $\pu{0.4 M}$ solution was around -0.6. Could these values be correct? The $\mathrm{pH}$ meter was calibrated before use.
I'm thinking not. I guess $\mathrm{pH}$ meters work in the interval 2-12 $\mathrm{pH}$.


texts: What does the prime symbol mean in organic nomenclature (e.g 2')?

texts:
I encountered the following compound on Wikipedia:

$\hspace{6cm}$

Its systematic IUPAC name is:

  4,4',5,5',6,6'-hexahydroxy-2,2'-biphenyldicarboxylic acid

What do the prime symbols in the locants 4', 5', 6', and 2' signify?


texts:
I'm looking into uses of zeolites as water absorbers for heat storage and absorbtion cooling. However, I don't find hard numbers on the likes of absorption enthalpies at different temperatures, saturation moistures, etc.

I'm not an institution, chemical suppliers are traditionally reluctant to sell to private individuals. I found zeolitic absorbers in few catalogues, but only with a descriptor of the type, no further data. One company I asked (that sell zeolites in amounts of kg to private customers) was unwilling to share data on their product (They're an engineering company doing product developement with zeolitic absorbers for heating/cooling etc.).

I only found (sketchy) data on single zeolites in working papers, but no comprehensive source.

So: seeing that vendors don't share the info, where do I find datasheets of zeolites?


texts: Why add H2O when calculating the pH of an acid?

texts:
My question is very easy.

Case 1: I have to calculate the $\mathrm{pH}$ of $0.01\ \mathrm{M}$ of $\ce{HNO3}$ solution.

This is my solution:

Case 2:I have to calculate the $\mathrm{pH}$ of a $0.01\ \mathrm{M}$ $\ce{H3PO4}$ solution.
This is the provided solution:

My question is why do we add the watermolecule in our calculations in the second case and not in the first? (or vice-verca)


texts: Which relatively simple molecules violate the octet rule?

texts:
I'm learning how to draw Lewis diagrams. Everything I've read emphasizes the octet rule. However, to the best of my knowledge, that rule only applies to elements in the first three periods.

On our exam, I expect our professor will ask us to draw some Lewis diagrams of molecules whose atoms do not comport with the octet rule. However, I haven't seen any diagrams of these; it'd be useful to get a sense of what they look like so that my gut doesn't disapprove of what will otherwise be strange looking diagrams.

What are some relatively common molecules that comprise atoms that comprise a great number of valence electrons?


texts: What purpose does mercury dichloride have in fireworks?

texts:
My local newspaper ran an article covering the local rules about fireworks.  One of those rules specifically calls out "snakes and fountains containing mercury bichloride" as forbidden.

Neither Wikipedia's article on mercury(II) chloride nor its article on mercury lists any fireworks-related use.  What purpose does the mercury dichloride serve?  Is it just a way to color the sparks, or does it have some more fundamental purpose?


texts: Resources where I can find approachable applied literature to understand general chemistry topics?

texts:
I am trying to find resources where I can learn about general chemistry topics outside the scope of a textbook, preferably in primary literature. Note, I have read through a general chemistry text and finished studying topics in the scope of a general chemistry course, so the informational foundation is there. My ideal "resource" is a place where I can find something akin to a 1-5 page experimental setup or design, or maybe a discussion, in which these concepts are applied and I'm forced to think about relationships in general chemistry, or what happens when things are changed. For example, I'd love to see some paper where I can see the ideal gas law applied as an approximation in the lungs or in deep sea divers, or some maybe some experiment where ion solubility is discussed in the scope of "hard water" in pipes. I know these applications exist, but I want to read about them on the level that makes me think about general chemistry concepts.

I can use VPN connections to login as a institution from my school and access some primary literature. However, sometimes I can't get full access becaue my institution is small and does not a subscription to a journal. Moreover, sometimes this primary literature is too complex in explanation, too longwinded, and goes beyond the scope of a general chemistry student. Now, I still want to think critically, but most of these papers include applications in engineering and use quantum physical assumptions beyond the scope of wave function solutions and electron configuration in general chemistry courses. My background includes a year of cell and molecular biology, an understanding of physics I and II, and math a little past integral calculus. I'd like the mathematics to be minimized, however, as I want concept.


texts: What is chemical decomposition in the context of a crystal or amorphous solid?

texts:
The IUPAC Gold Book definition of chemical decomposition is:

  The breakdown of a single entity (normal molecule, reaction intermediate, etc.) into two or more fragments.

That is a very general definition, but I am not sure if it is supposed to be this inclusive. For example, think of a diamond crystal. It is a single entity. Now if chemical decomposition occurs, it can break down into multiple fragments. These fragments are not defined more closely, so it could be that the fragments are single C atoms, polyatomic C molecules... or even diamond fragments again.

In this sense, simply cutting or polishing a diamond would be a special case of chemical decomposition. This seems quite absurd to me. So the question is: Is chemical decomposition really that broad, or is there some better definition that is more commonly used in chemistry? It seems to me that the intuitive definition of chemical decomposition would be that a molecule is broken into smaller fragments, while a crystal or an amorphous solid would need to be broken into non-crystalline (non-amorphous) fragments in order for it to be considered chemical decomposition. Otherwise it's just cutting!

The question is relevant to me because I am writing my PhD thesis on laser-induced breakdown spectroscopy. The "breakdown" in the name of the technique refers to a chemical breakdown, which is the same as chemical decomposition. Usually, solid samples are analyzed, in which case some material from the sample surface is removed by laser ablation. Laser ablation is basically the same as laser-induced breakdown, if you look at the definitions. So there is some confusion on the terminology in general, and I want to unravel it as good as possible in my theory chapter.

Thank you very much for your input!

(Note: By the way, some non-IUPAC definitions I have found for chemical decomposition also confusingly define it as relating to compounds. As far as I know, the definition of a compound excludes crystals and amorphous solids, but it also excludes homonuclear molecules. So this definition seems way too exclusive, because it makes sense that decomposition can also occur for homonuclear molecules.)


texts: How to measure the water content of opaque liquids?

texts: Water content of (semi) transparent liquids could be approximated via absorption spectra. What method(s) can be used to measure the water content of an opaque liquid such as milk for example?


texts: Reaction of moist egg shell powder and acid?

texts:
So I performed an experiment to investigate the effect of fluoride ions on the rate of reaction between egg shells (calcium carbonate) and acid.

When doing this I had a dry sample of crushed egg shells and a sample previously soaked in distilled water which had dried for 3 days but was still slightly moist in a 'gloopy' texture.

When I reacted the moist egg shells with hydrochloric acid they made a frothy mixture of bubbles where the carbon dioxide was trapped in bubbles while the dry egg shells fizzed and the carbon dioxide was not trapped in bubbles.

What could be a reason for the differences in the way the carbon dioxide was trapped?

(membranes were removed from both samples)


texts:
The structure of an atom is well known to me as something like this:

But what is the accurate structure of the Nucleus ? What is the arrangement of the Protons and the Neutrons or any of the other nucleons? I will be glad if anybody give an image of its structure.
Thanks!


texts: Why does the oxides that form change down the alkali metals?

texts: Why does Li2O primarily form when Li has reacted with O2 but the Na2O2 forms for sodium? Moreover, the primary product for the other alkali metals are superoxides instead of oxides and peroxides. How does the increase in radii relate to the products formed?


texts: Why Does Electrical Work Cause Changes in Internal Energy of the System?

texts:
If we look at system at constant temperature and volume which is galvanic cell, first law of thermodynamics states: $$ dU = dQ + dW'$$
Where W' is electrical work done by galvanic cell and Q is heat exchanged with surroundings.
As far as I know electrical work is work done by electric field when charge moves between certain potential difference. In galvanic cell, potential difference exists between two electrodes.
Internal energy is sum of total microscopic kinetic energy of all molecules and atoms and their potential energy of interaction (energy stored in intermolecular and chemical bonds).
What does work done by electric field have to do with internal energy of the system? Why does electrical work cause changes in internal energy of the system?
In galvanic cells, electrical work is negative as work is done by the system and from the first law it tends to decrease internal energy of the system.
I can't really see the connection between work done by electric field in the galvanic cell and sum of microscopic kinetic energy and microscopic potential energy of interaction.


texts: There are many resources online which talk about projects making bioplastic from egg shells. However none of these actually show or describe the procedure needed to make it. Does anyone know a site/paper which one could use to figure out how to do this for a science fair project?


texts: Hyperconjugation and inductive effect on carbocations

texts:
(I know there are many related questions, so please tell me which posts can solve my doubts before you close this question, thank you.)

$1$. $\ce{^+CH2F}$ is very unstable. This is because $\ce{F}$ is very electronegative, pulling the electron density from the already electrophilic carbon (empty $\text{p}$ orbital), thus increasing the positive charge.

For $\ce{CH3CH2+}$: E.N. of $\ce{H}$ = $2.2$, $\ce{C}$ = $2.5$, so the carbon in the methyl group is partially negative - like the $\ce{F}$ in $\ce{^+CH2F}$. To my understanding, the methyl group should be electron-withdrawing instead of donating, thus decreasing its stability, but this is false, why?
Some say that the partially negative carbon can donate some electron to the carbocation to increase stability, if it is true, why can't $\ce{^+CH2F}$ do the same thing?
$2.$ I know hyper-conjugation can form partial orbital overlap ($sp^3$ - $s$($\sigma$) for $\ce{H}$ & empty $p$ orbital in carbocation), thus delocalizing the electron density giving stability. However, the $\ce{C-C}$ $\sigma$ bond is always rotating, so from my view, hyper-conjugation is a bond that is continuously forming and breaking. Therefore, how come this is the predominant reason for carbocation stability?


texts: For what processes is Mayer's formula applicable?

texts:
I know that

$$C_p - C_V = R, \label{eqn:1}\tag{1}$$

but I have also seen

$$C_p - C_V = R/M \label{eqn:2}\tag{2}$$

being used in case of ideal gas.
In what cases \eqref{eqn:1} is used and in what cases \eqref{eqn:2} is used?


texts:
As a lab experiment, I am preparing a mixture of iron tablets dissolved in sulfuric acid so they can be titrated against $\ce{MnO4-}$. The tablet contain insoluble filler material.

Why is it important this 'filler' be removed when preparing the iron tablets solution?


texts: The anode and cathode when corrosion happens

texts:
Let's say $\ce{Fe}$ reacts with $\ce{Cu^{2+}}$ ions. $\ce{Fe}$ would oxidize and therefore give electrons to $\ce{Cu^{2+}}$so that:

$$\ce{Fe-> Fe^{2+}  +2e-}$$
$$\ce{Cu^{2+} +2e^- ->Cu}$$
The overall reaction:

$$\ce{Cu^{2+} +Fe ->Cu +Fe^{2+}}$$

Now this is an example of corrosion, right? And when this type of corrosion happens, the anode is the electrode where oxidation happens and the cathode is the electrode where reduction happens, right?
Therefore iron ($\ce{Fe}$) is the anode where oxidation happens and Copper 2+ ions ($\ce{Cu^{2+}}$) is the cathode where the reduction happens.

My question is, is this all correct? Have I successfully described corrosion (of this type) and given an example of it? Or is there something wrong? I'm 15 and soon I'm having a test in chemistry, and because of my age there's no point in making it "super-advanced", but if there's something I missed or did wrong please point it out, I would be grateful for that!


texts: What is the correctly diagrammed electron probability distribution for p orbital?

texts:
This is what my book shows (the darker the more probable):

The obvious places where the electron probability is zero is the midsection of the dumbbell.

My question is how the probability distributed inside the dumbbell.


texts:
My question is based upon the statement found here:

  an element may be homogeneous on a larger scale, compared to being heterogeneous on a smaller scale. This is known as an effective medium approach, or effective medium approximations.

So, is it acceptable to say that water molecule is a heterogeneous molecule?


texts: Finding the charge passed in electrolysis of water using volume of hydrogen released

texts:
During the electrolysis of water we have gotten $\pu{10 dm3}$ of hydrogen. Temperature was $\pu{0 °C}$ and pressure was $\pu{101325 Pa}$.
What charge has passed trough the electrolysis article/joint?

I don't know how to find the charge while knowing pressure, temperature and volume. How do I proceed with this question?


texts: How can we know whether a compound has a coordinate bond or not? I know that I have to draw the Lewis Structure for the compound. But what to do after that? Is there anything to do with formal charges?


texts:
In my textbook, the following information is given about Ellingham diagram:

The interpretation of $\ce{\Delta_rG^\circ}$ is based on ${K}$ ($\ce{\Delta G^\circ = -RTlnK}$). Thus it is presumed that the reactants and products are in equilibrium:
$\ce{M_xO + A_r_e_d <=> xM + A_r_e_dO}$
This is not always true because the reactant/product may be solid. In commercial processes, reactants and products are in contact for a short time.

I am not able to understand why this is not always true. How does the reactant or product being solid determine if the equilibrium will be reached or not? (Presence of solid doesn't even influence the value of K as it's activity is always taken as 1.)
Also, what does the fact that "reactants and products are in contact for a short time" signify? Do they mean that due to less time of contact, the equilibrium will not be reached (because it takes some time to attain it)?


texts: Does chemistry change under high voltage?

texts:
Do chemical reactions change when you charge the entire reaction vessel plus or minus $\pu{1 MV}$ or more?  Is there a name for such chemistry?

I was looking at "electrochemistry" expecting to see a host of information on charged reactions (either statically or with a constant charge applied) but it all just appears to be focused on batteries, not so much on synthesizing novel materials.


texts: Why x in equilibrium calculations can be "ignored"

texts:
You don't need to work out anything for me. I am just giving an example so you can explain something to me.

For example:
$$\ce{ClF3(g) <=> ClF(g) + F2(g)}\\ \ \ K_c=8.77\times10^{-14} \ \ @\  279\ \text{K}$$

What is $[\ce{ClF}]$ at equilibrium if initially $[\ce{ClF3}]=2.50 \ M$ and $[\ce{F2}]= 1.00\ M$?

$$K_c= \dfrac{[\ce{ClF}][\ce{F2}]}{[\ce{ClF3}]} = \frac{(x)(1.00+x)}{(2.50-x)} = 8.77\times10^{-14}$$

I get everything that just happened above. Thats how I would do it but then, my lecturer said the $x$ then becomes negligible for some reason something about the CIF. and now the equation becomes:
$K_c= \dfrac{(x)(1.00)}{2.50}$ and so $x=2.2\times10^{-13}$.

What happens to the $x$ and why? Also, what exactly is $K_c$ in chemistry what does it represent? I know how to work out questions but I don't know why.


texts: Stability of furanose vs. pyranose form of glucose?

texts:
I am trying to imagine the cyclization of the Fischer projection of glucose as it forms an $\unicode[Times]{x3B1}$-D-glucofuranose and an $\unicode[Times]{x3B1}$-D-glucopyranose (right now I am trying to understand the Haworth projection, and as my 3D visualization gets better, I will extend to the more thermodynamically stable chair representations of these monosaccharides). Now, if I understand correctly, in the pyranose form, the alcohol on $\mathrm{C5}$ attacks the carbonyl carbon on $\mathrm{C1}$. In the furanose form, the alcohol on $\mathrm{C4}$ attacks the carbonyl carbon on $\mathrm{C1}$. These results in 6-membered and 5-membered rings, respectively.

I understand in nature, these are the most stable rings. However, what thermodynamic incentive does the furanose form have? That is, why would $\mathrm{C4}$'s alcohol attack and form a 5-membered ring at the expense of the $\ce{CH2OH}$ group and the $\ce{OH}$ group being near each other as a side chain on the 5-membered ring? Doesn't this introduce considerable strain? My idea is that the 6-memebered ring is more thermodynamically stable and it doesn't have the problem of a hydroxymethyl and a hydroxyl group on a single carbon of the 5-membered ring.


texts: Degradation mechanism of hydroxymethylfurfural to 2,5-dioxo-3-hexenal and 4-oxopentanoic acid

texts:
I want to understand the degradation mechanism of hydroxymethylfurfural (HMF). According to the Wikipedia article, HMF is degraded in honey. Someone said that the degradation proceeds via 2 possible routes and that the products are 2,5-dioxo-3-hexenal and 4-oxopentanoic acid.

What is the mechanism by which these compounds form? If you add a picture of the mechanism, it will be better.


texts: Does this reduction mechanism of an diazonium via stannic chloride sense?

texts:
Is this mechanism possible.
I didnt find any sources of a mechanism of this specific reaction.


texts: Reducing strength of (i-Bu)2AlH vs Lithium aluminum tri(t-butoxy)hydride

texts:
Hi Im trying to figure out which of the following is the stronger reducing agent.

(i-Bu)2AlH vs Lithium aluminum tri(t-butoxy)hydride

From my understanding, the Lithium aluminum tri(t-butoxy)hydride should be the stronger reducing reagent since it has a negative charge on the aluminum which would help push electron density onto the hydrogen. But on the lecture slides it says that Lithium aluminum tri(t-butoxy)hydride is a milder reducing agent. Can someone provide reasoning why that is the case. Thanks


texts: Can secondary alkyl halides be used in the Corey–House synthesis?

texts:
I've been told by my teacher that the Corey–House synthesis cannot proceed with secondary alkyl halides; they will prefer to undergo elimination over $\mathrm{S_N2}$ substitution. [used as the pseudo halide, not the diorganyl cuprate.]. My book, however says that secondary alkyl halides do undergo the reaction. A quick google search on Wikipedia says:

[...]RX, R = methyl, benzylic, allylic, primary, or cyclic secondary alkyl, aryl, or alkenyl

These seemingly varied responses have really left me rather confused. Is the applicability different for different secondary halides? If yes, why? And if no, then which is the correct answer?
Secondly, my teacher also tells me that in R-X, using Br, Cl, or F as the halogen will not produce a satisfactory yield. Again, Wikipedia goes on to say:

[...] X = Br, I, OTs, or OTf; X = Cl is marginal.

Again,  could anyone help me out in resolving these differences? I've never really had the opportunity to see these reactions in the lab, so I feel that someone with real experience would be able to help me out.


texts: Action of KMno4/H+ and heat in this reaction

texts:
The first step uses LAH which is a hydride donor. So H- attacks any one carbonyl carbon and forms an aldehyde and acid attached to the ring.

Then Conc. KMno4 is used. As far as i know, it cleaves c=c and oxidises them into acids.
 The third step then says heat, so it leads to the formation of the anhydride on both sides.

However, this product has nothing to do with the correct answer which is option (A) . Somehow the product formed consists of 2 seprate 5 membered rings. Any idea on where i went wrong?

edit::


texts: Why is density fitting not used to reduce four-center integrals further down to two-center integrals?

texts: In density fitting, why don't researchers turn all the 4-center integrals into 2-center ones instead of stopping at composing them from 3-center integrals?


texts: How were silver and gold separated using the salt cementation process?

texts:
Gold and silver are often extracted from the same ores and are difficult to separate due to their chemical similarity, which prevents the use of techniques such as cupellation. Acid-based methods were discovered during the medieval period but were too expensive for use, so the main method of gold parting (the separation of gold from other metals) until the C16th was by salt cementation, in which sheets or granules of low-purity gold were heated with salt (NaCl) and/or other other compounds.

I would like to understand how this process was actually used. Wikipedia says the silver chloride (AgCl) produced is 'removed' but does not describe how. It also mentions that AgCl is volatile and the vessel used for the process is sealed to prevent its escape, which seems to contradict the previous statement. At the same time, it mentions the process is kept below 1000degC to stop the gold from melting, which is a long way below the boiling point of AgCl at atmopsheric pressure (although I don't know what pressure would be reached inside the vessel or how that would affect the volatility of AgCl). Furthermore, I thought that upon heating AgCl would normally decompose to silver (and chlorine) anyway, which in a simple, sealed vessel would presumably just remix with the gold. Some sort of alembic arrangement, maybe? I'm pretty sure I've misunderstood something fairly basic here.

I'm then further confused by this 1974 paper by Notton (open access) which seems to describe a recreation of what sounds like salt cementation process but then compares it to cementation (meaning it must differ significantly in some way I'm missing), and also sheds no light on the mechanism for recovering silver, although notes that the alumina plug of the sealed container ends up discoloured by silver salts after heating. Were the silver salts absorbed by the walls of the container, as in lead/silver cupellation?

I am interested in historical (pre-C16th) application of this process, rather than modern solutions.


texts: Calculation of the cell potential of a lemon battery experiment

texts:
I have the following problem that I would like to get checked.

I’m told to calculate the cell potential of a simple lemon battery experiment.

After Finding out the oxidizing agents and the reducing agents I find that the cell reaction is as follows:

$$\ce{2H+(aq) + Zn(s) —> H2(g) + Zn^2+(aq)}$$

with a cell potential of $E_\mathrm{cell} = +\pu{0.76 V}$.

Are the reactions and the cell potential correct?


texts: Why is solid phase peptide synthesis limited to 70 amino acids?

texts:
I'm reading document about Solid phase protein synthesis (SPPS) from Wikipedia, and according to the document:

  SPPS is limited by yields, and typically peptides and proteins in the
  range of 70 amino acids are pushing the limits of synthetic
  accessibility. Synthetic difficulty also is sequence dependent;
  typically amyloid peptides and proteins are difficult to make. Longer
  lengths can be accessed by using native chemical ligation to couple
  two peptides together with quantitative yields.

I'm a bit not understanding why this synthesis method is limited to 70 amino acids in length. Anyone please help me to explain what is the issue?


texts: Testing for nitrate ions with NaNO3 in Devarda's test

texts:
When we use Devarda's test on $\ce{NaNO3}$ solution (we add $\ce{NaOH}$ and $\ce{Al}$ powder, heat the mixture, and produce ammonia), what is the equation of the process?

I understand that $\ce{Al}$ reduces $\ce{NO3-}$ to $\ce{NH4+}$ then $\ce{NH4+}$ and $\ce{OH-}$ have a reversible reaction to produce $\ce{NH3}$, and water, but I'm not sure how to summarize this in an equation. In particular, what happens to the aluminium?


texts: Can you explain DFT and TDDFT functioning (math aside)?

texts:
I have been recently reading a lot on the quantum mechanical theory regarding Density Functional Theory, DFT, and Time Dependent Density Functional Theory, TDDFT (Oscillatory and Rotatory Strengths in particular) in order to understand how first principle calculations fundamental theory work.

I get that DFT is used to calculate the ground-state configuration of a system and TDDFT gets you the excited states useful for spectra determination and that there have been developed several algorithms in order to make calculations more efficient (timewise).

But I still can't answer myself in a short way how does each one works (math aside).

If you were to explain them to a person that is not necessarily familiar with quantum mechanics, how would you do it?


texts: For chemical reactions occurring in the interstellar medium, which involve metal-ions, will the metal ions be solvated or not?

texts: Usually, metal-ions in terrestrial chemistry will be solvated - either by gas-phase solvent molecules or by liquid-phase solvent molecules. But the interstellar medium (ISM) is never in local thermodynamic equilibrium. Moreover, the solvation of any system is driven by the system's proclivity to attain thermodynamic stability. But given the lack of local thermodynamic equilibrium in the ISM, solvation should not at all be an important factor in the ISM. Is it right or wrong? Any reference from the Astrochemistry/Astrophysics community will also be highly appreciated.


texts: Why do we add copper when testing a salt for nitrate ion?

texts:
In our chemistry curriculum we are doing these lab experiments where we are supposed to test salts for certain anions,cations and other stuff.

I was told that if I dissolved the salt in concentrated $\ce{H2SO4}$ and then heated it for a while over a flame, the evolution of light brown vapours would indicate the possibility of $\ce{NO3-}$. To confirm its presence, however, I would have to repeat the test but this time also add some copper bits to the solution and check for dark brown vapours.

I figured the reason was that the copper reduced the $\ce{HNO3}$ gas to $\ce{NO2}$ which increased the amount of $\ce{NO2}$ gas produced, resulting in a darker shade of brown.

My question is that why copper, which is a very weak reducing agent, used here? Why not a real reducing agent like zinc which will give more $\ce{NO2}$ even with lesser salt?


texts:
I am considering the hydrogenation of 2-butanone with respect to its Re and Si faces.

So if we look at 2-butanone as I've drawn below from above we are looking at its rectus face.

And from below we are looking at its sinister face.

Now, time to consider hydrogenation.

We'll keep the wedge and dash groups as they are and the carbon and oxygen both on lines. In other words we keep two points as is in the originally trigonal planar 2-butanone and when the hydrogen inserts itself, the other two points (a hydrogen and an alcohol group) pop up out the plane to form the classic tetrahedral shape of an $\ce{sp3}$ carbon atom.

So it appears that hydrogenation from the sinister face adds an hydrogen to the central carbon and forms an alcohol, and the alcohol is above the added hydrogen spatially, and this gives us the R isomer. Hydrogenation from the rectal face gives the opposite S isomer.

How's the reasoning? Am I right? I am fairly sure. But not completely sure.


texts:
It's well known that activated charcoal is an adsorbent and due to very big surface area per unit of mass it can adsorb a lot of particles.

Let's take as an example for my question this product on Amazon.

My questions are the followings:

How much do this apply to the air purifiers? According to them it is supposed to work as an air purifier but I don't see it working unless the air you want to purify is being pushed through a activated charcoal filter. AFAIK by itself the activated charcoal is not attracting the smelly particles. Or is it?
I have read that activated charcoal adsorbs bad smells(gases from air) and when the activated charcoal is placed in a hot environment it releases the adsorbed gases. What is that temperature at which adsorbed gases are released back in the air? Is this why they advice placing the product in the sun? Taken from product description: "Placing activated bamboo charcoal bag in the sun for 2 hours once a month, naturally rejuvenates the charcoal by removing excess moisture - extending the life of these charcoal room odor absorbers for up to 2 years."


texts: Excitation of an electron of H-atom from n=2 to any $n_2 $

texts:
I got taught that if an electron de-excites from any $n_2 $(where $n_2 >3$) to $n=2$, the  energy change can be represented by $$\Delta E=13.6\left(\frac{1}{n_1^2}-\frac{1}{n_2^2}\right)\ \mathrm{eV}$$
What if an electron excites from $n=2$ to $n_2 $(where $n_2 >3$)?

Do we have to reverse the signs in the brackets?

Also, if it excites like I said, will it be absorbing visible light?(Because in de-excitation, it emits visible light)


texts: How to explain the dipole moment anomaly of methyl fluoride and methyl chloride with respect to their hydracids?

texts:
I was checking dipole moment orders, and came across a very peculiar result:
Methyl fluoride $(\ce{CH3F})$ has lesser dipole moment than methyl chloride ($\ce{CH3Cl}$), but hydrofluoric acid ($\ce{HF}$) has more dipole moment than hydrochloric acid ($\ce{HCl}$).

At first I thought it was about distance, but upon seeing the second one, it led me to think about polarizability. So my question shortens to this:
Which factor dominates while checking dipole moments and when?


texts:
I recently learned about the Stork enamine alkylation method of adding electrophiles to the beta carboxyl position on a molecule. But I can't seem to find out why a direct synthesis is not possible (or perhaps favoured).
I've used an online resource to draw a mechanism that I thought would work, but clearly because we use the Stork enamine method I am missing something here and this can't be true.
Is it perhaps that the double bond is too weak of a nucleophile to attack?


texts: Surfactants decrease surface tension between two fluids.  What do you call a substance that increases the surface tension between two fluids?  How is this effect acheived?


texts: Formation of polymers - addition polymerisation

texts:
In addition polymerisation, a double bond in the monomer is broken and a long chain of polymers is formed. How is this bond broken (where is the energy input) and how is the long chain formed?

(something to do with free bonds?)


texts:
I tried to make Italian buttercream icing the other day and followed this recipe.

Unfortunately, the icing was completely runny / liquid. So I know I made a mistake somewhere.
But since I don't understand the chemistry of egg whites I am not sure how to figure it out.

I think the key to the change from liquid to creamy/spreadable is when you pour hot syrup down the side of the bowl while keeping on mixing at high speed.

So what exactly happens there? I think this is where something went wrong but I am not sure what. I had my perfect egg whites beaten to nice firm froth and my no longer boiling syrup that I poured down the side of the bowl while furiously mixing and yet the result was close to water in consistency, even after adding the butter!

I appreciate any help in understanding how something liquid can be turned into something of high viscosity with this process! Thank you so much in advance for giving me insight into egg whites in the kitchen!


texts: What is generally meant by distinct line spectrum?

texts:
In a single hydrogen atom the electron is excited to 6th orbit. The book says maximum 5 distinct spectral lines are possible when the electron comes to the ground state.

Looks like they have only considered those lines when the electron jumps from shell 6 to ground, shell 5 to ground, shell 4 to ground etc. But in my opinion we should also consider the lines produced while transfer of electrons from 6 shell to 5 shell etc. As the elctron can jump from shell 5 to shell 1 directly only when it has jumped from shell 6 to 5 earlier. That would lead to more number of spectral lines than just 5.

So, am i thinking something wrong here (the word "distinct"  seems to be the reason)?


texts:
I just learend about an interpenetrating polymer network (IPN) and that this is a way of mixing polymers. But I thought it was thermodynamically impossible to mix 2 polymers because in ∆G= ∆H -T.∆S the enthropy will never be big enough to overcome ∆H. So why is it possible with an interpenetrating polymer network (IPN)??

thanks in advance


texts: Is there a Python module for calculating Ovality of a molecule?

texts:
Ovality gives a measure of how the shape of a molecule approaches a sphere (at one extreme) or a cigar shape (at the other). Ovality is described by a ratio of volume to area (see https://en.wikipedia.org/wiki/Ovality).
So, it is basically "just" about intersecting Van-der-Waals spheres. Although this sounds simple, it can get pretty complicated.

There is a nice paper from M. Petitjean explaining how to get correct values of Van-der-Waals volumes and surfaces (see https://hal.archives-ouvertes.fr/hal-01955983).
According to this paper, inacceptable approximations have been used in the past.
I can follow this paper to a certain extent, but when it comes to implementing this in Python it would exceed my mathematical and programming knowledge.

Therefore my question:

Is there maybe already a Python module which can calculate Ovality from a given molecular structure?
Input would be: atom types, atom positions, and Van-der-Waals radii of the atoms.

I'm already using RDKit and maybe it can do it, and I just haven't found this feature.
Thank you for any hints.

I guess there was need for clarification:

The ovality (O), a parameter used as shape descriptor, is defined as the ratio between actual surface and minimum surface for the same volume (the surface of a sphere with a volume that equals the actual volume) (see
https://www.sciencedirect.com/topics/chemistry/molecular-size)

For this, the van-der-Waals surface and the van-der-Waals volume of the molecule need to be calculated, basically by intersecting spheres with different sizes at different positions.


texts: Why does contaminated brake fluid conduct electricity? Using a voltmeter to test for water contamination in brake fluid

texts:
Contaminated brake fluid conducts electricity. In the automotive repair world, brake fluid is considered contaminated by two ways:

Brake fluid is hygroscopic. Higher water content in brake fluid means lower boiling point. Brake pads/rotors get hot which can boil the water near near the pads/rotors. Boiled water is steam which is a compressible gas. Having a gas in the brake lines leads to a spongy brake pedal. So, high water content absorbed by brake fluid is considered contaminated.
Brake lines contain copper. When microscopic bits copper get in the brake fluid, they can build up in the ABS unit causing failure of the ABS system. Thus, high amounts of copper mean contaminated brake fluid.

Since pure water and copper are both nonelectrolytes, how can brake fluid conduct electricity? Is there some other contaminant I am missing here that is an electrolyte? Is the water being absorbed, somehow, by the brake fluid not strictly H2O?
I am asking because I want to know if I can use a voltmeter to test if there is too much water contamination in brake fluid.


texts: Spontaneity and nature of attack of fluorine gas on aluminum

texts:
What is the nature of the reaction of attack of fluorine gas on aluminum metal? Is it spontaneous in nature?
I have studied reactions of halogens on aluminum but it had no information about the attack of fluorine and I would like to know about this reaction.

Aluminium has a tenacious oxide layer so the reaction of gaseous fluorine with aluminium metal is firstly the reaction of fluorine with aluminium oxide.

So finally $\ce{F2}$ will react with $\ce{Al2O3}$? Also will $\ce{F2}$ react with fresh $\ce{Al}$ metal surface.


texts: Separating two sugars according to their heavy atoms - Steered Molecular Dynamics

texts:
I am trying to separate two methyl-N,N'-diacetylchitobiose sugars using steered molecular dynamics in AMBER. I have tested out:

&rst
iat=-1,-1,
r2=2.5,
rk2=10.0,
r2a=12.5,
iresid=0,
fxyz=1,1,1,
outxyz=1,
igr1=2,5,6,8,9,11,14,16,18,20,22,24,26,27,28,32,33,35,36,38,41,43,45,47,49,51,53,54,55,59,60,
igr2=65,68,69,71,72,74,77,79,81,83,85,87,89,90,91,95,96,98,99,101,104,106,108,110,112,114,116,117,118,122,123
/

Which should apparently separate the two sugars relative to their heavy atoms from a distance (between each other) of 2.5 A to 12.5 A along the x,y and z axes and using a force constant of 10 (I think kcal/mol). The solvent I am using is water.

I ran this separation for 100 ns and the two sugars refused to separate. I am not sure if my force constant is too small, or if something else is wrong with my reference file. I have googled it and spoken to m supervisor about it, and unfortunately I have not succeeded in finding a solution.

Any help would be appreciated.


texts: Hydrogenation of 1-hexene with Raney nickel

texts:
For my high school senior chemistry project, I need to create and perform a lab. I've chosen to do the hydrogenation of 1-hexene with the catalyst of Raney nickel.

I'm struggling because I'm not exactly sure how to perform a hydrogenation. Some websites tell me I need nitrogen gas, some don't. I'm most likely performing a batch hydrogenation under atmospheric conditions.

Any advice on the actual procedure of the hydrogenation would be helpful.


texts: Alternative explanation of ethene's pi bond

texts:
This tutorial about ethene's bonds has the following paragraph that I hope someone can paraphrase in a better way:

The pi bond dominates the chemistry of ethene. It is very vulnerable to attack - a very negative region of space above and below the plane of the molecule. It is also somewhat distant from the control of the nuclei and so is a weaker bond than the sigma bond joining the two carbons.

What does it mean by:

"vulnerable to attack"?
"negative region of space"?


texts:
I was looking for an accurate definition of halogen bonding.
I was able to find quite a few good ones, but none of them would explain if a X---H intermolecular interaction would count as a form of halogen bonding. Where X is any halogen and H is a hydrogen from another molecule. Does this count as halogen or hydrogen bonding? Or maybe as both?

Thank you,


texts: What are the possible concentration pathways for a 3-species system?

texts:
Inspired by this question, which asks if a multi-species system could oscillate around its equilibrium, I thought about the possible concentration pathways the following more narrow specified system could take:

$$ \ce{A ->[\text{$k_1$}] B} $$
$$ \ce{B ->[\text{$k_2$}] C} $$
$$ \ce{C ->[\text{$k_3$}] A} $$

What I was interested in are the ratio of those concentrations $A:B:C$. The initial conditions are $A(0)=1$, $B(0)=0$, $C(0)=0$. (For simplicity, $[\ce{A}] \equiv A$, and analogous for $B$ and $C$)

  What are the possible concentration pathways for different values of $k_1$, $k_2$ and $k_3$?


texts: Could the net equations for burning hexene be used as a means of energy source?

texts:
$6\ce{CO_2} + 6\ce{H_2O}\xrightarrow{some\;catalyst}9\ce O_2 + \ce{C_6H_{12}}$
$\ce{C_6H_{12}} + 6\ce O_2\to 6\ce{CO_2} + 6\ce H_2$
$6\ce H_2 + 3\ce O_2\to 6\ce{H_2O}$

At one point, I had made a balanced set of equations while starting college. Those equations are listed above. I had wanted to get into chemistry to see if there was any possible way those equations could be used as a means for a new kind of energy source; one that could catalyze its fuel, hexene, that it could later use, but then also take the byproducts of the combustion of hexene and produce the same chemicals it needs to produce hexene, and repeat the process. I don't know if it's possible, and I don't know what, if any catalyst would be needed to make it possible. However, as time went on, my major changed to software development and I gave up on becoming a chemist. So this is both a question and a challenge: Can anyone figure out if the system described above is possible, and what would it require to make it available as an energy source?


texts: How is a reduction in the number of molecules associated with a decrease in Entropy? For example, stoichiometric equations like $\ce{H2 + O -> H2O}$ are enthalpy driven if I am correct. But it also implies that entropy is decreasing because the system is becoming "more orderly." Is this intuition correct?


texts: How can the dipole moment of carbon monoxide be rationalised by molecular orbital theory?

texts:
Despite the fact that oxygen is much more electronegative than carbon, the bond in $\ce{CO}$ presents a weak dipole moment.
This observation can easily be explained using the concept of "dative bond", that is, one bond is formed with two electrons from oxygen, producing a polarization $\ce{O\bond{->}C}$ which equilibrates the expected polarization $\ce{C->O}$.
I would like to know if the molecular orbital model could be used to explain this phenomenon.
Here's the diagram for $\ce{CO}$:


texts: Is there a substance that would react with seawater to produce a dense, insoluble, nonporous precipitate? Alternatively, is there a hygroscopic substance that will absorb water and expand into a dense/tough non-permeable mass? This is a material to seal off a small inner diameter pipe once water intrudes into it


texts: Vapor pressure and boiling point for solutions in open containers

texts:
Question 1: If we have an open container which has water in it and is heated. If there is no lid over the container then how can this water ever boil as there will be no vapor pressure created over the water surface.

Question 2: What is the logic in the fact that boiling starts when vapor pressure becomes equal to atmospheric pressure.


texts: I'm aware that tritium undergoes beta decay forming Helium-3. But in the case of HTO, what does it decay into? I don't suppose it decays into HeHO.


texts: How does density of alkali metals increase down the group?

texts: Size of alkali metals increases down the group, so volume also shows increment, and since volume is inversely proportional to density, how does density also increase down the group?


texts: Can catecholamines be quantified by HPLC-MS/MS at high pH?

texts:
It seems that most HPLC-MS/MS methods used for quantitation of catecholamines (epinephrine, norepinephrine and dopamine, specifically) operate at low pH (commonly 3.0), and therefore demand the addition of ion pairing reagents if a C18 column is to be employed. From my understand, these conditions are used to improve catecholamine stability, and avoid formation of quinones by oxidation. Fair.

My question is; why are high pH solvents not used (> pKa + 2.0, so pH ~ 10.5), with the addition of antioxidizers, such as EDTA? I understand that this would require MS operation in negative ion mode, but should circumvent need for ion pairing reagents. Might this be possible? Has this been attempted?


texts: Why is there an increasing solubility in water for chlorides, chlorates, perchlorates in that order?

texts:
According to Wikipedia $\pu{100 mL}$ of water dissolve at $\pu{25 ^\circ{}C}$ about $\pu{35 g}$ of $\ce{NaCl}$ (1), but about $\pu{79 g}$ of $\ce{NaClO3}$ (2), and around $\pu{210 g}$ for $\ce{NaClO4}$ (3).

This looks to me roughly like its doubling solubility for every single higher level of oxidation.

Earlier I was under the impression that the % of $\ce{Cl}$ or % of $\ce{Na}$ in the water would still be the same, and the amount of additional oxygen is what could be causing the increase in solubility.... ie. now each molecule has 3 oxygen atoms as opposed to none in case of $\ce{NaCl}$. But this doesn't hold true.

I would also like to know what is the effect of multiple solutes sharing same atoms on each other.  For example does dissolving some chlorate cause the solvent to hold more chloride ?

As you may have guess Chemistry isn't my strong suite, I know basic chemistry, but now when I am looking at it again.. the whole thing has changed atleast w.r.t what I was taught during my school days. (right from how we determine the number of electrons)


texts: Which is more stable? CF2 (singlet) or CF2 (triplet)

texts:
Generally, we know that triplet carbene is more stable than singlet. But in my book, it is written that singlet difluorocarbene is more stable than triplet difluorocarbene.
What's the reason for it?


texts: Find out of the friend is getting a good deal

texts:
I have a strange chemistry question that I've never came across before, and I have no idea about how to solve it.

  Your friend comes across a good deal to purchase a gold ring. She asks you for advice for you to test the ring. The ring has a mass of 4.54 g. When the ring is heated with 94.8 J of energy, temperature rises from 23.0 °C to 47.5 °C. The gold specific heat capacity is 0.1291 J/g. Is she getting a good deal?

So I did the equation to solve for Q which is 14.35 J, and I have all the numbers the (considering they are given) but I have no idea how to actually calculate how much of this ring is pure gold.

I came here as a last resort.


texts:
I am trying to figure out which rings in callistephin are aromatic:

I know that the benzene rings definitely are aromatic, but I'm not sure about the ring with the positively charged oxygen (highlighted in red).

How does the Hückel $4n+2$ rule apply to this ring?


texts: Why benzene has more heat of hydrogenation than cyclohexene?

texts:
According to me, benzene is more stable than cyclohexene due to its aromatic nature. Therefore the heat of hydrogenation of cyclohexene should be more than benzene (because I read that heat of hydrogenation is inversely proportional to stability).
But then also the heat of hydrogenation of benzene is more than that of cyclohexene.
Does it indicate the idea that non-aromatic compounds may be more stable than aromatic ones?


texts: How to calculate valence factor (n-factor) for a element?

texts:
Suppose I am given some reaction in which
$$\ce{C6H12O6 -> CO2}$$
and I want to calculate n-factor for this reaction to ultimately calculate equivalent weight of carbon for this reaction. Since $$E=\frac{M}{n}$$
I know that n-factor is no of electron gained/lost by one atom of a compound.

So Initial Oxidation state of carbon is $$6x + 12-12=0$$ $$x=0$$ meaning
and final oxidation state of carbon is $$-4$$ Hence, n-factor of this reaction should be $4$ but it's given to be $28$. How is this possible? Can someone explain how to correctly calculate n-factor with few more examples?


texts: Do the salt bridge ions have to match the ions in the half-cells solutions?

texts: Does the salt bridge in a galvanic cell have to have the same ions as the ones in the solutions? E.g. does it need to have nitrate ions if the half-cells contain copper nitrate and zinc nitrate, or could nitrate ions still be used if the solutions had sulfate instead?


texts: What does the ‘−1’ superscript mean in units?

texts: For example, the rate of a chemical reaction can be expressed in $\mathrm{mol}/\mathrm{L}^{-1}/\mathrm{sec}^{-1}$. Why is it ‘−1’ and not, say, ‘−2’? Does it change the meaning if the minus is removed and we simply express the rate in $\mathrm{mol}/\mathrm{L}/\mathrm{sec}$?


texts:
While explaining haloform reaction my teacher told me that Me3C-(C=O)-CH3 does not give haloform reaction.
What is the reason behind it since it does have a CH3 group?


texts: When is a reaction said to be under kinetic control, is it not easily reversible?

texts:
If we consider this reaction: Compound 1 + Compound 2 --> Compound 3

I understand that if a reaction is under kinetic control, the less stable (e.g. a mono-substituted diene) is formed and if the reaction is under thermodynamic control the more stable stable (disubstituted diene) is formed.

However, if we wanted to go from the kinetic product to the thermodynamic product, would this reaction be considered as being under kinetic control? In other words, are the reactants under kinetic/thermodynamic control, or is it the products?

I think this is more of a terminology question.


texts: Why is the HOMO always lower in energy than the LUMO?

texts: We say that increasing the energy of the $\ce {HOMO}$ of molecules increases their reactivity towards electrophiles while decreasing the energy of the $\ce {LUMO}$ increases their reactivity towards nucleophiles. However, this seems to be built on the implicit assumption that all molecules will always have a $\ce {HOMO}$ that is lower in energy relative to all $\ce {LUMO}$s in every single other molecule. How can that be justified?


texts: Comparing the strength of metallic bonds

texts: Why is the boiling point of iron higher than magnesium?


texts: Determining the order of molar conductivity

texts:
This was a question which came in a objective type examination.

Which of the following have a $\lambda^\infty$ (molar conductivity at infinite dilution) larger than $\ce{KCl}$?
A. $\ce{CH3COOH}$
B. $\ce{HC}$
C. $\ce{NaOH}$
D. None of the above

I was not provided any experimental data to arrive at the answer.I know that $\ce{KCl}$ is a strong electrolyte and so my guess was that it must have greater molar conductivity than at least $\ce{CH_3COOH}$. But the answer key gives all A, B, and C. Is there a definite rule here?


texts: What are the specific dangers associated with Grignard reagents?

texts:
I would like to know if anyone has had any specific safety-related problems with Grignard reagents.  I have taught the year-long introductory Organic Chemistry sequence for about 15 years and have never had a student get any Grignard Reagent on their skin, but I've always questioned how safe it really is to have students work with these compounds (specifically PhMgBr).  I have never allowed my students to work with n-butyllithium (we don't even have any in our stockroom), so it seems an odd contradiction that I have much less reluctance to have them work with Grignard reagents.

The dangers of organolithium reagents, particularly t-BuLi and -- to a lesser extent -- n-BuLi are well documented.  It seems to me that the danger of these reagents largely arises from the flammability of the solvent (hexane) in which the compounds are dissolved as opposed to their extreme reactivity as bases.  The organolithium reagent as it reacts with moisture provides the energy needed to ignite the solvent. Since Grignard reagents are themselves extremely basic and dissolved in highly-flammable ethers, it would seem that the dangers of physical contact with a Grignard reagent would be equal to if not greater than those of using an organolithium reagent.  Just out of curiosity, has anyone actually had experience with any accidents and/or injuries involving Grignard reagents?


texts: Purification of water with ferric chloride

texts: Ferric chloride ($\ce{FeCl3}$) is a chemical used in water treatment. If ferric chloride is added to a water sample containing calcium bicarbonate, would the $\mathrm{pH}$ of the solution decrease or increase?


texts: How to determine the packing geometry of compounds with contradicting coordination number and radius-ratio values?

texts:
Determine the packing geometry of the following compounds by using the radius ratio rules. For your convenience assume a coordination number of six for both cation and anion.
Be specific in the your answer, "body-centered cubic with the anion occupying the corners of the cell [1 atom] and the cation occupying the central hole [1 atom].

Below is the table we are given, and we're are choosing between geometries of cubic, body-centered, or face-centered.

The compound I'm on is $\ce{LiBr}$
I did $\frac{r^+}{r^-}=\frac{79}{182}=0.43$ for the Radius-Ratio value.
But from here would I choose square planar because it's closer to 0.414 or do I choose octahedral because we're assuming coordination number 6? And how would I determine the locations of the cation/anion?
My best guess is cubic geometry because the cation is too large to fit tetrahedral holes and octahedral holes, with $\ce{Li}$ and $\ce{Br}$ taking occupying complementary corners.

I'm making the assumption that the coordination number 6 is used as a reference to the atomic radii.
I've currently adjusted my answer based off of other examples I could find to

FCC with OH holes occupied by $\ce{Li^+}$ [4 atoms] and the $\ce{Br^-}$ forms the FCC Lattice [4 atoms (by stoichiometry}] for a 100% occupancy rate.

But I still have an issue as to how to conceptually approach the problem.


texts:
I want to use FAS (fluoroalkylsilane) in my molecular dynamics study. How can I find it's real structure? So that I can find proper forcefield for simulating the molecule. It would be very nice if you mention a better method for simulating this molecule. Like making a initial configuration in a software and then optimizing the geometry. I don't know about DFT so much, but can I use that somehow?

Best,

-Kazem


texts: What is the degree of unsaturation of oxalate anion?

texts:
I was practicing a DPP for JEE Mains & Advanced exam. There is a question in organic chemistry, a reaction sequence was given whose answer was oxalate anion.
But the next question was what is the degree of unsaturation of the compound formed in the previous question .
I simply did it 2 because there are 2 C=O bond but the answer was given 3. Please help me in making out, why it is so.


texts: Flame Test: Why does the flame colour of calcium disappear quickly?

texts:
While performing flame tests for calcium fluoride and strontium fluoride, I observed strontium gives a long-lasting rose-red flame color but the brick red color for calcium quickly disappears. I also found some books mention the flame color for calcium as transient red.
Why does the flame color of calcium is transient?


texts: How is the process of converting calcium carbonate (CaCO3) into calcium oxide (CaO)?

texts:
I need to provide accurate information in relation to the production process of calcium oxide from calcium carbonate.

$$\ce{CaCO3 -> CaO + CO2}$$


texts: What is the maximum pressure that JB Weld can withstand?

texts:
JB Weld, a brand name of steel-reinforced epoxy, makes claims of being the "world's strongest bond".

What is the maximum pressure it can withstand, and what is it about the interaction between the steel and the epoxy that makes it so strong?


texts:
Question

Which hydrogen among the four in the conjugate base of aspartic acid is most acidic?

Answer

 No answer given

My attempt
I am confused between Hb and Hc
I know Hd has $\mathrm pK_\mathrm a \approx  9$, so it will not be the most acidic.
$\ce{NH3+}$ has very high -I effect but no mesomeric effect, so Hc appears to be quite acidic.
But at the same time it is at the alpha position of the carboxylic acid and may not be effectively conjugated in the $\ce{C=O}$ bond.
Here can the electron pair if formed by loss of Hc be conjugated on the $\ce{C=O}$ bond? This will prevent the lone pair on oxygen from being delocalized, however, something that is not characteristic of carboxylic acids.
Hb may be acidic but no special effect may be attributed to it, similar to Ha.
I think the order will be Hb > Hc > Ha > Hd
Is my assumption correct?


texts: Did my teacher specialist about sulfur compounds made an error in part of Ramberg-Bäcklund rearragement mechanism?

texts:
I have a lot of troubles with what I circled in red with the big question mark near. I am not speaking about stereochemistry but about conservation of number of hydrogen atoms, and also there is actually no reason for the electrons on the carbon near $R_1$ to attack the other carbon. In my lesson, the teacher didn't show how the extra hydrogen was removed.

Can you explain what my teacher didn't show or forgot to include?

Thank you in advance!


texts: (Energetics) Potential Energy and Kinetic Energy

texts:
This question came up when I was reviewing the energetics unit. In my notes I wrote "systems with a lower potential energy are more energetically stable, because they have a higher kinetic energy and higher kinetic energy means higher level of disorder." Is this correct? If so, does it mean potential energy stored in chemical bonds are converted to kinetic energy during a chemical reaction?
Is energetically "stable" the same thing as energetically "favourable"?


texts: can metamers contain N as differing functional group?

texts: Are $\ce{Ph - NH - CH3}$ and $\ce{Ph - CH2 - NH3}$ metamers?


texts:
I've been seeing a lot of GAMESS and Gaussian questions around here, and most of them seem very hard to answer. I extrapolated that they might be some sort of Chemistry programs, but what do they do exactly?

Instead of looking it up, I feel like most of you would be more knowledgeable in this.


texts: Why is water evaporation not more commonly used to cool buildings

texts:
Water has a very high heat of vaporization (2260 kJ per kg). Why not just gradually sprinkle water on your roof to keep the building cool in opposed to using air conditioners?

It wouldn't take much water to keep the building a few degrees cooler for a long time. Air conditioners use a lot of electricity which is bad for the environment. I read some places ban water vaporization cooling systems because of droughts and because tap water is government subsidized but that seems silly.

As a society it would be cheaper and more environmentally friendly to use water. The water will simply evaporate and return as rain which it will do anyway regardless. The energy air conditioning uses puts more greenhouse gases  in the environment which (allegedly) causes more global warming and puts more chemicals in rain water.


texts: How can compounds be called reduced if nothing is known about the reaction they formed in?

texts:
I'm reading a research article about a model trying to explain the elemental compositions of meteorites.[1]

What confuses me, are statements of the following type (here in chapter 2.1, second paragraph about enstatite chondrites, a type of meteor):

  [...] Enstatite condrites contain minerals that are remarkably reduced chemically, including abundant sulfides like oldhamite (CaS).

In my understanding reduction or oxidization only refers to a specific element in a specific reaction, but here they talk about a compound  with unknown reaction path to form it.

How can CaS be considered to be (remarkably) reduced, if it is not an element in a reaction?
How can CaS be considered to be (remarkably) reduced, if we don't know the reaction path that it formed in?

Steven J. Desch, Anusha Kalyaan, Conel M. O'D. Alexander. The Effect of Jupiter's Formation on the Distribution of Refractory Elements and Inclusions in Meteorites. arXiv:1710.03809 [astro-ph.EP]


texts: Effect of temperature on Hydrogen Bonding?

texts:
We had this question in a test and I am not sure of the answer

  Q. Temperature changes don't effect the extent of inter and intra molecular hydrogen bonding. State true or false.

I think that raising temperature would increase the kinetic energy of molecules and would thus lead to weakening of inter molecular hydrogen bonds. But am not sure what will happen to intra molecular hydrogen bonds...

For e.g. if ortho-nitrophenol is heated, will the intra molecular hydrogen bonds between hydrogen of the hydroxyl group and oxygen of the nitro group break?

Any ideas/suggestions?


texts: How can temperature be constant during a reaction?

texts:
So I was reading my textbook about the topic thermodynamics.

Here the second paragraph States that the above equation describes the combustion of liquid ethanol at constant temperature and pressure.

But how can the reaction occur at constant temperature. The enthalpy change stated is accompanying the reaction at standard state. So it should be heat released at constant pressure and from temperature 25°C. So temperature of reaction mixture should be decreased.


texts: Equilibrium :. Why does a system at equilibrium try to undo the effect of external stress applied on it?

texts:
" Le Chatelier principle states that a system at equilibrium when subjected to external stress tries to undo the effect of that stress"

In short, why does system at equilibrium follow Le Chatelier principle?


texts: IUPAC naming for compounds containing carboxylic acid and anhydride together?

texts: According to IUPAC, the carboxylic acid comes first in priority order for functional groups, while anhydride has no prefix. Then how do you name a compound which contains both a carboxylic acid and an anhydride in it?


texts:
I did an experiment of gas chromatography which contained the compounds: octane, butanone and propanol. We injected a mixture of the three compounds in the polar column and then a mixture of it in the non polar column. I have certain data which say that the most polar compound of the three is octane,then butanone and the least polar is propanol. As for the boiling points, the highest boiling point belongs to octane,then propanol and the lowest boiling point is for butanone.

I know that the lower the boiling point is, the higher the vapor pressure of the compound and the shorter retention time usually is because the compound will spent more time in the gas phase. I also know that If the polarity of the stationary phase and compound are similar, the retention time increases because the compound interacts stronger with the stationary phase. As a result, polar compounds have long retention times on polar stationary phases and shorter retention times on non-polar columns using the same temperature.

But after seeing the results, the order that these compounds appear are:
For the non-polar column:

1)air(I get it)

2)propanol

3)butanone

4)octane

I get about octane but between propanol and butanone how do we know which factor(boiling point or polarity) plays the most important role?

I get confused because if we take into consideration polarity, the retention time of butanone should be bigger but if we take into consideration the boiling point, the retention time for propanol should be bigger.


texts: Why it is not yet possible to produce ethanol selectively in the Fischer Tropsch reaction?

texts: The Fischer Tropsch reaction between $\ce{CO}$ and $\ce{H2}$ has the potential to give a wide range of products. However by judicious choice of catalytic metal it is possible to produce $\ce{CH4}$, $\ce{CH3OH}$, and other alkanes selectively. $\ce{Fe}$ and $\ce{Co}$ are most commonly used catalysts where $\ce{Fe}$ produces less $\ce{CH4}$, more oxygenated products and more alkenes and $\ce{Co}$ produces more $\ce{CH4}$, less oxygenated products and more alkanes. There are a number of other catalysts that can be used, for example $\ce{Rh}$ which can produce $\ce{C2}$ and higher oxygenates and hydrocarbons. This includes the production of $\ce{CH3OH}$. However, it is not selectively produced but is produced in a mixture of other products and in small amounts. My question is why can $\ce{CH3OH}$ not be produced selectively?


texts: Lennard-Jones potential and vibrational energy level diagram explanation

texts:
I don't understand how to interpret graphs like the following:

Forget the difference between the Harmonic and Morse (I think I get that), It's more what the horizontal lines mean and what the boundary line means. I know that vibrational energy is quantized and I can rationalize the shape of the Lennard-Jones potential but I don't understand how they're combined in this diagram. Please could you walk me through what's going on?


texts: What would be the unit for the calculation of the rate of reaction?

texts:
In a reaction between magnesium and hydrochloric acid, I measured the change in mass of the magnesium strip (Initial weight: 0.03g). I calculated the the time for the reaction to reach completion. A sample set of data we collected for during our investigation was:

With 8 molar of HCl the reaction took an average of 15.49 seconds to completely evolve into hydrogen gas.

To calculate the rate of reaction, I used the formula:

I suppose, change in mass would be 0.03 g as we went to the completion of the reaction, and change in time would be noted as the average time 15.49. My question is, what is the unit supposed to be in this formula?


texts: Why does the isoelectric range decrease as an Alanine chain grows longer?

texts:
The pK1 and 2 values for alanine are 2.3 and 9.7. In the dipeptide Ala-Ala, they are 3.1 and 8.3 and in tri-peptide Ala-Ala-Ala, they are 3.3 and 8.0. Why does this trend in pKa values exist? Why does the isoelectric range decrease?
The reason I can think of is the extra Alanine dumps electrons towards the C terminal and so makes the O-H bond less polar and thus less acidic while it also pulls more electrons from the N terminus to make that more polar and thus more acidic.
Thanks!


texts: Entropy of Irreversible Isothermal Compression

texts:
If I want to find the entropy change of universe in isothermal irreversible compression, I use 2 approaches:

I use q/T. Which gives me positive entropy change for surroundings positive and negative entropy change for system. So, using clausius inequality to say that net entropy change is positive.
I find entropy change for irreversible isothermal expansion which comes out to be positive (again using clausius inequality) and say that the compression process is just the reverse of the expansion. So, entropy change being a state function must be negative(as it is just the reverse process).

What am I doing wrong here?


texts:
Triplet carbene has a carbon with 6 electrons, of which 2 are unpaired. I would expect the carbon to be $\ce{sp}$ or $\ce{sp^3}$ hybridised and the two singly occupied orbitals to be degenerate. However, Clayden et al. (p. 1011) say that, since the triplet carbenes are almost always bent, they are best considered to be $\ce{sp^2}$ hybridised, with the unpaired electrons occupying a $\ce{p}$ and an $\ce{sp^2}$ hybrids .

The very basic explanation I see why the two SOMOs are not degenerate is simply that $5E_{\ce{sp^2}} + E_{\ce{p}} + 2E_{\ce{sp^2},\ \text{pairing}}$ is less than $4E_{\ce{sp}} + 2E_{\ce{p}} + 2E_{\ce{sp},\ \text{pairing}}$ or $6E_{\ce{sp^3}} + 2E_{\ce{sp^3},\ \text{pairing}}$. However, I wonder if there's a better explanation.


texts: Convergence of spectra calculated from molecular dynamics trajectories

texts:
How can we check whether or not the power spectra (vibrational density of states) calculated by taking the Fourier transform of the velocity auto-correlation function (VACF) from a molecular dynamics trajectory is converged? How to estimate the statistical error in it?

What is the meaning of the word "convergence" in this context?


texts: Reducing olefinic bond in conjugation with C=O bond using LiAlH4

texts:
I'm studying the synthesis of alcohols. One of the methods given is "Reduction with metallic hydrides like $\text{LiAlH}_4$". Under this title the following reaction has been listed [1, p.635]:

$$\text{CH}_{3}-\text{CH=CH}-\text{CHO}+\text{LiAlH}_{4}\rightarrow \text{CH}_{3}-\text{CH=CH}-\text{CH}_{2}\text{OH}$$

Also on [1, p.298], the following proposition is made which seems to contradict with obtained results of the above reaction.

In certain scenarios, these reagents may reduce double bonds in conjugation with $\text{C=O}$ as well as reduce the $\text{C=O}$ bond.

It would be great if someone could clarify exactly under what cases and conditions would the double bond reduce as well. Thanks.
Reference:

Shahi, R. Essential Organic Chemistry for JEE Main & Advanced; Arihant  Prakashan: New Delhi. ISBN: 978-93-13192-10-7.


texts: Attached is the structure of one aminoglycosides, kanamycin. I understand that the ring binds to 4 position of 2-DOS is numbered with prime (') and sugar that links to 4 or 5 position of 2-DOS is numbered with double prime ('') but my question is how to do the numbering for 2-DOS (center ring). Can anyone teach me how? I have searched through Google and still have no idea on it.


texts: Why is glycine hydrochloride more acidic than chloroacetic acid?

texts: I cannot figure out why glycine hydrochloride is more acidic than chloroacetic acid. Could I have figured this out from a $\mathrm pK_\mathrm a$ table and maybe am just not seeing it? On the table I have in my book (Organic Chemistry, Seyhan Ege, 3rd edition), neither acid nor its conjugate base are there.


texts: This question is generated by my attempt to answer this one.  I thought I could demonstrate that electronic conduction in water is possible because of the impact of an electric field on the band structure, but I am being hit with comments questioning the existence of band structure in liquids.  I thoughtot was self-evident, but I was asked for references showing water has a band structure and what I am coming up with does not appear to be working (the comments are getting more upvotes than my answer).  So I need help.  Can anybody come up with more clear-cut references demonstrating that water, or liquids generally, has such a band structure?


texts: Solubility of potassium silicate in water

texts:
It is somewhat surprising to me that there is almost no data about solubility of potassium silicate in water under normal conditions. The only thing I was able to find is the following:

<0.336 g/L @ 25ΕC, increasing  to 300 g/L @ 80ΕC. Once  dissolved,
material will not  precipitate out
Technical Document for Potassium silicate also referred to as a
BRAD

However, it is not clear what does the last statement mean. Does it mean that the silicate will not precipitate even if the solution cools down to 25°C?
The solubility of sodium silicate can easily be found on Wikipedia. It is mystery in case of potassium silicate.
So let us assume we want to dissovle potassium silicate in water with initial pH of 7. What amount of potassium silicate can be dissolved?
Edit:
Regarding the comment of @M. Farooq about being more specific. The second sentence on Wikipedia says:

The most common potassium silicate has the formula K2SiO3, samples of
which contain varying amounts of water.

We can consider the anhydrous form of K2SiO3 and couple of most common hydrates. Also, if the exact amount is not known then at least knowing the order of magnitude is fine as there is huge difference between 0.336g/L and 300g/L.


texts:
I am an engineer and not the best at chemistry, I am horrible at it, but I was wondering if it is safe to mix sodium hydroxide and calcium oxide to make a desiccant that also captures carbon monoxide?

I am asking because I am trying to make a high quality zero air generator and need to lower the humidity and carbon monoxide and this seemed like a way to do it.


texts: Predicting the generation of singlet oxygen

texts: On Wikipedia, I saw the reaction $\ce{H2O2 + NaOCl -> O2 + NaCl + H2O}$, where the $\ce{O2}$ is in the $^1\Delta_g$ (singlet) state. Can anyone offer an explanation for why it isn't in the usual triplet state, maybe using the theory of molecular orbitals?


texts: entropy of vaporization vs entropy of fusion

texts:
Is the entropy of vaporization greater than entropy of fusion, for elements? And in which case they can be same, if it so happens?
I have asked this here because I couldn't find any satisfactory answers anywhere on the Internet and most of them were very limited in their description.


texts:
Two highly respected books: Atkins, Chemical Principles 5th ed. and Clayden Organic Chemistry 2nd ed. don't agree on the orbital arrangement of the $2p$ orbitals of $\ce{N2}$. Clayden on page 94 states that it is $\sigma_{(2p)}, \pi_{(2p)}, \pi^*_{(2p)}, \sigma^*_{(2p)}$ and Atkins on page 118 states that it is $\pi_{(2p)}, \sigma_{(2p)}, \pi^*_{(2p)}, \sigma^*_{(2p)}$.

I am a retired engineer with a consuming interest in how the brain works and am trying to give myself a good grounding in organic chemistry. This may be a trivial issue, but to a novice it hardly seems so. This kind of division within the chemistry community is very concerning.

Any ideas as to what's going on here?


texts: What substances form crystal structures?

texts: Just getting interested in this stuff. People are saying I should crystallize salt, for example. What substances besides salts form a crystal structure?


texts: What is the "blue spirit" (or "red spirit") in mercury-free thermometers?

texts:
I surmise it's some kind of alcohol, but is there a standard chemical used for these?

One of them just exploded in my students' lab! It was the kind with blue fluid in it.


texts: Trend of thermal stability of Group 2 chlorides down the group

texts:
Thermal stability of group 2 chlorides follows the order: $\ce{BeCl2>MgCl2>CaCl2}$.

Talking about carbonates of group 2 metals, the thermal stability increases as we move down the group due to decreasing polarizing power of the cations. Why is the similar trend not observed in halides?
I found an answer here which had an elaborate explanation of the fazan's rule and effect of polarizability of anions. However, that comparison was made for a single cation bonded with different halogens bonded one on one as one moves down the group. Surely, the stability in that case increases down the group as the charge density on anion decreases.
The comparison made here is different. I want to know the trend when the cation is being changed and anion is same. According to Fazan's rule, the trend should be same as that for carbonates: their stability increases on moving down because charge density of cation decreases. But this is not observed in the case of chlorides. Why is that so?


texts:
This is a question from IIT-JEE 1993:

  For the reaction

  $$\ce{[Ag(CN)2]^- -> Ag^+ + 2CN^-}$$

  the equilibrium constant at $\pu{298 K}$ is $\pu{4e-10}$. The silver ion concentration in a solution which was originally $\pu{0.10 M}$ in $\ce{KCN}$ and $\pu{0.03 M}$ in silver nitrate is?

This is what I've done:

$$
\begin{align}
[\ce{K^+}] &= 0.1 \\
[\ce{CN-}] &= 0.1 - 2x \\
[\ce{Ag+}] &= 0.03 - x \\
[\ce{NO3-}] &= 0.03
\end{align}
$$

$$\frac{(0.03-x)(0.1-2x)^2}{x} = 4\cdot 10^{-10}$$

But this gives $x = 0.03$, hence, $[\ce{Ag+}] \approx 0$.

The answer key says $[\ce{Ag+}] \approx 7.5\cdot 10^{-18}$. Where am I going wrong?


texts:
The addition of $\ce{HBr}$ to $\ce{CH2=CHBr}$ produces $\ce{CH3-CHBr2}$. Why is this so?

According to me, halogens have a stronger $-I$ effect than a $+M$ effect (for example a halogen substituent on benzene, deactivates the ring), and hence the $\ce{CH3-CHBr+}$ carbocation should be more unstable as compared to $\ce{CH2+-CH2Br}$. Where am I going wrong?

Edit : I have seen this question but it doesn't answer my query.


texts:
How will the dielectric constant of water change when ethyl acetate is added?

The $\mathrm{p}K_a$ value of weak acids in aprotic solvents will be lower than in protic solvents because the dielectric constant does not favor ionization. If I increase the $\mathrm{\text{%}}$ concentration of ethyl acetate in water and gradually increase it to nearly $\mathrm{100\text{%}}$ ethyl acetate, how will the $\mathrm{p}K_a$ values of a weak acid in this solvent change?

I want to determine the endpoint with an indicator dye and a suitable titrant of a strong base such as sodium hydroxide. My general aim is to calculate pKa in an easier way.


texts: Combining solutions with multiple concentrations - Mixing NPK fertilizer ratios

texts:
I'm trying to mix my own fertilizer to grow some peppers.
Fertilizers are labeled with NPK ratios, so mixing two volumes and finding the result is easy: Just multiply the concentration of each component by the ratio of the solution over the total volume. For example, $\pu{1L}$ of a $3:4:6$ solution plus $\pu{1L}$ of a $5:2:6$ solution yields $\pu{2L}$ of an $4:3:6$ solution.
Something like:
$$ NPK_\mathrm{final} = \left(NPK_{s1} \times \frac{V_{s1}} {V_{s1} + V_{s2}} \right)+ \left(NPK_{s2} \times \frac{V_{s2}} {V_{s1} + V_{s2}}\right) $$
However, if I have a desired ratio in mind, how can I solve for how much of each of 2 solutions to add? I can plug in different values till I get close, but I'm curious if there's a general formula. I figured there's probably a way to get there with linear algebra (but I never took linear algebra!).


texts: Is 2-oxobicyclo[2.2.1]heptan-1-ide resonance stabilized?

texts:
Is the following compound resonance stabilized?

I think its not resonance stabilized because the p-orbital of carbanion and pure p-orbital of carbonyl carbon are not in same plane. So they can't overlap. (Pure means that the p-orbital is not a part of the $\ce{sp^2}$ orbital. One p-orbital of carbonyl carbon is pure).
Am I correct?


texts: Sources for files for testing a thermal ellipsoid (ORTEP) program

texts: I am trying to reimplement the functionality of the classical program ORTEP for producing thermal ellipsoid plots of a crystal/molecule in a modern computer language. Unfortunately, I am having trouble finding usable sample files with the required thermal displacement parameters so that I can test my program. Is there any good source of thermal data for various molecules? Alternatively, if I have e.g. a MOL file of a molecule (or some other easily produced chemical file format), is there any way to produce reasonable(?) simulations of the required thermal parameters? Ideally I would want a sampling of molecules of various sizes.


texts: Does this equation - involving calcium carbonate and a lead (II) cation - balance?

texts:
$$\ce{CaCO3 + 2H2O + Pb^{2+} -> Pb(CO3) + Ca(OH)2 + H2}$$

Does this equation balance?
On the right you have lead with 2+ charge, whereas on the right its completely neutral. So my question is do you need to balance the charges in order to make the equation correct?

If that equation is wrong, what is the right equation?

I need to show that hydrogen gas is formed (or some other gas but I don't know what else it can be), that the solution will become more basic (proven with $\ce{Ca(OH)2}$), and that the lead has to replace the calcium.


texts: What is C2H33O28? (Empirical Formula to Molecular Formula)

texts:
I'm doing the final question on my homework, and got an issue with this question:

  "A 76.8g sample of a liquid used as a coolant in automobiles is found to contain 3.7 g of carbon, 5.1 g of hydrogen and the rest is oxygen.  The formula weight of the compound is 60.0 g/mol.  What is its molecular formula?"

After scouring the web, youtube, and my textbook, I can't find any reason my answer doesn't make sense. My math is as follows:

Convert each of the given masses to moles, resulting in 0.30805mol of Carbon, 5.1mol of Hydrogen, & 4.25mol of Oxygen. Dividing by the small to convert to a ratio, the result is 1mol of Carbon, 16.5mol Hydrogen, and 14mol Oxygen. Finally, to get a whole number for the ratio of moles, multiply by 2, resulting in C2H33O28.

The issue with this, is that both the mass is way too large for what we are learning, and when converting this formula to a molecular formula by dividing the given mass of the molecular formula by the mass of the empirical formula results in a 0.12 multiplier. Multiplying each of the subscripts by 0.12 gives an odd result of C0.237H4O3.

I have no idea what I did wrong here besides maybe rounding, but after trying this four separate times with different rounding. If anyone can provide any insight whatsoever, I would be ecstatic, thank you so much!


texts:
So if you had the equilibrium $\ce{A <--> B}$ and you increase the concentration of A. I understand that equilibrium will shift to the right. To say this (I believe) is to say that the $\ce{A -> B}$ reaction is favoured. But when at equilibrium again will the position of equilibrium be back in its original position, as I believe the position of equilibrium to be defined as the amount of A relative to B.

If this is true, does it follow that a shift in equilibrium does not necessarily mean a permanent change in the position?

If it was a $\ce{A + B <--> C}$ equilibrium and you increase the concentration of A the equilibrium will shift to the right. How would you determine if the position had changed at equilibrium?
Thanks very much.


texts: Does clove oil/eugenol interact with nylon type plastics?

texts:
So I am aware that the eugenol in clove oil readily melts #6 type plastic (polystyrene). Polypropylene has a higher resistance, while HDPE type plastics seem to have the highest resistance.

My main question is whether the clove oil will interact with nylon. Say, the bristles of a toothbrush.


texts:
Which of the following has higher enol content?

The enol form of (A) and (B) is:

Both the enols have hydrogen bonding.

If the oxygen were to accept the pi electrns from carbon forming a carbocation like this (a resonance structure):

the compound becomes stabilized due to resonance as well. So isn't (B) the answer?


texts: What does it mean by 'the residue was taken up in solvent' in synthesis protocol?

texts:
The below is a synthetic protocol I need to perform:

N-trifluoro acetoxy succinimide Synthesis
Trifluoroacetic acid anhydride was added to N-hydroxysuccinimide at 0 °C. The reaction was allowed to warm up to r.t. over 24 h. Then toluene (50 mL) was added and the volatile was removed in vacuo. The residue was taken up in DCM (15 mL) and the remaining solvent was removed in vacuo.

I don't quite get the last sentence. What does it exactly mean by 'taking up a residue in solvent'? Does it mean I just need to add 15 mL DCM to the reacting mixture?
Also, the second bit also gets me confused — if I put my mixture under vacuum, wouldn't all the solvents get sucked up? what would be the point of adding DCM if I am placing my mixture under vacuum immediately after adding DCM?


texts: Symmetries and degeneracies of the s,p, and d orbitals

texts:
Consider the molecular AB_8 (complex with central atom A and 8 B ligands (coordination number 8), for which I determined the point group D_4d) and determine the symmetries and degeneracies of the s, p, and d orbitals of A.

So I believe the general procedure here is to determine a reducible representation for each s, p, and d orbital of the central atom, but how do I do that? Is the s orbital just A1? Is p just B2 and E1? How do I computer these representations?


texts: Why did my deep eutectic solvent solidify?

texts:
I'm finally getting around to beginning to test this deep eutectic electrolyte.  I mixed choline chloride with urea in a 1:2 mole ratio in a glass container.  It formed a sludge.  I sealed the container and then came back two days later to begin electrolysis and the mixture had formed a hard solid!

The whole time the mixture was at room temperature, and except for the mixing stage it was sealed.

So what am I missing?  Is this a sign my reagents are bad?  Or do these eutectics have a limited mixed life?

Update: Following Beerhunter's suggestion I ran the reagents in a blender until they formed a very liquid (low viscosity), homogenous mixture.  But one day later the DES is crystallizing again at room temperature:


texts: What governs the merging of globs of inmiscible liquid?

texts:
If I add a small amount of chloroform to a bunch of water, it falls to the bottom as a glob.

If I shake the container vigorously (being carefully not to spill any of the dangerous substance!), the globs of chloroform break apart into many tiny globules. These globules immediately sink to the bottom and collect together by the action of gravity the moment I stop agitating my mixture.

If I watch this pile of globules for some time, I observe that they tend to merge after several seconds, perhaps even a minute or more for some. I suspect that if I reached in with a needle and prodded the globules, they would merge faster. Also, I suspect that if I were to tabulate how long each individual globule survives before merging, I would obtain a half-life curve.

What governs the merging of these globules (I'm guessing surface tension)? Why don't they instantly merge? Why do a few little globules sometimes persist for many minutes, stuck to the side of a much larger globule?


texts: I understand the bulk of MO theory , the formation of the bonding and anti bonding MOs etc. However, the topic about s-p mixing is quite puzzling to me. As a general rule of the thumb, I was taught that diatomic molecules up to N2 would exhibit s-p mixing, while the molecules past that threshold, O2 and above, would have insufficient amount of s-p mixing for the bonding MOs to be swapped. So my question is for heteronuclear molecules , eq CO , NO etc, how would I know whether s-p mixing occurs for that molecule? Ive found some sources online stating that molecules with <= 14 electrons would show s-p mixing, but this doesnt work for the NO molecule as it has 15 electrons and apparently exhibit s-p mixing


texts: Number of aromatic rings in triphenylene

texts:
My question is how to find the number of aromatic rings in triphenylene:

My professor said that there are 3 aromatic rings, after which he added that the carbons of the middle rings are only supporting ortho-fusion of rings and hence the center ring is not to be considered.

But I am not satisfied. Why not consider the center ring since the electron after all delocalizes in the entire system giving me 4 as the answer? Someone, please clear my confusion out here.


texts: At what point does Avogadro's law not apply?

texts: A mole of hydrogen gas takes up 22.4 L, but so does a larger molecule like $\ce{CO2}$. Methane ($\ce{CH4}$) is an even larger sized molecule, but a mole of it will still take up 22.4 L. I would assume that an even bigger molecule like decane ($\ce{C10H22}$) would still act the same as the others. A mole of sand however does not take up 22.4 L. This begs the question: is there a certain size particle at which Avogadro's law is not valid anymore? Perhaps at a molecular size larger than buckyballs ($\ce{C60}$)? (This also happens to be the point that wave-particle duality does not apply.)


texts: I can't find the $K_{sp}$ value for Manganese Phosphate ($\ce{Mn_3(PO_4)_2}$) anywhere online. Has it been measured? What is it?


texts: Why don’t compounds with high boiling points not necessarily have high attraction constants (a) in the Van der Waals equation?

texts:
You can find a list of constants $a$ and $b$ for the van der Waals equation in a Wikipedia website. Accordingly, hexane has a higher attraction constant ($a$) than that for water (24.71 vs 5.536), but water has a higher boiling point than hexane. So, intuitively water would have stronger attraction between gas molecules. In general, the alkanes demonstrate high $a$ values. Why is this?

My guess is that since the alkanes are symmetrical, it does not matter how the molecules near the edge of a container are oriented, they will be attracted toward the middle of the container no matter what. On the other hand, water’s asymmetry means water molecules have to be oriented a certain way in relation to the other molecules in order to be attracted to them. While in liquid form, water is more often oriented in this attractive way, but in gas form water’s orientation is more random and therefore there is less attraction while water is in gas form.


texts: Is it possible to synthesize a benzene ring with every carbon on the ring substituted?

texts:
We recently began covering aromatic electrophillic substitution in my first year organic chemistry course, and we've been discussing the nature of certain functional groups being activating $(\ce{-OH},$ $\ce{-OCH3},$ $\ce{-NH2})$ or deactivating $(\ce{-SO3H},$ $\ce{-NO2}).$

We haven't learned how to do everything obviously, so this probably why I can't answer this question myself, but we've learned how to add nitro groups, sulfonic acid groups, alkyl and acyl groups, and halogens.

In any case, is there way out there in the world of organic chemistry to create a benzene ring with every single carbon substituted?


texts:
What is the mechanism for the electrolysis of water? I understand that hydrogen and oxygen gas are made, but how exactly does this happen when electrons are passed through water? A diagram would be very useful.

Would this have anything to do with electronegativities?


texts: Distinction between whole molecules and functional groups in IR spectra

texts:
Are infrared spectra specific to compounds or to functional groups?

For example, which of the molecules below best fits the IR spectrum shown?

I'd have to say #2, which is a ketone based off of looking at a similar graph of a linear chain ketone. Is there a better way to approach IR graphs than learning them for functional groups?


texts:
I asked a similar question earlier that lead me to ask this question.
NH3 and O2 react in the following way $$\ce{4NH3 + 3O2 -> 2N2 + 6H2O}$$  From my understanding Ammonia will explode(react quickly/release a lot of heat quickly is how I understand the term explode) when there is 15%-25% ammonia vapor in Air.

If I injected ammonia vapor into the air (above autoignition temperature of 651°C so that it's fuel to air ratio was more like 30% ammonia to air.  Would it follow this reaction slowly until it reached the 25% mark then explode/react quickly until it reached the 15% ammonia balance air, and then react slowly from 15% ammonia to lower?

Here is the link to my similar question. Meaning of Flammability Limits and reaction in Air of Ammonia


texts: Why does acetate aldol with Evans auxiliary give almost no diasteroselectivity?

texts:
The following acetate aldol reaction gives no diasteroselectivity:

Because I don't know what the basis of above statement is (I heard it in a lecture and read it on some internet web pages), I expect the two products are formed as a racemic mixture.

For the related propionate aldol we can draw two (considering R of aldehyde to always be equatorial) possible transition states:

The question is why we don't get good selectivity if we compare the acetate aldol with the same transition states for the propionate aldol?

As a side-note: in practice chlorine is used instead of Me to obtain good selectivity and the chlorine will be eliminated finally by use of Zn/AcOH.


texts: Do enolates get protonated at the carbon or oxygen atom?

texts: An enolate has two resonance structures. When it gets protonated, where is the $\ce{H+}$ more likely to go? On the oxygen to produce an enol, which tautomerizes to the keto, or on directly onto the carbon (no enol intermediate). I know that both lead to the same product, but when drawing the mechanism this would be good to know.


texts: Why are complex basis functions not used in electronic structure calculations?

texts: I've noticed while reading about Hartree-Fock in Modern Quantum Chemistry (Szabo and Ostlund) that most basis sets use only real basis functions. What I'm wondering is why aren't complex basis functions used? I might be mistaken, but from my experience it seems as though integration on the complex plane would have a lot of convenient properties that would make computations easier. Put another way, are complex basis functions not used because of some difficultly in implementation or is it because of difficulty in interpretation of properties like the molecular orbitals?


texts: Can one dichlorotriazine molecule form two bonds with cellulose?

texts:
In all the reactions I saw online, dichlorotriazine is shown to form only one bond with cellulose (example 1, example 2; paper).

But cellulose has many potential sites for bonding. Can dichlorotriazine actually give up both Cl atoms for forming two bonds with cellulose?


texts: Why do tetrahedral organic molecules show stereo-isomerism, but not tetrahedral transition metal complexes?

texts: Both types of molecules show different arrangements of the molecule in space, so they should qualify for optical isomerism right?


texts: Nomenclature for an alkane substituted with a branched alkyl group

texts:
Consider, for example:

From what I've learned in chemistry class, this molecule would be unofficially named 3-isopropylpentane.

What would the official IUPAC name for this molecule be? And what's the general way to name these types of molecules?

EDIT: For this specific molecule, the naming can be simplified by looking at the main carbon chain differently.
For a more general case, consider heptane instead of pentane, in this case there's one chain that you're stuck with.


texts:
Recently, I have started to learn about nuclear magnetic resonance (NMR) in school and something which I cannot seem to reconcile is the fact that all aromatic protons on any substituted benzene ring would give the same chemical shift. This is very, very strange... Clearly, the aromatic protons are in different chemical environments due to the fact that they are different distances away from the substituents from the benzene ring. I understand that the strong delocalisation in the aromatic ring may tend to "even out" the electron distribution across all the aromatic $\ce {C-H}$ bonds. However, I would not think that this effect would result in all the aromatic protons having the same chemical shift. Could anyone propose a explanation to this peculiarity?

The following image was taken from p. 279 of Clayden, Warren & Greeves (2012):

It also seems to suggest the equivalence of aromatic protons despite them being of different physical distance from the substituent. Here's another one from p. 278:

If strong delocalisation and aromaticity really is the effect responsible for this apparent chemical equivalence of the aromatic protons, then would we also observe such equivalent signals in other aromatic heterocycles or even in polyaromatic hydrocarbons?

Reference

Clayden, J., Greeves, N., & Warren, S. (2012). Organic Chemistry (2nd ed.). New York : Oxford University Press Inc.


texts: Constrain bond angle In Gaussian molecular structure optimization

texts:
I am computing the optimized molecular structure of an organic molecule in the Gaussian 09 computational chemistry package.
As I have it now, I do not think that the optimized structure that I am getting from Gaussian is correct, in part due to the symmetry of some of the bonds.  To try and correct this, I want to fix two of the bond angles in the molecule in order to help/force it to produce a more believable structure.  Even though I want to fix these bond angles, I want to leave everything else variable and open to optimization, including those bond lengths.

How can I specify this in the input file?

Fixing the bond angle to a set value seems like an extreme solution to this problem.  Perhaps I can just constrain the angle within a certain range, is this possible?

After a lot of work and playing with settings, I have figured out how to fix bond angles, but now my difficulty is fixing them to 180 degrees (my desired value), for linear bonds. It seems that this is very hard to do.

Fixing the bond angle to 179 degrees (or 179.9 degrees), results in an error saying "Error in internal coordinate system." A lot of people online say this is because of linear/nearly-linear bonds in the molecule being optimized. Some people also say this might be avoided if I try to optimize in Cartesian coordinates, instead of internal coordinates, using the cartesian parameter after opt. However, I do not think I can use ModRedundant and cartesian parameters at the same time.

How can I fix a bond angle to be linear, but still optimize the rest of the structure in Cartesian coordinates? Is it even possible to fix angles to 180 degrees?