texts: Can someone confirm and/or correct my logic regarding this mechanism?

texts:
In the picture, Ethyl 2-oxocyclopentanecarboxylate (I) reacts with ethyl 2-(4-chloromethylphenyl)propionate (II) in the presence of KOH in hot DMF to afford ethyl 2-[4-(1-ethoxycarbonyl-2-oxocyclopentan-1-ylmethyl)phenyl]propionate (III), which is then hydrolyzed and decarboxylated by treatment with 47% HBr in refluxing dioxane. I'd just like to walk my way through this and see if my theories regarding the mechanism are correct.

(I) has an $\alpha$ carbon that is deprotonated (the one beside the ester group). This creates a carbanion that is stabilized both by resonance as an enolate and inductively by electron withdrawing from the ester group. This stability leads to marginal nucleophilicity; chlorine is a marginal leaving group here (although the carbocation is resonance stabilized by the aromatic ring), and no inversion is observed, which leads me to believe an $S_N1$ rxn occurs between (I) and (II) to yield (III). DMF is used as a solvent so as not to inhibit nucleophilicity by using a polar protic solvent.
It's not specified, but I suspect (III) can be  captured via distillation to due boiling point/density differences between it and (I) and (II).
(III) is reacted with HBr in dioxane (I'm not sure why 47% is used; I'm assuming at STP, it's the maximum concentration of HBr(g) in water) is used, as dioxane is relatively stable at extremely high and extremely low pH values. The hydronium acts as an impetus for hydrolysis on the ester groups on both rings. I think the Bromide anion acts as just a counterion here (but I'm not sure why).
The step where (III) is reacted with sodium hydroxide is where I get lost. I'm not sure how the sodium hydroxide spurs decarboxylation and selective decarboxylation, at that (why not the ester on the aromatic ring as well?).


texts: Is the phenyl group in benzophenone electron donating/withdrawing?

texts:
The ketone carbonyl group is less reactive to nucleophilic attack than aldehyde since the alkyl group in ketone is electron-donating towards the carbon.

Is this the same case for benzophenone, where there is a phenyl group?

Phenyl groups are usually electron-withdrawing, but in the case of benzophenone, would it be electron-donating through resonance?


texts: Both wikipedia and Toxnet list the half-life of Nitrofurantoin as 20-60 minutes in the blood plasma. Can anyone explain how this is so short, especially for an antibiotic, and how it still has time to be effective.


texts: Why doesn't diffusion take place between immiscible liquids?

texts:
If we take a test-tube of bromine and invert an upside-down test tube of air on top of it, it'll diffuse with the air, until the bromine is thoroughly 'mixed' with the air in both test tubes. But why doesn't the same thing happen with two immiscible liquids? Say oil and water.
When you put a layer of oil on top of water, the two don't mix, but they should. By diffusion.


texts: Are these alternate names for long chain hydrocarbons with complex substituents accepted?

texts:
Let's consider the following compound:

$\ce{CH3-CH2-CH(CH3)-CH2-CH2-CH(CH(CH3)-CH(CH3)-CH2-CH(CH3)3)}$

Its IUPAC name is 2,2,7-trimethyl-4-(1-methyl-propyl)-nonane

$\ce{CH3-CH2-CH(C2H5)-C(CH3)(C(CH3)3)-CH2-CH2-CH(CH3)-CH2-CH2-CH3}$

Its IUPAC name is 3-ethyl-4,7-dimethyl-4-(1,1-dimethyl-ethyl)-decane

I wish to ask if the following names are acceptable (respectively):

4-(1-methyl-propyl)-2,2,7-trimethyl-nonane
4,7-dimethyl-4-(1,1-dimethyl-ethyl)-3-ethyl-decane

Do complex substances follow a rule regarding where they should be placed in the IUPAC name or can they be placed anywhere?
Do prefixes like bis, tris, tetrakis, etc. need to be considered while naming?


texts: Why does LDA solution gradually turn dark brown?

texts:
LDA (lithium diisopropylamide) solution in THF/hexane gradually turns red-brown liquid. Especially commercially available one is extremely dark red-brown. What makes it brown?

I've searched online journals, but I couldn't find possible theories.
When I synthesize LDA, at first LDA solution in THF/hexane is light yellow. Of course, I keep it under nitrogen/0-10 degrees celsius but it gradually turns brown.

Does LDA react THF or the THF stabilizer BHT? Do they make LDA solution brown? Please give me any plausible explanations.


texts:
How would tautomerism take place in 3,5‐dimethyl‐4H‐pyrazole?

I am aware of nitro–aci nitro and keto–enol, but I haven't seen such a compound before. I recognize that a hydrazone formation was done but nothing more. From what I was able to reason, an alkadiene is formed but that is unstable, so tautomerism shouldn't be possible. How does this compound show tautomerism?


texts:
If we have  $\ce{A + T -> P}$
where $\ce{A}$ is the analyte, $\ce{T}$ is the titrant, and $\ce{P}$ is the product,
photometric titration happens only in one condition, that one of the following substances will absorb the electromagnetic radiation.

When stable complexes formed such as $\ce{Bi}$-EDTA, they will not absorb the radiation (or in small amounts), but when unstable complexes formed such as $\ce{Cu}$-EDTA, they will absorb highly. The same goes also for the acids. Strong acids will absorb much less the electromagnetic radiation than the weak acids.
The reason for this is that strong acids are completely dissociated.

Why does that indicate the photometric titration ?


texts: What is the difference between doxycycline HCl and doxycycline hyclate?

texts:
I would like to ask what are the main differences between doxycycline HCl and hyclate?

I work in the pharmaceutical/veterinary raw materials industry and some clients are saying that they prefer hyclate because it is more concentrated than HCl, but I have yet to come on any articles confirming this. Is this true?


texts: How can I identify and neutralize the chemical leaching out of new nitrile gloves?

texts:
I have a few cases of brand-new, nitrile gloves of a type and vendor that used to be good.  But apparently, the vendor has moved manufacturing to a different country and outsourced customer service to Hell. I can't return the gloves.

The gloves all have a chemical smell, resembling a burnt transistor with a hint of burnt rubber. If worn for a while, they irritate the skin.

Since this model of glove used to be outstanding, and the cases were not cheap, I'm hoping there's some way to salvage the gloves.  I've tried repeated washings in mild detergent, or just airing them out for 4 weeks. No change.

What chemical(s) is/are this likely to be?  How can I tell?
Is there a way to neutralize this/these compound(s) without otherwise destroying the gloves?


texts: Bond Dissociation Temperatures for Hydrocarbons

texts:
I'd like to know the temperatures that various hydrocarbons such as methane, butane, and propane, etc. will dissociate into hydrogen and carbon.  Is there a reference where I can look up these temperatures?

Does pressure or partial vacuum effect these temperatures?


texts: Will a Grignard reagent react with an epoxide or episulfide first?

texts: In this question, I am confused whether the Grignard reagent will attack the epoxide or the episulfide (thiirane) first. The solution says ring opening of the episulfide will occur due to greater strain.


texts:
I can't figure out this stoichiometry question!

10.0 mL of 1.15M copper(II) nitrate reacted with 20.0 mL of .85M ammonium hydroxide.  The solution is filtered. Determine the molarity of the filtrate.

I figured out that the net ionic equation is Cu + 2OH -> Cu(OH)2, so the 2NH4NO3 dissolves, and the Cu(OH)2 probably doesn't pass through the filter, but I don't know where to go from there. Thanks in advance!


texts: How to retrieve excited state molecular orbital coefficients in Gaussian?

texts:
Currently I am doing TD-DFT calculations in Gaussian and want to calculate transition dipole moment for $S_1$ transition manually. However, I do not manage to retrieve molecular orbital coefficients for the excited states in Gaussian, just the ground state with population keyword and a few hours of search through the Internet hasn't helped to move forward. Is it possible to do that and if it is possible, how to achieve that? And just to make sure that I understand the output corrently: the molecular orbital coefficients are given in their casual forms (like $c_1, c_2, etc.$), not a square modulus of them?
Thanks in advance for your help!


texts: What happens to an acid when it completely dries out?  Does it stop being acidic?  And if there is a base there also, does it give back it's H's?


texts: What is the difference between an angular and linear skeletal formula?

texts:
When drawing a skeletal formula, what is the difference between an angular version and a linear version?

I was asked to draw the Z isomer of Resveratrol:

For which I drew:

However the markscheme states that:

  skeletal structure must be correct and angular not linear

I haven't come across the difference between the two before and can't find anything on google to suggest one.  Their drawing of the correct answer is equivalent to mine, however I am concerned that I may have drawn the linear version as my benzene rings are in a line and theirs are not. What am I missing here?

Their version:


texts:
I'm currently doing some DNA extractions and I realized that in some protocols, they are saying that ethanol is hygroscopic.

In this source, they are saying:

  85% ethanol made with nuclease free water (Note: 85% ethanol is hygroscopic. Fresh 85% ethanol should be prepared for optimal results)

I know that this is even more pronounced for 100% ethanol. But I'm wondering if

70% is still "very" hygroscopic so that the concentration might change over time. Say differently, how stable is the ethanol concentration over time?
How long would a 70% ethanol solution last? That may depend on the volume made, but I want to know if there could be a "best before" date so that it's no longer considered as a 70% ethanol solution. A year? A decade? 2 minutes?


texts: How to determine the concentration of a base through indirect titration?

texts:
$5.267~\mathrm{g}$ of $\ce{Na2CO3}$ was dissolved in $250.00\ \mathrm{mL}$ of water. $10.00\ \mathrm{mL}$ of this solution was titrated with $\ce{HCl}$. The end-point occurred at $21.30\ \mathrm{mL}$. This acid was titrated with $25.00\ \mathrm{mL}$ of $\ce{Ba(OH)2}$. The end-point occurred at $27.10\ \mathrm{mL}$. Calculate the concentration of the $\ce{Ba(OH)2}$.
  [Answer: $0.1013~\mathrm{M}$]

Using the mass they gave me ($5.267~\mathrm{g}$) I worked out the moles of $\ce{Na2CO3}$ which was $0.0497\ \mathrm{mol}$.
I then worked out the concentration of $\ce{Na2CO3}$ using the moles I just worked out and the volume they gave me ($0.25~\mathrm{L}$) and I got $0.1988~\mathrm{M}$.
The question says that only $0.01~\mathrm{L}$ was used, so I worked out the number of moles this would be which was $0.001988\ \mathrm{mol}$.
Using stoichiometry, I multiplied this value by two to get the moles of $\ce{HCl}$ that would have reacted with this, which was $0.003976\ \mathrm{mol}$.
It says that the end-point occurred at $21.30~\mathrm{mL}$, which if you subtract the volume of $\ce{HCl}$ which was already there, I worked out that $11.3~\mathrm{mL}$ or $0.0113~\mathrm{L}$ of $\ce{HCl}$ must have been used.
From here, I worked out the concentration of $\ce{HCl}$ (using $0.0113~\mathrm{L}$ and $0.003976\ \mathrm{mol}$) and got $0.35186~\mathrm{M}$.
It says that for the next reaction, $25~\mathrm{mL}$ of $\ce{Ba(OH)2}$ was used and the end-point occurred at $27.10~\mathrm{mL}$. From this information, I worked out that $0.0021~\mathrm{L}$ of $\ce{HCl}$ must have been used in this reaction.
By knowing the volume of $\ce{HCl}$ used, I worked out the amount (moles) of $\ce{HCl}$ used in the reaction, using the previously found concentration. I got $0.0007389\ \mathrm{mol}$.
Using stoichiometry, I worked out the amount of $\ce{Ba(OH)2}$ which must have reacted with this many moles of $\ce{HCl}$. I divided the $\ce{HCl}$ moles by $2$ and got $0.00036945\ \mathrm{mol}$.
By using the volume of $\ce{Ba(OH)2}$ used which they give me ($0.025~\mathrm{L}$) and the moles I just found ($0.00036945\ \mathrm{mol}$) I finally worked out the concentration of $\ce{Ba(OH)2}$, which was $0.0148~\mathrm{M}$.

My answer, $0.0148~\mathrm{M}$ is different to the answer the question gives ($0.1013~\mathrm{M}$), and I'm not sure why.


texts: Calculating the viscosity of water using particles

texts:
There are two particles with radius 0.212 μm. The particles are in a thin liquid film and the microscope can only detect movement in the $x$- and $y$-axis. The temperature is 25 °C.
$$
\begin{array}{c|rrr}
\hline
t/s & 30 & 60 & 90 & 120 \\
\hline
x_1 & 4.4 & 10.7 & 11.0 & 12.4\\
y_1 & -3.1 & -5.2 & -10.8 & -9.3\\
x_2 & 3.9 & 2.0 & 8.3 & 5.8 \\
y_2 & 3.5 & 6.4 & 14.1 & 12.0 \\
\hline
\end{array}
$$
Use this information to estimate the viscosity of water.

I know that I should use the equations:
$$x^2 = 2Dt \tag{1}$$
$$D = \frac{kT}{6πηa} \tag{2}$$
Where if I plot $x^2$ against $t,$ I can calculate the viscosity from the slope $\displaystyle\frac{2kT}{6πηa}.$ However, what I don't understand is how to calculate $x^2.$
I tried taking the average of the two particles in direction $x$ and squaring the result, but that doesn't give me the right answer. I also tried taking the average of $x^2$ of the two particles, but once again I get the wrong answer.
How should I calculate $x^2?$


texts: How many grams of CH3OH can be made from 30.0g of CO if it all reacts?

texts:
Once made by heating wood in the absence of air, methanol ($\ce{CH3OH}$) is now made by reacting carbon monoxide and hydrogen at high pressure:
$\ce{CO_{(g)} + 2 H2_{(g)} -> CH3OH_{(l)}}$

How many grams of $\ce{CH3OH}$ can be made from 30.0g of $\ce{CO}$ if it all reacts?


texts:
In a lecture, teacher said

"Nucleophilicity is about 'kinetic', and basicity is about 'thermodynamic'"

but I saw the picture below from another source.

Here, both pathways start with an acid/base reaction (it's about basicity) and then nucleophilic addition happens (it's about nucleophilicity). as a result, 'kinetic' and 'thermodynamic' product come up.

So here's my question.

Are the terms 'thermodynamic' and 'kinetic' that are used above in two cases different?


texts:
Take the reaction:
$$ (1) \; \ce{A + B <=>X + Y}, \; K_1=\frac{[X][Y]}{[A][B]} $$
Now assume that X isomerizes to Z according to:
$$ (2) \; \ce{X <=> Z}, \; K_2=\frac{[Z]}{[X]} $$
We can then add the equations to obtain:
$$ (3) \; \ce{A + B <=> Z + Y}, \; K_3=K_1K_2=\frac{[Z][Y]}{[A][B]} $$
It's pretty easy to show that $ K_3=K_1K_2 $ when considering the ratio of products and reactants, but this makes less sense when considering the actual numeric value of $K_3$. The fact that $ K_3=K_1K_2 $ can be explained by the statement of multiple equilibria: all equilibria must be satisfied simultaneously. This is what I'm having trouble conceptualizing. Does the equilibrium constant in $(1)$ already take into account $(2)$, and vice versa? Equation $(3)$ will reach a state of maximum entropy in which $K_3$ applies. This must also occur when both $K_2$ and $K_3$ are satisfied? I can do the math all day, but I'm not quite getting the link between the three equilibrium constants.


texts: nickel-copper fabric: shielding viability after being subjected to weathering

texts:
I know the solution can be as simple as a well-sealed garbage can, but I am contemplating making a more malleable fabric based faraday-cage-esque contraption. The plan is to use nickle-copper fabric to achieve the shielding, I'll experiment with how many layers/folds create the best seal. It is to be placed outside, exposed to the elements, potentially incurring moderate to heavy rain. Before I get too heavily invested in this, I would like to really think about the shielding viability of the fabric in the long-term.

For reference, here is a generic picture of the nickel-copper fabric. Amazon has its fair share too, for those interested.

Question:

Unlike its ferrous counterparts, nickel/copper do not rust but rather have a patina or tarnish that develops after weathering. Will nickel-copper fabric tarnish like we might expect a penny to tarnish? If so, what compromises to shielding would be sustained? Also, if so, would that compromise the structural integrity of the fabric (more prone to tears, ect)?

Further Clarifications:
 - exact chemical makeup of the fabric is uncertain, the one I bought was simply marketed as "nickel-copper fabric" so I assume its mostly nickel and copper, but it seems to have a fabric-like feel, so perhaps its mixed with some kind of substrate or something. If the consensus is that this information is crucial I'll try to track down the manufacturer and get specifics, but at the moment I don't have a practical means of going about that(manufacturer is unknown). You are free to speculate about common implementations of nickel-copper fabric and state your assumptions accordingly

shielding: I'm concerned that if the fabric weathers poorly, the shielding will be affected
tear resistance: I'm concerned that if the fabric weathers poorly there may be more points of failure, leading to easier tears in the fabric
health: the fabric will occasionally come in to close contact with humans (me) and I'm not sure if tarnished nickel-copper has any adverse health risks
set up: my design is too hypothetical to put into words at the moment, but you can imagine a tarp-like thing, outside layer is cordura (water-resistant, not water-proof) and inside layer is nickel-copper fabric
placement: outside, exposed to the elements, incurring rain


texts: Why do old buildings in the UK smell like ammonia / boar taint?

texts:
As a US resident who visited the UK, I was surprised that many wooden buildings built before say 1800 smelled strongly of pork, an ammonia-like smell but most precisely like boar taint. I have never smelled this in old buildings in other countries.
What is the smell? Is it residue from centuries of cooking pork? Is it from an old type of varnish? Decaying wood?


texts: Difference between starch surfactant and CTAB, SDS, Tx-100

texts: I am doing a research on the effect of surfactant on ZnO nanoparticles properties. There is a confusion here between starch surfactant and CTAB, Tx-100 and SDS. I need point on what is the difference between these surfactants in terms of their costs and effects on environment.


texts: Organic conversion involving Grignard reagent and alkyl group with a carbonyl carbon on an benzene ring

texts:
I have been asked to synthesize the organic compound shown below using the following reagents and solvents.

$\ce{Mg, Zn, Hg, FeBr3, AlCl3, Br2, LiAlH4, KMnO4}$, dil. $\ce{H2SO4}$, conc. $\ce{NH3}$, conc. $\ce{HCl, H2O, D2O}$, ether, ethanol, $\ce{CH3C(O)Cl, CH3C(O)CH3, C6H6}$.

I have done it as shown below.

But in the answer given that the -$\ce{C(O)CH3}$ group attached to the benzene ring is reduced to -$\ce{CH2CH3}$ before introducing $\ce{Mg}$/dry ether.
Then the $\ce{Mg}$/dry ether is introduced followed by $\ce{D2O}$. Then the alkyl group is oxidized and so on...

Is there is specific reason for doing that or is my method correct?


texts:
A 2 g mixture of cyclohexanol, acetone and pentanal is completely burnt in oxygen. When the gaseous product is passed through $\ce{P2O5}$, the mass of $\ce{P2O5}$ increased by 1.998 g. Find the average molecular mass of the mixture.

$\ce{P2O5}$ absorbs water, so the amount of water absorbed is 0.111 mol. I attempted constructing an equation for the combustion reaction but realized that the proportions and thus the mole ratios of each gas are unknown.


texts: Software for compound database creation\enumeration

texts:
The only program I have found is Plexus Suite from chemaxon. (I asked for trial, but no answer to me yet).

The task is: create variation of compounds, where is scaffold and different substituents:

And I need to create dataset/database of all possible variations.

How to deal with this problem? Or I need to use some scripting to make the database?

UPD1: best option - creation of SMILES (Simplified molecular-input line-entry system), 3d structure is automated and easy step if there is correct SMILES/connectivity of molecule (which is the same, as smiles)
Using XYZ - it means, you should make substituent database in correct position for adding.  I am asking for software with functionality

https://www.youtube.com/watch?v=s4CgtUgGuzk

Vega ZZ has the module for database enumeration, but it is working as Python script.


texts:
Why can the equilibrium reaction which exists in water be simply represented as

$$\ce{H2O <=> OH- + H+}$$

rather than

$$\ce{2 H2O <=> OH- + H3O+}$$

Doesn't this change both the equilibrium constant AND the enthalpy change?

Why would this still give the correct answer when you use the ionic product of water in solution?


texts: Is vapor-liquid equilibrium in contradiction with Pascal's law?

texts:
When in a closed container a small amount of liquid is introduced then at a fixed temperature $T$ we will have a vapor-liquid equilibrium and the pressure of the vapor at that temperature is called vapor pressure. In order to derive the relation between vapor pressure and temperature we must equate their chemical potentials i.e.:
$$μ_l (T,p)=μ_g (T,p)$$
What I don't understand is how is it possible for two phases to have the same pressure. For example when we have in a closed container liquid water with its vapor in equilibrium, the pressure of vapor can be approximated by ideal gas law. The liquid will also exert a pressure in the walls of the container (which can be approximated by another equation of state). Will the pressure of the vapor equal the pressure of the liquid? Initially I thought that it won't because the  pressure that the liquid exerts is:
$$p_l=p+p_g$$
where $p$ is the pressure from the corresponding equation of state for the liquid and $p_g$ the extra pressure that is transferred due to Pascal's law. But in a vapor-liquid equilibrium and in general when a system reaches equilibrium $T,p,μ$ must be same everywhere in the system. Where I got it wrong?
Edit
After reading the comments I think I should add the following. In order to find the coexisting curve that is the set of points $(T,p)$ where the phases coexist we must equate their chemical potentials. My problem is where the pressure ,when we write $μ(T, p)$, refers. Is the total pressure of the container (from both liquid and vapor) or the vapor pressure? I am thinking it must be the pressure of the container which must be the same throught both phases (equilibrium). But if is this pressure then I can't understand how for example Clausius-Clapeyron can be derived (where the $p$ refers to vapor pressure). Is the pressure of the liquid (neglecting gravity) so small that we can approximate the total pressure with that of vapor?


texts:
Can dichromate in acidic media be titrated directly with buffered thiosulfate solution using $\ce{H2O2}$ as an external indicator instead of  using $\ce{KI}$ which is a standard procedure?

$\ce{H2O2}$ is used as an external indicator because dichromate in the presence of excess acid reacts with $\ce{H2O2}$ to yield a transient blue color due to formation of $\ce{CrO5}$.


texts: Group 15 elements reactivity towards water

texts: Why only tin in group 14 elements react with water and others do not?


texts: Why are activities of solids and liquids taken to be unity?

texts:
First, I should mention that the question was already asked here: Why is active mass of a pure solid or liquid always taken as unity?
However, the treatment there is qualitative and I do not really understand the reasoning for the disclusion of solids and liquids from the reaction qoutient that is presented there. I have attempted to derive this fact mathematically and failed, which why I ask this question again.

Let us look at an example reaction which involves solids and gases. The treatment for other reactions or reactions with liquids shouldn't differ significantly. A very simple reaction for this matter will be the combustion of graphite

$$\ce{C(s) + O2(g) -> CO2(g)}$$

Reaction quotients are derived from the equation for change in Gibbs free energy at nonstandard pressures, so let's find that. Suppose the reaction is carried out in nonstandard pressure, and $\Delta G^o_r$ is known. Let's (I) compress the system isothermally to standard pressure, (II) carry out the reaction and then (III) return it isothermally to the original pressure.

I. $\Delta G$ for the oxygen here is the well known $RT\ln (1/(P/P_o))$. For the carbon: In any isothermal process $dG=VdP$, let's assume for our ideal solid that the volume is constant (I have also tried this in a model where the volume changes with pressure with bulk moduli, the result does not differ significantly), so $\Delta G=V(P-P_o)$.

II. Here simply $\Delta G=\Delta G^o_r$.

III. Here it's just gas compressing so again $\Delta G=RT\ln (P/P_o)$

Adding the contributions from all three stages we have
$$
\Delta G=RT\ln (1/(P/P_o))+V(P-P_o)+\Delta G^o_r+RT\ln (P/P_o)=\Delta G^o_r+V(P-P_o)
$$

This result is different from what a model of an activity of unity for the carbon would predict. What went wrong? And why are activities of solids and liquids taken to be unity? Any help will be appreciated.


texts: In a multi equilibrium system, how does change in one equilibrium affect the other?

texts:
Suppose in a reaction vessel of fixed volume we have the following equilibria established (existing simultaneously in the vessel),
\begin{align}
\ce{A (g) &<=> B (g) + C (g)}\tag{i}\label{i}\\
\ce{D (g) &<=> E (g) + C (g)}\tag{ii}\label{ii}
\end{align}

Frankly speaking I do know that when we increase, say, $\ce{A (g)}$ concentration in $\eqref{i}$ then indeed the concentration of $\ce{C}$ or $\ce{B}$ is going to increase as per Le Chatelier's Principle. However if we increase the concentration of $\ce{E (g)}$ in the vessel what impact will it have on the concentration of $\ce{C}$ and $\ce{A}$?

From my perspective, when $\ce{E}$ is increased in concentration, it will now combine with $\ce{C}$ to give $\ce{D}$ so that reaction goes backwards, and so more of $\ce{C}$ needs to be formed as a result $\ce{A}$ concentration in equilibrium $\eqref{i}$ goes down. However I am not convinced with my own explanation as I feel I am missing out on something. Please feel free to help me out.


texts: Are precipitation and crystallization both analogous between Chemistry and Meteorology?

texts:
A comment under the Space SE question Is there really precipitation on Mars? Does frost count? brings up the use of the term "precipitation" in chemistry and we wonder if precipitation in weather and in chemistry are in fact analogous insofar as they both start as small particles suspended in the 3D medium (atmosphere or solution) and only fall to the ground or the bottom of the container if/when sufficiently large to make headway against Brownian or other motion.
In chemistry, on Earth in gravity, if a material from solution conformally, over all surfaces vertical and horizontal (e.g. the sides as well as the bottom of a container) is that still sometimes considered precipitation? Or is that crystallization from solution, and analogous to frost formation but not snow or rain?
Images of frost formation: http://www.its.caltech.edu/~atomic/snowcrystals/frost/frost.htm


texts: What is the freezing point of sulfuric battery acid?

texts:
As we all know, the freezing point of absolute sulfuric acid is 10 °C. The average lead-acid battery (sulfuric) uses ~30% sulfuric acid, and has a freezing point much lower than 10 °C.

What constituents contribute to this effect? What is the diluent used in these batteries? What would the freezing point be?


texts:
I had a quick question on virtual libraries. I'm hoping to perform a virtual screen using a library that contains very small, soluble compounds - think glycerol and smaller (<100MW). As far as I can tell, the majority of virtual libraries contain mostly larger, drug-like compounds. Is anyone aware of any libraries that might contain ideally 10,000+ or so of these tiny soluble compounds?
If not, any idea how difficult it might be to construct a custom virtual library enriched for these compounds?
Thank you!!


texts: Boiling of water does not involve temperature change, so why is there a change in internal energy during the process?

texts: in an isothermal process, the value ΔT = 0 and therefore ΔU = 0 but during boiling if water at constant atmospheric pressure temperature doesn't change so why internal energy changes


texts:
Something I noticed today, when adding some pure caffeine powder to apple cider.

Why does caffeine powder cause apple cider (or any carbonated drink?) to foam?

It seems to foam (with around 150mg caffeine added) slowly, but constantly so that it almost seems that it will eventually make all the carbon dioxide fizz to air.

Is this really related to caffeine or the powdered form in general?


texts:
"London (dispersion) forces are responsible for the fact that non-polar substances can be condensed to form liquids and sometimes solids at low temperatures"._

I learned that what results in London fores between molecules is the "cloud of electrons" that  results in an instantaneous dipole and induced dipole, which eventually results into forming these weak London forces._

The aforementioned statement suggests that as we lower the temperature we form a solid or a liquid meaning that the inter-molecular forces (London forces in this case)became stronger._

My question is: if we lower the temperature we subsequently decrease the kinetic energy of the electrons,  i.e. we decrease the frequency/probability of these "electron clouds" moving to one side of the molecule and forming instantaneous and induced dipole, which means that London forces should be weaker and not stronger to form a liquid or a solid.

This is how I thought of it, can anyone suggest what's wrong with my way of thinking of it? Is it that what we relate to the strength of the London forces is how long the electrons cloud stay on one side rather than how often that happens?


texts: Mechanism of electron delocalisation from the other end of alicyclic chain

texts:
When one adds $\ce{Br2}$ and $\ce{CH2Cl2}$ to 5-Methylhex-5-enol, this mechanism follows;

Also,in adding $\ce{Br2}$ to 2,2-Dimethylhexa-3,4-dienol, this follows;

What is the mechanism here, in which the electrons from a hydroxyl on the other side of the C-chain is delocalised to the other side?


texts: Mechanism for formation of amides from ammonium carboxylate salts

texts:
One of the reactions that you can do with a carboxylic acid is to react it with ammonia or an amine, which produces the corresponding ammonium carboxylate salt. When this salt is heated, amide is obtained by elimination of water (although it seems that the yield is not that good).
$$\ce{RNH2 + RCOOH->RCOO- ^+NH3R->(heat)->RCOONHR + H2O}$$
So what sort of mechanism can we draw for the elimination of water? It seems to me a bit complicated because the amine is already protonated in the salt, so it does not have any lone pair remaining for nucleophilic attack. Does the acid base reaction go backward under high temperatures? Or is it something else?


texts:
My Theory:
Since atomic mass increases down the group, the van der Waal's forces should also operate to a greater extent, thereby making it difficult to change the phase of the substance. Hence, boiling point should increase down the group from boron to thallium.

But in my book, the answer given is that the forces of attraction decrease down the group because of the increase in size of atoms down the group. Hence, the boiling point decreases down the group.

I'm confused. Even though the size of the atom increases, shouldn't the boiling point follow the same trend of increasing because atomic mass increases?
 Moreover, due to poor shielding of d-electrons the increase in size down the group is very minimal.

Experimental data: (source) shows a regular decrease in boiling point down the group

$$
\begin{array}{|c|c|}\hline
\text{Element}&\text{Boiling point (K)}\\\hline
\ce{B}&\pu{4200K}\\\hline
\ce{Al}&\pu{2743K}\\\hline
\ce{Ga}&\pu{2673K}\\\hline
\ce{In}&\pu{2345K}\\\hline
\ce{Th}&\pu{1746K}\\\hline
\end{array}
$$

EDIT:
Can we explain the above trend with metallic bonding present in these elements? Boron has its highly networked structure so let us leave it alone. As we move down the group, size of the element increases. This increase in size, decreases the strength of metallic bonding as the same number of valence electrons now have to hold a larger cation. Metallic bonding is viable in liquid state too. So could this be the reason?


texts: Angular dependence of x-ray and neutron scattering factors

texts: Why are neutron scattering factors essentially independent of $2\theta$, whereas X-ray scattering factors drop off with increasing $2\theta$ ?


texts: How can multiplets in para-disubstituted benzene rings be described?

texts:
How should I label the multiplicity of the aromatic signals in an 1H-NMR spectrum with the following substitution pattern?

I have seen lots of people labeling both signals in this kind of system as doublets, probably because the resolution of the spectrum was not high enough, or because we are often told, these look like doublets. However, what looks like a doublet doesn't necessarily have to be one and thus, should not be called doublet, because it doesn't reflect the actual couplings in this system:

The ortho-coupling (3J) for both signals should be about 6.0 and 9.0 Hz.
The meta-coupling (4J) for both signals should be between 0.9 and 3.0 Hz.
The para-coupling (5J) for both signals should be between 0.0 and 1.0 Hz.

(These numbers are from the Hesse-Meier-Zeeh, a German textbook about spectroscopy in organic chemistry).

I am inclined to call these signals multiplets rather than doublets, because I can only guess the coupling constants, especially for the right signal at about 7.36 ppm.

Or is it good practice to call them pseudo-doublets? And what would be the symbol (like s for singlet, d for doublet, etc.)?


texts: Why can't sulphate ion be discharged in the anode of electrolysis?

texts:
Given that there is an aqueous solution of sulfuric acid ($\ce{H2SO4}$), $\ce{2H+}$ is reduced in the cathode and $\ce{OH-}$ is reduced in the anode. Why is $\ce{OH-}$ preferentially discharged over $\ce{SO4^2-}$ in the anode?

One explanation I've found is that because $\ce S$ in $\ce{SO4^2-}$ has an oxidation number of $+6$ which is a maximum and thus cannot be oxidized any further. However, can't the $\ce O$ in $\ce{SO4^2-}$ be oxidised instead as it has an oxidation number of $-2$ (just like the case in $\ce{OH-}$ where $\ce{O^2-}$ is oxidised and $\ce{H+}$ is not oxidised according to the half equation $\ce{2OH- <=> 1/2 O2 (g) + H2O (l) + 2e-}$)? Therefore, the argument that $\ce S$ cannot be oxidised because it has an oxidation number of $+6$ doesn't seem to be valid.


texts: Why does pKw first decrease but eventually increase when temperature rises?

texts:
I understand the initial decrease in pKw.

$\ce{Heat + H2O (l) <=> H+ (aq)  + OH- (aq)}$

Temperature increases, reaction shifts to the right, so
$\ce{H+} \text{ and } \ce{OH}$   concentration increases.

Higher $\ce{H+} \text{ and } \ce{OH}$  concentration results in lower $\ce{pK_w}$, as $\ce{pK_w = - log ([H+][OH-])}$

But why then does the $\ce{pK_w}$ start to increase beyond $250$ degrees C?


texts: Vinegar salt reaction to produce acid; does it matter what type of vinegar I use

texts: I am trying to get get hydrogen chloride gas by using the reaction sodium chloride + vinegar = HCl(g) + sodium acetate, does it matter what type of vinegar I use eg apple cider vinegar, malt vinegar; if it does matter where could i find some pure vinegar at a reasonable price


texts:
In this site, https://www.princetoninstruments.com/userfiles/files/assetLibrary/Technical%20posters/Poster-Aberration-Free-Raman-Spectroscopy-with-the-IsoPlane.pdf the raman spectrum of cyclohexane shows higher peak at the right.

While in this site, http://group.nanovietech.com/products/advantage-raman.html, the raman is showing higher peak at the left:

Both are raman spectra of cyclohexane. My questions relate to the 2853 cm-1 peak and 802 cm-1 peak. Based on structure of cyclohexane. Which of them should be higher? Ignore the other peaks which I wasn't concerned.

I found this too:

Should the 802 cm-1 peak be higher than the 2853 cm-1 peak based on the molecular structure of cyclohexane?


texts:
"The Lanthanide Contraction refers to the fact that the 5s and 5p orbitals penetrate the 4f sub-shell so the 4f orbital is not shielded from the increasing nuclear change."

First, 5s and 5p are filled before 4f, so if the atom wants to give an electron out, which energy shell does the electron come out of? How 5s and 5p penetrate 4f? Isn't 4f outer than 5s and 5p?


texts: What is the recipe for the Belousov-Zhabotinsky reaction for correct simulation with the Oregonator model?

texts:
For a school project I'm trying to model the Oregonator and perform some experiments with the Belousov-Zhabotinsky reaction. Like predicting the reaction and the swings in concentrations. For that it is of course crucial that I perform the correct BZ-reaction, the reaction where the Oregonator is based on.

In the paper 'An Analysis of the Belousov-Zhabotinskii Reaction' by Casey Gray I found a mathematical analysis of the Oregonator. For the experiment at school I want to perform the experiment exactly as described in the images below (the images are from the same paper).

Now I have a problem, because there are many different recipes on the internet, all a bit different. I am no experienced scientist, so I have difficulty determining which recipe I should use. So my question is: what is the exact recipe I should use for the (below) BZ-reaction? Which concentrations, how much of them and in what order I should add them (and any additional things that I should do).

Second, are the ingredients used in the BZ-reaction common in most laboratories? I need to perform the experiment at school; what are the chances they have those ingredients? And if school does not have some of chemicals, are they expensive?

Third, is ferroin the best (visual) indicator for the BZ-reaction? Is ferroin expensive (to make)? Are there alternatives that visually indicate the changes in concentrations?

Description of BZ:

FKN mechanism:

An the Oregonator model (based on the FKN):

CORRECTION: HBrO2 is not hypobromous acid, but bromous acid.


texts: Why does water boil vegetables, but oil does not?

texts: When we add vegetables to hot water (boiling), it boils the vegetables, but when we add vegetables to hot oil (boiling) it fries the vegetables. Why?


texts: Calculate the flow rate in the steady state of a dynamic equilibrium

texts:
I have the following situation:

I am interested of the reactions rate of an enzymatic reaction, depending of the substrate concentration. The thing is, that I don't add the substrate directly to the enzymes; the substrate has first to pass (I think diffuse) through a membrane.

I assume an infinite amount of substrate (outside of the membrane), so it won't run out. Further I assume that the product of the enzymatic reaction is eliminated immediately.

$Substrate_{outside} \leftrightarrow Substrate_{inside} \rightarrow Product $

The first reaction ($\leftrightarrow$) is k1 and the second ($\rightarrow$) is k2 (I didn't figure out how to name the arrows, sorry)

k1 is the diffusion trough the membrane which I think should be proportional (fick's law) to the difference of $Substrate_{outside} - Substrate_{inside}$, so it is:

$k1 = D * Substrate_{outside} - Substrate_{inside}$, where $D$ is some constant.

k2 is Michaelis-Menten:

$k2 = \frac{V_{max} * Substrate_{inside}}{K_m +Substrate_{inside}}$

when I solve eq. 1 to $Substrate_{inside}$ and insert it to eq. 2, I got :

$k2 = \frac{V_{max} * (D *Substrate_{outside} -- k1)}{K_m + D *Substrate_{outside} -- k1}$

in the steady state is k1 = k2 so:

$k = \frac{V_{max} * (D *Substrate_{outside} -- k)}{K_m + D *Substrate_{outside} -- k}$

but if I solve it, I get some strange function, which does not looks like I think it should look.

In short words: I am looking for $k(Substrate_{outside},D,K_m,V_{max})$, whereby k is the speed of the reaction.

I am not really into this topic, so sorry if I was unclear or not 100 % correct. Thanks for your help.


texts: Compensating for hardness in aqueous NaOH solution?

texts:
I'm trying to strip the seasoning (polymerized oil) off a carbon steel skillet.

Following online instructions, I've prepared a lye solution, using tap water, 2.5% concentration by weight, which ought to produce results in a matter of days; two weeks in, it's still far from being done.

It occurred to me we have hard water here, 13 dKH/15 dGH, so I'm guessing the solution just isn't as basic as it was expected to be.

Heating it up isn't an option, so I'm planning to add more crystals of sodium hydroxide to speed the reaction up.

Assuming that my diagnosis is correct, and the instructions were based on tap water hardness that is typical for the US, how much more hydroxide should I be adding to compensate for the higher hardness?


texts: What do we learn from an isotope peak (or M+2 peak) in a mass spectrum?

texts:
Mass spectrum of a molecule showed molecular ion peak and its isotopic
 peak in 1:1 ratio. What is the possibility of the atom present in the
 molecule?

Since it is mentioned that it has a molecular ion peak it gives the fact that it must be aromatics, olefins and not alcohols or branched hydrocarbons since the latter have less probability to show molecular ion peaks . Since they contain isotopic peaks it must mean they have chloro or bromo compounds. But I do not understand how to use ratios to identify the atom present in the molecule


texts: How to measure the percent weight of NaCl in a potato chip

texts:
I want to determine the weight percentage of sodium chloride in a potato chip.  I can see from this answer that atomic absorption spectroscopy (AAS) can be used to quantify sodium chloride in a solution.  I propose the following measurement scheme:

Dissolve the potato chip in a sample of water with known mass
Homogenize the solution until it has a uniform composition
Draw 10 aliquots from this solution
Use AAS to measure the weight percentage of salt in each aliquot
Use the mean and standard deviation of the weight percentages from
the 10 aliquots to generate an estimate of the true weight
percentage with a confidence interval

My questions:

1) What is the best way to get the mass of the aliquot that belongs to the potato chip?  I want to minimize measurement uncertainty.

2) There could be compounds other than sodium chloride that contains sodium or chloride in a potato chip.  I fear that the AAS won't detect sodium chloride, but sodium and chloride ions separately.  What is the best way to measure the concentration or mass of sodium chloride with AAS?  If AAS is not the best way, can you name an alternative method?


texts: Which has a high melting point, cocoa powder or cocoa butter?

texts:
I have been doing some research into chocolate, and after looking at the chemical compositions of cocoa butter and cocoa powder, struggled to determine which had a formula/structure that would have a higher melting point.
Which has a higher melting point, natural cocoa powder or cocoa butter?

(For those unfamiliar with the differences between cocoa powder and cocoa butter, here is some helpful information:
Cocoa powder:
https://en.wikipedia.org/wiki/Cocoa_solids
Cocoa butter:
https://en.wikipedia.org/wiki/Cocoa_butter
Composition of both:
https://www.icco.org/faq/61-physical-and-chemical-information-on-cocoa/106-physical-and-chemical-information-on-cocoa-beans-butter-mass-and-powder.html
Thanks!)


texts:
I'm not too sure on how to get the empirical formula for Glauber's salt because water ($\ce{H2O}$) is included.

The question is:

  Glauber's salt contains $14.3\%$ sodium, $10\%$ sulphur, $10.9\%$ oxygen (not in water) and $55.8\%$ water. Find this substance's empirical formula.

This is what I did. I got $\ce{Na4SO.H2O}$ as my answer.


texts: Purification of Solid Phase Synthesized Peptide

texts:
I began working in a newly setup lab, and I'm having a dilysine (K2) peptide synthesized by solid phase method. I plan to cleave the peptides from the resin with a cleavage cocktail of TFA. Unfortunately, our freeze-drier is missing a part and not working then. We also don't have a rotary evaporator yet. We have our HPLC setup, but do you think it is a good idea to take the resulting solution of cleavage (after filtration to remove beads), which contains Boc, Fmoc, TFA, and possibly other impurities, directly to the HPLC?

I've read that HPLC sample should be dissolved in initial composition of my HPLC solvents, but it is in the case of having a crude dry sample.

It is my first time doing a peptide synthesis so I appreciate your ideas.


texts: How do I calculate the hydronium ion concentration if I know the strontium hydroxide concentration?

texts:
This is my first question so I would appreciate feedback on how to ask better questions. Forgive me if I don't know how to properly format math/chem. The guide is confusing.

I was taking a practice test on Brønstead–Lowry acids and bases and I came across a question that has totally stumped me:

  Calculate the $\ce{[H3O+]}$ in a $\pu{0.010 M}$ solution of $\ce{Sr(OH)2}$.

Here are my steps:

Write a balanced equation:

$$\ce{Sr(OH)2 <=> Sr^2+ + 2OH-}$$

Initial concentrations:
$$\ce{[Sr(OH)2]} = \pu{0.010 M}$$

$$\ce{[Sr^2+]} = 0$$
$$\ce{[OH-]} = 0$$

Change in Concentration:
$$\ce{[Sr(OH)2]} = (0.010 - x)~\pu{M}$$

$$\ce{[Sr^2+]} = +x$$
$$\ce{[OH-]} = +2x$$

I am not sure whether $\ce{OH-}$ loses 2 moles to every one of $\ce{Sr(OH)2}$.

Assume $x\ll\pu{0.010 M}$. Now I will set up a $K_\mathrm{a}$ expression:

$$K_\mathrm{a} = \ce{\frac{[H3O][OH]}{[Sr(OH)2]}}$$

$$\frac{K_\mathrm w}{K_\mathrm b} = \frac{x\cdot 2x}{0.010}$$

I don't know what to now.  I feel like I have probably started the problem wrong.


texts: Controlling the reaction of alcohols with acid to either ether synthesis or elimination

texts: Let’s say you take ethanol: $\ce{CH3-CH2-OH}$ and you add an acid and heat. You can get water, the acid, and $\ce{CH2=CH2}$ (a dehydration reaction). However, you can also get $\ce{CH3-CH2-O-CH2-CH3}$, water, and an acid (symmetric ether synthesis). How would you make one reaction preferable over another?


texts: Why do compounds form if overall energy of free ion increases according to CFT

texts:
According to crystal field theory, a free ion has certain energy and its energy increases when it is symmetrically surrounded by ligands. Now the degenerate d orbitals split into two new set of degenerate orbital, (eg and t2g) of which t2g has lower energy than symmetrically surrounded ion (the Bari centre) but still the energy of t2g is greater than the energy of the FREE ion according to diagram. (And energy of eg is much greater than free ion and Bari centre)

Now, my question is, if the energy of the overall ion afterwards is greater than the energy of the free ion, then why are coordinate compounds considered more stable than the free ion?( according to books)
Or why do they form?


texts: Forging steel inside a zero oxygen environment

texts:
Intro: I have watched one too many blacksmithing videos and now I have a question: is it possible to forge steel (either just reshape or "forge-weld") inside a no-oxygen environment?

Scenario: considering the amount of material that turns into iron oxide during the forging process, would it be possible (or plausible) to fill a room with some non reactive noble gas (maybe helium or neon) and proceed to forge inside this room? Or would it be possible to forge in a complete vacuum?

If any of these two options are possible, what are the hindrances and requirements?

Extra info: I am not from the chemistry area and I haven't  studied chemistry in years. I took a look at some old textbooks of mine and also did some research on on Google but did not find anything specific to this question. This is purely out of curiosity, and since I don't know how reddit works (therefore can't do a more relaxed inquiry there) , I thought it was not a bad idea to ask here.


texts: influence of neucleophiles in substituition reactions

texts:
in the image the substitution  reaction of 1-bromobutane and 2-bromobutane is shown. In presence of NaCN 1-bromobutane reacts fast and with the other it becomes slow, which is understandable since CN-  is a poor leaving group compared to Br-.

But OH- is a poorer leaving group compared to CN-(pKa of HCN and water is 9.1 and 16 respectively) , so shouldn't the substitution reaction of 1-bromobutane with water be even faster than it's reaction with NaCN instead of slowing down?

the image was taken from: http://www.masterorganicchemistry.com/2012/06/27/two-types-of-substitution-reactions/ and a detailed discussion is given here


texts: What is the purpose of ammonium chloride in anti hydrogenation of alkynes?

texts:
In my organic chemistry textbook, lithium is used to create a free radical of the alkynes, to then allow the anti addition of hydrogen to get an alkene.

"The Dissolving Metal Reduction of Alkynes" is a reaction that then uses $\ce{NH4Cl}$. Why put $\ce{NH4Cl}$?


texts: How to Visualize the crystal planes of calcite?

texts:
I've been struggling to visualize the structure of calcite. Most papers say it grows in a rhombohedron capped by (104) faces. However, I don't see why it would do this when looking at it using CrystalMaker

Can one, by looking at the unit cell, discern which crystal faces will be expressed? How?


texts: So I was thinking about something to do for a science fair and photosynthesis sounded like a good idea.  I was wondering what the exact process of photosynthesis was on a chemical level.  I know the formula, but how exactly is water and carbon dioxide converted into glucose and oxygen?  And where does sunlight come in, not in the equation but the chemical process.  Finally, any ideas for artificial photosynthesis?


texts: Why does internal rotation of ethane give an energy spectrum asymptotically approaching a rotation based on $\nu=1$ rather than $\nu=0$?

texts:
I'm a physicist with very little knowledge of chemistry. Recently a chem colleague left a molecular model in my classroom, so I brought it back to her, and as I was walking down the hall with it, a hydroxy group started spontaneously swinging around in circles. This made me curious about whether such motions could actually be observed. After asking around and doing some web searching, my understanding is that this sort of thing is called an internal rotation, and usually there is a barrier to rotation, which is modeled by a potential $V(\phi)=(1/2)\sum V_n(1-\cos n\phi)$.

If I'm understanding the history correctly, then originally people thought that the spectrum would be that of a free rotor, but that produced incorrect thermodynamic predictions. Then in 1937 Pitzer published a famous paper, "Thermodynamics of Gaseous Hydrocarbons," in which he showed that you could get correct thermodynamic predictions if you put in a barrier to rotation.

The classic textbook example seems to be ethane. I found this explanation  of the physics (di Lauro, "Floppy Molecules," in Rotational Structure in Molecular Infrared Spectra, 2013), which I only partly understand. He gives the following theoretical spectrum of energy states:

So at low energies we have roughly a set of vibrational energy levels with energies $\hbar\omega (\nu+1/2)$, which makes sense to me because I guess we're sitting in a minimum of the potential where the geometry is staggered. He says, "The high levels, on the contrary, correlate and eventually almost coincide with the free internal rotor eigenfunctions, whose energy increases parabolically as $AK_i^2$, where $K_i$ is the eigenvalue of $J_γ$, in ℏ units." This also sort of makes sense to me, because if you put in a lot of energy, you shouldn't see the effect of the little hills and valleys in the potential $V(\phi)$, so it should act more like a free rotor.

Do the units of inverse cm mean $1/\lambda$, or $2\pi/\lambda$? If the former, then $1/\lambda= 200\ \text{cm}^{-1}$ corresponds to have $\hbar\omega_0/k\approx 300$ kelvin, so it makes sense that the barrier to rotation would have significant thermodynamic effects at temperatures on the order of room temperature or below, since the rotational-vibrational modes are not available. Am I getting this right?

But why is it necessary to place this fictitious rotational band on top of the $\nu=1$ state, rather than $\nu=0$? I would think that the fictitious band should be build from the ground state, it wouldn't match the actual energies at low energies, and then at high energies they would match up.


texts:
Lets say we have the reaction

$$\ce{H2 + O2 -> H2O}$$

And we are given 10 moles of $\ce{O2}$ and are asked that
How many moles of hydrogen gas do we need to complete the reaction ?

Stoichiometry gives the answer as 10 moles but by applying Principle Of Atom Conservation,  we get

$$\text{Moles of }\ce{H2}  =2\cdot\text{moles of }\ce{O2}$$

Why is the POAC giving wrong results?


texts: What word is to chalcogen and pnictogen what halide is to halogen?

texts: Would "chalcide" be understood as a group 16 dianion (and something less electronegative)? Would "pnictide" be understood as a group 15 trianion (and something less electronegative)?


texts:
How can I separate iron from blood, without doing any damage to the blood/haemoglobin?

I have thought about using a magnet, but apparently iron in blood is not magnetic, and I have also looked at filtration techniques but not sure if that will affect the haemoglobin.

Updated Dec 2017: Let me add some context, I was/am looking for an alternative for chelation therapy such as Desferaloxamine infusions to remove iron in patients with iron overload as a result of repeated transfusions due to anemia


texts: Why aren't primidone's lactam groups acidic?

texts:
I understand that 5,5-disubstituated derivates of barbituric acid only show lactam-lactim tautomerism opposed to the lactim-lactam and keto-enol tautomerism of barbituric acid, hence the 5-mono and 5,5-disubstituated derivates are less acidic.

Primidone differs from phenobarbital in a C2 oxo group, so it's lactam groups are not acidic and it is not soluble even in alkali-bases. Why aren't the lactam groups acidic exactly? The oxo groups should still present quite a bit of electron withdrawing effect, shouldn't they?


texts: Balancing chemical reactions, issues of Gauss's elimination method

texts:
I am trying to balance some chemical reactions by using the Gauss' elimination method and I noticed that this method does not work if the creation of a matrix with exactly one degree of freedom is not possible.

In this example

$$\ce{H2O2 + NO3- + H+ → O2 + NO + H2O}$$

I succeeded in creating just 4 equations

$$\ce{\alpha H2O2 + \beta NO3- + \gamma H+ → \delta O_2 + \epsilon NO + \zeta H2O}$$

$$
\left\{
\begin{aligned}
2\alpha+\gamma&=2\zeta &\qquad &(\ce{H})\\
2\alpha+3\beta&=2\delta+\epsilon+\zeta &\qquad &(\ce{O})\\
\beta&=\epsilon &\qquad &(\ce{N})\\
-\beta+\gamma&=0 &\qquad &(\text{electrons})
\end{aligned}
\right.
$$

obtaining

$$(\alpha, \beta, \gamma, \delta, \epsilon, \zeta)=\left(\zeta-\frac{1}{2}\epsilon, \epsilon,\epsilon,\frac{\zeta+\epsilon}{2}, \epsilon, \zeta\right)$$

I know that the solution should be $(3,2,2,3,2,4)$, but, in having two degrees of freedom, I am not able to choose the two free variables in order to obtain what I expect, i.e. $\epsilon=2$ and $\zeta=4$.

Is there any (just one more) equation that I missed?
Is there anything else that I have to add further?
Or do I have to consider that Gauss' elimination fails with problems with a number of free variables $\neq 1$?


texts: What fluorescent materials absorb visible light and emit UVC light?

texts: What fluorescent materials, if any, exhibit anti-stokes shift such that they absorb visible light and emit ultraviolet light in the range of 250-285 nm? I'm interested in particular in materials that are efficient in their conversion and not difficult to acquire.


texts:
I was asked to comment on the planarity of the carbon suboxide molecule. I thought that the Lewis structure of the molecule looks somewhat like an Allene and must have similar bonding. The two terminal pi bonds must be out of plane and hence the molecule would be non planar. But the answer given in my book states that it is planar.
I couldn’t find a satisfactory description of its structure anywhere. The molecule would be linear, but that doesn’t imply that the molecule should be planar.


texts: Chemically producing sodium metal from magnesium

texts: Anyone with experience making sodium metal ($\ce{Na}$) with the following process? Reactants: $\pu{14 g}$ magnesium powder, $\pu{20 g}$ sodium hydroxide; Catalysts: $1$ to $\pu{2 g}$ menthol crystals; Reagent: $\pu{125 mL}$ mineral oil with no additives. Can use $3$ to $\pu{4 g}$ sodium metal to remove any $\ce{H2O}$ in the $\ce{NaOH}$ during the first two hours of stirring at $\pu{120 ^\circ C}$. Then $\pu{13 h}$ stirring at $\pu{200 ^\circ C}$. My understanding is this process was identified by NurdRage on YouTube and is a proven process. I've run it 4 times and the sodium never solidified even though it is present in the resulting paste like product. I'm looking for someone who's run this for advice. I hope this is an appropriate question to ask. I'm new and don't know the protocols followed by everyone. If not an appropriate question please let me know so I can avoid such questions in the future. Thank you!


texts: What is the chemical equation, along with the change in heat of the crystallization process of Sodium Acetate

texts: This is the reaction found in chemical hand warmers, and I can't figure out the equation and the change in heat. Any help would be greatly appreciated


texts:
A. $\ce{Cr2O7^2-}$  B. $\ce{H+}$  C. $\ce{OH-}$  D.
  $\ce{Cr^3+}$  E. $\ce{Ba^2+}$

  Which of the above is the appropriate ion for each blank in the
  following series of reactions?

  $$\begin{array}{ccc}\ce{OH-} + (5) \xrightarrow{} & \ce{CrO4^2- + H+}
 & \\  & \ce{v} (6) & \\  & \ce{BaCrO4 (s)} & \ce{<=>[(7)][(8)]} &
 \ce{Ba^2+ + Cr2O7^2- + H2O}\\  & \text{(yellow precipitate)} & & \ce{v
 SO2 (g), H+} \\  & & & \ce{BaSO4(s)} + (9) + \ce{H2O} \end{array}$$

This question can also be viewed at https://i.stack.imgur.com/i08sR.jpg

So while studying, I came across this reactions' question, which I believe is called a 'cascade reaction'. I have no idea how to do it. I can figure out a few parts, like ($6$) is obviously $\text{E}$, but how do you do the others?


texts: Negative potential of the oxidation of iron(II) to iron(III)

texts:
The oxidation potential which I found on the internet the following reaction

$$\ce{Fe^{2+} -> Fe^{3+} + e^-}$$

is $\pu{-0.77 V}$. But how can it be negative? Negative oxidation potential means oxidation tendency is very less or we can say negative oxidation potential means $\ce{Fe^2+}$ has very less tendency to lose electrons. But it doesn't make sense, because $\ce{Fe^3+}$ is in $\mathrm{3d^5}$ configuration, which is half-filled $\mathrm{d}$ orbital, which is very stable than $\ce{Fe^2+}$. So, $\ce{Fe^2+}$ should get readily oxidize to $\ce{Fe^3+}$. Then why do we have negative oxidation potential for this reaction?


texts: How would you synthesise tetrahydrohyperforin and octahydrohyperforin from hyperforin?

texts:
The chemical structure of the compounds in question are:

Figure 1: Hyperforin

Figure 2: Tetrahydrohyperforin

Figure 3: Octahydrohyperforin

Would heating hyperforin in the presence of water manage to saturate the required bonds and thus allow one to synthesise these compounds?


texts: How to approximate the pH of a box of water molecules with one proton?

texts:
I have a cubic box of length $L = 12.42\ \mathrm{\overset{\circ}A}$, containing $60\ \ce{H2O}$ molecules and $1\ \ce{H+}$ ion. How can I approximate the $\mathrm{pH}$ of the system?

Following the basic definition, $\mathrm{pH}=-\log\left([\ce{H+}]\right)$, I tried to calculate it like the following two ways:

\begin{align}
  \mathrm{pH} &= -\log\left(1/60\right) = 1.78 \tag1\\
  \mathrm{pH} &=
    -\log\left(
      \frac{1/6.022\times 10^{23}}{12.42^3\times 10^{-30}\times 10^3}
    \right)
    = 0.0621 \tag2
\end{align}

However, I am not sure whether these approximations are valid or not in this regime.


texts:
It seems there are some electronic kits sold around nowadays by major retailers (e.g., Home Depot and Amazon) claimed to remove built-up scale from water pipes.

But, do they actually work? If so, then how?

Perhaps, inducing high-frequency eddy currents inside copper piping somehow lessens its ability to support limescale? Or, perhaps it gets broken down by some specific radiation (emitted by the kit) in the limescale's absorption spectrum?


texts: Do all conversion factors have an infinite number of significant figures?

texts:
I believe conversion factors have an infinite number of significant figures. They should be exact values; but not all of them are, are they?

I looked at a pdf document (via the Internet Archive) and it agreed with the fact that all conversion factors have an infinite number of significant figures.

I know this is true with a conversion factor such as $\frac{\pu{1 cal}}{\pu{g ^\circ C}}$, because this is how a calorie is defined. Similarly, it's the same for $\frac{\pu{1 kg}}{\pu{1000 g}}$, $\frac{\pu{4 quarts}}{\pu{gal}}$, etc.. We know these are exact, and in dimensional analysis, if you multiplied by the first conversion factor, you wouldn't end up with one significant figure because of the single significant figure in $\pu{1 cal}$.

However, what is the case with measured conversions, such as $\frac{\pu{4.184 J}}{\pu{cal}}$ or $\frac{\pu{1.60934 km}}{\pu{mi}}$? These were measured using significant figures, so it would make sense to round with significant figures when multiplying (dimensional analysis), but the above link says otherwise.

What should I do, especially with the below type of conversions?


texts: Safe, easily detectable gas or aerosol for testing fume hoods

texts: I've recently started undertaking a project to construct a small fume hood. So far I'm considering its use for soldering, 3d printing with ABS and polystyrene, and PCB etching using a muriatic acid/hydrogen peroxide solution, however I'd also like to leave my options open. I want to test the fume hood once completed - I've seen some videos that use dry ice for this purpose, and I figure I might also be able to test the hood by smell using bathroom deodorant, but I'm wondering what sort of concentration these would have to reach in order for me to detect them, and whether there are any other tests I might consider.


texts:
Consider the following analysis ( rev and irrev respectively refer to a reversible and an irreversible path, between the same initial and final states):
$dU_{rev}=dq_{rev}+dw_{rev}$,and,$dU_{irrev}=dq_{irrev}+dw_{irrev}$.
$dU_{rev}=dU_{irrev}$. Therefore, $dq_{rev}+dw_{rev}=dq_{irrev}+dw_{irrev}$. Rearranging,
$$dq_{irrev}-dq_{rev}=dw_{rev}-dw_{irrev}\tag{E01}$$
Now: If the volume increases, then $dw_{rev}$ and $dw_{irrev}$ are negative: with $|dw_{rev}|>|dw_{irrev}|$. Thus $dw_{rev}-dw_{irrev}<0$.
On the other hand, if the volume decreases, then $dw_{rev}$ and $dw_{irrev}$ are positive: with $|dw_{rev}|<|dw_{irrev}|$. Thus, again, $dw_{rev}-dw_{irrev}<0$.
We can thus conclude, in general, $dw_{rev}-dw_{irrev}<0$. E01 thus becomes:
$$dq_{irrev}-dq_{rev}<0\tag{E02}$$
Now the Gibbs free energy (G) is defined as $G=H-TS$. Thus, $dG=dH-TdS-SdT$. At constant pressure and Temperature, $dH=dq$ and $dT=0$. Thus,
$$dG=dq-TdS= dq-T(dq_{rev}/T)=dq-dq_{rev}\tag{E03}$$
If the process is reversible , then E03 becomes $dG=0$. If the process is irreversible, E02 implies $dG<0$. Combining these together, we get $dG \leq0$.
This analysis ensures that $dG$ is never positive...... Which seems to suggest that (if we take $dG$ as the criteria for spontaneity) every process is spontaneous.
The logical conclusion is that there's something in my analysis that isnt general: it holds for spontaneous processes only. What is it? Is it that the first-law requires some modification to be general?


texts: Are there ionic solids that conduct electricity?

texts:
We are taught in school that ionic substances don't conduct electricity, and when they do, it is either because they are in a molten state or because they are in solution. I understand these concepts.

Are there any exceptions? By exceptions, I am looking for ionic compounds that may not conduct electricity well, but they conduct electricity better in comparison to other ionic compounds. Additionally, what makes such a compound a better conductor of electricity?


texts: Why is the IUPAC name of 1H-benzo[d]naphthalene not 1H-benzo[i]naphthalene?

texts:
In the nomenclature of fused arenes you need to add a 'fusion locant'. The first face should correspond to positions 1 and 2 and is lettered ‘a’, continuing alphabetically clockwise around the exterior of the parent structure.
In this case, the parent is naphthalene and using numbering of naphthalene the benzo is fused on position d so the name would be 1H-benzo[d]naphthalene

But IUPAC also has some rules about the orientation of such structures:
(a) maximum number of rings in a horizontal row (b) the maximum number of rings in the upper right quadrant. (See the drawing on the right.) Subsequent the numbering of peripheral atoms in the preferred orientation starts from the uppermost ring. (If there is more than one uppermost ring, the ring furthest to the right is chosen.)
 Using that numbering scheme the face of fusion should be i.


texts: When is it okay to use $Q=mc\Delta T$, is this equation only for calorimetry questions?

texts: When is it okay to use $Q=mc\Delta T$, is the equation only for calorimetry questions? When a question talks about heat how do I know if i'm measuring $\Delta H$ or Q?


texts: What is the difference between these wave functions?

texts:
My chemistry textbook introduces the wave function as

$$\psi(x)= A \sin\left(\frac{2\pi x}{\lambda}\right)$$ Therefore, the Schrödinger Equation is:
$$\frac{d^2\psi(x)}{dx^2} = -~\left(\frac{2\pi}{\lambda}\right)^{2}\psi(x)$$
and by multiplying each side by $\frac{-h^2}{8\pi^2m}$ you get:
$$-~\frac{h^2}{8\pi^2m} \frac{d^2\psi(x)}{dx^2} = \frac{p^2}{2m}\psi(x) = (T)(\psi(x))$$ where $T$ is kinetic energy.

Now, I don't fully understand that last bit, and I am willing to see an explanation on it, but my main question is that, when the book transitions from discussing the Schrödinger Equation in the context of a "particle-in-a-box" to the context of a one-electron atom, it seemingly changes the wave function to
$$\psi_{(n,\ell,m)}(r,\theta,\phi) = R_{n,\ell}(r) Y_{\ell,m}(\theta,\phi)$$
where n = principle quantum number, $\ell$ = angular momentum number, m = magnetic quantum number, r = radius (distance between nucleus and electron), R = the "radial part" of the equation, Y = the "angular part" of the equation, and $\theta$ and $\phi$ are some angles that I still don't know how to get.
I guess my question is did the wave function $\psi$ change? Why is suddenly so different and why do r,$\theta$ and $\psi$ suddenly come into the picture? Is it because you are going from the one-dimensional, Cartesian "x" version of the wave function to the three-dimensional, polar coordinate version of it?


texts: Seeking titanium compound, melting point <1600 °C, decomposes to TiO

texts: The title says it all.  I’m new to glass making, and I need a titanium compound that will render me $\ce{TiO}$ through decomposition, and has a melting point under 1600 °C.  Hopefully I can get one that goes under 1500 °C, because that’s the max these guys usually keep the furnace at.  The compounds I’ve found so far are typically in the 1800 °C range and we can’t do that.  Any input is appreciated.


texts: When water undergoes electrolysis where in the beaker does the water molecule break apart?

texts:
When I was thinking about it I remembered reading two things, one was that certain gases "form" on certain electrodes. The other was something like, such and such ion "travels" towards such and such electrode.
Does the molecule break up on the electrodes?
Or perhaps it breaks up at a random spot between?


texts: Cause of uniform glow in cathode ray tubes

texts:
I got the following extract from a chemistry book (emphasis mine):

  It is observed that current does not flow through the gas at ordinary pressure even at high voltage of 5000 volts. When the pressure inside the tube is reduced and a high voltage of 5000–10000 volts is applied, then an electric discharge takes place through the gas producing a uniform glow inside the tube. When the pressure is reduced further to about 0.01 torr, the original glow disappears. Some rays are produced which create fluorescence on the glass wall opposite to the cathode.

This excerpt is about cathode rays discovery in a chapter on atomic structure. Here, the author is talking about a uniform glow appearing when the pressure was reduced. Then he says that the rays (which he then refers to as cathode rays) appear after the disappearance of the glow. I have never noticed this glow in any experiment. Does anybody know what this is?


texts: Predicting molecular geometry from a formula

texts:
Can someone explain the following types of molecules and predict their structure and shape?

It will help my understanding if you could provide an example.

AX3E,AX5 and AX6

note that A = central atom and X = bonding atoms.


texts: quantum capacitance of supercapacitor electrodes, high or low needed?

texts: quantum capacitance of supercapacitor electrodes should be low or high? to achieve high specific capacitance. The quantum capacitance forms among the layers of low DOS materials when used as an electrode for supercapacitor.


texts: Will water allow salts to be dissolved in methanol (that are otherwise poorly soluble)?

texts:
If we make a mixture of water, methanol and a salt like $\ce{FeCl2}$, $\ce{NaCl}$ etc, will the ability of water and methanol to mix allow $\ce{FeCl2}$ and $\ce{NaCl}$ to be a part of this mixture and form a solution as opposed to when $\ce{NaCl}$ and $\ce{FeCl2}$ are just added to methanol in which they are poorly soluble?

Or will we see layers forming (which I don't see happening because of the strong tendency for water and methanol to mix)? Or will we just see a methanol-water layer with some salt dissolved in it and some salt left at the bottom (even though they are soluble in water)?
Thanks in advance


texts:
I am exploring (non-experimentally!) the methylation of a perchlorate precursor, either the acid or pre-existing salts, to produce the alkali methyl perchlorate. The methylating agent would be methane itself, and I would like to understand whether:

The product is possible from these (or more) reactants,
Whether the methane, as an organic combustible, would not simply deflagrate with perchlorate, leading to no other products (beyond fire or explosion),
If methyl perchlorate is deliquescent (as I believe that perchlorate esters hydrolyze rapidly with water), and
If low temperature conditions (< 5 °C) might permit '1' and avoid '2'.

Reference to any answers would be much appreciated, my interest being in recent events in the Siberian tundra...


texts: Why are axial bonds are longer than equatorial bond in sp3d hybridized atoms?

texts: Why are axial bonds are longer than equatorial bond in case of $\mathrm{sp^3d}$ hybridization? I have done some research but I can't seem to find the answer.


texts: Reaction of amines with diethyl oxalate (Hofmann amine separation method)

texts:
Why does only one molecule of secondary amine react with diethyl oxalate and two molecules of primary amine react with diethyl oxalate?

I feel secondary amine also should have reacted similar to primary amine.

From JEE-Main 2015:

  Reaction with diethyl oxalate

  1°, 2°, and 3° amines can be distinguished by their reactions with diethyl
  oxalate. Primary (1°) amines react with diethyl oxalate forming N,N-oxamide, which is a solid.

  Secondary (2°) amines react with diethyl oxalate forming oxamic ester,
  which is a liquid.

  Tertiary (3°) amines do not react with diethyl oxalate.


texts: Are centre of symmetry(COS) and alternate axis of symmetry(AAOS) dependent on each other?

texts:
COS=Centre of symmetery
AAOS=Alternate axis of symmetry

Lets suppose a molecule has a COS. Does it need to have AAOS?

What about the converse? If a molecule has AAOS does it necessarily have a COS?

With some research and help I can see that having AAOS doesn't mean it has COS. Still problem with the 1st question does COS imply AAOS?


texts: Calculating the volume of 2 M solution needed to make a 0.1 M solution

texts:
I need help with a basic concentration problem.
If I have a $\mathrm{2~M}$ solution, and want to make a $\mathrm{0.1~M}$ solution of $\mathrm{100~ml}$, how would I go about that?
My work:
$$M_1V_1 = M_2V_2$$
Where $M_1 = \text{initial concentration}$, $M_2 = \text{final concentration}$, $V_1 = \text{volume needed from initial}$, $V_2 = \text{volume needed from final}$
$$2~M \times V_1 = \pu{0.1 M \times 100 ml}$$
$$V_1 = \frac{\pu{0.01 M\cdot L}}{\pu{2~M}} = \pu{5 ml}?$$
Therefore I need $\pu{5 ml}$ of my $\pu{2 M}$ solution, increased to $\pu{100 ml}$ to make a $\pu{0.1 M}$ solution of$\pu{100 ml}$?


texts:
someone asked a question about this mechanism and there were 2 answers as shown below.

but these two answers seem contradict.
and my questions are
  1. which one is right?
2. does the protonation by H2SO4 and free proton both mean the protonation by H3O+?
3. I know sp2 hybridized C is more electronegative, but at the same time it's losing e- to oxygen through pi bond. is C=O still less polarized than C-O even considering pi bond?
4. in answer #2, it's saying like free proton(H3O+?) is less acidic than hydrogen attached to positively charged oxygen(ROH2+?). how is this right?

Hope somebody can help me understand it !!


texts: What is the advantage of having aromaticity in biological compounds?

texts:
I am studying aromaticity, and apparently, aromaticity is common in biological molecules, just like 6-member rings (relieve ring strain and angle strain). I was wondering: is it because aromaticity makes the compound more stable to prevent unwanted reactions/modifications?

Thank you!

EDIT:

I finally found something interesting. Tyrosine, phenylalanine, and tryptophan interacts with cation-pi interactions in proteins to stabilize secondary structures. They are also over-represented in protein binding sites.


texts:
Which hydroperoxides undergo a Hock rearrangement?

e.g. Cumene hydroperoxide undergoes a Hock rearrangement to yield acetone and phenol

Would the following hydroperoxide of ethylbenzene also undergo any similar rearrangement? How does one decide if a Hock rearrangement is likely?


texts: Ethyl acetate produces red colour on ceric ammonium nitrate test

texts:
When I did CAN test on ethyl acetate red colour was seen. I thought water may get added with Ethyl acetate to produce
this compound which in turn gave red coloration but carbon should not make three bonds with oxygens easily.
What could be the possible explanation to this phenomena?


texts: Is 1.5M NaOH a strong enough base to deprotonate benzyl alcohol? I realize that NaOH generally does not deprotonate benzyl alcohol, but we performed an extraction in a Fischer esterification lab with benzyl alcohol an acetic acid to synthesize benzyl acetate. Acetic acid was added in excess, and the final ester product was purified with extraction techniques. I know that addition of NaOH removes acetic acid from the organic, diethyl ether layer, but would 1.5M NaOH also remove any remaining benzyl alcohol?


texts: What chemical process occurs when dead leaves make a mark on concrete?

texts:
In autumn, leaves that fall on concrete make marks that remind me of fossils.

Is this caused by a chemical reaction that occurs between the concrete and the leaf? Or would a leaf leave a stain on any surface as it decays? What circumstances can intensify the process?


texts: Examples of molecules with D4 and C9 point groups

texts:
Trying to come up with examples of (hypothetical) molecules/shapes that have $D_4$ and $C_{9h}$ point groups.

For $D_4$, I thought a cyclobutane structure, but with 4 substituents coming off of the ring all pointing in the same direction. However, I'm not sure if this is $D_4$ because in a book I am reading it says that all the $D_n$ point groups show chirality, which this molecule does not.

For $C_{9h}$, I really can't think of any shape/structure that doesn't just end up being $D_{9h}$. $C_9$ would be a 9-bladed propellor shape, although I'm not really sure how to draw this, and I don't see how I could alter that to get $C_{9h}$.

Thanks


texts: Why is distilled water such a poor conductor of electricity?

texts: Water is composed of hydronium ions and hydroxide ions. Since ions do conduct electricity, why is distilled water such a poor conductor of electricity?


texts: Kinetic energy of molecules in liquid state?

texts:
My book (book link) has this question:

  The kinetic energy of molecules at constant temperature in gaseous state is:

  more than those in the liquid state
  less than those in the liquid state
  equal to those in the liquid state
  None of these

The answer given is (3). It gives the reason as KE per molecule is still $=3/2\cdot k\cdot T$. So, the KE are both same!

But, I wonder, how can the kinetic energy of atoms in gaseous state be equal to that in the liquid state? Being in the gaseous state implies rapid and random motion of molecules, with little to no intermolecular attraction, spreading in all directions of any container. A liquid, however, is bound by intermolecular forces and is not so free to move.

In fact, I even wonder whether the formula $\text{KE per molecule }=3/2\cdot k\cdot T$ is valid in the liquid state, as it's derived from the kinetic theory of gases.

  What exactly is correct in this situation here?


texts: Is this Fischer Projection of (3R, 4S)-3-ethyl-3,4-dimethyl-1-hexene wrong?

texts:
(3R, 4S)-3-ethyl-3,4-dimethyl-1-hexene

Draw the Fischer Projection of the compound above.

Here is the answer:

Is there a mistake at the upper stereocenter? I think so.


texts: Why is there a doublet instead of a singlet in this Wittig reaction salt configuration NMR?

texts: I did an NMR sample to my salt p-carboxybenzyl triphenylphosphonium bromide. I got a doublet at 5.26, and according to every article it belongs to the $CH_2$ next to $P^+$, but how come I didn't get a singlet for that?


texts: The van't Hoff rule for stereoisomers with planes of symmetry

texts:
We know that the maximum possible numbers of stereoisomers of a molecule is given by the van't Hoff rule, which says that:

$$Total \space stereoisomers = 2^{n}$$

Where $n$ is the number of stereocenters. However, this is just the theoretical maximum: in fact, if the molecule has a certain number of planes of symmetry, the number of isomers drastically decreases. Is there a formula that accounts for the number of planes of symmetry? The only contribution I could find was here:

How to derive these general formulae for number of stereoisomers of a compound with a possible plane of symmetry?

But this only accounts for one plane of symmetry. What if we have more? Things obviously get more difficult, as not only the number of planes, but also how they divide the molecule will influence how many stereoisomers we'll have. Do you think it would be possible to generalize the formula above anyway?


texts: Enthalpy of Reaction and Efficiency of Electrochemical Energy Devices

texts:
For electrochemical energy devices such as batteries or fuel cells working reversibly, efficiency is defined as: $$ \eta = \frac {\Delta_rG^⦵}  {\Delta_rH^⦵} $$ Since cell operates reversibly Gibbs energy change of the system is equal to electrical work done by the cell, so we can instead just use standard Gibbs energy of reaction as energy output. What I am not clear about is why is enthalpy of reaction used as energy input? Since electrochemical energy devices transform chemical energy of electroactive materials to electrical energy, energy input should be chemical energy, but I am not sure why enthalpy of reaction represents chemical energy? Enthalpy of reaction is given by this equation: $$ \Delta_rH^⦵ = \Delta_rG^⦵ + T\Delta_rS^⦵$$
Since cell operates reversibly, $\Delta_rG^⦵$ represents reversible electrical work (maximum non-PV work done by the cell) and $T\Delta_rS^⦵$ represents heat exchanged with surroundings to keep cell at constant T in reversible operation since change in Gibbs energy as measure of non-PV work is only applicable for closed systems at constant p and T.
Why is chemical energy sum of these two quantities physically speaking since I do know how to derive this equation from 1st and 2nd law of thermodynamics, but I am not sure in its physical interpretation in context of electrochemical cells?


texts: How is change in entropy of universe related to the energy released by system that can be used to do work?

texts:
What does change in entropy ($\Delta S$) represent ? How does change in entropy of a universe ($\Delta S_{univ}$) give us information about energy available to do work.

I would like to know the physical significance of entropy of universe and how it is related to energy energy released by system that can be used to do work (Not in terms of equation. I would want to know its physical significance).


texts:
I'm trying to make my 13C{1H} (hydrogen decoupled) nmr more quantitative. From the literature I've noticed that researchers either

increase the delay time in the experiment (which I can't do, as it takes too long to collect the spectra)
run the decoupling pulse only during data acquisition (to reduce the nuclear Overhauser effect), and/or
add a paramagnetic relaxation agent to the sample.

I want to try a paramagnetic relaxation agent (I'm working with $\ce{CDCl3}$ as a solvent).  The most common one seems to be $\ce{Cr(acac)_3}$.  Are there better relaxation agents out there (i.e. more effective at lower concentration)?  Also, the literature I've read shows all sorts of concentrations of the relaxation agent... would a low (0.01 M or less) concentration work, in your experience? Do these agents lead to too much spread in the peaks?

Also, will using a relaxation agent ruin the nmr tube for further use?


texts: Better functionals to work with transition metals

texts:
My Masters in inorganic chemistry is focused in magnetic properties of transition metals; great part of the work is done with DFT methods using softwares like ORCA and NWChem, but since my University has a lack of resources, we are performing computations with not much computational power. That is why we are focusing in results and using functionals like PBE and B3LYP (since many papers are showing good results).
Nevertheless, as said by Martin in this thread, today we have "better and more efficient functionals" available, because PBE and B3LYP are very popular, but kind of old. That is why I’d like to ask: what are good, modern, functionals to work with transition metals (mostly Ti…Zn)?

Aditional information:

We are working with systems  that have no more than 200 atoms, most of the time, usually dimers.


texts: Stoichiometry of alkane-perchlorate reaction

texts:
What are the products of an alkane and a perchlorate reaction?
e.g., making the alkane methane and the perchlorate anhydrous for simplicity:

My effort:
$$\ce{Mg(ClO4)2 + 4CH4 -> MgCl2 + 4CO2}$$
leaves 16H free so obviously incorrect, but shouldn't a salt and a gas be part of the products? I guess that the anhydrous form would make this explosive.


texts: Change in pH when changing the sequence of acidic solution

texts:
I have 4 acidic solutions: Barium nitrate, aluminium nitrate monohydrate, cobalt nitrate hexahydrate, and hexachloroplatinic acid. Everything is dissolved in water.

I mixed them in order to create a final acidic solution. Following is the mixing procedure

1)Platinic acid =>Cobalt Nitrate=>Alumnium Nitrate=>Barium Nitrate
(This means Aluminium Nitrate was added to Barium Nitrate , to the mixture of which cobalt nitrate was added, and finally, chloroplatinic acid was added.)

Now, when I add everything to barium nitrate, the final $\mathrm{pH}$ of the mixture is always around 1.5,

2)Barium Nitrate =>Aluminium Nitrate =>Cobalt Nitrate =>Platinic acid

When I add everything to chloroplatinic acid, the $\mathrm{pH}$ of the mixture drops to around 0.3-0.5. Also if I do some other sequence, the $\mathrm{pH}$ is different.

The following are the details of the solutions-

Barium Nitrate- 2.1 g in 40 ml of water (0.008 moles) (0.2 M)

Aluminium Nitrate Nonahydrate-33.1 g in 40 ml of water (0.088 moles) (2.2 M)

Cobalt Nitrate-1.86 g in 40 ml of water (0.0064 moles) (0.16 M)

Hexachloroplatinic acid-0.83 g in 40 ml of water (0.0016 moles) (0.04 M)

I am trying to understand why this is happening because ultimately every time the constituents are the same, but why is the sequence of the addition causing this change?

Since always conceptualizing $\mathrm{pH}$ in terms of $\ce{H+}$ and $\ce{OH-}$, I am having a hard time trying to understand how the nitrates and the chloroplatinic acid are behaving with each other and with the water molecules and how exactly the final $\mathrm{pH}$ is dependent on them.

The $\mathrm{pH}$ of individual solutions when I measured them in our lab are:

barium nitrate: 6.2;
aluminium nitrate: 1.71;
cobalt nitrate: 5.46; and
hexachloroplatinic acid: less than 1.

Looking at these numbers, I can see why adding everything to hexachloroplatinic acid is giving less $\mathrm{pH}$ than adding everything to barium nitrate, but what mechanism is playing part here?

Any help would be greatly appreciated.


texts: Does mixing two different foaming soap make it ineffective?

texts:
To save soap during this pandemic, I mixed foaming soap of two different brands and then the solution became cloudy (both originally transparent) . It seems foaming okay. But does this make the soap less efficient in washing away germs/virus? Does the foaming show that the mixture is still working as a regular soap?
I know that soap is both hydrophilic and hydrophobia which makes it capable of washing away bacterias. Is it possible for the ingredients of two soap make it non polar?
Thanks.

According to the answers, more details are added. The ingredients of the two foaming soaps are given below. According to the ingredients, can we tell if the effectiveness of soap is reduced by mixing them?

About 1/3 is method foaming hand soap with ingredients--WATER (AQUA), SODIUM LAURYL SULFATE*, COCAMIDOPROPYL BETAINE*, GLYCERIN*, ALOE BARBADENSIS EXTRACT*, TOCOPHERYL ACETATE (VITAMIN E), CITRIC ACID, SODIUM CHLORIDE*, SODIUM CITRATE*, METHYLISOTHIAZOLINONE, METHYLCHLOROISOTHIAZOLINONE, FRAGRANCE (PARFUM: LINALOOL, LYRAL), EXTERNAL VIOLET 2 (CI 60730), BLUE 1 (CI 42090).

2/3 is equate anti-bacteria foaming soap with ingredients in the picture.


texts: What do the phase space and slope fields of the iodine clock reaction look like?

texts:
The iodine clock reaction is a fun experiment shown to undergraduates to illustrate that chemical reactions can show periodic behaviour. Presumably, or hopefully, there is a system of differential equations for this system that can be studied qualitatively. Some qualitative approaches are visual, including slope fields and phase diagrams. An example of a qualitatively discoverable property of a system is the existence of attractors.
Has someone made visualizations of the phase space or slope fields for the differential equations governing the iodine clock reaction?


texts: MO scheme for coordination complexes (tetrahedral) - Heteroligand vs. homoligand

texts: How is the MO diagram drawn for a tetrahedral complex with heteroligands (e.g. $\ce{[NiCl2(PPh3)2]}$) different from a tetrahedral complex with the same type of ligand? Do we consider the same "a1 and t2" SALCs as in the case of same ligand type tetrahedral?


texts: Deprotection of carboxybenzyl (Cbz) in the presence of Methyl ester?

texts:
Deprotection of carboxybenzyl and methyl ester can easily be achieved by using ammonium formate followed by addition of 10% Pd/C and LiOH/MeOH respectively.

But how we can achieve deprotection of carboxybenzyl group in the presence of methyl ester?


texts:
What effect does stereochemistry have on the number of signals in an H-NMR?
For example, if you consider the two structures below, would the number of signals and splitting differ due to the restricted rotation? If so, which hydrogens are being affected?

EDIT: This is what I think the splitting would look like.


texts: How many peaks of HCl are found in a mass spectrum?

texts:
In a mass spectrometer some hydrogen chloride molecules will split into atoms. Chlorine has two isotopes. The hydrogen involved here is the isotope $\ce{^1_1H}$ only.
How many peaks does a mass spectrum will show?

My answer was two with $\ce{H^35Cl}$ and $\ce{H^37Cl}$ but I found the answer to be wrong. Where have I been deceived?
I also found the mass spectrum in CIE 9701/02 2003:

Why are there peaks for $m/z = 35$ and $37$? Even if I consider them to be chlorine's, why aren't there any for hydrogen?


texts: If I mixed two powdered herbal extracts together and put them through distillation process, then would I end up with a high concentrated form of the two extracts combined together? I'm trying to make an all natural energy drink. I'm not sure if i should just mix the powdered herbs or use some chemical process to combined the herbs into a concentrated form. I figured I would need high doses of the herbs in order for the drink to have an affect. So, should a chemical process to combined my ingredient, or just use herb tictures to avoid a powdery taste?


texts: How do zeolites catalyse the cracking of hydrocarbons?

texts:
Been learning about catalytic cracking of long chain hydrocarbons into shorter chain hydrocarbons, in which the catalyst zeolite is used so that the temperatures needed for the cracking are much lower (about $500\,^\circ\text{C}$ instead of $700\text{-}1000\,^\circ\text{C}$). The question is, how exactly does the zeolite help with the cracking process? Everywhere I look doesn't give a detailed answer, just that zeolite is porous, riddled with holes that can trap molecules. The only clue I have to the process I suppose is this video

https://www.youtube.com/watch?v=nTse5_wXup4

which shows an animation of some hydrocarbons whacking against a tunnel-like zeolite into smaller chain carbons. But to me the video can't be that accurate, because the whole thing seems out of proportion, the hydrocarbons are made from hydrogen and carbon which are pretty small atoms, whereas the zeolite is made from aluminium or silicon which are much larger. Even if this is the actual way it works, why not just have a plane surface to hit the hydrocarbons off to break them then? (Perhaps the rate of collision is much smaller? I'm just pulling at straws here.) Any light shed will be helpful, thanks.


texts: What should be the name of this substituted cyclopentane?

texts: I think its name is 5-amino-3-bromo-4-chloro-2-hydroxycyclopentan-1-carbonitrile. Is that correct?


texts:
Why do the bond dissociation energies of the O−H bonds in water differ? Is it related to an increase in lone pair-bond pair repulsions upon the breaking of the first O−H bond (decrease in stability, so lesser energy is required to break the bond)?

Bond dissociation energy of the first O−H bond: 502 kJ/mol

Bond dissociation energy of the second O−H bond: 427 kJ/mol


texts: How to evolve hydrogen from aluminum when the household drain cleaner is safe to use on aluminum?

texts: I live in Japan. I would like to evolve hydrogen to demonstrate to my son buoyant balloons (we have helium aerosol cans here which barely fill one balloon). There are drain cleaners here with low concentration of sodium such as up to 4% and say safe for aluminum (probably the calcium hydroxide also contained). I have obtained some wire and batteries and I think electrolysis could help- what should I do  for the best chance of evolving hydrogen?


texts:
Would the atomic absorption from FAA for Sulfur be from 3s2 -> 3p4 or 3p4 -> 4s0?

I think according to the electronic partition function, there would be zero electrons in the 4s0 state at the temperatures for ICP
N = pe^(-E/kT), where p is the # of electrons in the state.

Perhaps I'm thinking about this wrong.


texts: How to calculate the temperature from heat of neutralisation?

texts:
The heat of neutralization of $\ce{HCl(aq)}$ by $\ce{NaOH}$ is $\pu{-55.9 kJ/mol}$ $\ce{H2O}$ produced. If $\pu{50ml}$ of $\pu{1.6M}$ $\ce{NaOH}$ at $\pu{25.15^\circ C}$ is added to $\pu{25ml}$ of $\pu{1.79M}$ $\ce{HCl}$ at $\pu{26.34^\circ C}$ in a plastic foam cup calorimeter, what will be solution temperature be immediately after the neutralization reaction has occurred?

I'm always overwhelmed by the question if it provided me too much information. I don't know what equation and concept to use first. (But I know all related-equations in this unit.)
I need a detailed explanation to understand! I'm not sure which one is the initial temperature? $\pu{25.15^\circ C}$ of $\ce{NaOH}$ or $\pu{26.34^\circ C}~\ce{HCl}$?


texts: Why does Potassium Chloride less soluble than Sodium Chloride in water, isn't it supposed to be other way round? Since Potassium Chloride would be more ionic than Sodium Chloride?


texts:
What is the function of silica, $\ce{SiO2}$ in the equation
$$\ce{CaO + SiO2 -> CaSiO3}$$
  a) A basic oxide
  b) A acidic oxide
  c) A reducing agent
  d) An oxidising agent

Please explain.


texts: Is it true that all of the physical laws and mathematics needed to describe chemistry are known?

texts:
This question comes from a rather famous quote by Paul Dirac which goes like this,

  The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.
  -Paul M. Dirac

I have seen this quote a number of times and it never struck me as being peculiar because to my knowledge the actual physical laws describing everything we care about in chemistry are known. However, I was recently at a talk (it was a presentation to one of my classes, but the speaker gave a talk about his research) about density functional theory, and this quote was shown as a sort of introduction for why density functional theory was developed and is applied as a form of approximation. After showing this quote, the speaker said "well that's not strictly speaking true..." and then moved on and didn't say anything else.

I meant to ask what he meant by this after the talk, but I forgot because I was asking about something else.

So, to expand on this:

Are there any physical laws which are unknown (or believed to be unknown) which directly relate to chemistry?

Are there any mathematics which have not been developed which are necessary to fully describe some aspect of known chemistry?


texts: Would it be possible to produce a non-toxic atmosphere using a coal fire and frozen oxygen?

texts:
A Pail of Air is a classic science fiction short story by Fritz Leiber from 1951 describing how a family survives on an Earth that has left its orbit around the sun, using desparate low-tech methods: a shelter isolated by many layers of blankets and a coal fire to thaw frozen oxygen gathered in the eponymous pails.

I am curious how realistic this scenario is from a basic chemistry and biology perspective. I think not for a number of reasons, but don't know enough to quantify these factors:

Would a coal fire produce enough energy to thaw the oxygen the fire itself uses?
Would the resulting atmosphere (at sufficient pressure for the oxygen to support human life) contain toxic levels of carbon dioxide?
...or carbon monoxide?
How does oxygen at lower pressures affect flammability? Wouldn't it all go up in a blaze at the drop of a hat?


texts:
A while back, I used chemspider.com at some point to get structures from a SMILES string. I found that it wouldn't get some strings, so I switched to chemicalize.org. The site appears to have been taken over and doesn't read SMILES strings anymore. I found this site in this answer, but yet again there are some strings it won't read.

I want to do a SMILES demonstration in a comp lab, so I'd rather have a website instead of having to install a program. Is there any online, free SMILES interpreter?

Edit: I'm looking for an entirely online, no-install-required translator.


texts:
I understand Enthalpy, the exchange of energy between products and reactants. But what is Gibbs Free Energy and Entropy? I know that Gibbs free Energy is the difference between the change in Enthalpy - [(the change in entropy)*the Temperature]. However I am not able to understand the physical meaning. What does this really mean? On the molecular scale where is it stored? If you can make it less abstract than it is right now, that would help a lot.

I am assuming once I understand Entropy, I should be able to understand Gibbs Free Energy. So, my question on Entropy is, where is entropy stored? I know it is the total disorder in the ENTIRE system, not just one molecule, the units for Entropy are J/K, and by disorder I mean the preference of the system to go to a chaotic/disordered state.

So, when solving for Gibbs Free Energy, what are we finally getting by subtracting the energy from the system (dS) from the reactions exchange in energy (dH).


texts: How does gefitinib affect the EGFR(ecptor) and why is there relapse

texts:
Gefitinib has been shown to be an effective tyrosine kinase inhibitor in a fraction (~$10$%) of non-small cell lung cancer patients.

These patients are characterized as having a mutation (usually a deletion or missense) in the EGFR gene affecting the ATP-binding site.

I have two questions:

-- How does gefitinib impede the proliferation and apoptosis pathway? Does it in effect "ace out" the binding of EGF? If this is correct, how does it accomplish that? If not, I would appreciate a brief explanation as to what the successful mechanism is.

-- It seems that (similar to imatinib, another tyrosine kinase used to treat CML) successfully treated patients tend to relapse after a period of time. Why is this?