texts: How do steric effects affect inductive effect in compounds with tetravalent nitrogen?

texts:
I want to compare the electron density on methyl group between tri‐tert‐butyl(methyl)azanium (1) and triisopropyl(methyl)azanium (2), i.e. essentially the inductive effects of $\ce{-\overset{+}{N}R3}$ groups.
$$\underset{\large\textbf{1}}{\ce{Me-\overset{+}{N}(t-Bu)3}}\qquad\underset{\large\textbf{2}}{\ce{Me-\overset{+}{N}(i-Pr)3}}$$
The only difference I see in these compounds is that due to steric effects the bond angle would be greater in compound 1 than in 2. Based on this info alone I am not able to judge which one would have greater electronegativity on $\ce{\overset{+}{N}},$ or so as to say greater inductive effect due to the $\ce{-\overset{+}{N}R3}$ group.
How should I go about comparing the electron density on methyl group in both of these species?


texts: How to determine crown ether cavity size?

texts: I want to determine the cavity radius/ dia of crown ether. Which technique should I follow?


texts: Clarification on the term: coordination number

texts: Based on what I've been reading the coordination number of a complex is defined as the number of atoms/molecules that the central atom is bonded to. However, it is simulaneously said that [FeEDTA] has a coordination number of 6. So which is it. Is the coordination number the number of atoms/molecules, or the number of dative covalent bonds?


texts:
So I'm carrying out the distillation of some essential oil and I have to remove the water content in it. The usual method is using diethyl ether but I'm looking for a greener method.

What can I do?


texts: In terms of remediation, what is sequestration?

texts:
I am reading about use of zero valent iron in remediation of heavy metals.
Is sequestration just a broader term for sorption?


texts: Is this a possible structural isomer for Butene(C4H8)

texts:
Today in school, my teacher was explaining the different types of alkenes. Examples included ethene, propene, and butene.  She also showed us their structural formulas.
I tried to draw butene's formula and came up with this:

Is it correct?


texts: Is the specific heat of salt the same as Na + CL when dissolved?

texts:
I had this question when my friends were discussing how salt influences boiling time.  When crystal salt is dissolved into water, it turns into a single Na and a single Cl atom.  If knew the total heat capacity of the salt I want to add to my water, could I be confident, that when dissolved, total heat capacity I added to the water is equal to the undissolved salt's heat capacity?

On one hand my intuition tells me that heat capacity should remain the same.  Salt is salt.

On the other, doesn't the salt lose a rotational vibration mode when is dissolves into its two monatomic elements?

I am not trained in chemistry, so sorry if this is a naive question.

Thanks!


texts: Formation of a bubble which is not a sphere

texts:
Recently a friend of mine received a project from her college which was like -  "Bring a bubble which isn't spherical in class. ".  Could anyone please suggest how to prepare such a bubble sufficiently big and which can sustain enough. So that she could bring in class.  I confirmed that a soap film(like a cylinder) could also do.
Please help me in suggesting a method and the liquid we should use to develop this bubble


texts: What happens when an explosion can't lead to volume increase of the thermodynamic system?

texts:
What if an explosion is not able to exit the container?

Take a pipe bomb for example; assuming that the pipe bomb was hypothetically made out of such a strong material that the explosion is not able to rip the material apart, what would happen?

Asking this because I was told: NO MATTER WHAT the explosion has to and WILL "exit", but what if it just can't?


texts: What is the oxidation state of nitrogen in nitrate ion and what is its structure?

texts: What's the oxidation state of nitrogen in $\ce{NO3-}$ ion. Simple calculation depicts that it's $+5$. But second period elements never show variable oxidation states. And it's structure is so confusing to me. Some people show dative/co-ordinate bonds, whereas others show a positive charge on nitrogen. Which should be considered as correct one?


texts: Relation between activation energy and temperature sensitivity

texts:
In my reaction engineering textbook (Levenspiel), it is stated that reactions with high activation energies are very temperature sensitive, while reactions with low activation energies are relatively temperature-insensitive. This principle was then applied to a homework problem of ours where for two reaction pathways in competition, at high temperature, the reaction rate of the higher activation energy pathway would dominate, with the opposite being true at low temperatures.

Could someone explain why the high activation pathway dominates at high temperatures? In my mind, I still expect the rate of the low activation energy pathway to dominate due to path of least resistance principle.


texts: Why is diluted sulfuric acid more corrosive than concentrated sulfuric acid?

texts: It is said diluted sulfuric acid can't be stored in iron tank because it is more corrosive than concentrated sulfuric acid. I know there is a oxidation film will be formed for the concentrated sulfuric acid one. So, why doesn't diluted sulfuric acid have a film as well, is it because of the difference concentration of H ions?


texts: How can geometric isomerism arise due to steric factors?

texts: I can see how a double bond and a ring structure can lead to geometric isomerism but can't see the same for steric factors. Could you help? Thank you!


texts: What temperature is required to burn pencil lead graphite?

texts: I tried to burn a bunch of 8B pencil lead in a gas flame the other day. None of it actually caught fire, but being made of carbon (in the form of graphite) should cause it to burn, as graphite is essentially purified coal. What temperature is required to set it burning, and is extra oxygen required?


texts: Does the hydrolysis speed increase when more H+ ions are in the solution?

texts:
In hydrolysis of polysaccharides, does the hydrolysis speed increase when more $\ce{H+}$ ions are present in the solution?

So if I were to use $\ce{H2SO4}$ instead of $\ce{HCl}$ (same volumes) then $\ce{H2SO4}$ will be the most effective?


texts:
I've been studying organic chemistry and I think trans fats are actually more stable than cis fats. This is because the steric hindrance (for trans) would be lower and the molecule energy would be lower too (more stable).

Why are unsaturated fats usually cis at room temperature if the steric hindrance is higher?

Is that because the room temperature provides enough energy to break the pi bond in the double covalent bond (for example) making the molecule rotate and have a isomer of higher energy?


texts:
I just started organic chemistry in university. I have no idea what I'm doing — it's wonderful.

My assignment was to produce $\pu{10g}$ of fluorescein, the theoretical yield is $70~\%$ — I need at least $60~\%$ yield. I've made $\pu{11.07g}$ of product and my lab instructor analysed a sample of my product on the NMR spectrometer, which gave us the following result:

There are some impurities in my product (I know that f.e. $1.12$ is from the impurity and $3.42$ is from the fluorescein, same with $1.00$ and $3.46$) and I have no idea how to use that data to compute purity or actual yield.

Can somebody help?


texts:
When visiting a botanical garden in Stockholm, I stumbled across the following mosaic tile:

I have tried to identify it using MolView, but it does not seem to identify it. Also, I have tried their advanced search (similarity), but that provided no results.

I have also tried searching for it based on SMILES formula on Chemspider.

I am wondering if there any other tools that can help me in finding what substance it is.

Extra context information: it was next to a DNA structure artwork, so I guess it is somewhat related to the evolution, DNA etc.

Question: How can I find out a substance name based on its structural formula?


texts: Number of Sigma Bonds in this Structure Containing a Ring

texts:
(This question was on my last gen. chemistry exam.)

I counted 12 sigma bonds, but the answer was 13. I'm taking this course online so there is no explanation given. Could anyone offer a quick explanation on how this structure could give 13 sigma bonds?


texts: Isopropyl and Butyl Groups - Relative Priorities

texts:
This does not compute for me:

Why would the four-carbon butyl group have a lower relative priority than the 3 carbon isopropyl group?

If we compare the carbons one by one between the isopropyl and the butyl group, we'd run out of carbons in the isopropyl group first! How then can isopropyl possibly have a higher priority than the butyl group?


texts: How to clean out a contaminated aluminum automotive radiator

texts:
I have a very expensive custom made automotive aluminum radiator that has had a mouse or mice nesting inside the top tank.  I have removed most of the nesting material through the top inlet but I want to clear the radiator tubes that may be plugged up with the nesting material (looks like cotton of some sort) and be sure the radiator is flowing water through it as it should. As it is an aluminum radiator I am told they cannot remove the tank and "rod out" the radiator tubes.  The only solution offered by the company is replacement.  The radiator cost about $1200.
I have thought about an enzymatic drain cleaner but am not sure that it will not harm the aluminum radiator internally.  What ideas do you have?


texts: What is the first organic compound to be discovered ? Urea or alloxan?

texts:
It is widely accepted that urea is the first organic compound to be synthesized from inorganic chemicals. Wikipedia states that:

In 1828, the German chemist Friedrich Wöhler obtained urea artificially by treating silver cyanate with ammonium chloride.
$$\ce{AgNCO + NH4Cl → (H2N)2CO + AgCl}$$
This was the first time an organic compound was artificially synthesized from inorganic starting materials, without the involvement of living organisms. The results of this experiment implicitly discredited vitalism — the theory that the chemicals of living organisms are fundamentally different from those of inanimate matter.

But, alloxan (a not-so popular organic compound!) was isolated in 1818 by Brugnatelli (according to Wikipedia) 10 years before the discovery of urea!
So, is urea the first ever organic compound to be discovered or is it alloxan?
I also found a link which claimed that urea is not the first organic compound to be discovered.


texts: Why hydrogen bonds are stronger than Van der Waals forces?

texts:
Why the hydrogen bonds are more intense than Van der Waals forces in the case where the molecules with the Van der Waals forces have a stronger dipolar moment than the molecules with the hydrogen bond?
For example, ethanol (hydrogen bond) has a boiling point of 78 ºC and ethanal 20 ºC (Van der Waals forces) but their dipole moments are respectively 1,69 D and 2,69 D.
I thought the intensity of the hydrogen bond was due to the high polarization of the bond between a small and very electronegative atom like N, O, F, but this is not the case in the previous example, as I understand.


texts: How does alcohol infusion (maceration) work chemically?

texts:
To make liqueurs (e.g. lemon liqueur) you take some fruit and/or plant and let them macerate in pure alcohol to make the alcohol have the fragrance and color of the original ingredient.
How does it work from a chemical standpoint?
Is it simply a process in which the aromatic substances are soluble in alcohol and so the solution inherits their characteristics, or are there (as I expect) more complicated processes at work?


texts:
Q)The derived name of (CH3)4C is

A)Tetramethylmethane

B)2,2-Dimethylpropane

C)Neopentane

D)None of these

The answer was A.

What is a derived name?Never heard of it in any book.

Thanks


texts:
Consider submerging a plate of pure silver in a solution with $\mathrm{pH} = 1$. Does the redox reaction with hydrogen happen spontaneously?

  The composition of the solution is not given.

My attempt:

I considered the standard potential for $\mathrm{pH} = 0$. Since the silver must be oxidised, the reaction happens at the anode.

$$
\begin{align}
\ce{Ag+ + e- &-> Ag} &\qquad E^\circ &= \pu{0.80 V} \\
\ce{2 H+ + e- &-> H2} &\qquad E^\circ &= \pu{0.00 V}
\end{align}
$$

At this point, it is obvious that the reaction cannot be spontaneous since the potential for this cell is less than zero. In fact:

$$\Delta E = E_\mathrm{red} - E_\mathrm{ox} = \pu{-0.80 V}$$

From Nernst equation, the potential for the hydrogen at $\mathrm{pH}=1$ must be negative. Thus the reaction is all the more non spontaneous ($E = \pu{-0.059 V}$).

However, this seems to be wrong. I must be applying the $\Delta E$ wrong, because the solution for this problem states clearly that it is given by:

$$\Delta E = E_\mathrm{red} - E_\mathrm{ox} = \pu{-0.059 V} - (\pu{-0.80 V}) = \pu{0.741 V}$$

This is driving me crazy. Where does the minus sign come from?


texts: What explains the stability of aromatic compounds?

texts:
We are taught in High school that aromatic compounds are highly stable. Why is that true?

Also,
Why are Antiaromatic compounds highly unstable?

Aromatic compounds have 4n+2 (n is a whole number) electrons whereas anti-aromatic compounds have 4n electrons (n is a natural number)

The difference in number of electrons in aromatic and anti-aromatic compounds is just of two, right? So what role do those two electrons play in making the compound so stable?

Please explain in detail.


texts:
My book says a. But i think it is wrong.

Rearrangement is not  possible in anion me, ans also
 there is group migration but here the group has been  divided .


texts: Reaction mechanism of aqueous ammonia with 3,4-dibromopyridine

texts:
I am struggling on how this mechanism would occur. I am aware that the bromine will be removed by for some reason I cannot figure out the $\ce{NH3}$ attaches onto the ring, can anyone prove me with any help?

I have also had a feeling that deprotonation occurs and a benzyne is formed, in which a bromine gets kicked off and one of the $\ce{:NH3}$ attaches onto the ring. Is that correct?


texts:
I was reading up on the buffering effect of the ocean and I was quite confused about how the buffer is able to do anything. The buffer I will refer to is below:
$$\ce{CO3^{-2} +H2O <=> HCO3 + OH^{-}}$$
$$\ce{HCO3^{-} +H2O <=> CO3^{-2} + H3O^{+}} \tag{2}$$

When we have an excess of $\ce{CO2}$ this reaction (between sea water and carbon dioxide) will shift to the right:
$$\ce{CO2 +H2O <=> H2CO3}$$
Thus it should also protonate
$$\ce{H2CO3 + H2O <=> HCO3^{-} + H3O+} \tag{1}$$
However the products of this ionization produce species that are on the opposite sides of Equation 2. Therefore how can the equilibrium shift away to counteract this increase as both sides would have had an increase? I've heard that what should happen is that Equation 2 shifts to the left and decreases the concentration of carbonate ions but I don't understand why it shifts.


texts: Why boiling can't take place in closed containers

texts: I am being told that boiling can't take place in closed containers. Can someone please explain why this is so.


texts: Is there another name for compound "delta-7 sterine", does it exist alone?

texts:
Is there a more common name for "delta-7 sterine"? Is this spelled correct?

I read all over the internet and this compound exists in many articles, but I cannot find any information on it at all, also it doesn't show any information it. Can you please direct me to more information on this compound on what it is, it's more common names, chemical makeup, etc. All I could find in articles is that it's a steroid found in pumpkin seeds.

I would like to buy this compound for experimenting but cannot find a supplier that recognizes this name of the compound, does it exist alone in this form?


texts: Molecular orbital diagram for terminal metal-oxo complex with dative bonds

texts:
I am interested in terminal metal-oxo complexes and their electronic structure, specifically those with coordination numbers of 6, including the oxo ligand.

I know that Fe(IV)-oxo complexes tend to exhibit the 1+2+1+1 $d$-orbital energy scheme shown in the 3rd complex below. With this, I have two questions. Let's consider an Fe(IV) center for consistency.

Is there any way to predict, without performing calculations, what might occur if the ligands are not all identical? Does that change the likelihood of a 1+2+1+1 arrangement?
How does one account for the presence of dative bonds (e.g. if two of the equatorial ligands form dative bonds whereas the rest form traditional covalent bonds)?


texts: Help to kick out the anomaly in proving $Q$ = $K_\text{eq}$

texts:
Consider a hypothetical bidirectional reaction ,  $\ce{aA + bB <=> cC + dD}$
(A , B are reactant(s) and C , D are reaction product(s)) ,
As we know the following expressions $Q=\frac{P_C^c.P_D^d}{P_A^a.P_B^b}$ (Q=Reaction Quotient , $P_x$ = Partial Pressure od $x_\text{th}$ reactant/reaction product) and while the reaction is in equilibrium , $K_\text{eq}=\frac{[C]^c.[D]^d}{[A]^a.[B]^b}$ ($K_\text{eq}$= Equilibrium constant of the reaction , [ ] = Concentration for Ideal Solution or Activity for Non-Ideal Solution) please help me to understand why at chemical equilibrium $Q=K_\text{eq}$ holds ,
although $Q$ and $K_\text{eq}$ both are dimensionless quantity , "The expression of $Q$ contains Partial Pressure and The expression of $K_\text{eq}$ contains Concentration for Ideal Solution or Activity for Non-Ideal Solution"


texts: Why is hydrogen bonding more significant than any other interaction between dipoles?

texts:
Solvents can be categorized as polar and protic. I understand that to be protic there had to be a significantly polar bond involving a hydrogen atom. However, how is the a hydrogen bond different in any way to another dipole-dipole interaction and therefore, what's the need for the distinction between polar and protic solvents?

When considering the hydration enthalpy $\triangle_{hyd} G^{\theta}$ it is not sufficient to simply use the Born equation:
$$\triangle_{solv} G^{\theta}=-\frac{N_Ae^2z^2}{8 \pi \epsilon_0}(1-\frac{1}{\epsilon_r})$$
BECAUSE this only considers Coulombic interactions (i.e hydrogen bonds are not solely coulombic interactions). My textbook seems to suggest that hydrogen bonds are somehow different and more significant. My question is why? Surely there should be no distinction between different polar bonds; what makes $\alpha^{\delta-}-H^{\delta +}$ special?


texts:
"Solubility:    Soluble in water (>25 mg/ml), and DMSO (50 mM)."

It happens to be talking about a drug but that's irrelevant to my question.  Does this solubility statement reasonably indicate that I can dissolve 10mg/ml in water and expect it to stay in solution?  if possible, what does the dmso bit mean?  (maybe mM is a typo of mL?)


texts: How can I reach the two minima connected by a first-order saddle point (transition state) using the Gaussian Software

texts:
Currently, I have several transition state structures for a reaction of the kind A + B -> AB. These TS structures were calculated using Gaussian's own Berny-Optimization procedure and validated as first-order saddle-points by performing frequency calculations. Each of the structures has one, and only one, negative frequency. (It really doesn't matter for this question, but these are DFT calculations and they don't take too long as the system is moderatly small).

To validate and analyze these transition-states in the realm of the bigger picture of the whole PES some more, I would like to perform optimizations starting from them to yield the two minima connected by the transition-state.

Using the Gaussian software the most primitive idea to do this is to perform a regular optimization. I of course did this and, oddly, for every transition state the structure of the product of the reaction is yielded. Conceptually, a true transition-state on the PES should have zero gradient. This means that starting a primitive, gradient-based optimization from a hypothetical, 100% converged transition state should not yield another minimum anyway. I assume that the Gaussian software is in this case too "smart" and "user-friendly": The optimization might not be performed along the imaginary mode or using only the gradients, but most likely all convergence-accelearting black magic available is used. For most cases, this is a reasonable default scenario as it speeds up the optimization towards a truely relevant structure. However, I am also interested in the "path" of the optimization downward the imaginary mode. So this does not work for me.

It seems like the "EigenvectorFollowing" (EF) option for Opt in Gaussian is exactly what is needed to solve my problem. However, I cannot seem to get it to work for a regular optimization starting from the TS structure. Keywords that have failed include:

#p opt(z-matrix,EF) freq b3lyp/aug-cc-pVDZ
#p opt(cartesian,EF) freq b3lyp/aug-cc-pVDZ
#p opt(EF) freq b3lyp/aug-cc-pVDZ
#p opt(calcall,EF) freq b3lyp/aug-cc-pVDZ
#p opt(calcfc,EF) freq b3lyp/aug-cc-pVDZ
#p opt(readfc,EF) freq b3lyp/aug-cc-pVDZ

In every case, the error is the same:

 (Enter /apps/gaussian/g09_D/g09/l113.exe)

 EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-EF-
 EIGENVECTOR FOLLOWING MINIMUM SEARCH
 INITIALIZATION PASS

 ************************************************
 ** ERROR IN INITEF. NUMBER OF VARIABLES (  0) **
 **   INCORRECT (SHOULD BE BETWEEN 1 AND 50)   **
 ************************************************

Searching for this error on the internet yields many results, however they are all realted to MP4 / CCSD(T) optimizations and not to my scenario. I have also tried to specify the molecule as Z-Matrix or Cartesian coordinates.

Note that - speaking plainly - the system in concideration is two organic molecules and previous investigations showed that it is quite boring from a quantum-chemical viewpoint. By this I mean that the structures are "well-behaved" and not biradicals or other quantum-chemical-corner-cases where DFT fails.

I hope that this issue can be resolved by an experienced gaussian user. I am  using Gaussian 09 Rev. E. The first part of my question therefore is how can I use the EF option of Gaussian to perform an optimization along an imaginary mode starting from a transition structure?

Secondly, I still do not have any idea how to reach the "second" minimum connected by the TS (assuming the reaction is concerted, this would be the seperated educts). The only possible approach to tackle this which I can think of currently is to perturb the system manually along the imaginary mode and perform EigenVector-Following optimizations from these perturbed structres. Is there a more elegant way, circumventing manual structural modifications, to yield the two minima connected by the TS?


texts: Why is ammonia still considered polar despite undergoing rapid inversion?

texts:
Here it is stated that a molecule with a rotation axis cannot have dipole moment perpendicular to the axis, as any dipole moment would be changed upon rotation about this axis (which preserves the molecular geometry and hence the dipole).

The ammonia molecule (and other amines) are known to undergo inversion rapidly. When the molecule inverts, its dipole moment would be reversed. So why is ammonia still considered a polar molecule?


texts: Determining amounts of product and excess reagent remaining post reaction

texts:
$$\ce{2FeS2 + 11/2 O2 -> Fe2O3 + 4 SO2}$$
Mass of $\ce{FeS2}$ is $\pu{600 g}$ and mass of $\ce{O2}$ is $\pu{800 g}$. Find the amounts of $\ce{Fe2O3}$ and $\ce{SO2}$ and the remaining amount of the excess reagent.

My Attempt
$$\frac{n_\ce{FeS2}}{2} = \frac{600/120}{2} = \frac{5}{2} \lt \frac{n_\ce{O2}}{11/2} = \frac{800/32}{11/2} = \frac{50}{11}\implies \ce{FeS2}~\text{is limiting reagent}$$
By Mole-Mole Analysis, we have
$$\frac{n_\ce{FeS2}}{2} = \frac{n_\ce{Fe2O3}}{1} = \frac{n_\ce{SO2}}{4}\implies \begin{bmatrix}n_\ce{Fe2O3} \\ n_\ce{SO2}\end{bmatrix} = \begin{bmatrix}5/2 ~\text{mol} \\ 10~\text{mol}\end{bmatrix}$$
$$\text{Excess reagent remaining} = \frac{800}{32} - \dfrac{5}{2}\cdot\dfrac{11}{2} = \pu{11.25 mol}$$
However, my answer does not match with my other classmates. What am I doing wrong?


texts: What is the perfect definition for chirality?

texts:
Why is chirality defined differently for organic and inorganic compounds?

Why are inorganic compounds deemed to be optically active if they have more than one of the same ligands attached to the central metal atom, but glycine is optically inactive for having two $\ce{H}$ atoms attached to the carbon atom?

Finally, what should be the criterion for chirality (optical activity) and the perfect definition for it?

Could anyone explain how $\ce{$cis$-[PtCl2(en)2]^2+}$ is optically active, but the $trans-$isomer is not?


texts: How do I find Rf values & length size of paper in chromatography?

texts:
A student is designing an experiment using paper chromatography. From previous results, she knows that the Rf values for two dyes that she wishes to investigate are 0.72 and 0.80.
It is proposed that the dyes be run on the same piece of paper and, for various reasons, that the sports should have a separation of a at least 1cm at the end of the procedure.
What is the minimum height of the chromatography paper that she should use in this experiment?

Can someone correct my working out. I don't know what the correct answer is.

distance travelled by dye x = $x$
distance travelled by dye y = $y$
distance of solvent front = $p$
$x/p=0.72$ therefore $x = p(0.72)$
$y/p=0.8$, therefore $y = p(0.8)$
$y-x=1$, therefore $y=1+x$
new equation: $1+x=p(0.8)$ where $x=0(0.72)$, if we solve for $p$ we get $12.5$

so the piece of paper should be at-least 12.5 cm long.


texts:
In cresol both $+I$ effect as well as hyperconjugation work together to determine its acidity. When the methyl group is present in the ortho- and para-position both of them can act upon phenol.

Hyperconjugation as a rule dominates which increases the electron density of the aryl. This makes it less acidic because the conjugate base is now less stable. But when its meta-cresol, hyperconjugation no longer works.

Why is it so? It happens even though an empty $\mathrm{p}$-orbital is present near the $\alpha$-hydrogen. What else does it need?


texts: how do electromeric / inductive effect theories compare with resonance

texts:
Back in high school, long time and many seas away, I learned about electrons moving within organic molecules based on electromeric and inductive effect. Googling them today, I found that they are deemed obsolete by IUPAC, but still used, mainly in Russia and India.

True, today, for my limited chemistry needs, I can make do with resonance. But how did +E, -E +I and -I become obsolete? Is a mere statement of the various resonance structures enough to fully convey the information stated by describing those effects, or were they rejected for some inaccuracy?

Also, were these effects part of Chelintsev's "Marxist chemistry"? That would explain their historical and geographical extent.


texts: Making Lyophilized Cake Lookalike using household ingredients

texts:
I'm working on a machine learning model to identify flaws in vaccines in lyophilized cake form. To train the model, I need a number of samples that look something like this:

I have vials, but I'm having trouble making a suitable cake – I need something that will stick to itself when dried...

What I've tried so far:

Salt dissolved in water/isopropyl alcohol
Baking soda dissolved in water/isopropyl alcohol

Both of these turned back into powder (instead of caking) when dry.

Next, I'm considering using powdered detergent, adding water, then letting it dry...

How would you recommend making this using common household ingredients?


texts:
Sn2 has simultaneous bond breaking and forming because it's concerted.

Sn1....does it occur with a loss of stereochemistry at the reactive center? An online textbook says so.

Sn1 has both retention and inversion of config. So don't know which one fits Sn1. Only one statement is true for SN1.

Which of the energy diagrams shown below represents an exothermic SN1 reaction?

It would be graph A because Sn1 is stepwise two steps. And it's exo because of -E?


texts:
I have a PVC inflatable device (a custom made inflatable pillow) which is, according to the spec sheet, made out of PVC. The PVC material itself, however, is not the one you'd find on usual swimming rings or such, but something closer to that of the PVC pipes (matte texture, white color).

The problem I encountered is, after some time of storage (deflated of course) in a dark and dry room, some kind of an oily fluid appears on the surface of the device.

Initially I thought that, as it is a pillow, it might have accumulated some of the body sweat over time, and after some time it came out as the material was returning to its original size after being stretched due to inflation. So I thoroughly washed it, but after a couple of days of storage, oily stains can be seen again on it's surface. I didn't kinda think it through, but it might have been helpful to collect the accumulated fluid before I washed it off to run a pH test on it (can't do much other tests at home).

So, may that be a sign of PVC degradation of some sort, and if so, what is that? This occurs whether it's stored in a polyethylene bag or just plain put on a wooden shelf with nothing in contact.

I was looking in various sources but most only specify that PVC degrades either under higher temperatures (above 60ºC) or in contact with quite agressive fluids.

Picture of plain material texture:

Picture of material with stains that appear (reflective):


texts:
I was researching the Kyshtym (nuclear) Disaster, and it said that it released 20 MCi (20 megacuries) of radiation into the air in a dust cloud.
I read from this Yahoo Answers answer that:

The curie is the old unit of activity and a very big unit it was.
1 curie = 3.70 x 10^10 disintegrations per sec.
In today's units 1 curie is about 30 Giga Becquerel.
So a curie of any radioactivity (alpha, beta or gamma) would fry you.
A sealed microcurie source could be safely handled.

If a single curie is this powerful, then what would twenty million curies (a 20 MCi) be like? Could you give any examples of events that exemplify this scale of radiation and damage (if you can't think of any real ones, then maybe a theoretical example)?


texts: How to deposit a durable layer of sensing molecules in a PVC matrix on the tip of an optical fiber?

texts:
Here is the situation that I have been tacking for weeks and I have still not understood.

We are trying to understand how to do this:

  This mixture for the preparation of the "LI–PVC" was obtained from a
  batch of 80 mg of poly(vinyl chloride), 160 μl of tributylphosphate
  and 20 mg of Lophine dissolved in 2 ml of freshly distilled
  TetraHydrofuran (THF).

Paper:
http://www.sciencedirect.com/science/article/pii/S014381661400089X
which refers to :http://www.mdpi.com/1424-8220/8/2/847

We have no idea how to do this, since we dont have any step/by/step instruction, reaction time, environment we need to maintain for this.

How do we go about identifying this process and replicating this mixture. This is very critical to us. Any help on this matter would be of immense help, if you have a resource which may have be able to shed some light on this. It would be of help as well.

Many Thanks


texts: In my lab experiment for the synthesis of Aspirin we used hot water to quench the reaction. Why wouldn't we use cold water but hot water?


texts: Charge and spin multiplicity change in IRC search

texts:
I have successfully isolated the TS for a radical cation catalysed C-C bond formation using Gaussian with input

1 2

for charge and spin multiplicity.

But when I do an IRC search with the correct input for charge and spin multiplicity (1 2 as above), the IRC log files terminate normally but when seen on GaussView, it says the molecule is neutral with singlet spin.

Is this a problem with GaussView? Will it affect the interpretation of the IRC in any way? In other words, does the IRC search still occur on the doublet PES or has it (somehow) gone to the singlet PES?


texts: Partial hydrolysis of aluminium chloride

texts: What is the meaning of partial hydrolysis of anhydrous aluminium chloride? What does the partial term signify?


texts: Finding pH after dilution of acetic acid

texts:
We have $\pu{10 L}$ of solution of $\ce{CH3COONa}$ with concentration $C = \pu{1 M}$ and $\mathrm{pH} = 10$. Then we add $\pu{90 L}$ $\ce{H2O}$. What will be the pH of the new solution?

My work:
\begin{align}
  \ce{CH3COONa &<=> CH3COO- + Na+}\\
  \ce{CH3COO- + H2O &-> CH3COOH + OH-}
\end{align}
We have $\pu{1 M } \ce{CH3COO-}$ and let $x$ denote the concentration of $\ce{OH-}$. If the $\mathrm{pH}$ of the solution is $10$, it's implied that
$$\mathrm{pOH}=4\iff-\log_{10} x=4 \iff x=\pu{10^{-4} M}.$$
I know I have to use that the amounts of substances didn't change, so $$C_1V_1 = C_2V_2,$$
but I don't know what values I have to put in there. Is the $x$ I found my $C_1$?


texts: Triple Point of a compound and critical point

texts:
Is it necessary for all compounds to have a triple point? Also, how is the triple point determined?
Suppose a substance does not have a triple point, so how do researchers agree on the impossibility of existence of a triple point in such a case? Also, can there be multiple triple points for a compound?
Also, since the vapour equilibrium curve ends at point E, what is the phase of water beyond that point?


texts: How to debug a failed Gaussian IRC calculation?

texts:
During IRC calculation I found the following error message. Anybody can help me?

IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC-IRC

Error in corrector energy =          -0.0000002157

 Magnitude of corrector gradient =     0.0003105753

 Magnitude of analytic gradient =      0.0003306121

 Magnitude of difference =             0.0001786220

 Angle between gradients (degrees)=   32.1573

 Pt  9 Step number  20 out of a maximum of  20

 CORRECTOR INTEGRATION CONVERGENCE:

   Recorrection delta-x convergence threshold:    0.010000

   Delta-x Convergence NOT Met
 Maximum number of corrector steps exceded.

 Error termination via Lnk1e in /home/adhikary/g09/l123.exe at Sun Aug 21 05:49:50 2016.


texts: Which alkene has a higher Cahn-Ingold-Prelog priority in (2Z,5E)-hepta-2,5-dien-4-ol?

texts:
How do I determine whether the central carbon of this compound is (R) or (S)?

On both the sides of carbon, the groups are same. They differ only in the relative position of hydrogen atoms. On what basis do I assign priority in these groups?

Does the R/S nomenclature for the middle carbon really depend on E/Z nomenclature of the alkenes, in such cases of stereoisomerism? Or is there an entirely different argument in such a case?


texts: Conversion of a value between g/gmol and lb/lbmol

texts:
I am doing some air emissions calculations and I really just have a bad feeling about my results.  By definition, molecular weights are given in $\pu{g/gmol}$.  For the substance I have, I was told by a technical contact at Citgo that this material has a molecular weight of $\pu{140 g/mol}$ (which should be $\pu{g/gmol}$).  Whenever I convert this $\pu{lb/lbmol}$ (which is required for this particular equation), I'm getting a value of $\pu{0.3086 lb/lbmol}$.  There are 453 grams in a pound.  Is it not correct to divide 140 grams by 453 grams to get the total number of pounds?

My final result for annual emissions is pretty low.


texts: Comparing equilibrium constants between acetone and benzaldehyde in nucleophilic addition reaction

texts:
My teacher told me that the $K_\mathrm{eq}$ of acetone is greater than that of benzaldehyde in nucleophilic addition reaction.
But I am not able to understand how is this possible. Acetone has a +I group attached to it, so it will decrease the reactivity of carbonyl. If we talk about benzaldehyde, it has a −M group. Can someone tell what is the correct reason behind it?


texts: I have a nutty neighbor that said someone told them to put liquid lye into their above ground pool.  I said it would eat away the lining, their answer was to only use a little bit.


texts: How can a molecular orbital with a nodal plane still be considered "bonding"?

texts:
Explain how a molecular orbital can have a nodal plane and still be a bonding molecular orbital.

I understand the concept of how nodal planes are formed and how they have a probability of 0 when trying to find an electron in the nodal plane, but I don't understand how it can be considered a bond especially since these nodal planes are usually called "anti-bonding". This question itself seems contradictory and I'm having a hard time trying to understand how this is possible.


texts: How must elemental symbols be ordered in the formula for a compound?

texts: An online problem asked me to find the molecular formula of a certain substance given its mass composition. I found that it was $\ce{N_5P_5Cl_{10}}$. It was incorrect and told me the ordering of my symbols was wrong. I switched it to $\ce{N_5Cl_{10}P_5}$ because that's the order that they appear on the periodic table. It marked me wrong again and told me that the answer was $\ce{P_5N_5Cl_{10}}$, but didn't tell me why it must be ordered this way. Is there a convention that must be followed here?


texts: Have "molecular clusters" for azeotropes been identified?

texts:
A different question about azeotropes got me thinking about this point again. Azeotropes have a very specific composition so it seems that the azeotrope ought to have some sort of physical structure. It seems to be a "molecular cluster" of some sort.

The azetrope for water and ethanol is about 95.5% ethanol by weight. A little fiddling and it seems that the ratio is 8 ethanol molecules to 1 water molecule. Is there some particular physical configuration of molecules to which this would correspond?


texts:
I have a can of compressed air. The type you use to clean the insides of computer. It's "100% ozone friendly" and "pure compressed gas". So I assume its everyday regular breathable air. I used it to try blow out a candle. It had precisely the opposite effect.

Why?


texts: What will be the major product of the following dehydrohalogenation?

texts:
Question:-

My Attempt:-
I believe the answer should be C, because even if 2-butyne is formed $\ce{NaNH2}$ should cause it to rearrange into a terminal alkyne. Hence the answer should be 1-butyne. But the book says B as the answer.

Please correct me.


texts:
How small is the smallest known carbon ring containing only double bonds?

The stress from the double bonds makes small rings impossible to make something like cyclohexahexaene so I want to know how large the ring would need to be so the stress is small enough such that the ring can be made.


texts: What is the correct chemical formula for monosodium glutamate?

texts:
Recently, I am interested with home materials and I discover that the chemical symbol for MSG or monosodium glutamate is $\ce{C5H8NO4Na}$.
My problem is shouldn't it be $\ce{NaC5H8NO4}$ as we always write the metal first before the non-metal?


texts: Gas-Phase Functionalization of Carbon Nanotubes

texts:
I'm new to the subject of carbon nanotubes; However, I recently studied a little about them. But I failed to understand the gas phase functionalization.

As I understand, this technique is used to improve the solubility of the nanotubes.

However, I failed to understand the chemistry and physics of these processes so resumidad, considering that there have been many experiments in this field, but I failed to understand the basis of this process.

Someone could explain?

Another question: What causes that the nanotubes are hydrophobic?


texts: Why is the rate of a reaction always positive and why?

texts: Why rate of reaction can never be negative? And why rate is an experimental derived expression?


texts: Does pyrite retain the magnetic properties of its element iron?

texts:
You are walking in the mountains and pick up what looks like a nugget of gold. You're aware that fools gold (iron pyrite, $\ce{FeS2}$) exists. Create an experiment to test if this is pure gold or iron pyrite.

The simplest thing I could think of is to do a magnetic test on the assumption that if it was fools gold it would be attracted to a magnet due to the presence of iron. A quick google search reveals this to be true but I have a sneaky suspicion that I got lucky in assuming, because there is iron in $\ce{FeS2}$ the compound will be magnetic.

I'd like to know if chemical compounds retain the properties of their individual elements or if the compound gains completely new properties some of which may or may not be properties of the elements.


texts: Second ionization energies of copper(Cu) and silver(Ag)

texts:
The ionization energies of copper and silver are

First ionization energy: Cu-745.5 kJ/mol Ag-731.0 kJ/mol
Second ionization energy: Cu-1958 kJ/mol Ag-2073 kJ/mol

Now, looking at the ionization energies, it is quite clear why $\ce{Cu^2+}$ is formed readily but only $\ce{Ag+}$ is usually observed.
The first ionization energies can be rationalized by the fact that Ag is larger in size than Cu.
However, the second ionization energy of Cu should be higher than second ionization energy of Ag because in case of Cu the electron is being taken from the 3d orbital while it is being taken from 4d orbital in case of Ag. 4d orbital should be larger than 3d orbitals and so, the energy required to pull electron from 4d orbital should be lower than that in case of 3d orbital.
Is there any explanation to this anomaly?


texts: Number of gauche interactions in an alkane

texts:
The textbook states that (a) has 2 gauche interactions, (b) has 3 gauche interactions and (c) has 3 interactions.

But how do we determine this? I thought a gauche interaction would occur when two methyl groups are side by side, however I'm unsure where these answers are coming from.


texts: Galvanic cell involving a hydrogen electrode and copper electrode in sodium hydroxide

texts:
A galvanic cell consists of a standard hydrogen electrode and a copper
  electrode.  Suppose that the copper electrode is immersed in a
  solution that is $0.100\ \mathrm{M}$ in $\ce{NaOH}$ and that is saturated
  with $\ce{Cu(OH)2}$. Find cell potential

  $\begin{alignat}{2}\ce{2 H+ (aq) -> H2 (g)}\quad E_0 = 0.00\ \mathrm{V}\\
\ce{Cu^2+ (aq) + 2 e- -> Cu (s)}\quad E_0 = 0.34\ \mathrm{V}\end{alignat}$

  $K_\text{sp} = 1.6 \times 10^{-19}$ for $\ce{Cu(OH)2}$

I started by doing writing off the Nernst equation and realized I do not have $\ce{Cu^2+}$ concentration, and since I’m given $K_\text{sp}$ of copper, I assumed I should use it to find copper (after doing ice table for $\ce{Cu(OH)2 -> Cu^2+ + 2 OH-}$). But then I stumbled on $0.100\ \mathrm{M}$ of $\ce{NaOH}$, what should I do with it? and what does saturated mean in the given context of the problem?


texts: Why two ( or more) gases have proportional volumes at constant pressure and temp.? (Avogadro's Law)

texts:
I am in real confusion over Avogadro's Law..

In some of the problems I did on gas laws, there are the number of moles of the gas, the temperature. and the pressure. And it expects me to find the volume of gas.

But then in other problems there everything else is given including the volume of the container ( instead of the gas itself) and then something else is expected to be found.

The confusion starts here. If any gas occupy the volume of volumes, always, then why will volume change according the combined gas law?

In one of my previous post, I learned that volumes of different gases won't be proportional (meaning all of them will occupy equal space) unless the condition of constant tempt and pressure is reached.

But what really happen when constant tempt and pressure are reached? Do individual gases just separate themselves from one another? Because in order for their volume ratio to be equal to anything other than 1, their volume must be different.

you only have to answer the question in the title, the others questions are intended to help you understand what I mean. Sorry for the possible confusion

a link to my previous post


texts: How to desalinate seawater at freezing temperature or high pressure?

texts:
The deep ocean depths have very high pressure and freezing temperatures. Could one or both of these characteristics be used to desalinate seawater?

Reverse osmosis uses high pressure to separate salt from seawater to make
freshwater. Freezing seawater can also make freshwater. Less energy would
be utilized in both processes.


texts: Regioselectivity in Kharasch addition of bromotrichloromethane

texts:
When hex-1-ene is treated with bromotrichloromethane in the presence of a peroxide initiator (e.g. dibenzoyl peroxide), what is the regioselectivity of the addition?

I know that the radical addition of HBr to an alkene is considered anti-Markovnikov, but is this reaction considered a Markovnikov or anti-Markovnikov addition?


texts:
Are pen $\mathrm{pH}$-meters accurate? I know there are large table-top $\mathrm{pH}$-meters, but I keep seeing these small $\mathrm{pH}$-meters online that can read up to 0.1 units. My question is if these $\mathrm{pH}$-meters (look pretty cheap) are accurate or should I get the large table-top $\mathrm{pH}$-meter for my experiment (will need accuracy minimum of 1 decimal place).

(Edit: Is there also a minimum volume of sample I need before I can test it with a $\mathrm{pH}$-meter?)


texts: Why do some gases liquefy easily under pressure and normal room temperature?

texts:
Is this a combination of Boyle's and Charles' Laws or simply one of them?

I'm confused as to which applies. I don't feel I fully understand the implications of both laws individually and I'm wondering why it's easy to take a gas like butane and liquefy it under pressure at "normal" temperatures and why other gases need to be cooled to extremely low temperatures or very high pressures to liquefy.

I understand that temperature, pressure and volume are all related, I just don't know which rules apply and how and how they all interact. How do these laws apply to changes of state from gas to liquid?

I'm sure this is stuff I forgot from 10th grade but I'd love to hear an explanation again.


texts:
I'd like to preface this with a declaration of my understanding that this is not necessarily possible.

I was wondering if anyone knew of a chemical clock reaction where the period before the first change (the induction period?) is very long (between 3 hours and a day) and the change is à la Landolt or Old Nassau reactions (i.e they cross a concentration threshold to create sudden color change).

Bonus Question:
Is there any remote possibility that a reaction like this can happen in pigments or dyes once they are absorbed by a cloth?


texts: Do almonds smell like they do because of cyanide?

texts: I am guessing so otherwise it is quite a coincidence that cyanide smells of bitter almonds. And if so, are large quantities of almonds over a long period safe?


texts: Comparing the reactivity towards aromatic electrophilic substitution reaction

texts:
In the following pairs of molecules, which is more reactive towards electrophilic substitution reaction?

1)  1,4-dinitrobenzene or 1,3-dinitrobenzene (don't consider the ortho isomer)

2)  benzene-1,3-diol or benzene-1,4-diol (don't consider the ortho isomer)

3)  4-methylphenol or 3-methylphenol

4)  4-nitrotoluene or 3-nitrotoluene

I am having a conflict of concept.

In the first pair of molecules, according to resonance the presence of one nitro will make C3 negative and C4 positive. So if another nitro comes at C4 then the positive charge at C4 will intensify as nitro draws more electron density. If the second nitro comes at C3 then the negative charge at C3 will be absorbed by nitro. So which of these will reduce the electron density on benzene more.

In my opinion 1,3-dinitrobenzene will have less electron density on the benzene ring as (C3 is already negative due to nitro at C1) much of the electron density at C3 is absorbed. But in 1,4-dinitrobenzene the second nitro group is absorbing electron density from C4 (in which electron density is very less already due to presence of nitro at C1). So since the electron density is less at C4 then it won't be able to take much electron from ring (as its already positive and deficient of electron density).

If my concept is wrong with respect to above context, please correct me.

All of the remaining isomer pairs have same problem, but each is a bit different. I would like an explanation for each answer and especially the 1st one in detail. And try not to provide an answer by directly copying from a source (especially large) thanks.


texts: Major product of mononitration of 3-methylphenol

texts:
From NCERT Class Chemistry Part 2:

Example 11.5
Write the structures of the major products expected from the following reactions:
(a) Mononitration of 3-methylphenol
(b) Dinitration of 3-methylphenol
(c) Mononitration of phenyl methanoate.
Solution
The combined influence of $\ce{-OH}$ and $\ce{-CH3}$ groups determine the position of the incoming group.

Since $\ce{-OH}$ and $\ce{-CH3}$ are o,p-directing groups, shouldn’t the major product be 3-methyl-2-nitrophenol? Why not?


texts: Why is aluminium oxide solution amphoteric?

texts:
Is Aluminium oxide solution amphoteric due to aluminium's electronegativity being in between 1.5 and 2.1.
If so why?
I believe it is because a AL-O-H molecule is made and it can either disassociate into a aluminium cation and a hydroxide, or a aluminium oxide anion and a proton. In this case the Al-O-H disassociates into both giving amphoteric properties, but how does electronegativity affect this?


texts: Relative strength of intermolecular forces

texts:
My attempt at a solution:
First I look for hydrogen bonds:
The only compounds with hydrogen bonds are the second and fourth ones, so they have the strongest intermolecular forces. The second must have stronger intermolecular forces since it harbors three hydrogen bonds, while the fourth only has room for two.
Then I look for dipole-dipole interactions:
The first compound has the potential for a dipole-dipole moment. It would be the third strongest.
Then I look for potential for London-dispersion forces:
The third compound and The fourth experience London-dispersion forces. But I'm stuck on discerning which is stronger.
So, my working solution is: 3, 5, x, 4, x


texts:
Why cathode rays are produced if pressure of the gas discharge tube is lowered to about $10^{-4}$ atm?
How bombardment of glass of gas discharge tube from cathode ray result in a faint glow?


texts: I know that volatile substance creates smell but how a good smell produce? Is there any common characteristics of the compounds having good smell?


texts:
In ACS Sustainable Chem. Eng. 2018, 6 (10), 12542–12561, I saw the term "coexistent metals", but I could not find a definition for that on the Internet. So what does it mean?

Karapinar et al. utilized ammonium-loaded zeolite as a seeding material for precipitating calcium phosphate and suggested the possibility of using the precipitate-ammonium loaded zeolites as fertilizer. The efficiency of chemical precipitation is affected by alkalinity, organic matter content and the coexistent metals.


texts: Reaction Of Grignard's Reagent with Acyl Chloride

texts:
My organic chemistry book says that Grignard reagents react with acyl chloride just as hydride reagents.
Further in an in-text question

now using above theory, my answer is

But Answer in Solution Manual Is


texts: Standard Heats and Free Energies of Formation and Absolute Entropies of 2-Chloro-2-methylpropane

texts:
Does 2-Chloro-2-methylpropane have standard heats and free energies of formation and absolute entropies values in a liquid state?
http://www.wiredchemist.com/chemistry/data/thermodynamic-data
This website only provides the values in gaseous state and I can't seem to find the values for the liquid state anywhere.


texts: Oxidation of acetophenone to benzoic acid

texts:
According to the solutions manual, the oxidation of acetophenone to benzoic acid can be achieved through addition of chromic acid and application of heat.

The solutions manual refers me to a section in the book which explains that when a benzylic hydrogen is present, a strong oxidizing agent combined with heat can perform oxidative cleavage.

Problem is that I don't see any benzylic hydrogens on acetophenone. Neither does its enol tautomer have any benzylic hydrogens ...

So, how is the oxidation of acetphenone to benzoic acid possible given what the book and solutions manual has told me? Self-consistency aside is this even a possible reaction?


texts: Why are the boiling points of aldehydes less than those of ketones?

texts: Both aldehydes and ketones have a carbonyl group, but since the carbonyl group of ketone is between alkyl groups, wouldn't it be more difficult for it to form hydrogen bonds than aldehydes? Why then, do aldehydes have a higher boiling points than ketones?


texts:
What equipment can I put a substance or substrate under vacuum pack?
After buying this SERS silver substrates (which can rapidly decay in air). I need to immediately put them in vacuum packaging or container. How do I do that?


texts: How to understand MO diagrams for cationic octahedral transition metal complexes

texts:
I am having problems understanding the construction of MO diagrams in octahedral transition metal complexes within ligand field theory (LFT) when the metal center is asumed as an cation:

I am completely fine understanding the MO diagram when the metal is neutral and thus the (say) 3d, 4s, 4p orbital energies are above the ligand orbitals as shown e.g. here:

http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch12/ligand.php

However, when the metal becomes cationic, wouldn't the metal orbitals be significantly lower in energy?

In textbooks, you find quite a few pictures like these:

However, when I perform some quantum chemical calculations (it does not really matter if based on Density Functional Theory or Hartree-Fock), the metal orbitals drop significantly below the ligand orbitals (as you would expect).

With such an energy difference, the metal and ligand orbital should not be able to interact properly as they don't match energetically.

Consider for example orbital energies of [Fe(H$_2$O)$_6$]$^{2+}$ on BP86/SVP level of theory:

HOMO [Fe(II,LS)(H$_2$O)$_6$]$^{2+}$ : -12.0997 eV
HOMO [(H$_2$O)$_6$]            :  -4.7910 eV
HOMO [Fe(II,LS)]$^{2+}$       : -25.9057 eV

Now, if Fe is assumed neutral, the problem more or less "vanishes" as the metal orbitals rise in energy and the diagram makes way more sense:

HOMO [Fe(0)]             :  -5.1303 eV

However, this is not what the diagram shows.

Can you help in explaining the discrepancy?

Is the MO diagram making things way to easy?

Is the assumption of a cationic metal center non sensible?

Are orbital energies overrated and cannot be used for problems like these?


texts: More acidic - protonated carbonyl or protonated hydroxyl?

texts:
Consider two acetic acid derivatives, one with a protonated carbonyl oxygen and one with a protonated hydroxyl oxygen.

An argument for the one with the protonated hydroxyl oxygen being more acidic is as follows:

This structure has a lone pair on its protonated hydroxyl oxygen and the oxygen is adjacent to an $sp^2$ carbon. Therefore we can draw an extreme resonance structure in which the hydroxyl oxygen has a +2 formal charge. No such "extreme" structure exists for the one with the protonated carbonyl oxygen.

Now, we can definitely draw this resonance structure, but its contribution is likely very small and bordering on insignificant. I can't see how delocalization of electrons away from a highly electronegative, positively charged oxygen can help stabilize it.

Therefore: Which is more acidic? The argument that the protonated hydroxyl one should be more acidic seems to be flawed at best.


texts:
Find the EMF of the following cell :
  $$\ce{Pb(s)}, \ce{PbSO_4}|\ce{SO_4^{2-}}(\pu{0.100M})||\ce{Pb^{2+}}(\pu{0.004M})|\ce{Pb(s)}$$
  Given:  $E^0_{\ce{PbSO_4|Pb,SO_4^{2-}}}=\pu{-0.359V}$
  and $E^0_{\ce{Pb^{2+}|Pb}}=\pu{-0.126V}$

I first found the $\ce{Pb^{2+}}$ concentration in the oxidation half cell using the sulphate ion concentration and the solubility product of lead sulpahte ($2.53\times10^{-8}$) and found the concentration to be $(2.53\times10^{-7})$
And accordingly $E^0_{\text{cell}}=0.359-0.126=0.233$
Then using the Nernst equation,
$$E_{\text{cell}}=E^0_{\text{cell}}-\frac{RT}{nF}\ln\frac{[\text{Products}]}{[\text{Reactants}]}$$
And substituting,
$n=2$,
$[\text{Products}]=2.53\times10^{-7}$,
$[\text{Reactants}]=0.004$,
$T=\pu{298K}$,
$R=\pu{8.314JK^{-1}mol^{-1}}$, and $F=\pu{96500C}$. Hence, I got $E_{\text{cell}}=\pu{0.357V}$

Whereas, the answer given in my book is $E_{\text{cell}}=\pu{0.133V}$.

So, is my answer correct or have i  misunderstood something?


texts:
From school, I remember a very important rule: first you need to pour the water and then the acid (when you need to mix them) not vice-versa. This is because otherwise the aсid becomes very hot and splashing may happen.

So, why does it get hotter when water is poured into it? What reaction takes place?


texts: Why does electronegativity increase across a period?

texts: What explains why electronegativity increases as you move across a period? Does it have something to do with the shielding effect of added electrons?


texts: Activated Carbon - Desorption in sunlight?

texts:
I have some activated charcoal pads or small "pillows" that can be used to adsorb odors and chemical fumes from different materials.

The instructions say to put them out in sunlight to reactivate them once they have been used for a while.

What is the mechanism whereby sunlight is able to reactivate the charcoal?

I tried googling but could not find a definitive answer. I ended up assuming it must be just heat that forces the gasses trapped in the charcoal to come loose and evaporate, thereby restoring some of the adsorption potential. Is that the mechanism or what is the sorcery going on here?


texts: Predicting the pH of a weak acid and weak base solution

texts:
I know that it is possible to predict whether combinations of acids and bases will be acidic, basic, or neutral:

weak acid (WA) and strong base (SB) reacts basic
strong acid (SA) and and weak base (WB) reacts acidic
SA and SB reacts neutral

How does a WA react with a WB? I've been told that it isn't neutral. How do you predict what it is and why is it not neutral?


texts: Change of ionic packing upon crystals are pressurized

texts: When rock salt crystal is pressurized, its FCC structure changes to BCC structure whereby coordination ratio changes from 6:6 to 8:8. At the same time packing efficiency of the crystal decreases from 74% of FCC to 68% of BCC. So will the crystal actually expand or contract during this process?


texts: Do amino groups need to be protected during a Clemmensen reduction?

texts:
In class, we learned about the Clemmensen reduction of carbonyl groups to the corresponding hydrocarbon. This is all well and good, except that it would also seem that the conditions used in the Clemmensen reduction might also affect other groups, such as the reduction of nitro groups to amino groups.

Generally, would a Clemmensen reduction have any affect on either an aromatic or aliphatic amino group within the compound? If so, I am assuming that a protecting group would then be necessary. I know that nitro groups will be reduced to amino groups, and am also wondering if they would then be further acted upon by the reaction conditions.


texts:
This is my first post, so please bear with me.

At work I have some chlorobutyl plungers that I need to clean from any residual material that might be left after production.

A colleague of mine told me that he has seen a GMP (Good Manufacturing Practice) description of how to clean chlorobutyl plungers, but was unable to find it. It relates to pharmaceutical industry and the standard approved ways of working. The plungers I am referring to are commonly used in penfill cartridges for subcutaneous injections.

Any advice on how to clean the chlorobutyl plungers (e.g. with what chemicals, under what conditions) to ensure that there are no residual solutions/oils/materials on the plungers?


texts: How can I make a black precipitate without a sulfide?

texts:
I'm supposed to make a black precipitate using only the following chemicals: copper sulfate(II), lead nitrate, acetic acid, barium chloride, sodium hydroxide, copper(II) carbonate, methanol, potassium permanganate, hydrochloric acid, hydrogen peroxide, magnesium sulfate, and potassium dichromate.

I know that solid sulfides (used in qualitative analysis) are typically black in colour, such as copper(II) sulfide, but I don't have any source of the sulfide ion here. Is it actually possible to make a black precipitate?


texts: Industry Standards of Polymer Leeching Measurement

texts:
I am a research assistant currently researching the leaching of polymers the byproducts of the reaction of ethanol and wood coating from wood billets into water and I'm at a crossroads with my colleagues.
Do the the somewhat niche nature of the research, it is difficult to find a standardized method of testing leeching from wood. Is there a format approved and tested by NIST or is it wisest to search the literature for a tested method and build from there?


texts: How does a catalyst accelerate both forward/reverse reactions simultaneously?

texts: A catalyst is known to speed up both forward/backward reactions of a reversible reaction. But how does this work, because the mechanism for the forward and backward reactions could be different right? I mean the adsorbed species for the forward and backward reactions when conducted independently will be different right? Is that because all the steps are exactly reversible?


texts: In a condensation reaction, which of the reactants loses their OH group?

texts:
You have Propanoic Acid ($\ce{CH3CH2CO-O-H}$) so an $\ce{OH}$ on the end
You have Ethanol ($\ce{CH3CH2-OH}$) so an $\ce{OH}$ on the end

When you combine the two for a condensation reaction you have the $\ce{OH}$ group from 1 reactant and the $\ce H$ group from the other that joins to release a water molecule correct?

So which of these groups loses its $\ce{OH}$ group and which group loses its $\ce H$ group?

How can i determine this is im guessing it may have something to do with strength of bonding and shielding but can somebody please explain i cant find the answer


texts: The best method(s) to identify/verify the presence of a small organic molecule

texts:
What is the fastest or the most definite method (preferentially a single unexpensive method) for verifying the presence of a certain small orgnic molecule which is expected to be of >90% purity in a "powdry" sample (known solvent is also availble)?

Thank you in advance


texts: Is this really a comparison of the absolute energies in the reaction energy profile for ester formation?

texts:
In Clayden et al., Organic Chemistry, p. 332, the authors compare the reaction energy profile for ester formation from a) acyl chloride and b) anhydride:

They then write:

  The energy levels of the starting materials, the transition state, and the intermediate are all lower in the anhydride reaction than in the chloride reaction.

Are they really comparing absolute energies between different species?


texts: Mechanism for removal of trimethylsilyl directly bonded to carbons

texts:
I recently came across a scheme for the synthesis of panacene (Sabot et al., 2008OrgLett4629):

In this synthesis, the step from 14 to 9 in removes  a trimethylsilyl ($\ce{TMS}$) group directly bonded to an aryl ring with $\ce{TBAF}$ (tetra-n-butylammonium fluoride) and $\ce{CsF}$ with $\ce{DMF}$ as the solvent.
I understand that silicon has a strong affinity for Fluoride and am familiar with the mechanism for deprotection of silyl ethers. For silyl ethers the $\ce{RO^-}$ acts as a leaving group from the 5-coordinate silicon. Here, however, the aryl anion seems like a bad leaving group. So, what is the mechanism for this?


texts: Does the carboxyl group count as a branched chain

texts: Do carboxylic acids (or any compound with a carbonyl group) count as a branch chained organic compound due to the C=O? Or does it need a carbon - carbon branch?


texts: will two weak acids lower their degree of dissociation when put together in solution compared to when put separately

texts: When two weak acids are put in aqueous solutions separately they will have some value of degree of dissociation,  now when both are put together will there be a decrease in their dissociations, I think they should lower each other dissociation due to common ion effect (H+ from both) , the problem is that in my textbook they give resultant H+ion concentration by adding individual concentration , those values being same as if when put in separately .. can anyone please explain me what's correct mathematically ?


texts: How to rationalise the major product formed in a nucleophile promoted epoxide cleavage reaction?

texts:
The Problem is to find major product of reaction as given below (the star is a labelled carbon):

The two possible reactions that come to my mind are:

Nucleophile promoted epoxide cleavage reaction, ① in image below
SN2 substitution of chloride as a strong nucleophile $\ce{C2H5O^-}$ is being used, ② in image below

I thought that both these products should be formed, but to my surprise the answer is given as product ③ (in image), in which it appears that after ring opening of epoxide to ① they they have substituted the chlorine by using $\ce{OH-}$.

So my questions are:

Why is the product ③ major product, why not ①?
Is the product ② also formed and if no, then why not? If yes, then on what basis is product ③ the major product? Shouldn't product ② be also formed proportionately as in the final structure both product ② and product ③ appear very similar to me.
Can anyone please give me hints on how to solve such types of question when to form epoxides as in product ③ (even though epoxide is a ③ membered ring with ring strain also if $\ce{C2H5O^-}$ is left in solution it may again try to open the epoxide ring) and when not to form epoxide as in product ① which doesn't have any ring strain.
It would be great if anyone could also suggest the approximate percentage of products ①, ②, ③. However it is not necessary a simple explanation is sufficient.


texts: How does the equilibrium shift when concentration of reactant and product are increased simulatenously

texts:
Before answering my question, take a look at this example
$$\ce{2NOCl <=> 2NO + Cl2}$$
Let's suppose I have $\pu{2 mol/L}~\ce{NOCl},~\pu{2 mol/L}~\ce{NO}$, and $\pu{1 mol/L}~\ce{Cl2}$ in a closed system. If we were to calculate the equilibrium constant, it would be
$$K_c = \frac{(2)^2(1)}{(2)^2}$$
Now suppose I increase the concentration of both $\ce{NOCl}$ and $\ce{NO}$ by $\pu{1 mol/L}$. The equilibrium will stay the same,
$$K_c = \frac{(2+1)^2(1)}{(2+1)^2};$$
however, if I were to instead increase the concentration of both $\ce{NOCl}$ and $\ce{Cl2}$ by $\pu{1 mol/L}$, the equilibrium will shift to the product side
$$K_c = \frac{(2)^2(1+1)}{(2+1)^2}$$
Can someone explain this phenomenon in terms of rate of reaction or in terms of molecules?


texts: Different elements have different colours. Some elements may have similar colours like Sodium (Na) and Potassium (K), so that's why i'm asking "is there a way to calculate or even simply deduce the actual colour (not spectral lines) of an element based on its properties?"


texts:
Aromatic aldehydes do not give Fehling's test, which makes me believe that for the same reason acrolein should not. It has a double bond conjugated with the carbon-oxygen double bond as in benzaldehyde. Is my assumption correct? Or is extended conjugation a factor?

Glyoxal(CHO-CHO) and Glyoxalic acid(CHO-COOH) also don't give Fehling's test. Any reasons for that?


texts: Why does my professor use both the upper, and the lower, case literal of a letter to symbolize the same concept?

texts:
In one of our slides, the professor has written

  $ \Delta E_{sys} = -\Delta e_{sur}$

Where $E_{sys}$ symbolizes the energy of a given system, and $e_{sur}$ symbolizes the energy of the surroundings of that system.

On a few occasions, she's used both the upper, and the lower, case literal of a single letter as symbols of a single concept.

Is there a notational convention that requires the use of an upper case literal of a letter in some circumstances and the use of its counterpart in other circumstances?


texts: What is the product of a copper and vinegar reaction?

texts:
I put a copper wire through a hole in the cap of a water bottle, filled the water bottle ~ half way full with vinegar, and left it over night.  The part of the wire inside the bottle that wasn't in vinegar turn black.  Really black.  Why is this?!

UPDATE: I wiped the black stuff off on paper, and it now looks green on the white paper.  Seems like it oxidized over night.  Why so fast?


texts: Effect of nuclear spin statistics on the IR spectrum of CO2

texts:
Specifically, I am talking about $\ce{C^{16}O2}$. With a nuclear spin of zero meaning, it is a boson - it's total wavefunction must be totally symmetric. The total wavefunction is made up of an electronic, vibrational, rotational and a nuclear spin contribution. For this molecule the electronic and vibrational (in ground state) wavefunctions are symmetrical. There is no antisymmetric nuclear spin wavefunction so only the even J rotational levels exist.

Now consider the degenerate bending vibrational mode. Excitation of this mode leads to excitation into the excited vibrational state of this mode and the IR spectrum has a corresponding P, R, and crucially a Q branch (due to additional angular momentum from the degenerate bending mode).

I have been asked whether there are similar J restrictions in the excited state as there are in the ground state. I initially jumped into assessing the symmetry of the contributions to the wavefunctions and concluded that the vibrational mode is antisymmetric and thus the corresponding excited state wavefunction is antisymmetric leaving the possibility of only odd J values in the excited state. However, there is a Q branch so this must be incorrect since the Q branch indicates the presence of J=0 in the excited state.

Why is there seemingly no restriction on the excited state?


texts: Why is PLGA so expensive in comparison to PLA?

texts:
A Google search has lead me to believe that PLGA goes for anywhere between 8 USD and 100 USD per gram. Meanwhile, for PLA (3d printer grade), prices float around 50-100 USD per kilogram.
I understand there are differences in the two, but why is PLGA so much more expensive? Is it solely because of PLGA's application in medical-grade uses, while PLA has widespread consumer-grade application?


texts: Is there a name for the intersection of the graphs of first and second order reactions?

texts:
Is there a name for the point where a first order rate of reaction meets a second order one.

This point highlighted above.


texts: During electrochemical experiments, we consider the resistance of the electrolytes. What exactly is causing the electrolytes to offer resistance to flow of charges in them? Also, does the resistance also depends on the electrodes we use?


texts: Abundant substances which I may use like coupling agents

texts: What is the most abundant substances which I may use like coupling agent for Wood plastic composite with HDPE polymer? I don't want maleated polyolefin because they are not so abundant in my country.


texts:
How can I convert isoborneol powder to isoborneol flakes?

I have made the isoborneol powder from reduction of camphor using sodium borohydride.


texts:
We've been told our lab report has to be written with "% v/v" instead of volume. I understand how to calculate it, however I'm unsure if I'm doing the right thing when it comes to using it later on. Example:

  2ul 'W', 4ul 'X', 2.2ul 'Y', 1.8ul 'Z' is mixed in an eppendorf. It is incubated for 1 hour. After incubation, 0.95ml of 'B' is addded and then 150ul of the final mixture spread on plates.

I know the first bit would be:
20% v/v 'W', 40% v/v 'X', 22% v/v 'Y', 18% v/v 'Z' is mixed in an eppendorf.

But I dont know what to do when it comes to after the incubation?

I'm generally pretty good with this stuff but I've never had to think of it this way. Would, when 0.95ml is added, I do 0.95/0.95+2ul+4ul+2.2ul+1.8ul?


texts: Sodium thiosulfate and Hydrochloric acid

texts: If I was using this method (http://www.rsc.org/learn-chemistry/wiki/Expt:The_effect_of_concentration_on_reaction_rate) however used pre-prepared concentrations of sodium thiosulfate solution, which intervals would be more suitable, 0.1M, 0.2M, 0.3M, 0.4M or 0.5M, 1M, 1.5M and 2M? Also, what concentration of Hydrochloric acid should be used (I've seen a variety of suggestions elsewhere). This is for a secondary school practical. Thank you.


texts: I'm looking for some clarification on Lewis Acid/Base Chemistry.  For the Acids do they have to accept a full pair of electrons to be considered a Lewis acid, or do they just have to accept an electron, and vice versa for Lewis Bases?


texts:
An autocatalytic reaction is a reaction in which one of the products catalyses the reaction.
In general what will be the shape of curve if the rate of reaction was plotted against time for an autocatalytic reaction?

I think answer should be A (in image) as an autocatalyst should always increase rate of reaction until there is a limiting factor for example concentration but the answer is B.


texts: Degassing HI from Reaction (Via Ultrasound Maybe?)

texts:
I'm just going to put the questions first and the explanation after in case y'all don't have the patience.
I want to know if it's reasonable to think that :

Using an ultrasonic bath on something like a rotovap would prevent bumping, with the cavitation effects serving as basically the ultimate boiling chip.

Whether ultrasound could be used to degas an organic solution while a reaction is occurring, in order to definitely confirm that a gas is not supersaturating the reaction mixture.

Does it make any sense whatsoever that hydrogen iodide could stay in solution in toluene?

I'm considering strapping an ultrasonic transducer onto a metal pan we use as our oil bath. Is there a potential reason that this wouldn't be effective for 1) and 2)?
Context: working on a mild cannabinoid conversion (at a Canadian university, definitely not sketchy) via the following method:
https://pubs.acs.org/doi/10.1021/acs.jnatprod.7b00946
Long story short, we're investigating why side products are being produced and halving the yields when any larger amounts are used in the reaction. I'm seeing brown residue (immiscible with the reaction solvent of Toluene) collect and return down the condenser into the mixture, formed via this reaction:
4 HI + O2 → 2 H2O + 2 I2
Of which the HI and H2O then form concentrated hydroiodic acid droplets which return to the mixture.  I think this means that purging with nitrogen and otherwise degassing the solution is necessary. I think HI should basically boil out as it is formed due to very low boiling point and negligible solubility in toluene, so just doing it under nitrogen flow should be fine. Supervisor thinks some is sticking around in solution (which is why larger volumes at identical reagent concentrations also lower yields, as the smaller volumes means higher surface:volume and takes less time for the entire volume to boil/recondense/cycle compared to larger volumes), so basically what I'm trying to do is go so ham on degassing this solution that we can diagnose whether this is accurate.


texts:
I'm a grade 12 student trying to comprehend MOT & LFT in Co-ordination compounds.
For one of our salt analysis(practicals), the test for acetate ion includes the addition of Neutral Ferric Chloride to salt solution.
This results in the formation of the above Co-ordination compound.
I've been obsessed, and I'm probably at the brink of insanity trying to comprehend it's structure via MOT/LFT. I have seen many Lewis structures but I'd really know to know it in terms of MOT. I assume it's octahedral in shape, with the 2 oxygen atoms of the carbonyl group acting as ligands; But I'm not sure, hence the assumption.
Thanks!


texts: Is styrene more or less reactive than benzene towards electrophiles?

texts: Is styrene more activated or more deactivated than benzene towards electrophilic aromatic substitution? The C=C double bond doesn't seem to have any particular electron-withdrawing or -donating properties, so I'm not sure what to make of it.


texts: Reconciling electron configuration and valence electron distribution over separate energy levels in energy band theory

texts:
The electron configuration of a Silicon atom in its ground state is $\ce{1s^2 2s^2 2p^2 3s^2 3p^2}$, or equivalently, $\ce{[Ne] 3s^2 3p^2}$.

When looking at the energy-level scheme of a silicon atom, the valence electrons are distributed over two separate energy levels; specifically, the $\ce{3s}$ and $\ce{3p}$ energy levels. It is then said that, as you bring multiple Silicon atoms closer together, the two energy levels will split and overlap. And because the two energy levels are splitting and overlapping, they will produce two energy bands separated by a region of energy that is not allowed. Of these two energy bands, the lower energy band is referred to as the valence band, and the higher energy band is referred to as the conduction band.

I am familiar with the phenomena of valence and conduction bands, as well as the "region of energy that is not allowed", otherwise commonly referred to as the "forbidden energy gap".

However, I'm wondering what this phenomenon of the valence electrons being distributed over two separate energy levels is? How does one reconcile this with the electron configuration $\ce{1s^2 2s^2 2p^2 3s^2 3p^2}$, which seems to suggest that the electrons remain in discrete, well-defined energy levels (rather than overlapping)?

I would appreciate it if people would please take the time to clarify this.


texts: Rate-limiting in transition state theory

texts:
Suppose an initial state $A$ can transition to either state $C$ or state $D$. Suppose further that both of these two processes are rate-limited by a transition to the same intermediate state $B$, as follows:

Note that $\Delta G_{AB}> \Delta G_{BC}>\Delta G_{BD}$.

According to transition state theory, rates are determined by the rate-limiting step. So the rate of each process will be the same,

\begin{align}
r_{A\to C}&=r_{A\to B} \\
r_{A\to D}&=r_{A\to B}
\end{align}

from which it follows that the number of transitions made during some large $\Delta t$ will also be the same,

\begin{align}
N_{A\to C}&=r_{A\to B}\Delta t \\
N_{A\to D}&=r_{A\to B}\Delta t
\end{align}

However, if we were to consider the two pathways collectively then we would predict more transitions to be made to state $D$ than $B$ since $\Delta G_{BD}<\Delta G_{BC}$.

How do we resolve this apparent discrepancy?


texts: What is the volume occupied by the atoms and the edge length in these cubic lattices?

texts:
Consider a cubic unit cell of crystal that is composed of a single kind of atom. By placing atoms at every corner of the cube, a simple cubic lattice is formed. Assume that the atoms are perfect hard spheres with a radius $r$ and that the atoms are in close contact to minimize the volume of the cube.
In a simple cubic lattice, the volume occupied by the atoms is $(?)$ % that of the cube, and the length of the edge of the cube is $(?)r$.
To the simple cubic lattice described above, atoms are added to all face-center positions of the cube. In the resulting lattice, the volume occupied by the atoms is $(?)$ % of the cube, and the length of the edge of the cube is $(?)r$.

For the first one, I tried drawing a cube with quarters of spheres at each of its corners and finding the % by calculating the total volume of spheres over the volume of the cube, yet the answer isn't accurate. I get the length of the edge as $2r$.


texts:
(source: iupac.org)

I can't seem to understand why these compounds are meso compounds..... I don't see any plane of symmetry here. I have trouble identifying meso compounds so can you give me heads up on how to identify them


texts:
We see $\ce{2Mg + CO2 -> 2MgO + C}$ , quite often in lab experiments.

Under which conditions can $\ce{4Al + 3CO2-> 2Al2O3 + 3C}$ be used - if chemically feasible?


texts: Standard Enthalpy of Formation of H2(g) vs H(g)

texts:
My question is somewhat related to this quesion. When I look at a table of standard values there are two entries for Hydrogen:

$\ce {H2(g)} $  - 0 kJ/mol
$\ce {H(g)} $  -  218 kJ/mol

I understand the $\ce{H2(g)} $ is 0 because it is used as a reference, why is monatomic $\ce{ H(g)}$ given in the table and what does it mean? When would one use it in a calculation of enthalpy change?

From what I understand Hydrogen only exists as a monatomic gas at very high temperatures, the Standard enthalpies of formation are given at 1 bar, 298.15 K.


texts: Is Sodium Hydroxide a Bronsted-Lowry Base?

texts: I know that sodium hydroxide dissociates into sodium cation and hydroxide, so it must be an Arrhenius base. I am also aware of the rule that all Arrhenius acids and bases are considered to be Brønsted-Lowry acids and bases. However, when it comes to sodium hydroxide itself, it seems as if it does not accept proton, but hydroxide does. And someone on this StackExchange stated that it is not a Brønsted-Lowry base, but an Arrhenius base. I am confused now. Is this an exception?


texts:
What is geometry and hybridization of $\ce{[MnBr4]^2-}$ for $\ce{Mn}$ ($Z = 25$)?

I am not sure if it is tetrahedral or square planar.
I assumed $\ce{Br}$ is a weak ligand and got its geometry to be tetrahedral.
Am I right?

I am a 12th grader and I only know the basics of coordination chemistry.


texts: Is the surface of the planet Mercury made of copper minerals?

texts: I have been looking at photographs of the planet Mercury, and I notices that in most of the pictures I have seen, the rocks on the surface seem to be covered in blue in green. From this, is it correct to say that the surface of Mercury is mostly made up of copper deposits?


texts: Computing enthalpy of formation of dissolved gas from its enthalpy of dissolution

texts:
Provided that I know the enthalpy of formation $\Delta H_f^0(X_{g})$ of a substance $X$ in gas phase and its enthalpy of dissolution $\Delta H^0_{sol}(X)$ in the same conditions, considering that the dissolution reaction is $X_g \leftrightharpoons X_{aq}$
 is it legit to consider that the enthalpy of formation of that substance $X$ in aqueous phase would be $\Delta H^0_f(X_{aq}) = \Delta H^0_{sol}(X) - \Delta H_f^0(X_{g})$?

As a concrete exemple, considering that the enthalpy of formation of $H_2$ in gas phase is 0 kJ/mol and that its enthalpy of dissolution is approximately -4.15 kJ/mol (using the data provided here), can we conclude that the enthalpy of formation of $H_2$ in aqueous phase is approximately -4.15 kJ/mol?


texts: Is strength of an acid proportional to concentration or dilution?

texts:
I have a confusion between two seemingly contradictory factors.

Since pH =-log[H+], it suggests that more the concentration of the acid, lesser will be its pH, and therefore the stronger it is.
But, according to Ostwald's dilution law, the degree of dissociation of an electrolyte is directly proportional to the square root of dilution. Though this exact relationship is true only for weak electrolytes, I believe that the degree of dissociation of any electrolyte would increase with dilution, keeping the temperature constant. And, more the degree of dissociation, more would be the H+ions released, and stronger the acid.

Where am I wrong in my reasoning?
Thanks in advance.(Please give me an answer and not just a comment)


texts:
When are two orbitals considered to be orthogonal?

It will be helpful if you can provide an example molecule (or molecular orbitals in a molecule) since I can't really think of a scenario where molecular orbitals can be exactly 90° to each other.

I'm not well-versed in quantum mechanics, so would prefer a simple answer - but all explanations are welcome.


texts: Nucleophilicity in Polar Aprotic Solvent

texts:
Why is it that fluoride is more nucleophilic than iodide in an aprotic solvent? The Clayden textbook suggests that lower-row elements of the periodic table are more nucleophilic since their valence electrons are in higher energy levels and are therefore more reactive. However according to the slides from my lecture class, the order of nucleophilicity for halides in an aprotic solvent goes from F- > Cl- > Br- > I- which is opposite from what is stated in the Clayden textbook. Can someone please explain this?

Thank you


texts:
Forgive me if this isn't the best forum for this question, and guide me elsewhere if so.
I have two identical smartphones, both made by Sony (Xperia z2 to be exact). One I purchased new and one second hand. I want to affix an adhesive-backed mounting system to the back of both of them.
With one phone (that I had from new) there's no trouble, everything (e.g. adhesive-backed Velcro) sticks really well. But with the other phone nothing will stick . I've checked that there's no protective overlay sheet and can only assume it's been treated with some sort of chemical coating. Every solvent I've tried to remove this coating just forms a meniscus and runs straight off. Water, detergent, isopropyl, acetone, WD-40 - nothing makes any difference. Any suggestions?


texts: Is it possible to boil a liquid by just mixing many immiscible liquids together?

texts:
In open air, when vapour pressure reaches 1 atm, boiling takes place.

I read that if we add two immiscible liquids together, the total vapour pressure of the 'mixture' is close to $p = p^*_A + p^*_b$, means that the vapour pressure of the 'mixture' is higher than the vapour pressure of both the constituent liquids, subsequently means that the 'mixture' boils at lower temperature than both of the constituent liquids.

If we have many liquids which are not immiscible with each other, and we add them together to form a 'mixture' such that  $p = p^*_A + p^*_B + ... > \pu{1atm}$ , will boiling results at room temperature?

I suspect we have many liquids which are not miscible with each other, since we classify solvents as organic solvent and inorganic solvent only, but let's say we indeed have that (or we have two immiscible liquids volatile enough to make $p>\pu{1atm}$), what will be observed? Boiling at room temperature? In that case, we can use the vapour to do work (e.g. rotate turbine), but when we mix immiscible liquid together there should be no energy transaction right? The particles do not react with each other. If all these are true, we are actually doing work without any input which violates the first law, so there must be something wrong with my reasoning above.


texts: Why doesn't pure water conduct when it dissociates?

texts:
Sorry if this is an obvious question.
I am told water dissociates, one product of which is negatively charged hydroxyl ions. This makes sense, but then why doesn't pure water conduct electricity? Surely the hydroxyl ions could act as charge carriers to allow current to pass through the solution?
Thanks


texts: What is the difference between free energy and standard free energy

texts:
As I understood $\Delta G^0$ is just $\Delta G$ but at standard conditions i.e. $\pu{1 bar}$ and $\pu{298 K}$. But formulas like:
$\Delta G^0 = \Delta H^0 - T \Delta S^0$
$\Delta G^0 = - RT \ln K$
make me uncertain about that as these are dependent on $T$ and don't seem to be used at standard conditions only i.e. $T = \pu{298 K}$.
Could someone explain to me what the difference is between $\Delta G$ and $\Delta G^0$?


texts: Acid dissociation constant and equilibrium constant

texts:
What is the relationship between acid dissociation constant and equilibrium constant for an acid's reaction with water?
If we have this reaction:

$\ce{CH3COOH + H2O → CH3COO- + H3O+}$

I would calculate the equilibrium constant to 0,005241 M at 25 celcius

Acid dissociation constant for acetic acid is as known 1,75 × 10$^{−5}$. How can this be true? The equilibrium constant I have calculate is about 300 times larger than the acid dissociation constant!


texts: Why is o-toluic acid (2-methylbenzoic acid) more acidic than benzoic acid?

texts: Why does the methyl group at the ortho-position stabilize the carboxylate ion? I recognize that there will be a steric clash between the carboxyl group and the methyl group but I don't understand why this would help increase acidity. If there was any resonance occurring then this steric clash would DESTABILIZE the anion and make it LESS acidic given that the carboxylate group would not be in the same plane as the ring and thus delocalization, which would stabilize negative charge, would be impossible. Clearly there is no conjugation with the aromatic ring in "benzoic acid based compounds" from the carboxylate group. So why does having a methyl group at the ortho-position increase acidity?


texts:
Is visible spectroscopy the only non-electronic method of all the spectroscopy method?

I know some of the spectroscopy method is possible being used because of electronics.


texts: What does the Pi stand for in the reaction for biological nitrogen fixation?

texts:
In the reaction for biological nitrogen fixation, what does the Pi stand for in the products?
$$\ce{N2 + 8H + 8e- + 16 ATP -> 2NH3 + H2 + 16ADP + 16 P_{i}}$$


texts: Protein Data Bank: Asymmetric Anit/Biological Assembly

texts:
For a schoolproject I have to interpret the 3D structure of an imatinib-BCR ABLC kinase complex. When I visited the PDB website I downloaded the PDB file corresponding to this complex. Once I opened it on my 3D modelling program it struck me that the protein complex was portrayed twice, looking almost the same but not completely. So after that I stumbled upon something called the Asymmetric Unit/Biological Essembly on the PDB site. I read the description  down this post here, but didn't fully understand it. Could anybody explain me what this is and how I'm able to import the right complex in my program?

Thanks in advance.

http://pdb101.rcsb.org/learn/guide-to-understanding-pdb-data/biological-assemblies


texts: Organic chemistry, hybridization concept

texts: Hybridization of phenyl cation and venyl[sic] vinyl cation and acetylene cation ,I am totally confused , I think that the hybridization of both phenyl and the venyl cation is SP , I think that in both cases the positive charge remains at pz orbital , but my tuition teacher said me that the hybridization of phenyl cation is SP2 but the hybridization of venyl cation is SP now please give me a proper explanation of hybridization of those cations


texts: The potential range of the cyclic voltammetry of CoCat in KPi made of D2O

texts:
I have a phosphate buffer adjusted to pH 7, and another phosphate buffer made of deuterium oxide (D2O) adjusted to pH 6.6 (pD 7). I want to conduct cyclic voltammetry of cobalt oxide catalyst in these buffers.
I want to apply the following potential range for the buffer made of normal water: 0.9 to 1.25 V vs. NHE. So, my question is here: shall I apply the same potential range for the buffer made of D2O? or I should take the pH difference into account*?

*The pH difference would be: (7-6.6)*0.059 = 0.0236 V.

Then the potential range for buffer made of deuterium oxide would be: 0.9236 to 1.2736 V vs. NHE.


texts: White granular substance from restaurant with interesting properties - what is it?

texts:
It isn't salt or sugar.

Was in a shaker at a restaurant - caused burning/bleeding sensation after consumption. Made up of small white granules that seem moist - all sticking together. The restaurant did not know what it was.

Tested properties:

Dissolves in water and vinegar.

When dissolved in water there was little effect. In vinegar, it produced substantial heat.

When mixed with lemon juice, the powder turned orange, heated up enough to crack the plastic container it was in, and gave off smoke.

No other information - based on these observations can any suggestions be made as to what it is?


texts: Effect of EWG on groups undergoing decarboxylation

texts:
I have been reading Peter's Sykes and there I came across certain compounds which show decarboxylation.
My doubt is that how the acidity of the groups attached to the carboxyl groups will help in decarboxylation.
For example we have one EWG and one EDG then which will show faster decarboxylation.

I am quite aware of the mechanism but somehow I can't relate here.


texts:
Conducting an experiment, I found that very little salicylic acid was evolved performing hydrolysis at $\mathrm{pH \ 2}$ and at $\pu{45 ^\circ C}$. In fact, far more salicylic acid was evolved at $\mathrm{pH \ 7}$. This comes as a surprise to me because I expected an acid-catalyzed ester hydrolysis to actually quicken the rate of reaction and thereby evolve MORE salicylic acid.
Is aspirin generally more stable at lower $\mathrm{pH}$s then?
UPDATE 1: This graph shows that aspirin hydrolysis doesn’t lend itself well in low $\mathrm{pH}$ conditions, specifically at $\mathrm{pH \ 2}$.
UPDATE 2: No answer has been found — a reword to this question can perhaps be “Why is aspirin less susceptible to hydrolysis at $\mathrm{pH \ 2}$ when theoretically, lower $\mathrm{pH}$s are advantageous for ester hydrolysis?”

Source: https://compoundingtoday.com/Newsletter/Science_and_Tech_1112.cfm
What seems to be the explanation to this?


texts: What happens to the nitrous oxide in the whipped cream when it is on your food?

texts: Nitrous oxide is used to create whipped cream but there is no information available on what happens to that gas when you eat it in the cream.


texts: What is this glassware between flask and condenser to collect liquid?

texts: I've been trying to identify this piece of glassware for ages now. I've been combing the internet and can't seem find anything similar. It looks like some kind of adapter/collecter/trap that sits on the pot and the condenser goes on top.


texts: Splitting of atomic orbitals due to Stark effect

texts:
I am performing graduate level research on ZEKE Photoelectron Spectroscopy and central to this form of spectroscopy is Rydberg states and the Stark effect. The Stark effect is caused by an electric field polarizing the species, thereby inducing a non-zero dipole moment. This causes degenerate states to split. However, say for the hydrogen atom's $n = 2$ state, there is 4-fold degeneracy: $\mathrm{2s}$, $\mathrm{2p}_x$, $\mathrm{2p}_y$, and $\mathrm{2p}_z$. When an external electric field is applied to the system, two spectral lines, each red and blue-shifted, are observed for the $\mathrm{2s}$ and $\mathrm{2p}_x$ orbitals. Each has an azimuthal quantum number equal to $0$.
Why are only these orbitals shifted? I do not understand why each of these orbitals are split; is it because each is centered on the $z$-axis? Is what I described only apply to the linear Stark effect, and the $\mathrm{2p}_x$ and $\mathrm{2p}_y$ orbitals are shifted according to the quadratic Stark effect? If so, what is the difference between the linear and quadratic Stark effects?
I have read several research papers about the matter, but I don't have a strong understanding of math involved in quantum mechanics. Typically, when the author explains the Stark effect using Dirac notation, I quickly become confused.


texts: Methyl anthranilate sulfuric acid - acid base reaction

texts:
When methyl anthranilate is added to sulfuric acid a white precipitate forms. I am assuming this is an insoluble salt produced in the acid base reaction, where the lone pair on the nitrogen will accept a proton.

My question is, does sulfuric acid lose both protons in the reaction, so that there are 2 ions of the protonated methyl anthranilate with one sulfate ion. Or does it form one protonated methyl anthranilate ion with an HSO4- ion?


texts: Equilibrium involving water and solid component

texts:
$$\ce{A + B <=> C(s) + H2O(l)}$$

Why when $\ce{H2O}$ is liquid and $\ce{C}$ is solid, the equilibrium constant of the reaction is

$$K_\mathrm{eq} = \frac{1}{[\ce{A}][\ce{B}]} \quad ?$$


texts:
There exists the basic chemistry lesson with induced dipoles where the electron density of one atom changes causing a dipole to form and causing a cascading effect where other atoms adjacent to that polarized atom also become polarized.

How do those atoms lose their dipole if their wavefunction changes to "line up" with the dipole? Does a probabilistic event need to happen at the same time for all atoms in order to "lose" the dipole where the electron density goes back to its normal state?


texts:
I've been unable to find an energy diagram for propane either in my book or online via Google. So I resorted to making my own. I suspect that propane isn't covered because it's essentially the same deal as ethane - we can have one staggered conformation and one eclipsed conformation (only in propane it's a methyl eclipsing a hydrogen, not hydrogens eclipsing each other).

So I drew the Newman projections and an energy diagram.


texts: Mechanism of hydrolysis of polycyclic oxetan

texts:
The reaction is this:

The only idea I have thus far is if we have a chloride acid that can form an ester, then we might be able to find a suitable mechanism. This would require a chloride reagent.


texts: Differences between Urushibara nickel and Raney nickel

texts: The Wikipedia article about Urushibara nickel catalyst is rather short and vague. What is the mechanism for its preparation, and furthermore, in what sense does it differ from Raney nickel (i.e. when should you prefer the one over the other)?


texts: Calculate activation energy of intermolecular displacement on a nano particle

texts:
I'm simulating a nano particle and wish to calculate the activation energy of the reaction where an atom is displaced from one point on the lattice to a neighboring void( might be at higher energy than initial).
Calculating this activation energy using energy difference will require me to calculate the complete trajectory to determine the point with highest energy, which is computationally very expensive.
Is there any other tested method to find this activation energy without having to perform so many computations each time.
Note: the new site is a neighbor of the old site and I expect( not assume) the atom to roll over two of its adjacent atoms to reach this new site.
Also all the atoms are identical.