texts: How to calculate wavenumbers of normal modes from the eigenvalues of the Cartesian force constant matrix?

texts:
I would like to get the wavenumbers (Frequencies -- in Gaussian) from the eigenvalues of the force constant matrix (Force constants in Cartesian coordinates: in Gaussian).

Could someone please explain how to perform this calculation? The Cartesian force constants are given in Hartrees per Bohr squared, while the wavenumbers are in $\pu{cm^-1}$.


texts: Decomposition of axial vector and vector representions of C4v group

texts:
Let $R$ be the orthogonal matrix corresponding to an operation in $O(3)$. If
R is a proper rotation, then both vectors $\vec{V}$ and axial vectors $\vec{A}$ are transformed in the same way

$$ \vec{V} \rightarrow  \vec{V}' = R\vec{V}$$
$$ \vec{A} \rightarrow  \vec{A}' = R\vec{A}$$

if $R$ is an improper rotations, then
$$ \vec{V} \rightarrow  \vec{V}' = R\vec{V}$$
$$ \vec{A} \rightarrow  \vec{A}' = -R\vec{A}$$

And let $\mathcal{V}$ be the vector representation of $O(3)$ and $\mathcal{P}$ be the axial-vector representation of $O(3)$. Thus we can write,
$$\vec{V} \rightarrow  \vec{V}' = \mathcal{V}(R)\vec{V}$$
$$\vec{A} \rightarrow  \vec{A}' = \mathcal{P}(R)\vec{A}$$

My question is, considering $\mathcal{V}$ and $\mathcal{P}$ as representations of $C_\mathrm{4v}$ group, how can I find their composition in terms of irreps ?

$$\begin{array}{c|ccccc|cc} \hline
C_\mathrm{4v} & E & 2C_4 & C_2 & 2\sigma_\mathrm{v} & 2\sigma_\mathrm{d} & & \\ \hline
\mathrm{A_1} & 1 & 1 & 1 & 1 & 1 & z & x^2+y^2, z^2 \\
\mathrm{A_2} & 1 & 1 & 1 & -1 & -1 & R_z & \\
\mathrm{B_1} & 1 & -1 & 1 & 1 & -1 & & x^2-y^2 \\
\mathrm{B_2} & 1 & -1 & 1 & -1 & 1 & & xy \\
\mathrm{E} & 2 & 0 & -2 & 0 & 0 & (x,y),(R_x,R_y) & (xz,yz) \\ \hline
\end{array}$$


texts:
I have a doubt regarding the shape of the $\mathrm{sp^3}$ hybridised orbital. I looked up for it on stackexchange and found a post where the guy said that where ever the orbitals interfere with opposite signs of the wavefunction they cancel out and hence we get a small lobe .
He further said that when the right side of the p orbital overlaps with s orbital( i have linked the post) they both add up.

But the $\mathrm{s}$ orbital wavefunction can also have negative sign (in the post the guy has assumed that s orbital wavefunction is always positive) . So in all four interference combinations are possible : ++ , +- , -+ , - - . Hence the shape should be different  but its not.

I am really confused about this.
Any help is appreciated.

Thanks in Advance.
Link to original post : https://chemistry.stackexchange.com/a/15909


texts: How does the surface tension of water decrease with an increase in the concentration of NaCl?

texts:
Can anyone help me with the theory of surface tension? My chemistry experiment is related to the surface tension and concentration of NaCl. I am confused about my hypothesis. On the internet, I found that increasing salt concentration also increases the surface tension of the water. But in my experiment, surface tension is decreasing with the increase of NaCl. So can anyone help me with the theory behind this?
With the help of needle and water drops, I was able to calculate the value of surface tension of water for each concentration of NaCl.


texts: I've written m/z 300 - 1100 Thomson in my paper, but the reviewer said that the Th is already deprecated. So in this case, should I write m/z 300 - 1100 Da? or something else?


texts: Why are my microgels not centrifuging (sticking to tube)?

texts:
I have created a hydrogel water in oil emulsion using a microfluidic flow focusing device. I have been able to collect the microgels/particles from the device and then pipette/manipulate them. When I try to centrifuge them to wash them they seem to aggregate and stick to the tube walls instead of collect at the bottom of the tube. What could be causing this and how do I fix it? Below are some relevant details.
Water phase: 2 wt% Norbornene-modified hyaluronic acid, DTT (crosslinker), .1% Irgacure I2959 (photoinitiator)
Oil phase: Light mineral oil with 2% span 80 (surfactant), .1% Irgacure I2959 (photoinitiator)


texts: ordering the hydrophilicity of some polymers

texts:
I need to compare the hydrophilicity of those materials to compare contact angles of water with those materials' surfaces for surface tension measurement. Materials are:

PTFE (Teflon), PVC, PS, PVDF, Si-Wafer-Si-SiO$_x$, Parafilm and PMMA

Ordering the polarity can also work. Where can I found such a comparison? Can someone help me with the ordering. Thanks.


texts: Name of the intermediate in between phosphono and phosphonato group

texts:
$\ce{R-PO3^2-}$ is called a phoshonato group (https://www.ebi.ac.uk/chebi/searchId.do?chebiId=30931)

$\ce{R-PO3H2}$ is called a phosphono group (https://www.ebi.ac.uk/chebi/searchId.do?chebiId=48108)

So, what is: $\ce{R-PO3H-}$ called ? I can't find it, it seems to be largely ignored.
Auxiliary question, is one of the two possible enantiomers of this form dominant ? Is there anyway to know this ? Or is it by definition distributed in a 50%/50% manner ?


texts: Why does iron oxide form hydrous iron oxide while chromium oxide does not?

texts: Both Cr2O3 and Fe2O3 share a similar structure, and both can form some sort of passivating layer, but only one of them hydrates, thus turning into rust and providing a pathway for more water and O2 to further oxidize the iron. I believe the same applies to aluminum and nickel as well. iron seems to be the only one to do this, but I cannot figure out why.


texts: What is the difference between n-heptan (CAS 93924-37-9) and branched, linear and cyclic heptane (CAS 426260-76-6)?

texts:
I am looking at the substitution of hazardous substances in my company. I would like to explain what makes the branched, linear and cyclic heptane (CAS 426260-76-6) safer than n-heptane (CAS 93924-37-9).

I do not know what is the influence of molecular structure of heptane on the properties of this substances. I mean here two different primers (chemical adhesion promotor) on heptane basis. One of them includes branched, linear and cyclic heptane and methylacetate mixture (this primer is not carcinogenic) and the second one n-heptane only (is carcinogenic).

Is there someone who can explain it?


texts: What are the differences between monotropic and enantiotropic polymorphic transformations?

texts:
I'm studying polymorphism and came across the terms "enantiotropic" and "monotropic" transformations. The first is described as reversible, whereas the latter, irreversible due to metastability. But what does "reversible" and "irreversible" means practically? What exactly is metastability? What makes these two types of polymorphism distinguishable between each other?

For instance, it's used as an example of monotropic polymorphism the transformation of graphite to diamond. However, the same source claims the reverse operation is possible. As for enantiotropic polymorphism, it used the example of silica polymorphs (cristobalite and alpha-quartz) which also can be transformed from one another. If both are reversible, why are they different?


texts:
So, another question from my side.
I have been thinking about the folowing reaction:

The reaction above exists and was already done on two occasions and reportedly works really well and it seems to be a no-brainer to me as well. Now, my question is related to the reaction below with the alkylated amine. First question: the alkylation of the compound above seems difficult, BECAUSE how can I make sure that I only alkylate the primary amine in meta position to the bromine? Can I use a protection group before for the other primary amine?

Second question: if the alkylation is possible as I imagine it here, can I still perform the reaction as depicted? Or is it unfavored because suddenly a positive charge appears?

Greetings


texts: I am new to chemistry and saw a "portable mercury vapor monitor." How do these machines work?


texts: How would you measure the rate of this SN1 reaction?

texts:
I am performing the following $\mathrm{S_N1}$ reaction:

$$\ce{t-BuOH + HCl -> t-BuCl + H2O}$$

I would also like to measure the rate of this reaction, but I cannot seem to find a way. I initially envisaged measuring the rate by using an indicator to tell when the conc. $\ce{HCl}$ had been used up.

However, I do not believe the reaction has gone to completion, thus why, when using my method of using an indicator, the indicator never changed colour, due to leftover acid - also Clayden's Organic Chemistry [1, p. 348] cites a 90% yield, presumably meaning not all of the acid reacts.

The reaction should take 20 minutes [1] at room temperature and so I don't think I can measure the rate by looking measuring a change in temperature. I do not know how else I could measure the rate.

Clayden, J.; Greeves, N.; Warren, S. G. Organic Chemistry, 2nd ed.; Oxford University Press: Oxford; New York, 2012. ISBN 978-0-19-927029-3.


texts: Calculating atomic mass of unknown element in given compound (gas) at STP

texts:
A gas $\ce{X2O5}$ has the density of $\pu{5 g L-1}$ at STP. What is the atomic mass of $\ce{X}$ given $A_\mathrm{r}(\ce{O}) = 16?$

Note: The problem is my homework for school and has been translated from another language. It is probably either missing something or it contains wrong data. Just leaving it as a cautionary tale to anyone who might also have it.
I solved, or at least tried to, by expressing the given density $\rho = \pu{5 g L^-1}$ as
$$\rho = \frac{m}{V}.\tag{1}$$
Also,
$$m = Mn\tag{2}$$
$$V = V_\mathrm{m}n,\tag{3}$$
where $n$ is the amount of substance and $V_\mathrm{m} = \pu{22.4 L mol^-1}.$ So:
$$\rho = \frac{m}{V} = \frac{Mn}{V_\mathrm{m}n} = \frac{M}{V_\mathrm{m}}\tag{4}$$
$$\pu{5 g L^-1} = \frac{M}{\pu{22.4 L mol^-1}} \quad\Rightarrow\quad M = \pu{112 g mol^-1}\tag{5}$$
Then obviously by subtracting the atomic mass of oxygen:
$$M_\mathrm{r} = 5A\mathrm{r}(\ce{O}) + 2A_\mathrm{r}(\ce{X}) \quad\Rightarrow\quad A_\mathrm{r}(\ce{X}) = 16\tag{6}$$
But that is not possible, as $16$ is the atomic mass of oxygen and there is no such thing as $\ce{O2O5}$ as far as I know. What am I doing wrong? Or is the problem wrong altogether?


texts: Effect of substituents on Ullmann reaction

texts:
This question that I recently encountered asked what the most suitable substrate for the Ullmann reaction would be. The answer given is (b) but I think it has to be (d) as the nitro group acts as EWG and thus facilitates the reaction.

However I do not know the mechanism and thus am not sure if (d) is indeed the correct answer.

Any reason why the answer might be (b) and not (d)?


texts: Is it possible to graph the equivalence of p[Cu²⁺] with pH?

texts:
In no way I am a chemistry major, so please forgive me if my question seems stupid. I just need a way to find the "equivalent $\mathrm{pH}$" of $\mathrm p[\ce{Cu^2+}]$ if that makes any sense to you.

I'm making a paper about a transistor that can sense ions (ion-sensitive field-effect transistor); i.e. it's a potentiometric transistor. I was able to simulate voltage values with respect to $\mathrm{pH}$ activity in a simulation software named LTspice, but in order for this paper to be passable to whoever shall evaluate it, I must compare my data with a preexisting experimental data.

The only experimental data that I have is from my co-advisee. He measured the voltage values with respect to $\mathrm p[\ce{Cu^2+}]$ $(\ce{CuCl2 · 2 H2O}).$ I think it wouldn't be proper to compare the voltage vs $\mathrm{pH}$ graphs and voltage vs $\mathrm p[\ce{Cu^2+}].$

So, I figured that if I can express $\mathrm p[\ce{Cu^2+}]$ to its equivalent $\mathrm{pH}$ (I don't think this is possible and makes any sense), then I'd be able to compare the two graphs.


texts: Change in enthalpy and entropy when sugar dissolves in water

texts:
We know that dissolution of sugar in water is a spontaneous process.
So, change in Gibbs free energy $(ΔG)$ must be negative for the overall process:
$$ΔG = ΔH - TΔS < 0$$
Hence either the enthalpy or entropy must drive the reaction.
Now, after searching for the values, most websites suggest the process is endothermic (i.e. $ΔH > 0).$
But Jan's answer has me convinced that the overall entropy of a system should decrease (i.e. increase in entropy of sugar molecules is outweighed by decrease in entropy of water molecules).
So, what's the real reason for reaction to be spontaneous if neither entropy and enthalpy are driving the reaction?


texts: I was watching a SciShow video "Most dangerous Chemicals". It said that a compound called Azidozide azide explodes on being exposed to light. My question is: how does the the atom feel light. Heat can be felt (let us not go into the philosophical question why do we feel warm while standing below the sun) and can excite molecules. How can light excite molecules?


texts: Which substance has the higher oxidation strength?

texts:
I have to decide which one has a higher oxidation strength $\ce{ClO-}$ or $\ce{Cl2}$

$\ce{ClO- + H2O + 2e- -> Cl- + 2OH-}$

$\ce{Cl2 + 2e- -> 2Cl-}$

Will this reaction occur?

$\ce{ClO- + H2O + 2Cl- -> Cl- + 2OH- + Cl2}$

In my opinion not, because otherwise the $\ce{ClO-}$ is reduced to $\ce{Cl-}$. If the reaction works, the $\ce{Cl-}$ could react as reduction agent again. Therefore if I would add $\ce{Br2}$ to $\ce{ClO-}$:

$\ce{2 ClO- + 2 H2O + 4Br- -> \mathbf{2 Cl- }  + 4OH- + 2Br2 }$

$\ce{ClO- + H2O + 2Br- + \mathbf{2 Cl- } -> \mathbf{Cl- } + 2OH- + Br2  + \mathbf{Cl2}}$

So therefore chlorine has a higher oxidation strength than $\ce{ClO-}$?


texts: Is there any kind of program that is able to calculate the end result of a specific chemical reaction? Say I wanted to know what happens when you mix $\ce{HClO + NaOH}$, is there anything that could give me the answer to any question like this? Wolfram alpha works pretty good, but it doesn't give me an answer if it isn't a balanced equation, and I don't know what that means. $\ce{HClO}$ is an acid and $\ce{NaOH}$ is a base, so there has to be some reaction, balanced or not.


texts: Does hydroxytyrosol have the same neurotoxicity potential as dopamine?

texts:
It has the catechol group, and it's the oxidation of the catechol group that makes dopamine produce reactive oxygen species (ROS).

Hydroxytyrosol isn't that different from dopamine (the distal N being replaced with an OH). I'm not sure if that really affects anything. Yet - it's often sold as an antioxidant.

Couldn't it have the same ROS potential that dopamine and other catecholamines have?


texts: Energy levels transitions of an electron?

texts:
I have an example that tells me that the energy transition between $n=1$ and $n=3$ is $12.1\ \mathrm{eV}$ using the following formula:

$$E= -RH (\frac{1}{m^2} - \frac{1}{n^2})$$

and that the conversion from $12.1\ \mathrm{eV}$ gives a wavelength of $102.6~\mathrm{nm}$.

I understand that $-RH$ is the Rydberg's constant that corresponds to $13.60\ \mathrm{eV}$ and $m$ is the inner orbit and $n$ the outer orbit (but I might be wrong with the latter). So,

$$E= -13.60\ \mathrm{eV}\ (\frac{1}{1^2} - \frac{1}{3^2})$$

$$E= -13.60\ \mathrm{eV} \cdot 0.83$$

$$E= -11.288$$

I don't understand how they get the first value for the electron Volts and then convert these into wavelength. Additionally, my task is to find the energy level for the 4th orbit in the Lyman's series.


texts: Disinfection solution ( Trichloroisocyanuric acid 96%)

texts:
I'm going to make a 100 liter solution to desinfect various tools used in Shiitake production so it's important the solution kills mold and mold spores.

I've been looking into various methods and chemicals. At first I thought about going with H2O2 since it's safe and does not generate harmful by-products. Since I do not have peroxide stronger than 3% readly available I discarded this route.

I thought about a solution of calcium hypochlorite taking the PH below 7 but since that would probably be quite dangerous since I'm not sure about the concentrations / ph levels used to generate minimum ammounts of chlorine gas. I surely don't want to be dealing with the release of chlorine gas if I can avoid it.

I looked into chlorine dioxide and althought extremely effective it's also very toxic and even has explosive properties. I discaded it immediately.

Lastly I saw that my supermarket carries Trichloroisocyanuric acid (pool shock) at 96%.

I was reading some info here and it's dangerous to mix with small ammounts of water and also I need to be careful about the PH.

These are the recommended concentrations for each use:

  swimming pool disinfection: calculate the usage according to 2-3g/m3; take effect for 30-60 minutes.
  Public places and ground disinfection: use 1500-3000-fold diluted water solution for spraying and wiping for 30 minutes. Infectious
  disease epidemic area, use 150-200-fold aqueous diluted water solution
  for spray disinfection.
  disinfection of white clothing and blankets: apply 2000-3000 fold diluted solution for clean items; soak for 10 minutes; for seriously
  polluted items, diluted 500 times, soak for 20 minutes.
  disinfection of bathroom and toilet scrub; use 300-fold diluted solution for reaction of 30 minutes.
  sterilization of non-metallic medical equipment: use 500-1000 times diluted solution for soak of 30 minutes; disinfection of apparatus
  with pus and blood; apply 100-fold diluted water solution for reaction
  of 30 minutes.
  disinfection of non-metallic tableware: use 500-1000 times diluted water solution for reaction of 30 minutes.

My questios are:

1. How many grams should I had to 100 liters of water for sterilization / desinfection of equipement? (I'm looking into a strong solution but also safe to use)

[EDIT] I found this patent  that states

  with a sterilizing solution of a compound having an active-chlorine
  concentration of from 500 to 20,000 mg/l and being selected from the
  group consisting of sodium hypochlorite, calcium hypochlorite,
  chlorinated trisodium phosphate, chlorine dioxide, sodium
  p-toluenesulfochloroamide, p-toluene-sulfonsulfochloroamide,
  N-chlorosuccinimide, 1, 3-dichloro-5, 5-dimethylhydantoin,
  trichlororoisocyanuric acid, salts of trichloroisocyanuric acid,
  trichloromelamine and dichloroglycoluril, the pH of said sterilizing
  solution being from 8 to 10, and treating the thus sterilized article
  with an aqueous solution of hydrogen peroxide at a temperature below
  90° C to deactivate any remaining active chlorine, said solution of
  hydrogen peroxide having a concentration of lower than 30%.

Also fromhere

  using a solution of concentration of 200-400 mg/kg for environmental
  disinfection and utensils disinfection.

Since my solution will be made with water I would assume mg/kg = mg/l

So for a 100 liter solution I would need to dissolve 20-40 grams, correct me if I'm wrong.

2. What would be the recommended PH value for maximum effectiveness but also safe to use?

On a side note the desinfection will be carried at a open area using adequate PPE.

[edit: I would also need to know an approximate time the equipement needs to be submerged and how long the solution would be effective]


texts: Can I make a pH 7 buffer from phosphoric acid and sodium hydroxide?

texts:
I am an electronics guy with not so much knowledge of chemistry.
I would like to prepare a pH 7 buffer to test pH meters.

All web references I have found so far describing how to make a phosphate buffer use
disodium phosphate (Na2HPO4) and Monosodium phosphate (NaH2PO4) as ingredients.

I have a good supply of 85% phosphoric acid and solid sodium hydroxide. Can I make a pH 7 buffer from these ingredients instead or is there a catch?


texts: If no oxygen is present, will cut avocados stop browning?

texts:
Oxygen makes cut avocados brown, or at least it is necessary to facilitate the rapid browning reaction we see within 24 hours of cutting the avocados.

If oxygen was completely removed from the air surrounding the cut avocado, will the browning stop?

If a small fraction of oxygen remained, will the browning slow? In other words, is the rate of browning proportional to the percentage of oxygen in the surrounding air?

I never studied chemistry so my understanding comes from here:

http://www.compoundchem.com/2014/08/03/why-do-avocados-turn-brown-the-chemistry-of-avocados/


texts: Thermochemistry: On Units of Enthalpy Change and Implicit Given of Initial Temperature of Calorimeter

texts:
I would like to ask two separate questions. But first, so that we are on the same page, the experiment used a constant-pressure calorimeter, and it is a neutralization reaction of 1M of HCl and 1M of NaOH.
1. What is the difference between the units of ΔH: kJ and kJ mol^-1?
As I have read in Socratic at the end of the page, there are many units to represent the change in enthalpy. However, we are given a theoretical enthalpy of -2.79 kJ but my teacher gave an equation of Q_calorimeter/n_H2O thus my answer is -1.16 kJ mol^-1. How am I able to evaluate this by getting the percentage error? Should I multiply my answer to something with "mol^-1"? If so which mole would it be, the whole reaction or each species?
2. If you are not given data on the initial temperature of the calorimeter, is it correct to assume that its initial temperature is the initial temperature of the substance that is initially poured in (i.e. NaOH)?
In the other part of the activity, the initial temperature of the cold water is explicitly labeled also as the initial temperature of the calorimeter, and the cold water is initially poured into the calorimeter. Inferring from this, is my conclusion correct?


texts: I am trying to measure the absorbance of a solution at 882 nm, but this seems to be beyond the range of many UV-Vis spectrometers. Is this a job for the IR spectroscopy, or something else? I do not have much experience with IR spectroscopy.


texts: Is HF the only method for trying to solve the many-electron Schrödinger equation?

texts:
The Schrödinger equation can only be solved analytically for the smallest of "molecular" systems. The Hartree-Fock method is a method of obtaining approximate solutions to the many-electron Schrödinger equation, and a bunch of methods try to reduce the error associate with the HF method.

However, all ab initio electron correlated methods I know of and have read about are based on HF; that is, they all use the HF solution and adds to it. So basically there is only one way in use today of attempting to solve the many-electron Schrödinger equation?

Then of course there is density functional theory, but here you strictly don't try to solve the Schrödinger equation, you just try to obtain the solution, right?

So is this a correct assessment? Do we truly only use one method of trying to solve the many-electron Schrödinger equation? Is there any research being done on alternative methods (other than DFT)?


texts:
How would you draw the mechanism going from non-3-enoic acid to coconut aldehyde (5-pentyloxolan-2-one)? I know I added sulfuric acid and sodium carbonate, which I was confused how they worked into the mechanism. I am certain there is some type of internal reaction to create the five membered ring.

Those are the only chemicals that could, in my opinion, be involved. The others are not needed in the mechanism. Pretty much confused on the first step of what happens when sulfuric acid is added. What does it protonate? How does this lead to an internal reaction and where does that reaction take place? Does the C-C double bond have anything to do with it?

Would the lone pairs on the oxygen readily take the proton? But how would that affect the overall state of the compound in order to form that ring. I'm not seeing how that could be right.


texts: Why are inert gas (especially Xenon) compounds powerful oxidizing agents?

texts: I am curious as to why compounds with inert gases, such as $\ce{XeF4}$, $\ce{XeF2}$, and $\ce{XeO3}$ are considered powerful oxidizing agents. I would attribute the phenomenon to the highly oxidized state of the noble gas which would be unstable but I am not too sure about it.


texts: How are Pauling's rules applied to Nitric acid?

texts:
The Lewis structure of nitric acid is:

So, since Pauling's rule is $\mathrm{p}K_\mathrm{a}=8-5p$, where $p$ is the number of oxo groups, how is the rule applied in this instance? $p=1.5$? $p=2$?


texts: Is the ammonium substituent (-NH3+) really meta-directing in electrophilic substitution?

texts: If we make a resonance structure for the anilinium ion, with positive charge at either the ortho or the para position, we get a pentavalent nitrogen, which is not possible. So, how is the $\ce{-NH3+}$ group meta-directing in electrophilic aromatic substitution reactions, e.g. in nitration of aniline under acidic conditions?


texts:
If $4\ \mathrm{mol}$ helium gas expand against constant pressure in isothermal process, how can calculate $W$?

Is it $W=-nRT\ln\frac{V_2}{V_1}$ as defined by isothermal or is it $W=-p\left(V_2-V_1\right)$ as define from isobaric?

Also, is enthalpy equal to $0$ in such process?


texts: All possible determinants forms a complete basis

texts: How do we mathematically prove that the set of all possible excited determinants forms a complete basis for expanding the wavefunction (as in full configuration interaction)?


texts: How to get a "rechargable" chemical reaction for a glow stick

texts:
I want to create my own glow stick that lasts a while while ligting up the surroundings. How would I go about this? I know there are youtube videos and such. But the way they do it doesn't allow for any way of "recharging"

How can i make a "rechargable" glow stick?


texts:
Please tell if the 2 given conpound are Anti-aromatic or Non-aromatic,

I have confusions arising due to incosistent facts all around internet some of them are as follow :

1.) Arguments for Cyclopropenyl Anion

a.) Wikipedia which under the heading of "Effects on reactivity"
     clearly states that :

  "However, the cyclopropenyl anion has 4 π electrons in a cyclic system
  and in fact has a substantially higher pKa than 1-propene because it
  is antiaromatic and thus destabilized"

b.) This Answer on ChemSE which clearly states that its Non-Aromatic in
        Nature

c.) Also this NEPTL site which clearly states that:

  Cyclopropene is not aromatic because one of its ring atoms is sp3
  hybridized so it does not fulfill the criterion for aromaticity. But
  the cyclopropenyl cation is aromatic because it has an uninterrupted
  ring of p-orbital and (4n+2) π-system. The cyclopropenyl anion is
  antiaromatic as it has (4n) π-system.

2.) Arguments for cycloheptatrienyl anion

a.) This Question on ChemSE where the same question have 2 deflecting answer this answer is saying is that the anoin is antiaromatic and this states that the anion is nonaromatic

b.) Also my book (solomons and fryhle organic chemistry adapted for JEE) gives this as Antiaromatic

I don't know which one is correct, please help by providing a comprehensive answer with a reason that can be applied everywhere in such questions.

EDIT: Hello the one who closed the question can I ask the reason for closing as much I can do I abid by this guideline I asked my question straigthformward and then presented my research please tell me why my question is put on hold, I seek answers


texts:
I saw this graphic in Organic Chemistry by Klein (2nd edition too!) and this has to be wrong, correct?

The mirror images should have the double bond on the far side of the ring in both images, right? I am sure, unless my visualization skills have totally failed me.

Here's the result when I flip the entire image using an online mirror effect creator:


texts: Is oxygen above the critical point always supercritical fluid? Would it still appear to roughly follow the ideal gas law?

texts:
In this answer I've asserted (without a "Chemist's license") that as long as oxygen is above it's critical point in both temperature (154.5 K) and pressure (50.4 bar) it's going to be a supercritical fluid.

This comment by a user who I believe is an experienced diver says:

  Scuba divers use the idea(l) gas law for air and oxygen bottles to calculate the amount of remaining gas for 200 down to 10 bar. This would not be possible if there is supercritical oxygen in the tank.

In other words, the ideal gas law works pretty well for oxygen between 10 and 200 bar; for a given temperature the amount of oxygen (number of atoms or mass in kg) is close to linearly proportional to pressure.

The comment proposes that this is evidence that the oxygen couldn't be a supercritical fluid.

Question(s):

When oxygen is above both 50.4 bar and 154.5 K is it always a supercritical fluid, end of story?
If it is, would it nonetheless still tend to follow fairly closely the ideal gas law?


texts:
I need to determine whether or not a product that I am importing is "toxic" and or "corrosive" as defined below. But I am a chemistry n00b — that is to say I have virtually zero experience with and or knowledge of chemistry — which is why I am here. I am hoping that one of you guys can help me out.
Corrosive is defined as being

capable of inducing necrosis or ulceration of epithelial
tissue;
capable of causing an erythema or edema of the skin,
corneal or iris damage or conjunctival swelling or redness; or
let us not worry about this right now.

Toxic is defined as being

capable of causing a lethal effect on a human;
capable of causing a serious and irreversible but non-lethal effect on a human, such as a depressed level of consciousness, muscular weakness or paralysis, acute renal or hepatic failure, arrhythmia, hypotension, dyspnea, respiratory depression, pulmonary edema or optic neuritis; or
let us not worry about this right now.

Product Ingredients

Water
Water-soluble vinyl acetate polymer
Water-soluble natural wax
Water-soluble silicone
Natural glue

Please let me know if any information is missing or any other information is required. Also, please feel free to tag or re-tag the question however you see fit.
Thanks in advance for any help whatsoever.


texts: Why are the stoichiometric coefficients used as exponents in the chemical equilibrium constant?

texts:
From what I can ascertain, the formulation of the chemical equilibrium constant is somewhat arbitrary. I don't understand the motivation for putting the stoichiometric coefficients in the exponents. This seems like you are double counting. For instance, if A ->  4B, for every mole of A that decomposes to B produces 4 moles of B. So my reaction would already have a higher amount of B. Then I take those four moles and raise to the 4th power. So if I started with 2 moles of A and 1 decomposed, I would have one mole of A to 4 moles of B. Then I would have a equilibrium constant of 256. How is this superior to not having exponents and just having an equilibrium constant of 4? Or for that matter there are many arbitrary ways I can stick on or not the stoichiometric coefficients. Why not take the 4th root of B over the first root of A?

Edit: Many are saying that this is a duplicate of Law of Mass Action. However, in that question the stoichiometric coefficients just HAPPENED to be the exponents. And as pointed out in the answer the order in the rate law doesn't have to be the same as them. My question is dealing with the Eqilibrium Constant. The Equipibrium Constant is defined such that the stoichiometric coefficients are ALWAYS the exponents. Why?


texts: Correlation between the equilibrium constant and delta G

texts: I understand this up until the last two steps. How does $\ln(K_\mathrm{eq})$ become $2{,}303\log(K_\mathrm{eq})$ and how does $-RT\cdot2{,}303$ become $-1{,}42$?


texts: Finding change in activation energy from change in rate constant in catalysis

texts:
I need to find by how much the activation energy decreases when the rate constant increases by a '$x$' factor when a catalyst is used in the reaction.
I'm just super confused about how to solve this. Using Arrhenius relation I have
$$\frac{k_2}{k_1} = \frac{A\mathrm e^{-E_\mathrm{a2}/(RT)}}{A\mathrm e^{-E_\mathrm{a1}/(RT)}}$$
$$x = \mathrm e^{(E_\mathrm{a1} - E_\mathrm{a2})/(RT)}$$
I took natural log on both sides to get rid of the exponent and then ended up finally with an equation I can't seem to get any relation from
$$RT\ln x = E_\mathrm{a1} - E_\mathrm{a2}$$
Now I need a ratio of the two activation energies, but I don't know how I get that from here as I have just a addition/subtraction relation between the two. Would be grateful if someone has a clue about how I could proceed.
The problem is I have come across a question in Atkins' Physical Chemistry [1, p. 841] and the answer is provided in percent, but I don't see how you could arrive at a solution like that with where I am:

Self-test 20D.4 Consider the decomposition of hydrogen peroxide, which can be catalysed in solution by iodide ion. By how much is the activation energy of the reaction reduced if the rate constant of reaction increases by a factor of 2000 at 298 K upon addition of the catalyst?
Answer: 25 per cent

References

Atkins, P. W.; De Paula, J. Physical Chemistry: Thermodynamics, Structure, and Change, 10th ed.; W.H. Freeman: New York, 2014. ISBN 978-1-4641-2452-5.


texts: Is 1,2- Hydride shift possible in ketonic cations?

texts:
The question in my worksheet asks me to predict the result of the reaction between benezene and $\ce{(CH3CH2CH2CO)2O}$ in presence of anhydrous $\ce{AlCl3}$.

My attempt:

After complex formation with $\ce{AlCl3}$ we get this carbocation: $\ce{CH3CH2CH2CO+}$ that has two resonance structures.

But, if we consider hydride shift we get $\ce{CH3CH2C^+HC=O}$ which is not only stabilised by resonance but also by the $\text{+I}$ effect of ethyl group.

However, the answer is $\ce{PhCOCH2CH2CH3}$ which isn't formed by the second carbocation with hydride shift .

So I'd like to know if hydride shift is possible in ketonic carbocations or not? And if it is, is the answer wrong?


texts: How can some enzymes work faster than the diffusion rates of the reactants allow?

texts:
Quoting Wikipedia: "Some enzymes operate with kinetics which are faster than diffusion rates, which would seem to be impossible." Which are those enzymes and how can they be so fast?

One example is catalase in which peroxide is catalyzed faster than the diffusion rate of peroxide allows. Lionel Milgrom discusses this case in Water Journal no. 7.


texts: Why is the enthalpy of combustion higher for n-butane as compared to 2-methylpropane?

texts: N-butane has an enthalpy of formation of $\pu{-125.6 kJ/mol}$, whereas it is $\pu{-134.2kJ/mol}$ for 2-methylpropane. When comparing the heat set free at the combustion process, why is it higher for n-butane? Isn't the enthalpy of formation the negative of enthalpy of combustion and therefore 2-methylpropane should be higher?


texts:
I have read in my textbook (not very reliable) that density of interstitial compounds is lesser than parent compound. But how can this be true?

We add atoms to the lattice voids, so density should increase right?


texts: The Use of AI and Machine Learning in Organic Chemistry

texts:
I am trying to do a bit of research into the current use of machine learning in chemical industry. I've been told my original question was too general so I'll try to be more specific about what I'm interested in.
I've read several articles about the computational techniques used for retrosynthesis, where a desired molecule is set as an input and the output being a series of feasible chemical reactions beginning with easily sourced/purchasable materials.
I'd like to know if/where techniques like this are being used in industry with any frequency or is it something still in the early stages of development and sees little to no practical application.


texts: Getting an “index” of 7 for a Set of Powder Diffraction Data

texts: I know a value of $h^2 + k^2 + \ell^2 = 7$ is not allowed but I cannot understand where I am going wrong with the indexing here. Any insight would be greatly appreciated as I am wondering if this is made up data that has a typo? I calculated d using $d= \lambda{} /(2\sin{\theta{}})$ where $\theta$ (theta) is half the value of $2\,\theta$ (obviously) given


texts: When you dilute an acidic solution, pH increases towards 7 and pOH decreases. However, the decrease of pOH indicates that the concentration of hydroxide ions increases. This seems to contradict my understanding of how equilibrium systems respond to external disturbances, as it suggests the auto-ionisation equilibrium of water shifts to favour the ions (according to Le Chatelier's principle) to such an extent that the hydroxide ion concentration increases from prior to the dilution. However, I was under the impression that equilibrium systems can never fully undo the change due to the bi-directional nature of equilibria, meaning the reaction is using up ions as they are replaced. Please help to clear up my confusion! Thank you.


texts: Finding the major contributing tautomer of 1-(propan-2-yl)-1,2,3,5-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one

texts:
I am having a problem generating the correct tautomer for 1-(propan-2-yl)-1,2,3,5-tetrahydro-6H-pyrazolo[3,4-b]pyridin-6-one. I am told by my collaborator that the one I am generating is wrong.
I am not able to figure out why the structure below is the wrong tautomer.


texts:
I was trying to name the following compound but I got stuck in naming the aldehydic part of the compound.

I looked for the answer and found it as 6-bromo-2-oxocyclohexanecarbeldehyde. I had come to know earlier that carbeldehyde suffix is used when there are more than two aldehydic group in the compound but why carbeldehyde is used here? I am not able to understand this. If someone can explain which rule is used here. I will be very grateful for this.


texts: Is the absolute temperature concept 100% viable?

texts:
Maybe I'm wrong about it but I wanted to know whether the concept of absolute temperature is real or not.

As every element behaves differently at a particular temperatures how could we assign a common temperature to all these elements where they possess zero point energy? If they will do so then what will happen if we find an new element which ground state energy is at $\mathrm{-10\ K}$ theoretically?


texts: Hydrolysis of starch by means of amylase to unclog bathtub drain

texts:
After my son decided to pour a substantial amount of uncooked rice down the bathtub drain, I find myself in the situation of removing it.

After trying some common methods - to no avail - I thought I could resort to chemistry.
Specifically, I thought about dissolving (hydrolysis) the main component of rice (starch) by means of amylase (possibly bought in a shop, not salivating over the drain).

Would this be a good solution to unclog the drain?
Under what conditions should I operate to achieve the result hoped?
Would there be a better solution?

As you might guess, I'm not a chemist.


texts: Why are sodium and potassium displaced from soap by calcium and magnesium ions in hard water?

texts: Sodium and potassium are more reactive than calcium and magnesium still they get displaced. Why?


texts: Is there a difference between parchment paper for writing on and the type you use in cooking?

texts: I have tried searching this question many different ways but to no avail. My instinct and common sense say the processing is probably exactly the same but I would like to be sure.


texts: What is formed when hydrogen peroxide reacts with titanium?

texts:
I just got night contact lenses, and you are supposed to use a "one-step" cleaning solution to clean it over a period of six hours. At the bottom of the lenses case, there is a "titanium plate neutralizer", which causes the liquid to bubble. What is this gas?

Edit: it was platinum, not titanium


texts: Points needed to come up with a calibration curve

texts: Usually when you are doing your masters, what are the minimum points that you can have when doing a calibration curve?


texts: What is correct cyclopenta[a]phenanthrene numbering?

texts:
IUPAC BlueBook 2013 states:

  P-25.3.3 Numbering fused ring systems

  Fused ring systems with retained names, systematic names, or fused names are systematically numbered in the same manner. Anthracene, phenanthrene, acridine, carbazole, xanthene and its chalcogen analogues, purine, and cyclopenta[a]phenanthrene are exceptions; traditional numberings are retained.

  (…)

All except the last one, cyclopenta[a]phenanthrene are trivial retained names, this one is systematically created name (P-25).

All except cyclopenta[a]phenanthrene have the numbering explicitly depicted (in P-25.1.1 or P-25.2.1; anthracene and phenanthrene in errata).

It's natural and expected that there can be different numberings for the same compound for different naming system chosen (e.g. decahydronaphthalene vs bicyclo[4.4.0]decane – fusion carbons C-4a and C-8a vs C-1 and C-6).

So, what is (your qualified opinion on) the correct numbering of cyclopenta[a]phenanthrene? In other words, for example, what is the correct name for this compound:

1H-cyclopenta[a]phenanthrene
3H-cyclopenta[a]phenanthrene
17H-cyclopenta[a]phenanthrene

or other one?

(1.) would be correct systematic numbering (if I'm not mistaken; used by current MarvinSketch), (2.) a historic alternative one, (3.) would be for steroid (gonane, alternative name sterane in pre-IUPAC 1951 steroid nomenclature) numbering.

If it's (3.) that would be, in my knowledge, only exception from systematic numbering for systematically created name, however extraordinary claims require extraordinary evidence, which is not seen in the book. And, the book can have yet uncorrected mistakes.

Curiously, as gonane numbering is well defined (Appendix 3), most unambigous name seems to be 1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16-hexadecadehydrogonane (or gona-1,3,5(10),6,8,11,13,15-octaene).


texts: Which of the following atoms has the largest first ionization energy?

texts:
Of the following atoms, which has the largest first ionization energy?

$\ce{Br}$
$\ce{O}$
$\ce{C}$
$\ce{P}$
$\ce{I}$

I got confused between $\ce{O}$ and $\ce{Br}$. The answer given is $\ce{O}$ although in the periodic table $\ce{Br}$ is closer to Group 18 (noble gases). Why is the answer $\ce{O}$ then?


texts: Why does cyclooctene have three stereoisomers?

texts:
How does cyclooctene have three stereoisomers?

I thought that there are only two stereoisomers, cis- and trans-, but according to my textbook there are three stereoisomers. I want to know how?


texts: Oxidation states the elements in nitrosyl chloride

texts:
I have read that $\ce{NOCl}$ dissociates to $\ce{NO+}$ and $\ce{Cl-},$ and the various reasons stated as such seem fine.

But what I don't get is this: if we follow the actual rules of assigning oxidation numbers, we find that nitrogen has got an unit positive charge with an unit positive charge on chlorine too (if we follow the structure of $\ce{NOCl}$ closely).

So, am I wrong in judging the oxidation number of nitrogen in $\ce{NOCl}$ to be $+1$ instead of $+3,$ as the dissociation of $\ce{NOCl}$ seems to go against my interpretation? What should be the oxidation number of nitrogen in $\ce{NOCl}$ in that case?


texts:
I'm working through problems in my textbook. How much heat is required to convert 2.55 g of $\ce{H2O}$ at 28 °C to steam at 100 °C?

In simpler problems I've used the fact that $\Delta H_\text{fus} = 6.02\ \mathrm{kJ/mol}$ for $\ce{H2O}$ at a melting point of 0 °C to do these kinds of calculations. But here the temperatures are different. How can I approach this problem? Is there some other conversion factor I should be aware of?


texts: What is the mass of 1 Liter of ethylene at 2000 bar pressure?

texts:
I was wondering the weight of 1 liter of ethylene at 2000 bar and 310 Kelvin?

I have tried to just multiply the weight at 1 bar with 2000 but I don't think i got the correct answer because the answer I got was just below 2.4 kg per liter which seems way too high.

I calculated it with constant temperature.


texts: How can both kinetic and potential energy increase simultaneously in a open substance?

texts:
I have an open test tube containing a solid substance. In a school environment, we  heat it, which increases thermal (kinetic) energy, and this heat breaks its bonds, increasing its potential energy, turning it into a liquid. I understand in thermodynamics, there is a conversation of energy, yet since this test tube is open to other factors, such as air, can this occur?

Also, if this experiment were insulated what would occur?


texts: Atkins' Physical Chemistry 10th edition Question on steady-state approximation

texts: Please help me with Example 20E.2 of Atkins' Physical Chemistry 10th edition textbook on using the steady-state approximation. I have attached my attempt but am just not sure how to get to the final answer.


texts: Reaction of haloalkane with hydroxide ions

texts:
My teacher gave me the following question:

What are the possible products of these reactions? Then, what is the mechanism of those reaction (elimination (E1 or E2) or subtitution (SN1  or SN2)? Explain in as much detail as possible.
$$\ce {CH3Cl + OH- ->} ?$$
$$\ce {(CH3)3CCl + OH- ->}?$$

I suggest that the first reaction will produce methanol and chloride:
$$\ce {CH3Cl + OH- -> CH3OH + Cl-}$$
and it is a SN2 reaction, because $\ce{OH-}$ attacking from behind and this makes $\ce{Cl}$ leave the chloromethane. It becomes $\ce{Cl-}$ because it brings one electron from the carbon atom.
Then I suggest the second reaction is a SN1 reaction because there are some barriers behind the $\ce{C-Cl}$ (the barrier is $\ce {(CH3)3}$). But I don't know the product that can be formed.


texts: Rate-determining step and steady state approximation failure

texts:
1) When can't the rate-determining step be applied, and why? How do you recognize these cases?

2) When can't the steady state approximation be applied, and why?


texts: How can you tell if a metal ion will hydrolyze to form an acidic solution?

texts: I saw somewhere that all metal ions except for the alkali metals and alkaline earth metals will hydrolyze to increase acidity. If I'm interpreting things correctly, sodium ions, for example, will not hydrolyze because sodium hydroxide is strong, thus sodium ions will not react with water to form sodium hydroxide and hydrogen ions. But I was told that magnesium will not hydrolyze, but magnesium isn't on the strong bases list that was given. By the way, I'm a grade 12 student, so I would appreciate if you kept things down to earth. Can someone clarify please?


texts: What is the molar mass of a compound with 0.5 atoms in its molecular formula?

texts:
I'm trying to calculate the theoretical specific capacity of the $\ce{LiFePO4}$ cathode for a fully discharged state, let's say when the cathode has the following notation $\ce{Li_{0.5}FePO4}$. And I'm using the following formula:

$Q=\frac{nF}{3.6M}$ where F is the Faraday constant

The question is slightly related to this thread. The question is, what is the molar mass (M) of $\ce{Li_{0.5}FePO4}$.

Which one is the correct one for finding the specific capacity:

M = 157.751 g/mol, as if Lithium would be taken as a whole?
or
M = 154.285 g/mol, as if only half of Lithium would be considered?

Can anyone help me with this?


texts: Separate precious metals from catalytic converter

texts: I am looking to separate the small quantities of platinum and palladium in a catalytic converter. However since these are very inert metals I am unsure how to proceed about doing so. Melting the converter is an option I have considered but I am unsure whether I will be able to reach high enough temperatures in order to obtain a decent amount of metal, so I am leaning more towards performing reaction.


texts: What is the difference between a ylide and a betaine?

texts:
I'm not sure what the exact difference between a ylide and a betaine is...

Are both zwitterions?

Something along the lines of: ALL ylides are betaines, but not all betains are ylides(according to wikipedia the cation/anion group can be adjacent or nonadjacent)?


texts: Why are excited Slater determinants used to describe electron correlation?

texts:
Usually the first step in describing the electronic wave function of a molecule or atom is to describe it with a single Slater determinant. I get that this is an independent particle approximation, and that in the context of Hartree-Fock, each electron moves in the average field of the other electrons. That's fine.

But when we correlate the electrons, this is done by generating excitations out of the Slater determinant, and then taking weighted combinations of them. For example, configuration interaction mixes the ground state Slater determinant with singly, doubly, triply, etc excited determinants. A fancier way of doing this is coupled cluster, where cluster operators generate excitations out of the Slater determinant.

Hermann Kummel says that we can think about electron correlation this way:

  "The first thing one may imagine happening is that two particles mutually interact, thereby lifting themselves out of the Fermi sea, so that after the interaction both are in unoccupied orbitals"

Kümmel, Hermann. "Origins of the coupled cluster method." Theoretica chimica acta 80.2-3 (1991): 81-89.

Why can we (or should we) think about electron correlation that way?


texts: Software that determines whether a molecule can exist and draw it from a formula?

texts:
I have run calculations that predict atomic configurations.  As a simple example, in a system that contains H and O, I might get a list like:

Configurations for the O atom
O H
0 2
2 6

This would tell me that in my system, there's one O atom bonded to two H atoms and there's also a molecule made up of three O atoms bonded to each other and six H atoms.  My real systems are more complex.

I am not really a chemist and have no idea whether some of the molecules I have calculated actually exist and what they would look like if they did.  Does anyone know if there's software available that might help me with this; i.e., where I can enter a potential formula and the software draws the molecule and tells me whether it exists?

I have so far checked out ChemDraw Professional and Avogadro and it doesn't look like they do what I need.  Thank you for any tips.


texts: Can a network covalent solid be amorphous?

texts: All the definitions I'm seeing give examples of crystalline solids like diamond or boron nitride. But I'm wondering if it also includes amorphous macromolecules like vulcanized rubber. I'm thinking "network" probably == "ordered array" but not sure if that's correct.


texts: What are APG and AEO7 and should I be concerned?

texts:
I'm considering importing some granite cleaner for my stone business to save some money and the following is the list of ingredients:

APG, AEO7, silicone oil, water, White Mineral Oil

My question is should I be concerned about any of these ingredients?
 May primary concern is "AGP" and "AE07" as I do not know what these are.


texts:
I have a solution containing glucose and some sulfuric acid. I want to distill out the sulfuric acid to then reuse it for other purposes. The problem is the presence of glucose in the solution. I'm afraid that, when increasing the temperature, the sulfuric acid will dehydrate glucose to carbon and other compounds - something that I don't want to happen. Would distillation cause such a reaction?

And in case it would - are there any other methods to extract the sulfuric acid?


texts: When trying to develop mathematical models to show the concentration in a reaction, where can one find a database or good source of known equilibrium constants if it is not necessarily very convenient to find them empirically?


texts: I am a musician who wears custom-molded in-ear monitors made of silicone. They are rather expensive so I need to constantly clean them and carefully. I was told not to use isopropyl alcohol (96%) wipes because it will eat away at the silicone. I looked this up and somebody said it has to do with the molecular weight. Is it true that it would damage the silicone, or just make it bloat for a while until the alcohols are evaporated? What about carbamide peroxide, which is sold as an earwax remover?


texts: Why is there no formation of epoxide when the two OH-groups are on different planes? I do understand the epoxidation mechanism. However, I would be grateful if someone cleared the specific requirements for epoxidation.


texts: Is cyclopentadiene or cycloheptatriene more acidic?

texts:
Which of the following cyclic compounds are more acidic?

The most acidic proton is positioned on the carbon that is at the top of the above drawings (the methylene hydrogens) on each of the two species, as deprotonation allows resonance.
I am aware of Hückel's rule, which states that an aromatic species has $4n+2$ π-electrons. Only the five membered ring would fulfil this requirement. However, I can draw resonance structures where the seven membered conjugate base has the double bond at each position on the ring. I ask why is it not aromatic? Which conjugate base is more stable? Essentially it's a case of aromaticity vs number of resonance structures.


texts: Confusion about electron arrangement in elements

texts: My textbook says, "The first shell can hold only 2 electrons. The second and subsequent shells can hold 8 electrons to give a stable noble gas arrangement." Can someone explain me if it is MAXIMUM 8 electrons in the second and subsequent shells or is it possible to have more than that. I searched on the internet but it keeps showing this equation: 2n2. As I am a high school student, I have no idea about "quantum" stuff. Can someone explain? Thank you.


texts: Why does internal combustion engine smoke appear blue? Could there be "blue molecules" in it?

texts:
Four-stroke and two-stroke gasoline engines as well as diesel engines can all emit dense clouds of blue-tinged smoke under various transient loads or incorrectly tuned conditions.

Raleigh scattering - in this case probably from particulates of a limited range in size - strongly favors short wavelengths, so there is a possible physical explanation.

But I would like to know if there are any chemistry effects that could lead to or contribute to the slightly blue color sometimes seen in engine smoke under these conditions.

Could there be large "blue molecules" in the smoke? I don't think so; usually gases are transparent, though there are a few notable exceptions like molecular iodine and chlorine, but I'm not sure.

above: Iodine gas, from here

above: Chlorine gas, from here

below: snapshot sitting on a bicycle, looking at adjacent scooter while holding breath and waiting for the light to change.

below: screenshot from the YouTube video Big Engines Starting Up.


texts: How does electron localization/delocalization work?

texts:
I can't find a simplified explanation on this topic. My textbook just adds to the confusion and all I'm really left with are more questions rather than answers.

And adding to that question, does polarity have an effect on electron localization/delocalization?


texts: Reference for Hammett acidities of dilute H2SO4?

texts:
When $\ce{H2SO4}$ is dissolved in water in little amounts ($<\pu{1M}$), the $\mathrm{pH}$ scale can be used to measure the acidity of the solution. However, in larger concentrations, this breaks down and we have to use the Hammett acidity instead.

I have found this thesis, which has a table of $\mathrm{H_0}$ (Hammett acidity function) values for 95% and higher $\ce{H2SO4}$.

However, I would like a table with Hammett acidites of more dilute systems, like 70% $\ce{H2SO4}$ and 50% $\ce{H2SO4}$. Is there a reference for this?


texts: Planarity of given molecules in all conformations

texts:
Which of these have all its atoms in one plane in all the possible conformations (if any):
A) buta-1,3-diene
B) but-1-en-3-yne
C) $\ce{CH2=C=O}$
D) $\ce{CH2=C=CH2}$

While I was attempting this question, I got stuck in option B!
I was sure about option A that since it has conformational change possible between C2-C3 bond, atoms will be present in more than one single plane.
Next, I am also convinced that option D can't be the answer as allenes are non planar and they have H-C-H planes perpendicular to one another.
Then, for option C also, I know that since all the atoms are $sp^2$ hybridised, it has to be a planar straight molecule.
But, I am having a doubt in option B; how should we determine if the molecule is planar or not and whether all of its atoms are present in a single plane?


texts: How is Mn+7 in the Permanganate ion considered as momentarily reduced to +6 in LMCT?

texts: I saw this passage on a book and it says that Ligand to Metal Charge Transfer (LMCT) overpowers d-d transitions thus the permanganate ion has an intense purple color. However, it was mentioned that the Mn+7 ion was momentarily reduced to Mn+6 in the charge transfer, how is that?


texts:
Apologies in advance, I have a background in physics, so this question might seem awfully simple.

Anyway, I am interested in the chiral spin selectivity effect in organic molecules, and have read a paper in which they synthesize helicene molecules with side groups R = n-Pr, i-Pr with absolutely no reference only a slight hint as to what it is an abbreviation of in either the paper or supplementary information.  I thus assume that it must be some very common notation, and my guess is that Pr refers to some kind of propane/propene/propanol, and n and i refers to some normal and altered structure, respectively.  But I don't know.

I would be grateful if someone could shed some light on it for me.


texts: Formation of azobenzene from nitrosobenzene and N-hydroxyaniline

texts:
I'm trying to create a reasonable reaction mechanism for the reaction of nitrosobenzene and N-hydroxyaniline, which happens as part of the reduction of nitrobenzene to azobenzene using magnesium as reductor and methanol as solvent. Ron was very helpful to give me a general outline of this entire mechanism:

  The key step is formation of nitrosobenzene (this is just a reasonable proposal).

  Some of the nitrosobenzene can be further reduced to aniline and
  N-phenylhydroxylamine, both of which are nucleophiles and can react
  with the nitroso N=O bond (analogous to a carbonyl). Elimination of
  water in both reactions produces azobenzene and azoxybenzene
  respectively. The azoxybenzene can be further reduced to azobenzene.

I went on to try and create a reasonable mechanism for the reactions of N-hydroxyaniline with nitrosobenzene and aniline with nitrosobenzene (both in the presence of magensium with methanol as solvent):

I wonder whether this is a correct reasonable reaction mechanism. I tried to move radicals as much as possible from positively charged/highly electronegative atoms (e.g. the nitrogen in the nitro functional group / oxygen) to the less electronegative atoms (e.g. carbon). My reasoning was as follows (I have not yet learned about in radical chemistry, but I give it a try): radicals can be removed in two ways: 1) the radical electron leaves the molecule, which results in a positive charge. This is less likely to happen with a more electronegative atom like oxygen in comparison to for example carbon, so that the radical is more stable on oxygen. 2) The radical reacts with an other molecule and obtains an extra electron forming a new covalent bond (in this case the electron is donated by methanols C-H bond), resulting in a neutral molecule with no radicals. Since oxygen is more electronegative than carbon it is more "greedy" to fill the singly occupied orbital, making the radical more stable on carbon.
Furthermore the second way to lose the radical is much more likely than the first, since it leaves a neutral molecule instead of a charged one.

At last, I was told that reactions involving metal surfaces (like magnesium in this case) are often not well understood. Why is that? Because there are too many pathways?


texts: Can I somehow 'reuse' the chemicals in glow sticks?

texts:
I particulary enjoy performing chemical experiments without buying any chemicals for them.

I was always sad about the fact that one glowstick lights out, you just throw it into trash can (I like all means of recycling). So I was wondering if I could (pick one or more):

Recycle the chemicals in it to make it glow again
Use the chemicals for other interesting (and maybe even useful) experiment


texts: I was wondering why sulfur is Raman active but other elements (e.g. carbon) are not.


texts: What reagents can be used to distinguish pentose and hexose sugars?

texts:
I have been asked how I can differentiate D-glucose and D-xylose using the following reagents / reactions:

  Orcinol
  Benedict's test
  Ammoniacal silver nitrate
  $\ce{FeCl3}$
  $\ce{C6H5SO2Cl}$, excess $\ce{NaOH}$
  $\ce{NaOH}$, $\ce{H2O}$, heat
  t-Butyl chloride, $\ce{AlCl3}$
  $\ce{Br2}$ in water, dark
  $\ce{NH2OH.HCl}$, $\ce{KOH}$, $\ce{FeCl3}$
  Resorcinol
  2,4-DNPH
  Iodoform test

Usually, chemical tests identify certain functional groups in molecules which react in a particular way. However, here the two compounds only differ in the number of carbons and don't have any real difference in their functional groups, so what reaction can be used to differentiate them?


texts: What chemical will dissolve the plastic coating on circuit boards

texts: I'm trying to reclaim the metals on circuit boards and the vast majority is underneath the plastic coating. It is a brittle plastic that chips off in small flakes when etched but that process will lose to much of the precious metal.


texts: How long would it take for sucrose to undergo hydrolysis in boiling water?

texts:
I was reading the book Cocktail Codex and there was a snippet on avoiding boiling sugar and water to make simple syrup that made me a bit skeptical. Here it is:

  Heat also affects the molecular structure of sugar. For example, if sucrose, the disaccharide commonly known as white table sugar, undergoes an extended period of boiling, it will eventually convert to the monosacchariedes glucose and fructose, which taste sweeter (and cause nasty hangovers).

Does 100 °C water hasten hydrolysis, and if so, how long would you need to boil for the breakdown to occur?

(the hangover bit is a bit weird too considering your body breaks down sucrose into glucose+fructose?)


texts: What is the relationship between equilibrium concentrations in two similar experiments?

texts:
Two experiments were performed involving the following equilibrium. The temperature was the same in both experiments.
  $$\ce{H2 (g) + I2 (g) <--> 2HI (g)}$$

  In experiment A, $\pu{1.0 M}~\ce{H2}$ and $\pu{1.0 M}~\ce{I2}$ were initially added to a flask and equilibrium was established. In experiment B, $\pu{2.0 M}~\ce{HI}$ was initially added to a second flask and equilibrium was established. Which of the following statements is always true about the equilibrium concentrations?

  $\ce{[H2]}$ equals $\ce{[HI]}$ in experiment A.
  $\ce{[HI]}$ equals $\ce{2[H2]}$ in experiment A.
  $\ce{[HI]}$ in experiment A equals $\ce{[HI]}$ in experiment B.
  $\ce{[HI]}$ in experiment A equals 2 $\ce{[I2]}$ in experiment B.

Can someone explain why the answer is 3. Doesn't that mean 2 and 4 are true as well?


texts: Fischer indole synthesis: significance of choice of acid catalyst

texts:
Lately, as a matter of interest, I have been studying sigmatropic rearrangements. I came across the Fischer indole synthesis, whose Wikipedia article states:

The Fischer indole synthesis is a chemical reaction that produces the aromatic heterocycle indole from a (substituted) phenylhydrazine and an aldehyde or ketone under acidic conditions. ... The choice of acid catalyst is very important. Brønsted acids such as $\ce{HCl}$, $\ce{H2SO4}$, polyphosphoric acid and p-toluenesulfonic acid have been used successfully. Lewis acids such as boron trifluoride, zinc chloride, iron chloride, and aluminium chloride are also useful catalysts for this reaction.

The significance of the choice of acid catalyst to be employed in the reaction is beyond my scope of knowledge. Browsing available articles, it would seem that the [3,3]-sigmatropic rearrangement is stereoselective. In addition, if I am not mistaken, regioselectivity of the Fischer indole synthesis could be increased depending on which acid catalyst was used, such as methanesulfonic acid. However, I was still unable to understand the overall importance of using an appropriate acid catalyst.


texts: How to derive the Gibbs free energy for an ideal gas?

texts:
Determine the Gibbs Free Energy for an ideal gas and show that, this energy, and its derivative can be related to the enthalpy of the system via Gibbs-Helmholtz equation
  $$H = -T^2 \left( \frac{\partial (G/T)}{\partial T} \right)$$

So I need to determine the fundamental relation for an ideal gas in the Gibbs free energy representation.

My thoughts:

I know the Gibbs free energy, is defined by
$$G(p,T) = U + pV - TS = H - TS,$$
where $H$ is the enthalpy, then
\begin{align}
\mathrm{d}(U + pV - TS) &=
   V\mathrm{d}p - S\,\mathrm{d}T + \sum{\mu_i\,\mathrm{d}N_i}
   - \sum{X_i\,\mathrm{d}a_i}\\
\mathrm{d}G &=
   V\,\mathrm{d}p - S\,\mathrm{d}T + \sum{\mu_i\,\mathrm{d}N_i
   - \sum{X_i\mathrm{d}a_i}}\\
\therefore \mathrm{d}G &=
   V\,\mathrm{d}p - S\,\mathrm{d}T
\end{align}
Now, if the temperature is constant, and only the pressure change then $\mathrm{d}G = V\,\mathrm{d}p$. It follows that $$G(p)-G(p_0)=\int_{p_0}^{p}{V\,\mathrm{d}p}$$
If $V = \frac{nRT}{p}$, we have
$$G(p) = G(p_0) + nRT \ln\left(\frac{p}{p_0}\right)$$

But, I don't know if this is correct.


texts: During formation and breaking of bonds, can the terms potential energy and bond energy be used interchangeably?

texts: My chemistry professor uses these terms interchangeably and I was wondering if they refer to the same thing. From what I understand, bond energy is the energy required to break one mole of covalently bonded gaseous molecules. While potential energy refers to the energy gained or lost during bond formation which can be further characterised into endothermic or exothermic.


texts: Synthesis of 4-amino-3,5-dimethylphenol from N-(2,6-dimethylphenyl)hydroxylamine using perchloric acid?

texts:
I come across one reaction in which N-(2,6-dimethylphenyl)hydroxylamine is converted to 4-amino-3,5-dimethylphenol in the presence of strong acid (perchloric acid).

It,s seems rearrangement reaction, but i am unable to understand how does this rearrangement is possible.
What is the reaction mechanism of rearrangement reaction?


texts: Comparing Electron affinity and electron gain enthalpy at 0 K

texts:
In my book it is given that first electron gain enthalpy is greater than second for elements. Should we compare the magnitudes in such cases or the actual numbers with signs? Does the same comparision hold with Electron Affinity at 0K?
For example Be has positive Electron Affinity and F has negative Electron Affinity. So should I consider signs and say Be has more Electron Affinity than F or consider magnitude and say F has more Electron Affinity than Be?
How to compare their Electron gain enthalpies also at 0K?


texts:
Two substances A and B react with each other in such a way that A is 50% consumed in 33 minutes and 75% consumed in 66 minutes. Changing the concentration of B has no effect on the results. Which statement is true?

And the answer is:

  This reaction is 1st order in A and zero order in B.

I understand why A is first order but I don't get why B is zero order. The equation for the half life of a zero order reactant is $\displaystyle\frac{[\ce{B}_\text{inital}]}{2k}$.

Doesn't this mean that the concentration for a zero order reactant would affect the half life?


texts: Does intramolecular hydrogen bonding occur with carbonic acid and geminal diols?

texts:
Is an intramolecular hydrogen bond possible in such compounds?
What are the requisites to have intramolecular hydrogen bonding?


texts:
In chemical thermodynamics, the condition "constant temperature and pressure" appears almost everywhere. However, I felt a small ambiguity in the phrase so I wanted to clear my doubts. When we say "constant $T$ and $p$" in chemical thermodynamics, which of these two statements do we actually mean?

$T$ and $p$ are the same at the beginning and end of the reaction
$T$ and $p$ are the same throughout the entire reaction

If we care about path-dependent variables, then there is a major difference between the two meanings.


texts: How to calculate he equilibrium constant change for acid-base reactions in a different solvent?

texts:
So we know that $K_\mathrm w$ is $10^{-14}$. But what if I am working with non-aqueous systems? Suppose I were to add LDA to liquid ammonia, or dissolve HCl in concentrated sulfuric acid. How would I calculate the percentage of dissociation? I have some inkling of how to do this but I don't really see discussions online and want to make sure my procedure is correct. Furthermore, I don't know of what good keywords to find the self-dissociation constant of ammonia or sulfuric acid are and this is really frustrating.

To emphasize: I am looking for solutions for non-aqueous systems.


texts: Stability of superoxides of alkali metals

texts: Why are superoxide ions stable only in presence of large cations such as $\ce{K}$, $\ce{Rb}$ and $\ce{Cs}$?


texts: Container to minimise radiation exposure from U-238

texts:
Consider a sample of uranium-238 that is undergoing decay to thorium-234. During the transmutation, a gamma ray is emitted from the nucleus. However, the thorium-234 daughter particle does not decay quickly enough to be detected.

What kind of storage container should the uranium sample be stored in to minimise radiation exposure?


texts: What are the physico-chemical processes at play in ironing of clothes?

texts:
The process of ironing of clothes removes (to a large extend) the wrinkles that where introduced in the clothes while drying. Obviously this has to be some physico-chemical process that is initiated/sustained by the heat of the iron and (perhaps) the pressure applied with the iron.

My question is: what is the actual process that is going on when ironing? Let's assume we have a cotton shirt, do the polymers only physically rearrange or do they actual undergo a chemical change? If it is the latter, does ironing your clothes often cause more rapid degradation?


texts: What term should I use when I am quantifying the amount of matter, mass or weight?

texts: I am writing an academic article but I got confused as I am writing about the weight a specific metal got by using balance scale. Should I use the term mass, which has a unit of kg, or weight, which is a force created by gravity and expressed in N?


texts: How is the magnetic property of an element affected when the element is part of a compound?

texts:
Data on this site conveys that Neodymium is paramagnetic. Yet the Neodymium magnets out there make extremely strong magnets. I'm guessing these are not pure neodymium magnets but some kind of compound.

Is it possible to predict the change in magnetic property of a compound given the knowledge of it's participating elements?


texts:
I read that the heat capacity of water when it is at 100 °C or 0 °C is infinite because all the heat given to it will not be used to increase temperature but to change the state.

I am unable to understand this. Say, we have water at 100 °C. If we continuously provide heat, water will change to steam and then it's temperature will increase, right?
Sure, we'll have to provide more heat than before to break the bonds. But it will definitely become a 101 °C steam after a while.

So why is heat capacity infinite at state change?


texts: Reaction of Sulfur dioxide with Potassium

texts:
What are the products of the reaction: $$\ce{K + SO2->}$$
Here, $\ce{S}$ is in $+4$ oxidation state. Hence, $\ce{SO2}$ has both oxidizing and reducing character. $\ce{K}$ is a stronger reducing agent and hence, it will reduce $\ce{SO2}$.

So, $$\ce{K + SO2->KO2 + S}$$ is a possibility.

But the answer given is $$\ce{K + SO2->K2SO3 + K2S2O3}$$


texts:
I am new to organic chemistry and am confused regarding the following question:

Does the geometrical isomerism of 3-methyl-2-heptene fall into the category of trans vs. cis, or the category of Z vs. E? And what is the rule that determines whether it falls into the first or the second category?

My textbook is not clear on this.

Many thanks!


texts: A drop of water in a tin of sugar: Which one's the solvent, the sugar or the water?

texts:
The other day, when we were dealing with the chapter Solutions, our teacher asked us this:

  If I add a drop of water, to a tin full of sugar (without mixing it in), what's the solvent here? The water or the sugar?

Naturally we were taken aback by the 'unorthodox' nature of the question. Seeing that none of us were in a position to answer that any time soon, he gave us the "answer":

  It's the sugar. If you remember the definition we learnt ( solute + solvent = solution; between the solute and the solvent, the solvent is one present in a larger quantity and is in the same phase/state of matter as the solution ) you ought to have realized that, since there's more sugar than water, and at the end of the process the tin's filled with a solid.

Now that may seem like a clever way of testing our command of terminologies and definitions, but I saw a hitch there.

A solution is defined as a homogeneous mixture.

Adding a drop of water to a tin of sugar (without mixing it in) does not result in a homogeneous mixture. So as interesting as the question is, I feel it's flawed on this account... because what we're dealing with isn't technically even a solution.

Now I told this to my teacher, but he (quite deftly) side-stepped my query...a subtle way of indicating that he's not comfortable discussing this.

So I guess my question here boils down to this:

Was my teacher's "answer" correct? Or was the question seriously flawed to begin with?

EDIT-

I wouldn't call this a duplicate. Sure, I mean, both my question and the other one that was linked with this was about identifying the solvent and solute but I feel my question is distinct because:

1) It isn't answered well enough in the other question (that answer was too generalized... I've given a specific instance here)

2) I also want to know if a drop of water added to a tin full of sugar (without mixing it) can be considered a solution.


texts: How to dissolve beeswax on the underside of a porous wood structure

texts: Honeybees, like most insects, communicate through smell. They are attracted to the smell of beeswax. My profession is to rescue and relocate honeybees that have taken up residence inside walls, attics and chimneys. New bees should be discouraged to return by removing all beeswax residue so I recommend scraping down to bare wood and then encapsulating with oil based spray paint. The scraping process is laborious, time consuming and inferior since wood is soft and porous. It would be ideal if a chemical could be applied that would actually dissolve the beeswax without harming the structure. Occasionally bees build over electrical wire and galvanized hurricane ties with hundreds of 8 mm dimples making cleaning very difficult. Heat and a wire brush may work but I sense that heating beeswax only makes the oil spread out. Remember this is on the underside of studs, etc so letting solvent sit to dissolve will not work unless in gel form. Any chemist have suggestions?


texts: P2NP synthesis ammonium acetate catalyst?

texts:
I am going to try to prepare some P2NP from benzaldehyde and nitroethane following this procedure:

The aldehyde (5g), 5 ml. of the nitroalkane, and 2g of ammonium acetate were added to 20 ml of glacial acetic acid. The resulting solution was refluxed for two hours and then poured into ice-water. If a solid product was obtained it was collected and recrystallized from methanol, ethanol, or acetic acid. If the product was an oil it was separated and crystallized, if possible, from one of the above solvents.

However, I got a bottle of reagent grade ammonium acetate from a chem supplier and it is very wet. To be fair, they never marketed it as anhydrous, though.

Does that matter when I'm not using a dean-stark trap? If so, how much will it affect the yield, and is there a way accessible for a hobby chemist to dry it?

What hydration state it is in - like is it trihydrate? This is important in order to calculate the amount needed. I guess 2g of anhydrous is needed in the procedure.

Update:
10g Benzaldehyde was poured in 50ml Sodium bicarbonate water solution, stirred and left to settle down for 30 min or so.

3.5g of very wet ammonium acetate was measured - it was foolishly assumed the salt is trihydrate and calculated that 2g salt is present in 3.4g trihydrate. However, that was left for 30min on the open as an experiment and picked up another 500mg of water, so this calculation is more or less incorrect. Some of the water can be removed by pressing against something like a toilet paper btw.

20g of GAA was added to 500ml RBF. The acetate was added to the acid and shook for a few minutes until fully dissolved. 5.5ml Nitroethane and 5ml from the washed Benzaldehyde were added.

This was refluxed for 2 hours with the condenser hardly needed at all. After that, the heat was stopped and the hot solution was poured into 150ml ice-cold water. No crystallization occurred whatsoever. The organic layer was picked up with a syringe and was 5ml of thick deep-yellow oil weighting 5.87g and with PH of approx. 7. This was put in the fridge for two hours but no crystallization occurred, just a hint of some cloudiness like in this photo:  (not as much, though), probably contained some P2NP but frustratingly little, and was not worth the efforts.
This was poured in 50ml of ice cold IPA for fun and it partially dissolved but was poured down the drain.
Obviously, a dean-stark apparatus is needed to monitor when water evolution will stop so the reaction is complete, and to get a reasonable yield.

My question is - what is in that yellow organic layer? Unreacted benzaldehyde and some P2NP, right? So, how can those be separated easily and efficiently? I read somewhere that this can be washed with sodium bicarbonate solution but I don't see why.


texts: Suggestions for reaction conditions to prepare methyl 2,4,6-trimethylbenzenesulfonate

texts:
I'm a beginner in organic chemistry and I wish to produce methyl 2,4,6-trimethylbenzenesulfonate.

My reactants are 2,4,6-trimethylbenzenesulfonyl chloride (solid crystals) and methanol (solvent as well as reactant). The product of this reaction should be methyl 2,4,6-trimethylbenzenesulfonate and HCl.

Now I've tried these many conditions: distilling the methanol, nitrogen inert atmosphere, slight heating about 40 °C, room temperature, closed system.

After trying these conditions and their combinations I'm not getting the product in the desired amount.

Kindly help me out and suggest a few tweaks and optimizations if possible. As far as my knowledge goes the problem seems to be with methoxy group.

This is the entire synthesis process, please check it out. I am stuck on step two of this synthesis.


texts: How to characterize gaseous ethylene that forms as byproduct?

texts:
I'm running a reaction that has ethylene gas as a byproduct. I have observed gas evolution as my reaction proceeded and I have other ways of verifying the identity of the main product, but I thought it might be cool if I could also test for the presence of ethylene.
Are there any simple tests I can use for this purpose? Obviously it is not easy to detect since it's a fairly non-reactive gas, so it doesn't have to have 100% specificity.


texts: Would gold have the negative charge in gold phosphides?

texts:
It should make sense that phosphorus has the positive charge,and gold itself
should have the negative charge in gold phosphide(and for any other gold phosphides) because phosphorus has a lower electronegativity than gold (phosphorus is 2.19, gold is 2.54),but then, they can both just share electrons. Is this true or not?


texts: Time to effervescent an effervescent tablet

texts:
Say I have an effervescent tablet and I put in water.  I thought that if I break the tablet in two halves it would dissolve quicker than with the whole table (without breaking), but it actually takes the same time.

What would be the scientific reason of this?


texts: Why does changing the dilution of an aqueous equilibrium shift the equilibrium?

texts:
Say we have the equilibrium $$\ce{A_{(aq)} + 2B_{(aq)} <=> C_{(aq)} + D_{(aq)}}$$ meaning the formula for the equilibrium constant is $$\ce{K_{c} = \frac{[C][D]}{[A][B]^2}}$$ My understanding is that adding more water would shift the equilibrium to the left (in the same way that decreasing the pressure would shift the equilibrium to the left if it was a gaseous equilibrium).

Why is this the case? What mathematically (using the equation) and physically (in terms of kinetics?) means that $\ce{[A]}$ and $\ce{[B]}$ must increase?

And why does the equilibrium constant remain the same?

Apologies if this is a duplicate, but I couldn't find a specific answer to this question.

Many thanks!


texts: Colour of the transition metal complexes

texts:
I read in my Chemistry AP class that the colour of the transition metal complexes is due to the wavelength of the visible light that is left unabsorbed, when the d subshell is split due to the repulsion between the ligand electrons and d subshell electron in the transition metal ion. When white light is passed through the complexes, the wavelength that corresponds to the energy ($\Delta E$) required to promote electrons in the split d subshell is absorbed. The part of the visible light wavelength that is left unabsorbed becomes the colour of the transition metal complex.

I was intrigued by a concept of absorption of light, relating it to absorption and emittion spectra. My question is: If we keep that complex isolated in the dark, where no light could reach it would the colour of the complex still be blue? I understand if that is done it wouldn't be visible to the naked human eye. I wonder if there is a way to find that out. Secondly, I was wondering if the colour elements obtain their colour in a similar way?


texts: Why are the bond angles in sulfur dichloride and oxygen dichloride not the same?

texts: Why are the bond angles represented below for each molecule not the same? they have the same form: one central atom and two others in the sides, so the bond angle has to be the same for the three, doesn't it?


texts:
I searched the internet and most of sites say there are 38 transition metals. But our textbook says that group 12 or the group of zinc can not be counted as transition metals, which already puts the number to 37.
Moreover, Sc, La and Ac also can't be counted as transition metals. That puts the number to 34. Y being in the same group as Sc should also be cancelled as transition metals making the number 33.
These are all my thoughts and haven't been varied by any reliable sources. And also it's based on our textbook. I would like to know what is wrong with these thoughts.
Note: The book considers thorium a d block element. Thus, according to the book the number of d block elements is 41.


texts: Does 1-bromo-4-chlorobenzene have a permanent dipole moment?

texts:
My first thought was there would be a dipole moment as chlorine and bromine are unequal in electronegativity. I have since looked up the electronegativity of both chlorine and bromine through the Pauling scale. The difference between the electronegativity is 0.20 according to the table. For reference, the difference in electronegativity between carbon and hydrogen is 0.25 on the same table.

Since this is the case, I am very confused about the dipole moment of this molecule. Since the carbon-hydrogen bond is so negligible, why should this difference be significant?

To add to my confusion I found a source stating Dipole moment = 0.
And Wikipedia only states: Dipole moment = D.

However, my textbook questions lists it as having a dipole moment with the simple explanation that Br and Cl have differing electronegativities (question 1.61).


texts: How does a d4 high-spin complex have a spin-allowed transition without violating the selection rule for total angular momentum?

texts:
1) I am confused by the fact that the spin-allowed transition for a high-spin d4 complex is 5E→T2

Doesn't this violate the spin selection rule for total angular momentum?

2) Also, for a d6 complex, some sources I've consulted with mention a one spin-allowed transition for a high-spin complex, and no spin-allowed transitions for a low-spin complex.

From my understanding of the spin selection rules and the use of the Tanabe-Sugano diagram, I found no spin-allowed transitions for a high-spin complex and 4 spin-allowed transitions for a low-spin complex (i.e. 1A1→1T1; 1A1→1T2; 1A1→1A2; 1A1→1A2)


texts: How to prepare iron(II) carbonate from iron(III) chloride?

texts:
Now, this is an awkward reaction first of all. I know how to prepare $\ce{Fe2(CO3)3}$ from $\ce{FeCl3}$:

$$\ce{2FeCl3 + 3Na2CO3 -> 6NaCl + Fe2(CO3)3}$$

But the question is asking for $\ce{FeCO3}$. It seems to be an impossible task but since this was asked in a public examination, does anybody know how to prepare $\ce{FeCO3}$ from $\ce{FeCl3}$ (in one, two or three reactions)?


texts: Products formed when solid CuCN is dissolved in aqueous KCN solution

texts:
Copper cyanide forms a complex coordination compound, when dissolved in a solution containing excess ($\ce{CN^-}$) ions.

My question is whether it forms $\ce{[Cu(CN)_4]^{3-}}$ only or both $\ce{[Cu(CN)_3]^{2-}}$ and $\ce{[Cu(CN)_4]^{3-}}$ complexes?

Wikipedia says that both complexes are formed, but I am not sure if its a reliable source.


texts: What is the benefit of high surface area electrodes?

texts: Some electrolytic apparatus is equipped with high surface area electrodes. The number of reduced/oxidized atoms is proportional to the total charge flowing through the cell. Does increasing surface area somehow enable use of greater currents?


texts: How to determine if an unknown is potassium chloride or potassium bromate?

texts:
In class, we were given unknown substances. I've narrowed the possible substances down to either potassium chloride or potassium bromate.
We were given several acids, indicators, and other chemicals (silver nitrate, calcium hydroxide, ammonium hydroxide) to test with. How could one tell them apart? Maybe with a precipitate reaction?


texts:
Which polar covalent bond of the following:

Cl-F

S-O

P-N

C-Cl

It's trivia - I guess. And I got it wrong.

Electronegativity list was given for the following:
F, O, Cl, N, S, C, H, P

My wrong reasoning was:
why would two highly electronegative atoms bond with each other. Even they did, given their high electronegativity as both pull the electron cloud to each side (tug of war, weak dipole moments) with much strength by forming a weak bond. I refused to consider the difference between electronegativity of the species. (Even I did, S-O would be the highest).

I applied the same to S-O and P-N as well.
C-Cl was the pick and bad!

C-Cl has a acceptable dipole moment given C's less en 2.55 and Cl's high en. 3.16. The size of atoms wise, Cl-F is shorter compared to C-Cl. Which is questionable.

I checked few other related questions and answers, such as this peculiar one and this.

As I read ron's answer (the latter), the concept is not about a compound like CCl4 which negates the polarity between C-Cl bonds in the tetrahedral geometry. Thus C-Cl is a polar covalent bond. (isn't it?)

Where did I go wrong in reasoning, what did I miss?
PS: Not homework but some theory revision questions. Trying to reinstate/expand the understanding of concepts.


texts: Molality of solution to be used when finding water separated from solution as ice

texts:
Question

$\pu{1 kg}$ of a solution of cane sugar is cooled and maintained at $\pu{-4 ^\circ C}$. How much ice will separate out if molality of solution is $0.75$?
$K_\mathrm{f} \ \text{(water)} = 1.86\ \mathrm{K\ kg/mol}$

Solution given:

$\Delta T_\mathrm{f} = 0 - (-4)=4$
$i = 1$ for sucrose.
Therefore, since $\Delta T_\mathrm{f}$ is defined as
$$\Delta T_\mathrm{f}= K_\mathrm{f}\cdot i \cdot \frac {\text{amount of sucrose in } \pu{mol}}{\text{weight of water left in }\pu{kg}}$$
[...]

My doubts
$\Delta T_\mathrm{f}$  is the absolute value of the difference of freezing point of pure solvent and the solution with the non volatile solute. Here, the freezing point of the solution is not $\pu{-4 ^\circ C}$. So how can we say $\Delta T_\mathrm{f}$ is equal to $4$?
Why does the molality term contain amount of remaining water in the denominator? In the original equation shouldn't it be the original molality here?


texts: Structural entity for the tattoo resembling spine surgery involving 6AL-4V ELI alloy

texts:
I have very little background in chemistry, so forgive me if I sound ridiculous and uneducated.

I want to have a tattoo designed in honor if my spine surgery that I had. I think that molecular structures (I think that's what its called -- the hexagonal structure stuff?) look pretty cool and I'd like to look into getting something like that.

Anyways, I dug some stuff up and came up with the alloy that orthopedic implants are usually made of, 6AL-4V ELI. Now, this is where I get stupid. Do alloys have molecular compositions at all? And if so, what would this one look like?
If I just sound dumb right now and there is none, is there an alternative structure that could be used?

Again, I'm sorry if this is a silly question and is just wasting time, but this surgery is something I'm really passionate about and I would really like to have something visual to represent it by.


texts: Why doesn't graphite dissolve in organic solvent?

texts: The graphene layers are held by weak van der Waals' force, this should be comparable to the force holding solvent particles. Why doesn't graphite dissolve in organic solvent and separate into graphene layers?


texts: Reasons for low melting point of gallium

texts:
J.D. Lee writes in Concise Inorganic Chemistry:

Gallium has an unusual structure. Each atom has one closest neighbor at a distance of 2.43 Å.
This remarkable structure tends towards discrete diatomic molecules rather than a metallic structure. This accounts for the incredibly low melting point of gallium at 30 °C.

That's not all, this surprised me as well:

Note that the boiling point for Ga is in line with the others, whereas its melting point is not. The very low melting point is due to the unusual crystal structure, but the structure no longer exists in the liquid.

Why does gallium exist as diatomic units, that too in a solid crystal, instead of forming the usual metallic crystal structure? And why not in liquid state (where it seems to be more free to make diatomic molecules)?
I might guess that $\ce{Ga2}$ might form stable MOs, but why do the other members of group 13 abstain from such behavior?
It is quite weird to see an element in the middle of a group staging a drama of exceptions like this, it's usually the 2nd period elements which do that.


texts: Why do some old masters paintings deteriorate faster than others?

texts: Specifically, Wikipedia states that Sir Joshua Reynolds' "The Age of Innocence" was painted by the artist over another one of his paintings because the latter was "had suffered some paint losses," and goes on to say that "Innocence itself has deteriorated since 1859." Why?


texts: How can two electrons lie together in an orbital?

texts:
Two electron of opposite spin can lie in a single orbital.. But what about the electron-electron repulsion.
Okay! I got that the nuclear charge rather the large Z-effective overcome this repulsion by pulling them together towards the nucleus.

One thing more turned out in mind that it may be the attraction of the two unlike pole of the magnet developed due to opposite spin of the electrons of an orbital, which may be reason for the two opposite spin electron lying in an orbital..

Am I right ?


texts: Should I use Murexide or eriochrome black T for EDTA titration with milk? I am heating the milk to different temperatures and trying to find how the amount of calcium differs (or doesn't).


texts: Can the inverse of a micelle be formed with non-polar solvents?

texts:
A micelle is formed due to the clustering of soap molecules wherein the interior of the cluster is formed by the hydrophobic end and the ionic ends are on the surface of the cluster.

So, if a non-polar solvent is used (Assuming non-polar solvents dissolve non-polar solvents), can the reverse of micelle be formed? That is, wherein the ionic end forms the interior and the hydrocarbon end the exterior?


texts: Is the equation pH + pOH = 14 valid at different temperatures?

texts:
$\mathrm{pH} + \mathrm{pOH} = 14$

For water at 60 degrees Celsius,

$K_\mathrm{w} = 1 \times 10^{-13} = [\ce{H+}] \times [\ce{OH-}]$

Hence, $[\ce{H+}] = 1 \times 10^{-6.5} = [\ce{OH-}]$

So $\mathrm{pH} = -\log(1\times 10^{-6.5}) = 6.5 = \mathrm{pOH}$

which gives $\mathrm{pH} + \mathrm{pOH} = 6.5+6.5 = 13$, not $14$

So is my math or chemistry wrong, or are there limitations on $\mathrm{pH} + \mathrm{pOH} = 14$?


texts: f-electrons in chemistry of heavy transition metals

texts:
In one lecture at a recent MCR-X conference I was puzzled by a side-note "f-hole is critical to describe DoS of $\ce{IrO2}$ correctly." The context was DFT periodic plane-wave calculations with pseudization of the core electrons.
This implies that f-electrons are somewhat involved into chemistry of Ir. More precisely, it seems that polarizability of f-shell affects subsequent d-shell in somewhat dramatic way.
Could someone point at relevant articles, preferably discussing the matter from both ab initio and experimental perspective? Bonus points for generalization of the matter: d-electrons affect chemistry of heavy p-elements in no less way.


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Hi so I was studying chemical bonding where i encountered a problem which is stated below.

When we talk about ${NO_3}^-$ we draw its structure as following

But the thing which I dont understand is that in two of the O atoms there are three lone pairs(ie: $6 e^-$) but as we know from O's $e^-$ config. (which is $1s^2 2s^2 2p^4$) there are two unpaired $e^-$ which will take part in bonding as there is no vacant orbitals for $e^- $ to get excited to . Now if in this O atom only one sigma bond is present then technically we are left with $5e^-$ and not $6e^-$ which is shown in the figure.

Similarly in the N atom (whose $e^-$ is $1s^2 2s^2 2p^3$ ) does not have any other vacant orbital to excite its $e^-$ thus showing that it can make only 3 bonds then why is it making 4 bonds( 1 pi and 3 sigma) ?


texts: Energies of d orbitals relative to the barycentre

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Rather than referring to the energy of an isolated metal atom, the weighted mean of these two sets of perturbed orbitals $(\mathrm d_{xy}, \mathrm d_{xz}, \mathrm d_{yz}$ and $\mathrm d_{x^2 - y^2}$, $\mathrm d_{z^2} )$ is taken as zero. This sometimes is called the barycentre. The difference in energy between the two $\mathrm d$ levels is given either of symbols $\Delta_\mathrm O$ or $10~\mathrm {Dq}$. It follows that $\mathrm{e_g}$ orbitals have $+0.6 \Delta_\mathrm O$ above average level and $\mathrm{t_{2g}}$ orbitals are $-0.4\Delta_\mathrm O$ below the average.

It might be basic but why is orbitals split in $-0.4$ and $0.6$? If the barycentre is at the average then the orbitals should be split in $-0.5$ and $0.5$ below and above average, no?


texts: Equation of combustion of heavy fuel oil (HFO)

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We are researching the use of heavy fuel oil (HFO) on ship vessels, but are having trouble finding the equation of the chemical combustion process of HFO. I understand that it contains long chains of hydrocarbons, however it would be helpful if someone could help us towards finding it.

$$\ce{CH4 + 2O2 + N2 + H2S -> 2H2O + CO2 + NO + NO2 + SO2}$$

So far we have found that the base equation, including pollutants in HFO, comes down to to the above according to www.petroleum.co.uk.


texts: Is it possible to find fire outside the Earth?

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Excuse me if the question is silly, I have very little knowledge of chemistry.
We can find oxygen in many places in the universe, but all the combustibles we use to light fire seems to be organic: carbon, oil, wood, alcohol... so if that is true, we could only find fire on Earth, as long as we don´t find organic materials in other planets.

Another way of asking the same question could be: can we light a fire without organic material?

Note that I mean fire as a result of a combustion. The Sun would be a non-valid example, as it works by fusion.


texts: What causes the yellow colour in the Briggs-Rauscher oscillating reaction?

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The color changes are due to different concentrations of supposedly $\ce{I2}$ (which causes the yellow/amber color), $\ce{I-}$ (colorless) and $\ce{I3-}$ (dark blue).

Since iodine ($\ce{I2}$) is barely soluble in water, I do not understand why in this case it would be.

If one was to put just iodine in water and mix it thoroughly, the color change of said water would not be as visible to the extent of the Briggs-Rauscher reaction.


texts: IUPAC name of aldehyde with two functional groups

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I am confused as to what suffix to use for the following compound:

Should it be carbaldehyde or just -al, like should it be propane-1,2-dicarbaldehyde or should it be propan-1,2-dial?
Or maybe it's 1-methylethane-1,2-dial? I am pretty sure its either of these three or maybe something else.


texts: Cyanide complexes in Molecular Orbital Theory

texts: In molecular orbital theory, please explain why cyanide ion combines with metal from the carbon end and not from the nitrogen end?


texts: Standard abbreviations for polycyclic aromatic hydrocarbons, similar to those for nucleic and amino acids?

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The Nature paper Characterizing particulate polycyclic aromatic hydrocarbon emissions from diesel vehicles using a portable emissions measurement system addresses polycyclic aromatic hydrocarbons (p-PAHs) and both the text and the plot below make extended use of short, mixed-case abbreviations for various specific p-PAHs.

Question: Do these refer to some standardized naming convention for p-PAHs? If so, where can this be found?

  Figure 2. Average distance-based emission factors for each p-PAH component according to the engine type.

(electronically-controlled fuel injection (EI) and mechanical pump fuel injection (MI))

For amino acids and nucleic acids for example, standard one- and three-letter abbreviations exist:

Table of standard amino acid abbreviations and properties
Table of Amino Acids and Their Abbreviations
Nucleic acid notation

Here is an example of a plot where the abbreviations are not used. From Figure 20 of polycyclic aromatic hydrocarbons in automotive exhaust emissions and fuels: