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7,308 questions with no upvoted or accepted answers
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33
votes
2answers
974 views

How does the silver nucleate on glass in Tollen's reagent mirroring?

I want to know the exact mechanism for how silver would start to grow during a mirroring with Tollen's reagent. I've made two pictures to illustrate how I see the nucleation/growth process of silver ...
22
votes
0answers
2k views

How to Calculate Transition Dipole Moment from Two Known Wavefunctions

I am interested in calculating the transition dipole moment (TDM) from the information from two wavefunctions of different states. This is somewhat similar to calculating the molecular dipole moment ...
19
votes
0answers
294 views

Some materials emit more photoelectrons than others - why?

Again, I'm a physicist turning to chemists (so bear with me). So I've been measuring some materials by changing the wavelength of the incident light on the material and I have a detecting tip like in ...
19
votes
0answers
338 views

Manuals for a Cahn TG-171 Thermogravimetric Analyzer

Recently a Cahn TG-171 Thermogravimetric Analyzer was donated to my school. We did not get a service or user's manual with it, and some of it still needs to be put back together. I have tried to ...
18
votes
0answers
1k views

Do Cyclohexane-1,3-diones Give Positive Haloform Reactions?

Recently a post appeared on ChemSE asking why cyclohexane-1,3-dione (dihydroresorcinol) 1a doesn’t give a positive iodoform test. Unfortunately, the post was subsequently taken down after several ...
17
votes
1answer
6k views

In rovibrational spectra, when exactly is the Q branch forbidden?

I'm aware that the Q branch ($\Delta j = 0$) is usually not observed in rotational-vibrational spectra of diatomic molecules in the gas state, however, I've heard different things about when exactly ...
16
votes
0answers
197 views

Tetrahedrane Properties and Analogs

I took a look into some tetrahedrane (C4H4) analogs, platonic hydrocarbon, basically very strained tetrahedral geometry at every carbon. I was wondering what will be the predicted delta H of ...
15
votes
0answers
1k views

Can we use phosphorous triiodide in Hell-Volhard-Zelinsky reaction?

With the help of HVZ reaction, we can get alpha-chloro or alpha-bromo carboxylic acid. But can we make alpha-iodocarboxylic acid with the help of HVZ reaction? I could not find any reference of HVZ ...
14
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0answers
183 views

What happens when para-water ice is suddenly melted?

Background (hydrogen) In the case of recently liquified hydrogen (which is quite cold of course) it must be re-equilibrated before loading on to a rocket as fuel to avoid a sudden exothermic ...
14
votes
1answer
292 views

Does CN4 with the following structure exist?

I am a mathematician, not a chemist, so my questions are rather combinatorial. I am intrigued by the possibility of the following binary compound: $$\ce{\overset{-}{N}=\overset{+}{N}=C=\overset{+}{N}=\...
13
votes
0answers
226 views

MNDO integrals in the global coordinate system

In MNDO and its descendants (Sewart's PMx models, Austin's AM1, MNDO/d, etc.), the nonvanishing two-center two-electron "coulomb integrals" are evaluated via a classical multipole expansion in a local ...
13
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0answers
351 views

What is d-orbital collapse?

When I was perusing the works of Schwarz on atomic structure, I came across the unfamiliar term of d-orbital collapse. He describes it as a variation in energetic sequence from group 1 to 3 elements ...
13
votes
0answers
177 views

Can pi backdonation occur on non-metal centers?

The common example of back-donation is the interaction of a CO molecule with a metal center (d-orbitals) on a surface. Can a similar mechanism occur between CO and a non-metal center, like oxygen on ...
13
votes
0answers
308 views

What is the largest coupled cluster calculation that has ever been done (as of March 2019)?

I am doing some research and trying to make sure the numbers I am reporting are accurate. I found that the paper by Sylvetsky et. al. says:[1] We were, however, able to complete a ...
13
votes
0answers
311 views

Rotation around CC bond in 1,2-dioxetane: transition states and local minimum structures

TLDR: What: Potential energy surface associated with rotation around CC bond in the ring-opened version of 1,2-dioxetane. How: State average(4)-CASSCF(12,10)/VTZP constrained geometry optimizations ...
12
votes
0answers
184 views

Calculating Triplet-Triplet Spin-Orbit Coupling

According to the Q-Chem manual [1], the singlet-triplet spin-orbit couplings between a singlet excited state $I$ and a triplet excited state state $J$ is: $$\langle\Phi_\text{singlet}^I|\hat{\mathrm H}...
12
votes
0answers
277 views

Aza-enolates: why no reaction at N

My understanding is that aza-enolates have an advantage over enamines in enolate-type alkylations because the reaction at N is less likely. As a result, unactivated electrophiles can be used (i.e. ...
12
votes
0answers
206 views

Accuracy of quantum chemistry calculations on iodine neglecting relativistic effects

Triiodothyronine is a molecule with three iodine atoms. If we attempted to calculate its properties with ab initio methods like Hartree-Fock or more complicated ab initio methods which included ...
12
votes
1answer
6k views

Why do alpha-hydroxy ketones respond positively to Tollens', Fehling's, Benedict's, Schiff's and HgCl2 tests?

I learnt from a certain textbook that aldehydes and formic acid respond positively to Tollens', Fehling's, Benedict's, Schiff's and HgCl2 tests. However, in another textbook I read that even alpha-...
12
votes
1answer
307 views

What might serve as an initial starting photocatalyst for this large water-splitting solar simulator?

Question: What might serve as an initial starting photocatalyst for this large water-splitting solar simulator? Surely there must have been some planned experiments! The Gizmodo article Insane Light ...
11
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0answers
176 views

Constraints on pyrotechnic explosives that won't detonate spontaneously at 500 °C when landing on Venus?

The Space Exploration SE question Premature detonation of explosive bolts when landing on hot Venus? explains the need for and widespread use of pyrotechnic fasteners and cable cutters for Mars ...
11
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0answers
131 views

Rationalising diastereoselectivity of hydroboration using stereoelectronics

Using bulky reagents such as 9-BBN, hydroboration is often highly diastereoselective, giving rise to the 1,2-anti diastereomer: This is easily explained using a steric argument, with the major ...
11
votes
0answers
160 views

Green colour resulting from the formation of pi complex

Peter Sykes mentions in Guidebook to Mechanism in Organic Chemistry (6th ed.) on p.132 that there would significant differences in physical properties of the resultant mixture when we: React ...
11
votes
0answers
86 views

Is there a structured data source containing information on the World Health Organisation's Stability Testing Policies?

Hoping to automate some product testing guidance software, I've been attempting to find a (hopefully live, up-to-date) Database, Web-service, or other structured data source containing the ...
11
votes
1answer
204 views

Color of methoxy substituted phenyl rings when heated in the presence of acid

Anyone who's familiar with organic synthesis will probably have came across the DMB and PMB protecting groups. When TLC-ing compounds containing these protecting groups using common stains like ...
11
votes
0answers
232 views

Density Functional Theory with Generalized Gradient Approxmations (GGA) - What Happens if the Electron Density Shows a "Kink" at the Ion Position?

My question may be stupid, so please correct me if you find anything which is obviously erroneous. In the following I will place a question mark (?) besides points/steps I consider doubtful. My ...
10
votes
0answers
85 views

Using symmetry and group theory arguments to explain iron(II) in a tetrahedral crystal field

I am trying to figure out how to explain $1s \rightarrow 3d$ spectroscopic transitions for $\ce{Fe^{2+}}$ in $T_\mathrm{d}$ symmetry. These transitions make up the pre-edge region in K edge X-ray ...
10
votes
0answers
548 views

Why doesn't tantalum and tungsten form amalgam?

User @Poutnik has recently answered a question in which he quoted this statement from Wikipedia: Almost all metals can form amalgams with mercury, the notable exceptions being iron, platinum, ...
10
votes
0answers
695 views

Understanding two-electron integrals in Gaussian 09

I was comparing the two-electron integrals (electron repulsion integrals, ERI) printed by various well-established packages (Gaussian, GAMESS, Molpro etc.) and observed that Gaussian is the oddball in ...
10
votes
0answers
795 views

Finding the wavelength of maximum absorption of Tartrazine using Fieser-Kuhn

How would you use Fieser-Kuhn rules to calculate the wavelength of maximum absorption for tartrazine? Fieser-Kuhn rules states that: $\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$ ...
10
votes
0answers
126 views

In a molecular dynamics context, is the methyl rotation in propene a symmetric or asymmetric internal rotor?

In a prior question, I asked about the (a)symmetry of the potential energy surface of the methyl rotation of propene. In that context, the kinetic energy of the nuclear motions is of course assumed ...
10
votes
0answers
1k views

Why does magnesium prefer to insert into C–Br bonds over C–Cl bonds?

In the formation of a Grignard reagent from a compound possessing both bromine and chlorine, magnesium preferentially inserts into the C–Br bond over the C–Cl bond. For example, the formation of a ...
10
votes
0answers
97 views

Which potentials are suitable for molecular dynamics simulation of simple explicit solvents?

Which potentials (force fields) are suitable for adequately simulating (mixtures of) explicit solvents? Interesting rheological properties include viscosity, surface tension, heat capacity.
10
votes
0answers
891 views

Orbital and state correlation diagram for ring-closure of pentadienyl to a cyclic allyl

This is an exam question. I am to construct the orbital and state correlation diagram for one of the reaction below (disrotation or conratation). Also, I should explain whether the reaction is ...
10
votes
0answers
265 views

What is the difference between Fukui FMO approach and Woodward-Hoffmann rules?

If I understand correctly Frontier MO-theory is based on the perturbation theory of reactivity and the Woodward-Hoffmann rules consider conservation of orbital symmetry. Does FMO use symmetry ...
10
votes
1answer
3k views

Calculation of Atomic weight percentage in AAS

I am currently doing doping studies in a system similar to this ($\ce{A_{x}B_{1-x}}$) and I have to find atomic weight percentage of $\ce{B}$ element using atomic absorption spectroscopy(AAS). I have ...
10
votes
1answer
373 views

Does liquids that emit light when vibrated exist?

I am looking for a liquid that illuminates when vibrations are added. It does not have to be strictly chemical, it might as well be something else as well. Maybe a crystal in powder form mixed with ...
9
votes
1answer
125 views

Mutually immiscible liquids

How many mutually immiscible liquids can be stored in a glass bottle at S.T.P.? According to PATTLE, R. E. (1950). Systems of Mutually Immiscible Liquid Layers. Nature, 165(4188), 203–204. a ...
9
votes
0answers
167 views

Quantitative Transfer of Volatile Standards

(Edited w/ updates) Okay, long story short I work in a lab which has been working on cannabinoid analysis (in the licensed Canadian market) and have had a lot of issues surrounding the standards/...
9
votes
0answers
304 views

Vanishing integral rule for two-electron integrals

I understand the vanishing integral rule for a one-electron integral to be: $$\langle i | \hat{O} | j \rangle = 0 \hspace{1cm} \mathrm{if} \hspace{0.2cm} \Gamma_O \neq \Gamma_i \otimes \Gamma_j$$ ...
9
votes
0answers
143 views

What is this golden looking substance?

I am currently messing around with gallium compromising aluminum. I am using a titalium lock which is just a brand of aluminum padlock and I put a gallium-indium euctic alloy on the surface of it. It’...
9
votes
0answers
346 views

Cobalt Chloride in various solvent/water mixtures - tested

In a recent post the solvatochromic behaviour of cobalt chloride in acetone was discussed. There were some ideas how the acetone might influence the ratio between the blue $\ce{[CoCl4]^2-}$ and the ...
9
votes
0answers
127 views

What is required to achieve 999.9999 or finer gold?

After doing some research on gold purity, I found that the current record of gold fineness is at an astounding 999.999 fine achieved by the Perth Mint, Australia 1957. However, I could not find any ...
9
votes
0answers
63 views

Does the alpha effect apply to third row elements?

Alkylperoxy anions are stronger nucleophiles than alkoxides (the so-called alpha effect), but would an alkyldisulfide anion be a better nucleophile than an alkylthiolate anion?
9
votes
0answers
2k views

Why is the bond angle of N-N-N in hydrogen azide not 180 degrees?

Chen and Wang (2009) have reported an $\ce {N-N-N}$ bond angle in the hydrazoic acid molecule of $171.5$ degrees using B3LYP/6-311G** model. The wikipedia page for the molecule also reports a similar ...
9
votes
0answers
310 views

What "physical method" does Feynman refer to in The Feynman Lectures on Physics (Vol 1)

In the introductory chapter, Atoms in Motion, of the Feynman Lectures on Physics (Volume One), Feynman alludes to a certain "physical method", which can be used to determine the structure of ...
9
votes
0answers
208 views

Quenching rates in nucleation MD simulations

I am trying to perform nucleation simulations with molecular dynamics. To prepare the metastable fluid, I am equilibrating at temperatures about 30 K above the melting temperature, and then "quenching"...
9
votes
0answers
636 views

Free Web-Based Orbital Solver to look into the Walsh orbitals of a perturbed cyclopropane

There exists a free online orbital calculator. When I draw cyclopropane it plots three molecular orbitals, but unfortunately it doesn't use the Walsh orbitals. Are there any free online tools which ...
9
votes
0answers
821 views

Can I make Ferrofluid without evaporating Ammonium?

I want to make ferrofluid, which is ferromagnetic particles suspended in a carrier fluid. Three methods I have seen involve using magnetic ink (for MICR codes), cassette tapes, or ferric chloride as ...
9
votes
0answers
186 views

How to get defect-energy level diagram from PL data

I am reading this article Phys. Chem. Chem. Phys. , 2011, 13, 14902-14905 and seen that the authors have drawn a image of defect level using PL data Can you explain me how this diagram can be drawn ...

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