Unanswered Questions
8,716 questions with no upvoted or accepted answers
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How to calculate transition dipole moment from two known wavefunctions
I'm 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 ...
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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 ...
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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 ...
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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 ...
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Tetrahedrane Properties and Analogs
I took a look into some tetrahedrane ($\ce{C4H4}$) analogs, platonic hydrocarbon, basically very strained tetrahedral geometry at every carbon. I was wondering what will be the predicted delta H of ...
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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 ...
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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 ...
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Inter electronic repulsion in s and d orbitals
This was written in a lecture slide:
Two electrons present in the same d-orbital repel each other more strongly than do two electrons in the same s-orbital.
Why is there a difference in the amount ...
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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 ...
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What explains the color in clear sigma versus green pi complexes formed by methylbenzene?
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 ...
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13
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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-...
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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 ...
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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}...
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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 ...
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Is gallium slippery at room temperature in an inert atmosphere?
Ice is slippery when it isn't too far below it's melting point because the surface molecules are less loosely bound than the bulk and form a thin liquid layer.
Pressure melting is a much smaller ...
