Unanswered Questions
4,669 questions with no upvoted or accepted answers
42
votes
0answers
792 views
How can I update a map/mesh and coordinates in a PyMol session file?
I have a PyMol session file I was using to create my figures. It contains a protein and ligand broken into several groups of atoms with a fair bit of overlap. There are also a few meshes built from ...
21
votes
0answers
211 views
Synthesis Golf X: TAK-457
I shall try to revive this!
A full FAQ post has been written on chemistry.meta.SE, explaining the premise of synthesis golf and the 'rules'. Please take a look at this before answering (if you haven't ...
21
votes
1answer
406 views
Why are lithides not known?
In the last few decades, many alkalides - anions of alkali metals - have been synthesised. The most famous is undoubtedly that of sodium: $\ce{[Na(\text{2.2.2-cryptand})]+Na-}$, but the alkalides $\ce{...
17
votes
0answers
461 views
How does the cyclopropyl group influence conjugation and aromaticity?
While answering the question Why isn't cyclobutane planar?, I recollected that cyclopropane and its derivatives behave like double-bond compounds, e.g. a cyclopropyl group can potentially be ...
17
votes
0answers
222 views
Single-molecule magnet with electrically-controlled permeability: How does the Titan Shield from Deus Ex work?
In a recent installment of Deus Ex game series there is an augmentation called "Titan Shield" (it has nothing to do with $\ce{Ti}$ element):
A neodymium skin underlay matrix built of nano-meshed ...
16
votes
0answers
465 views
Ambimodal transition states in some organic reaction pathways
In many computational studies, mechanisms appear to have so-called ambimodal transition states, i.e. a transition state which can lead to multiple products, in conflict to the common undergraduate ...
15
votes
0answers
235 views
f-electrons in chemistry of heavy transition metals
In one lecture on 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 ...
14
votes
0answers
8k views
Melting and boiling point trend in Group II
The following picture shows the melting and boiling point trends down group II elements.
I have added question marks where the variability in data was rather disturbing (over two hundred degrees ...
14
votes
0answers
1k 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 ...
13
votes
0answers
356 views
What was the lithium concentration in 1940's 7-Up?
I just came across this article in the New York Times, where lithium (or more correctly, lithium salts), a known anti-depressant had been added to beverages in the 1940's. They also mention that a ...
13
votes
0answers
731 views
Neighbouring group participation with and without retention of configuration in nucleophilic substitution of 2,6-dichloro-9-thiabicyclo[3.3.1]nonane
Treatment of the dichloride A under the conditions indicated gives B with retention of configuration, while treatment of dichloride C gives D with inversion of configuration.
I am having ...
13
votes
1answer
1k 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 ...
13
votes
1answer
1k views
Why is the endo product the major product in a Diels-Alder reaction?
I understand that the endo product is, at least in all cases in my textbook, the major product in a Diels-Alder reaction. However, I don't understand why this is the case.
The explanation in my ...
13
votes
1answer
329 views
How to treat pressure in computational chemistry?
I have a reaction where a gas at high pressure and a solution with all kinds of species is involved. How do I take pressure correctly into account to get reasonable values for $G$?
Do I calculate ...
12
votes
0answers
248 views
Why does a Diels–Alder reaction not occur here?
I have recently come across this organic chemistry problem.
I thought it would undergo simple Diels–Alder reaction
But it didn't turn out to be. The product to me looks like a nucleophilic attack ...
