Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
840
questions
98
votes
2
answers
38k
views
What is Bent's rule?
I'm all bent out of shape trying to figure out what Bent's rule means. I have several formulations of it, and the most common formulation is also the hardest to understand.
Atomic s character ...
- 19k
69
votes
4
answers
28k
views
How does Walter White make pure crystal meth using a non-stereospecific reaction?
In the highly-rated TV series, Breaking Bad, Walter White, a high school chemistry teacher recently diagnosed with cancer, takes to making the illicit drug, crystal meth (methamphetamine), by two main ...
- 37k
44
votes
2
answers
109k
views
How to derive these general formulae for number of stereoisomers of a compound with a possible plane of symmetry?
These formulae are used if the molecule has a possible plane of symmetry. One such example would be:
Here the carbons marked with an asterisk are stereogenic centres (the asterisk is not used to mark ...
- 1,458
34
votes
3
answers
3k
views
Why is 1-ethylidene-4-methylcyclohexane chiral?
As far as I can tell, there doesn't seem to be a chiral carbon in the compound, 1-ethylidene-4-methylcyclohexane. The C-4 of the cyclohexane ring has two groups with exactly the same connectivity, and ...
- 71.6k
29
votes
3
answers
67k
views
How do you separate enantiomers?
There are some stereochemical reactions that result in the presence of enantiomers. When moving forward with a practical organic synthesis, how does one usually separate them in order to continue with ...
- 965
28
votes
3
answers
2k
views
How to assign E/Z configuration according to the Cahn-Ingold-Prelog rules when subsituents differ only by stereochemistry
I stumbled-upon this compound:
I'm wondering how to determine the configuration of the double bond. Is it E or Z? How do I decide on the priorities when the substituents can only differ in the ...
27
votes
2
answers
182k
views
What is the difference between D and L configuration, and + and −?
What is the difference between D and L configuration, and + and −?
My textbook says they are two different things.
It also says that the correct way to name glucose is D(+)-glucose.
Could someone ...
- 1,161
26
votes
2
answers
31k
views
Is cis-1,2-dimethylcyclohexane a meso compound?
I was watching a video lecture today on hydrocarbons and came across this. The instructor says that, as there is a plane of symmetry, cis-1,2-dimethylcyclohexane is a meso-compound:
However, the ...
user14857
26
votes
2
answers
12k
views
What does lowercase r-s notation mean?
I came across a naming convention which I haven't seen before. I let ChemDraw name the following compound for me and got a name containing lowercase "r" and "s" configurations.
Can someone tell me ...
- 17.9k
25
votes
3
answers
14k
views
Can heteroatoms with lone pairs be chiral centres?
If a compound has a carbon atom with four different groups covalently bonded to it, it is called asymmetric and enantiomers of the compound can exist.
But imagine if one has a different central atom, ...
- 667
25
votes
1
answer
9k
views
Why is trans-cyclooctene chiral?
How does trans-cyclooctene exhibit chirality if there are no stereocenters?
Related follow-on questions:
Are all higher cycloalkenes chiral?
Do more double bonds cause a bigger number of ...
- 14.4k
24
votes
3
answers
16k
views
Why are allenes chiral?
How is 1-bromo-3-chloropropa-1,2-diene ($\ce{BrHC=C=CHCl}$) chiral? It doesn't have any carbon that is connected to four different groups.
- 3,345
23
votes
3
answers
11k
views
Why is the inversion barrier larger in PH3 than it is in NH3?
The inversion barrier in $\ce{NH3}$ is approximately $5~\mathrm{kcal~mol^{-1}}$ and that of $\ce{PH3}$ is $35~\mathrm{kcal~mol^{-1}}$. This has well-known stereochemical consequences in that amines ...
- 740
23
votes
2
answers
2k
views
Why don't trigonal S and P compounds undergo inversion at room temperature?
Most molecules containing nitrogen atoms in trigonal pyramid configuration undergo a relatively fast process of inversion at room temperature. On the other hand, the free energy barrier for phosphines,...
- 23.8k
21
votes
1
answer
7k
views
Molecular chirality and optical rotation
Why does having molecular chirality result in optical rotation? The dissymetry or chirality of molecules translates to the rotation of plane polarized light, the magnitude and direction depending on ...
- 6,795