Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
702
questions
3
votes
2answers
40 views
Diastereomers - cyclic compounds [closed]
Why in this problem there isn't a diastereomer with the $\ce{-CH3}$ in the back (dash) and the $\ce{-CH2CH3}$ in front (wedge)?
-1
votes
1answer
23 views
Enantiomers and diastereomers [closed]
I don't understand why on the problem a. B and C are enantiomers, while on the problem b. B is identical to the last molecule.
1
vote
0answers
64 views
Determining priority for a cyclic compound
I have problem in determining the CIP priorities in (S)-ketamine.
What is the order of priorities for esketamine? Does the carbon bonded to the ring with chlorine have higher priority compared to the ...
4
votes
1answer
165 views
Assigning E–Z configuration for alkenes with cyclic substituent groups [duplicate]
I was taught that according to CIP rules, we must check the priority order for the substituents. But how can we do the same for molecules with cyclic groups as substituents?
How do we compare the ...
2
votes
1answer
166 views
How can a compound having a plane of symmetry be Chiral?
The compound( Given in the image below) is treated with $\ce{excess H2 in Pt}$.
Here, (a) - The given compound. (b) - What the answer should be according to me.
(c) - What the actual answer is:
Q1 - ...
-1
votes
0answers
41 views
Is glycine the only optically inactive amino acid? [duplicate]
Glycine is stated as the only optically inactive amino acid in one of my textbooks. But if you make up an amino acid, with another $\ce{-CH(COOH)(NH2)}$ for the $\ce{R}$, arranged in the opposite ...
1
vote
0answers
21 views
How do electrostatic effects effect facial selectivity in addition to cyclic oxo-carbeniums?
I was reviewing Dave Evans' notes for stereochemistry of C=X electrophile additions, and found this slide detailing differences in additions to cyclic oxo-carbenium electrophiles, but I don't ...
4
votes
1answer
77 views
How is chirality center defined for an atom with 5 substituents?
I understand that carbon atoms normally only have up to 4 substituents and the R and S chirality centers are defined for 4 substituents. Is there a similar convention of 'chirality' for an atom with 5 ...
6
votes
4answers
593 views
Ramachandran plot Phi(ϕ) Psi(ψ) dihedral angle Convention for Zero, Positive and Negative value- old and new
Update: possible duplicate: What is the precise definition of Ramachandran angles?. Question modified.
G.N. Ramachandran et al, in their own work (PMC) (DOI), did not used phi(ϕ) and psi(ψ) as we use ...
4
votes
1answer
62 views
Does syn-dihydroxylation form racemic mixture?
I have been asked to determine the nature of the product for the following reaction:
And as I recognized this reaction to be a case of syn-dihydroxylation, my obvious response was that the product ...
3
votes
0answers
29 views
Does optical isomerism fall under the category of stereoisomerism?
I have been asked to find the total number of dichlorination products (including stereoisomers) for the following reaction:
I have figured out nine possible structures out of which two are optically ...
-3
votes
2answers
99 views
Enantiomers or identical structures?
What is the relationship between the following pair of molecules? Is the underlined answer correct? Explain.
I'm getting mixed answers. Some say these are identical molecules. Other say these are ...
0
votes
3answers
69 views
What exactly is a 'chiral centre' in a carbon compound? [duplicate]
The typical progression (in books, YouTube videos) of explanation of chiral carbons in a compound is as follows:
Chiral compounds are non-superimposable by their mirror-image;
It is easily seen that ...
0
votes
0answers
55 views
Which would have higher priority according to CIP rule (Cyclic Substituents)? [duplicate]
So if we were to assign E-Z nomenclature to this compound :
then the Ethyl group would obviously have more priority than methyl group, but I am confused whether out of Cyclopropane and Cyclobutane ...
0
votes
0answers
40 views
What are the limitations of the D, L system and the (+), (-) system for naming organic compounds
In organic chemistry, both the D, L system and the (+), (-) system are widely used, in conjunction with the modern (R, S) system.
The D, L system names an organic molecule based on the direction that ...
1
vote
0answers
32 views
In a pair of diastereomers, which of the following is true?
While going through my book, I came across this question and got really confused. Here's what the problem was:
In a pair of diastereomers,
Both can be laevo-rotatory or both can be dextro-rotatory
...
3
votes
0answers
45 views
Fischer's projection, enantiomers and diastereomers
Given Fischer's projections of a few stereoisomers of some compound, how can we find out if they are enantiomers, diastereomers, etc.? From what I understand, we can rotate the projections to have the ...
1
vote
1answer
95 views
Does anyone know what program was used to make this molecular structure picture? [closed]
I am a quantum chemistry beginer, and this picture color scheme is classic. I wonder how to make such pictures by myself.
3
votes
0answers
48 views
What happens when tran-2-butene reacts with aqueous bromine in the presence of chloride?
$\ce{Br2-H2O}$, containing some $\ce{NaCl,AlCl3}$ ?
I initially though that there would be anti addition of Br and OH to give 3-Bromobutan-2-ol but then I also got the intuition that NaCl might ...
4
votes
0answers
48 views
Does the chlorination of 4-methylcyclopentene generate two enantiomers or two diastereomers?
Does the chlorination of 4-methylcyclopentene generate two enantiomers or two diastereomers?
I think it makes two enantiomers (or one pair of enantiomer) since the starting compound is achiral, but ...
2
votes
2answers
98 views
How to draw chair-form for trans-decalin (with slight variation)?
I understand how to draw chair form for trans-decalin (figure 1) for the usual structure, but I am having difficulty if taken as shown in figure 2 wherein the hydrogens at bridge-head carbons are in ...
1
vote
0answers
14 views
Why does hydrogenation of this compound not result in a diastereomeric mixture? [duplicate]
In a question, this compound was given and it was asked:
"Hydrogenation of the above compound in the presence of poisoned Palladium catalyst gives?"
When I was answering it, I thought that ...
0
votes
0answers
28 views
Is 1,1,2,2-tetramethylcyclohexane not meso? (And visualizing cis-1,2-dimethylcyclohexane)
Considering the fact that cis-1,2-dimethylcyclohexane is not meso, does that mean that 1,1,2,2-tetramethylcyclohexane is also not meso?
I'm also having trouble understanding how the chair ...
2
votes
2answers
67 views
How do we know the natural abundance of isotopes on Earth?
Without knowing the Average Atomic Mass or the percent abundance, how do we know that Protium is the most prevalent hydrogen isotope? What methods did scientists use to come to this conclusion? How ...
3
votes
0answers
37 views
Stereochemistry of the product of crotonic acid with bromine
Is there a a simple rule for determining the stereochemistry for the product of a reaction between an unsymmetrical alkene like (2E)-but-2-enoic acid and bromine (anti reaction)?
If it's an anti ...
5
votes
1answer
115 views
Why are complexes of type MA3B3 not optical active?
Complexes of type $\ce{MA3B3}$ have two geometrical isomers, namely:
fac-isomer
mer-isomer
If we look closely at the mer-isomer, it has a plane of symmetry, so it is optically inactive.
But the fac-...
1
vote
0answers
29 views
Hydroboration, steroselectivity and anti-markovnikov product [duplicate]
My first question has to do with the fact that Hydroboration produces an anti-markovnikov product, why?. I don't see how that happens. A wikipedia artical says that B has a partial positive charge ...
0
votes
0answers
45 views
Does 3‐ethyl‐1,1‐dimethylcyclohexane have a stereocenter?
I knew that we have a stereocenter if the carbon is bonded to four different groups.
According to the stereocenter rules, I should have $\ce{CH2}$ bonded to the carbon of the stereocenter (marked with ...
-2
votes
1answer
58 views
Why these compounds don't show and show Geometrical isomerism? [closed]
I was recently studying organic chemistry related to Isomerism. I have doubt based on an example that is,
Why Cumulenes show GI?
Why 1-chloro cyclohexene don't show GI?
3
votes
2answers
143 views
Is it correct to look at plane of symmetry in substituted cyclohexane for determining a meso compound?
I read this question and it's answer by @orthocresol. Now, he has written that the compound in question is meso not because there is a plane of symmetry but because of the rapid flipping of the ...
10
votes
3answers
348 views
1
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2answers
111 views
How many structural isomers does 1,2-dimethyl-cyclohexane have?
Can someone tell me how many structural isomers exist for 1,2-dimethyl cyclohexane? My teacher said there is one structural isomer but I believe there aren't any because there is no other way to ...
-1
votes
1answer
55 views
Why is ephedrine optically active? [closed]
Acyclic amine in which three groups are different with a lone pair of electron is optically inactive and nitrogen is achiral because of the rapid pyramidal inversion.
Does similar inversion happen in ...
6
votes
1answer
60 views
Does the mechanism of AChE inhibition by Isoparathion depend on chirality?
It is known that the inhibition of acetylcholinesterase by isomalathion can proceed either with diethyl succinate as the leaving group or thiomethyl, depending on the specific stereoisomer of ...
13
votes
1answer
484 views
What are the criteria for a molecule to be chiral?
What are the criteria for a molecule to be chiral?
(We frequently get questions of this type, so this is an attempt to construct a suitable general answer for duping.)
1
vote
0answers
33 views
Squiggly line in chemical bond notation [duplicate]
In general is there a convention as to how one interprets squiggly lines in chemical structure notation?
e.g. see the below sketch. I suppose it has something to do with cis / trans isomerism. But e.g....
3
votes
2answers
112 views
Chirality and Optical activity
Do all chiral objects rotate the plane of polarization of EM waves? For example my hand is chiral, will it rotate the plane of polarization of EM waves of suitable wavelength?
1
vote
1answer
37 views
Stereochemistry + isomer check
We start with compound M:
[Please imagine green bonds as dotted bonds going into the plane]
From compound M, we are told that the 3 membered ring is opened u using sodium azide yielding a mix of ...
0
votes
3answers
71 views
A question about rotational symmetry of organic molecules and in particular, the cyclic Isomers of C3H4X2
I was thinking about an organic chemistry problem a few days ago but reached a dead end. There were 2 parts to this question.
The first was thinking about the isomers of 'C3H4X2' [where X could be ...
1
vote
2answers
56 views
Diastereotopic methylene protons in achiral molecules
Are the protons in methylene groups of achiral molecules such as propane-1,2,3-triol or 3-hydroxypentanedioic acid diastereotopic?
Consider propane-1,2,3-triol. To me, replacing one of the protons in ...
6
votes
1answer
164 views
Is (1R,3aR,4S,6aS)‐1,4‐dibromo‐octahydropentalene chiral or achiral?
Is this molecule on the left chiral or achiral?
I believe it is achiral because its mirror image (on the right) is essentially the same molecule. But I was told that it is chiral because it doesn't ...
0
votes
1answer
591 views
Which are the Geometrical isomers of the complex [Cr(NH3)2Cl2(en)]+?Is it one or two?
I was recently studying coordination compounds and i came across optical isomerism shown by complexes.I think that the complex i gave above have 4 geometrical isomers(I think this is where I am wrong, ...
0
votes
0answers
25 views
Is writing D-(+)-glucose more correct than D-glucose? [duplicate]
In one of my books glucose is written as D-(+)-glucose everywhere.
D represents the position of
-OH group with respect to glyceraldehyde..
So D = (+)-Glyceraldehyde..
So won't writing D-(+)-Glucose ...
0
votes
1answer
83 views
stereochem of epoxide opening
Here I have an epoxide opening reaction, but I was wondering that when a nucleophile attacks, How would the stereochemistry work? I have 2 products I predicted and I'm not sure which one would be ...
0
votes
0answers
87 views
Number of stereoisomers of pentane‐2,3,4‐triol [duplicate]
What will be the number of stereoisomers of $\ce{CH3CH(OH)CH(OH)CH(OH)CH3}?$
By formula $2^n - 1 + 2^n + 1/2$ for $n$ being the odd number of chiral centres, it's $6;$ four optically active and two ...
0
votes
0answers
47 views
For a flat, planar molecule, how do you determine which side is up? Or down?
I was just reading about alpha and beta linkages in certain cyclic molecules, and it said that the alpha configuration was the one in which a hydrogen was sticking out above the plane, and an OH ...
3
votes
1answer
82 views
Chiral centres with stereoisomeric substituents
The structure of one particular isomer of 4-chlorohepta-2,5-diene is shown here. I am confused about how two of the propenyl groups attached to the central carbon have the same atoms with different ...
0
votes
0answers
52 views
In which of the these structures C-3 carbon is not a chiral centre?
In which of the these structures C-3 carbon is not a chiral centre?
I think that the answer to the above question should be both (b) and (c) as C-3 is attached to same groups and also they have a ...
0
votes
0answers
31 views
Are these molecular structures enantiomers or diastereomers?
What relationship exists between the two structures shown?
I think that since the configuration at the bridge head carbons remains the same and only there is an inversion at the carbon bearing $\ce{...
0
votes
0answers
58 views
What do γ (gamma) and λ (lambda) mean in organic chemistry?
From the Wikipedia entry on Cyhalothrin:
Pyrethroids such as cyhalothrin are often preferred as an active ingredient in agricultural insecticides because they are more cost-effective and longer acting ...
