Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
674
questions
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1answer
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Why is ephedrine optically active?
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 ...
4
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0answers
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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 ...
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0answers
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What is the difference between a quaternary center and a stereogenic center? [closed]
In other words, can a carbon with 4 substituents be quaternary but not stereogenic? For example, a carbon with an R1 group, an R2 group, and two R3 groups?
Thank you!
13
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1answer
360 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.)
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0answers
46 views
Checking chirality of a molecule [duplicate]
I know there are many symmetry elements like
Plane of symmetry
Centre of symmetry
N fold axis of symmetry
, but I am confused when will a molecule be chiral, if I say it should not posses any symmetry ...
1
vote
0answers
30 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....
0
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0answers
61 views
The nitrile isomers of C5H9N
I got the following 3 isomers of C5H9N correct:
I also got the following fourth isomer (ignore the blue dot, it was a slip of the pen!)
However, the given answers has the following 2 other isomers ...
2
votes
2answers
102 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?
0
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1answer
33 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 ...
1
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3answers
69 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
34 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
152 views
Is (1R,3aR,4S,6aS)ā1,4ādibromoāoctahydropentalene 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
70 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
23 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
55 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
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0answers
85 views
Number of stereoisomers of pentaneā2,3,4ātriol [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 ...
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0answers
44 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
67 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
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0answers
28 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
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0answers
28 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{...
1
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0answers
43 views
What do Ī³ (gamma) and Ī» (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 ...
1
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1answer
61 views
Identifying a meso compound
I am still a first year student; I was asked in the exam to identify the meso comound out of some choices. The answer key said that the compound below is meso. But I see no plane of symmetry here. Am ...
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votes
1answer
260 views
Why does [Ni(gly)2] show optical isomerism despite having no chiral carbon?
For optical isomerism chiral carbon should be present i.e. carbon with four different groups but this compound doesn't have one then why does it show optical isomerism?
1
vote
1answer
110 views
Understand Hexabromocyclododecane CAS numbers
Hexabromocyclododecane has 16 possible stereo-isomers. So far so good.
I found that:
134237-50-6 is the CAS of alpha-Hexabromocyclododecan
134237-51-7 is the CAS of beta-Hexabromocyclododecan
...
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0answers
62 views
How many monochloro products including stereoisomers of the given compound are possible?
I tried solving problems and I got 2 products.
However according to my book the answer is 3 products.
1
vote
1answer
97 views
How many dichlorinated products including stereoisomers can be isolated when (S)-2-chlorobutane reacts with Cl2 /hv?
This is my attempt at solving this problem. I get 6 products. However my book says the answer is 5 products.
0
votes
1answer
34 views
Stability of Gauche and Anti form in conformational Isomerism
I came through this question: Which form is stable Gauche or Anti in F-CH2-CH2-F?
My answer: Due to lone pair repulsion Anti form should be more stable but the answer is given Gauche form. Please tell ...
1
vote
1answer
61 views
Do we need to check for all kinds of symmetry in a compound to declare it achiral?
I know that a compound is achiral if it contains any one of the following kind of symmetry.
1.Plane of symmetry
2.Centre of symmetry
3.Normal axis of symmetry
4.Alternate axis of symmetry
It is ...
5
votes
0answers
57 views
Type of chirality in polycyclic compounds
Ignoring whether or not this molecule could exist, is there a name for this type of chirality? This molecule's mirror image cannot be superimposed on itself but there are no chiral centres.
Even ...
1
vote
3answers
2k views
What do (2S,3S) and similar notations mean?
When my textbook is discussing stereoisomers with more than one chiral centers, it's using notation like (2S,3S) being an enantiomer with (2R,3R) and so forth. I understand R and S configuration, and ...
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1answer
532 views
What does simplest optically active alkene mean? [closed]
I am confused between whether we will call 2,3-dimethyl-cyclopropene or 3-methylpent-1-ene as simplest optically active alkene. Does āsimplestā mean aliphatic, or does it mean having least number of ...
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votes
1answer
81 views
Terminologies used in isomerism [closed]
What is the difference between the terms constitutional isomers, stereoisomers, geometric isomers?
I know cis and trans-1,2-dichloroethane shows cis trans isomerism and 1,1 dichloroethene, 1,1,2 ...
1
vote
1answer
238 views
Stereo-isomerism in 7-methylbicyclo[2.2.1]hept-2-ene
The above are two compounds.
The objective is to find if the compounds are identical/enantiomers/diastereomers
I can see a plane of symmetry if we keep the $\ce{H-C-CH3}$ in the plane. So, ...
1
vote
1answer
268 views
Number of chiral centers in penicillin V
I have often seen that in many drugs chirality plays a role. So I was trying to analyze the structure of Penicillin V.
What is number of chiral centers in the structure of penicillin V? Is the ...
0
votes
1answer
64 views
Which chiral carbon do L and D in L- or D-glucose refer to? [duplicate]
I see and D- and L- glucose are mirror images of each other. and I understand D and L are for chirality. But it is not clear which carbon do D and L refer to. Could anybody let me know? Thanks.
What ...
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votes
1answer
83 views
Nucleophilic allylic substitution via SN2 [closed]
Since SN2 reaction is more favorable with primary substrates, do allylic primary halides undergo nucleophilic substitution reaction mostly on carbon 1 via "SN2". and in case of secondary ...
1
vote
1answer
618 views
Pseudo chiral centre
I was reading about stereoisomers and I came across a term pseudo chiral centre. I looked up on the net for its definition and found a weird formula for calculating no. of isomers if the compound has ...
6
votes
3answers
263 views
Diastereomers or not
Why is the first one not a pair of diastereomers while the second is?
The only reason I could think of was in the first $\ce{Me}$ is the same as $\ce{CH3}$ that is same groups even though differently ...
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votes
1answer
52 views
How to obtain optically pure mixture from racemic mixture [closed]
I recently studied stereo chemistry in school.All i know is that compound are optically active if they have no plane of symmetry and about the nomenclature we follow nomenclature.......
My questions
...
5
votes
1answer
171 views
In the absence of a physical model, how can I use free software to visualize stereochemistry?
In a different question, the task was to turn a wedge-and-dash representation into a Fischer projection. This involved rotation of a fairly complex molecule - either as a physical model or a mental ...
0
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0answers
37 views
Is nitrogen with 3 different substituents and lone pair a chiral center? Does it make the whole compound chiral too? [duplicate]
Is nitrogen considered a chiral centre or stereocenter when it has three different substituents attached to it along with a lone pair.
By definition LG Wade says
An asymmetric carbon atom is the ...
4
votes
1answer
185 views
Mechanism of three-membered lactone hydrolysis in base
I was reading up on the participation of neighboring functional groups and in the reaction below, I was wondering why hydroxide attacks the CāO bond instead of the carbonyl group of the lactone. ...
2
votes
0answers
35 views
Solvent shell collapse
In "advanced organic chemistry part A" book page:306&307 , the author uses the term 'solvent shell collapse' when talking about the reason for retention of conformation in tertiary ...
1
vote
1answer
106 views
į“ -amphetamine, Ź-amphetamine
The following structural formula (source: Wikimedia) is labelled į“
-amphetamine:
A Fischer projection of this molecule would contain, I think, the following line:
$$\ce{H2N-C-H},$$
and I would have ...
10
votes
1answer
516 views
R/S configuration of bridging carbon in bicyclic system
I am trying to figure out the R and S configuration of bridging carbons in bicyclic systems.
In the image, there are two bicyclic systems and depending on the position of the Br substituent, the R or ...
1
vote
1answer
179 views
sp2 hybridisation of alkyl radicals causing formation of racemic mixture
What I know about $\ce{^{.}CR3}$ radical is that it has both $\ce{sp^2}$ and $\ce{sp^3}$ character but the $\ce{sp^2}$ character dominates and so the radical is $\ce{sp^2}$ in nature.
So, suppose we ...
10
votes
1answer
500 views
How is plane polarized light rotated by chiral compounds? [duplicate]
There are plenty of questions related to this topic on this site but no proper answer.
Can anyone please explain to me how plane polarized light is rotated by chiral compounds, and why it cannot be ...
0
votes
0answers
65 views
Which has a higher enol content between 4-Pyridone and Cyclohexa-2,5-dien-1-one?
I am new to organic chemistry but here is what I feel. 4-Pyridone will have a lower enol content as in its keto form it has higher resonance stabilisation due to the involvement of lone pairs on ...
3
votes
2answers
257 views
Conversion of molecular structure into Fischer projection for compounds having more than two chiral carbons
Question
What is the Fischer projection of the given compound's enantiomer?
Answer
My attempt
I tried to solve this by first converting it into the Fischer projection of the given compound and then ...
2
votes
1answer
136 views
Assigning R/S configurations to Fischer projections of 3āchloroā2āhydroxybutanoic acid
A question requires you to assign the R/S configuration for 3āchloroā2āhydroxybutanoic acid:
In the answer, while assigning the configuration to carbon #1, apparently the group below is given the ...
