Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
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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 ...
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39 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 ...
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Is (Z)-1-bromo-2-chloro-2-fluoro-1-iodoethene optically active or optically inactive? [closed]
Is (Z)-1-bromo-2-chloro-2-fluoro-1-iodoethene optically active or optically inactive?
Need a solution of the given problem. My test says it is an optically inactive compound but there seems to be no ...
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1answer
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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?
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Number of geometrical isomers that are possible in the following compound? [closed]
The number geometrical isomers are present in the given compound is ?
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2answers
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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 ...
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2answers
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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 ...
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1answer
49 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 ...
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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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1answer
387 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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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....
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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 ...
4
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2answers
108 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?
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1answer
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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 ...
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3answers
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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 ...
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2answers
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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 ...
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1answer
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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 ...
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1answer
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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, ...
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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
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1answer
60 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 ...
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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 ...
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0answers
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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 ...
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1answer
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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 ...
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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 ...
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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{...
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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 ...
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1answer
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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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1answer
328 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?
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1answer
111 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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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.
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1answer
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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.
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1answer
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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 ...
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1answer
68 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 ...
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0answers
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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 ...
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3answers
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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
842 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 “simplest” mean aliphatic, or does it mean having least number of ...
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1answer
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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 ...
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1answer
252 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, ...
2
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1answer
415 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 ...
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1answer
68 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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1answer
90 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 ...
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1answer
845 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 ...
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3answers
266 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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1answer
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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
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5
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1answer
172 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 ...
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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
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1answer
198 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 C–O bond instead of the carbonyl group of the lactone. ...
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0answers
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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 ...
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1answer
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ᴅ-amphetamine, ʟ-amphetamine
The following structural formula (source: Wikimedia) is labelled ᴅ-amphetamine:
A Fischer projection of this molecule would contain, I think, the following line:
$$\ce{H2N-C-H},$$
and I would have ...
