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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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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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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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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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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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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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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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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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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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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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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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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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 ...
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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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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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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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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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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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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 ...
user92687
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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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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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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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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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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, ...
user98209
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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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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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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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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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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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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.......
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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 ...
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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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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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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 ...
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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 ...
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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 ...
user92687
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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 ...
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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 ...
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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 ...
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Assigning R/S configurations to Fischer projections of 3‐chloro‐2‐hydroxybutanoic acid
A question requires you to assign the R/S configuration for 3‐chloro‐2‐hydroxybutanoic acid:
In the answer, while assigning the configuration to carbon #1, apparently the group below is given the ...
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Is chirality absolute or relative?
While going through some questions on chirality and optical isomerism, I came across this compound:
Note that I have marked 3 carbons as $C_1,C_2,C_3$
Its obvious that $C_1,C_3$ are chiral carbons.
$...
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Why is biphenyl not planar? [closed]
I've seen in a lot of books that biphenyl is not planar. I don't know why that is because both the carbon are $\mathrm{sp^2}$ hybridized so it should be planar. Can someone explain it to me?
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Number of Stereoisomers of C(CHClCH3)4
I am having trouble understanding why the structure
$$\ce{C(CHClMe)4}$$
has only five stereo isomers. According to my textbook, the stereo isomers correspond to the following series of absolute ...
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Can geometrical isomers be enantiomers?
I have just been pondering upon the question above. I have found this example and I am sure they are enantiomers, but do they also count as geometrical isomers?
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I need help with Cahn-Ingold-Prelog (boat conformation)
I need to decide if the chiral carbon (with the attached hydrogen) is in R-configuration or S-configuration. To be able to do that, I need to know which of the atoms are pointing backward, forward and ...
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E-Z system without a double bond
Can we apply E-Z nomenclature to geometrical isomers without a double bond. For example, can we use it for cis and trans isomers of 1,2-dimethylcyclohexane?
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