# 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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### 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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### 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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### Is there a planar molecule that is optically active? [duplicate]

Can a planar molecule be optically active? As per my knowledge, any molecule which has a plane of symmetry cannot be optically active and planar molecules have a molecular plane of symmetry. So, can I ...
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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, ...
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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....... My questions ...
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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 ...
424 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 ...
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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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### What is the difference in dehydration of cis- and trans-1,2-cyclohexanedicarboxylic acid in anhydride formation?

Is there some required stereochemistry for anhydride formation? Do both of them form the same product, or does one not even undergo dehydration? I looked up cyclohexane-1,2-dicarboxylic anhydride's ...
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### Strains in conformations of cyclohexane

I know some the basic kind of strains that can exist in molecules namely Torsional strain (Vanderwaals' strain), steric strain and angle strain. Is it possible to associate a particular type of ...
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### Chemical shift difference methyl groups in 4-hydroxy-2,5-dimethyl-3-hexanone

Can someone explain why the NMR Spectrum of 4-hydroxy-2,5-dimethyl-3-hexanone shows a chemical shift difference for the methyl groups at the end? Why aren't the other carbons have a difference? Below ...
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### MA3B3 isomers - is this same as meridional one? [closed]

I'm new to studying stereo chemistry. (Now I'm studying coordination complexes.) In my class material and other some datas(from google), it says that there is two, fac and mer. I want to know is ...
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### How to check which compound will show optical isomerism?

So my teacher told that those compounds which have one or more chiral carbon present in them it will definitely show optical isomerism because it has an optically active stereoisomer, but there are ...
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### Is it possible to estimate the abundance of conformers from J values?

I have a system of two disubstituted cyclohexanes and I want to estimate the abundance/ratio of the two based on the J values and if possible, roughly estimate the difference in free energy. To get ...
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### Find stereo isomers of camphor

The compound given is camphor: We have to find the total number of stereoisomers for this compound. Now I can see two chiral carbons so I thought the number would be $4$ but it turns out that there ...
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### Converting Fischer formulas to Newman projections

How are line diagrams of molecules converted to their Newman projections? All I got from looking it up is that one may convert a Fischer formula to an eclipsed conformation directly, and that this may ...
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### Find the number of geometrical and optical isomers of 1,2,3,6-tetramethyl cyclohex-1,4-diene

The compound given to me is 1,2,3,6-tetramethyl cyclohex-1,4-diene. The geometrical isomers for the following compounds are: The isomer on the right can also be an optical isomer with its enantiomer....
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### How is exact racemization possible? [closed]

A racemate consists of 50 % $d$ and 50 % $l$ forms of an optically active compound. But how can someone ensure exact 50% quantity comparing molecule by molecule? There will always be some difference ...
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### R-S configuration or Cahn-Ingold-Prelog configuration [closed]

How to assign R and S configurations in alkenes and more complicated structures ? I know that the groups attached to the sp3 hybridized carbon is first prioritized by atomic number then we see the ...
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### Number of optically active isomers of [Co(NH3)2Cl2(NO)(OH)]?

My Attempt: Since Compound is of the form M[a2b2cd] I got three optically active isomers of the form M[(ab)(ab)(cd)] , M[(ab)(ac)(bd)] , M[(ab)(bc)(ad)] and since NO is a bidentate ligand, total ...
In the above question I know that the three reactions involved are $\mathrm{S_N2}$ reactions and therefore there shall thrice inversion of the substitute. So, I got the solution for the MCQ as: ...