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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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 ...
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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 ...
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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 ...
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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.
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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-...
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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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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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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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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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Can cis-trans isomers interconvert?

Can cis-trans isomers interconvert via tunneling ?
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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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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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1answer
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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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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 ...
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87 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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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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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 ...
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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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861 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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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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563 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.
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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 ...
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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, ...
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772 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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82 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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