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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Whether compound is optically active or optically inactive [duplicate]

Just wanted to ask whether a compound having chiral center but also symmetry(POS or AOS) is optically active or optically inactive. If there is no definite answer than what is most expected
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Meso Compound and Internal Line of Symmetry

Hey everyone:) I'm only learning orgo this year so please keep it relatively light! I am reviewing Meso compounds with a video by the organic chemistry tutor, where he draws the two molecules on the ...
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Is There a Problem with the Assignment of Stereochemical Descriptors by ChemDraw in Select Examples?

While using ChemDraw Professional 21.0.0.28 to construct some cyclic allenes and rotationally restricted biphenyls, I came across anomalous assignments of stereochemistry. [For the latest version of ...
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Reactivity of 1-bromo-4-tert-butylcyclohexane isomers with methanol

(1s,4s)-1-bromo-4-tert-butylcyclohexane (1) and (1r,4r)-1-bromo-4-tert-butylcyclohexane (2) are heated (E2) with $\ce{NaOCH3}/\ce{CH3OH}.$ Which isomer will react faster? What will change when $\ce{...
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1 answer
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Why is the 'side' of a double bond defined across the double bond horizontally rather than vertically? [closed]

When we are determining cis-trans isomerism, we seem to refer to a molecule's 'side' in relation to the double bond in a horizontal manner, as if we had drawn a mirror line through it horizontally. ...
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Optical activity of trans 1,2 - dimethyl cyclobutane [duplicate]

It is written in my textbook that the ultimate criteria for the compound to be optically active is that it must be unsymmetrical(i.e no plane of symmetry, no center of symmetry, no alternating axis of ...
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5 votes
1 answer
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Why 5-member rings prefer being cis-fused?

It always bothers me how whenever I am doing practice problems I never got a proper explanation as to why 5-member rings prefer(thermodynamically) being cis- rather than trans-fused( as opposed to ...
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What is the relationship between Ha and Hb in the given compound, trans-1,3 dichlorocyclobutane. Are they enantiotopic or homotopic?

The question is to find the TOPICITY relationship between Ha and Hb in the given compound, (trans 1,3 dichlorocyclobutane) They seem to be in the same chemical environment, so I tried the ...
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How does the size of a molecule subject to photo-isomerization affect it's isometric configuration?

When azobenzene is photo-excited to a higher energy configuration, the electron orbital take new energy levels and position's, changing the over all configuration of the molecule. Now, if various ...
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Is this formula for number of optical isomers correct?

For a symmetric molecule with an even number of chiral centres (for acyclic molecules with chiral centres only, not considering $\pi$ bonds or rings), the formulae (also mentioned in this question) ...
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When does the Mukaiyama-Addition follow which transition state and how does it affect the stereochemistry?

in the course on enantioselective organocatalysis, we discussed the route to hexoses via organocatalytic aldol addition and subsequent Mukaiyama addition. The use of either TiCl4 or MgBr2 leads to ...
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Number of stereoisomers of 1,3,5-trimethylcyclohexane

When I searched the stereoisomers of 1,3,5-trimethylcyclohexane, I got four structures given below. I don't get how structures 1 and 2, 3, and 4 are not the same. Could anyone explain?
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2 answers
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How can I find all possible isomers of a given molecule?

I attend a course on combinatorics (mathematics) which contains many examples related to chemistry. Unfortunately, I don't have enough chemistry knowledge to feel comfortable with the examples. For ...
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CIP Rule and giving priority to phenyl or alkene phenyl

The problem is to provide absolute configuration to Sulphur atom. I know that Oxygen atom will get the highest priority by Cahn Ingold Prelog rule but what about the next priority? I believe it should ...
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How many tetramethylcyclobutanes are possible? (structural+ geom) (no enantiomers)

I drew 5 structural isomers.(TMeCBut means tetramethyl cyclobutane) For 1,2,3,4-tetramethylcyclobutane I drew 4 geometrical isomers For ​1,2,2,3-TMeCBut I drew 2 geometrical isomers (similar to 1 ) ...
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What is the difference between Cholestanol 5alpha and 5beta?

What is the isomeric relation between 5Alpha Cholestanol and 5Beta Cholestanol. I know that those forms appear after Hydrogenation of Cholesterol but unfortunately I cannot find any article or ...
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8 votes
2 answers
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Identification of endo and exo products in this Diels-Alder reaction

This synthesis example is shown in the book Cycloaddition Reactions in Organic Synthesis by S. Kobayashi and K. A. Jorgensen (link), on p. 15: 8 is a chiral catalyst, which can be ignored, in the ...
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2 votes
1 answer
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Is it correct to class these two compounds as enantiomers?

This question is from GRB Problems In Organic Chemistry For Jee Advanced. Identify the relation between these two compounds: (a) Homomers (b) Enantiomers (c) Diastereomers (d) Different compounds ...
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Number of chiral centers in Proline

I think it's two, but I am not able to access/find any information on the net that supports my claim or justifies why it's wrong. One chiral center is the obvious carbon attached to $\text{-(COOH)}$ ...
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Can endo and exo products occur when the diene is not cyclic?

I have always thought that the diene needs to be cyclic for there to be endo and exo products. Perhaps, I formed this impression because most textbook examples that are used to illustrate the concept ...
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3 votes
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Why is 1,3-dimethyl-cyclohexane a meso compound?

So i was trying to find the plane of symmetry in 1,3-dimethyl-cyclohexane in chair conformation, but then i realised the plane is present only at a particular orientation [see figure]. So why do we ...
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1 answer
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Racemization on nucleophilic substitution by OH- ion [closed]

Here's the question I'm stumped by - According to the answer key, i) is the answer but why can't it be iv)? There is a chiral carbon in compound c) CH3(C2H5)CHCH2Br , so why won't the product (2-...
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Difference between threo/erythro and cis/trans nomenclature

According to what I have read, it seems that erythro isomers are defined in the same way as cis isomers and same holds true for threo and trans isomers. Is there any difference between these two set ...
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Relationship between the principal axes of inertia of an enantiomeric pair

If an object is chiral, its mirror image and itself are non-superimposable and represent two distinct versions of the same object. A hand, for instance, can be either the right hand or the left hand. ...
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Hydrogens of cyclohexanol are enantiotopic or diastereotopic, which is true?

I am studying spin-spin coupling theory in NMR. Below is an exercise from Mcmurry's organic chemistry. The textbook says that * stands for chiral center. But is it true? When I searched for it some ...
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Why this structure is diastereomers instead of enantiomers

In this diagram optical isomers has divided in to 2 categories, one is diastereomers and enantiomers. Is the example for diastereomers correct? For me its looks like enantiomers
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Why doesn't 2,3-pentadiene show geometrical/cis-trans isomerism?

There are two different groups bonded to each terminal C in the C=C=C system, and there is restricted rotation about the C=C=C. So why doesn't it show cis-trans isomerism? The most common answer I get ...
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1 answer
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Racemization of hydrocarbon in presence of AlCl3

Our textbook mentioned that the compound in the diagram racemizes in presence of $\ce{AlCl3}$, but it didn't explain anything. Any help regarding the mechanism of the reaction would be appreciated.
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Natural Sources for S-(-)-Limonene?

I'm interested in developing an undergrad organic lab that delves deeper into distillation/extraction, optical rotation and enantiomers. Our lab currently does a steam distillation extracting R-(+)-...
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How are these two enantiomers? [duplicate]

I was wondering how these two chair conformations are enantiomers, because they do not seem to be mirror images of each other. The molecule on the left undergoes a ring flip to achieve the ...
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Why is C-S-C bond angle in thiirane so small at 48.5 degrees?

Why is the C-S-C bond angle in thiirane (48.5 degrees) so much smaller than C-O-C bond angle in oxirane/epoxide (60 degrees). Source: https://coek.info/pdf-three-membered-ring-heterocycles-.html
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-4 votes
1 answer
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Why total stereoisomers is 1 even if no geometrical isomers and optical-isomers are present [closed]

Let's for example take the complex structure type $\ce{MA_6}$, What will be the Total number of Stereo-isomers (=[Geometrical-isomers]+[optical-isomers]). My effort was that There will be no G.I and ...
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How do chiral compounds rotate plane-polarised light? [duplicate]

I understand what decides if light is rotated but the exact mechanism through which it happens is still unclear to me. Could anyone explain the nature of the interaction between a specific chiral ...
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1 vote
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Total number of Isomers of [Co(NH3)5(NO2)](NO3)2 [closed]

I encountered this question in my country's Chemistry textbook of class 12. No solutions are published, but the answer given at the back states - "There are 10 possible isomers. (Hint: There are ...
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1 vote
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Prochirality and major/minor products

I got the following exercise question on configurations, which the textbook does not have an explanation that matches this question, so could someone please tell me whether my attempt is correct or ...
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1 answer
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Is a tetrahedral complex with two symmetric bidentate ligands optically active?

If the shape of of a complex $\ce{M(AA)2}$ (with $\ce{AA}$, a bidentate ligand) is tetrahedral, then is it optically active? Currently I know that it is optically inactive, but I want to know the ...
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For a structure of a compouund optically active, what is the number of stereo isomers if no geometrical isomers are present?

Suppose for example the compounds $\ce{M(AA)3}$ and $\ce{M(AA)3bc}$, with $\ce{M}$, the central metal atom and $\ce{AA}$, a bidentate ligand. What is the total number of stereo-isomers of both? I was ...
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1 vote
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Are these two molecules enantiomers or diastereomers?

I had a long discussion with my professor about these two molecules, and we both agreed to do some of our own research and reconvene. These two molecules appear to be non-superimposable mirror images ...
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1 answer
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Number of enol forms of acetylacetone

Here is what I tried: These are the two enolic forms that I could make. So according to me, the total number of distinct enol forms of acetylacetone is $2$. But the answer is 3, what am I missing?
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Converting Newman projection to dash and wedge structure

I want to convert the following Newman projection to a dash and wedge structure but the examples I've seen online are with simple molecules with methyl groups on the side. I wanted to show the long ...
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-2 votes
2 answers
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Why is the chirality center in (1R, 2S)-2-fluorocyclopentane-1-carboxylic acid 1R and not 1S?

I'm confused why the chirality center in (1R, 2S)-2-fluorocyclopentane-1-carboxylic acid, is 1R and not 1S. I'm personally think that the carboxyl carbon at C1 should have a higher priority than the ...
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2 votes
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Sn(II) compound stereoselectivity in aldol reactions

In "advanced organic chemistry: part B" fifth edition, page:130, the authors state that chiral proline-like additives to Sn(II) compounds can further increase stereoselectivity of aldol ...
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(How) can a reaction be both stereoselective and stereospecific?

From what I have learnt, stereospecific and stereoselective reactions are defined as follows - Stereospecific - The stereochemistry of the reactant dictates the stereochemistry of the product. Thus, ...
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Separation of Racemic Mixture

In the racemic mixture below, if it is reacted with Mosher's Acid Chloride, it would form X and Y. Can I ask why my book state that X and Y are not enantiomers and thus can based on differences in ...
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Stereochemical relationship between the given compounds

Are the given compounds enantiomers or diastereomers? Or are they identical? The compound is trans-1,2-dimethylcyclobutane: My reasoning is that they are identical. They are not mirror images, and on ...
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5 votes
1 answer
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The total number of stereoisomers of 1,2-dibromo-3,4-dichlorocyclobutane

I tried writing all the geometrical isomers for 1,2-dibromo-3,4-dichlorocyclobutane, and then saw if they were optical or not. And I am getting the answer as 10: However, the given answer is 8. I can'...
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Identify E/Z Configuration

[(2E)-4-ethylhept-2-en-3-yl]cyclopropane why it is named E Where according to cahn ingold prelog rules At left side Methyl is prior and on the right side the butane should be prior than cyclopropane
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2 votes
1 answer
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Determining R-S configuration with lowest priority groups in plane of paper

I was studying R-S nomenclatures and determining configurations of molecules when I came across a certain problem, which had the 4th priority group on the plan of paper (not on a dash or wedge) ...
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5 votes
1 answer
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stereoselectivity in aldol reactions

in "Advanced Organic Chemistry, part B" fifth edition book, page:103, the authors compare between aldol reactions where 1-substituted nucleophile is used. They stated that when the 1-...
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Why are glyosidic linkage of glucose and fructose rings often occurring at the 1' and 4' prime positions?

Here are some example combinations from my textbook: In all of these combined products, the reactive centres seem to be the carbon at first position/ fourth position from the oxygen in priority. Is ...
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