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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Converting structures into Fisher projections

I am really struggling with converting pyrano/furanosides into their Fisher projection counterparts. Especially when they are drawn like in the shown projection. When do you know to connect the ...
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Are substituents placed alphabetically in the name of a cycloalkane?

I named this molecule 1,5-diethyl-2-methyl-4-propylcyclohexane. Is this correct? Or should we somehow use the size of the substituents?
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In a diene/triene, how do I assign stereocenters correctly? [closed]

[![Example molecule I'm trying to assign stereocenters to. ][1]][1] I don't really understand how the stereocenters are assigned when double bonds are involved. [1]: https://i.stack.imgur.com/WVnmj....
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Is eta hexachloro cyclohexane optically active compound?

Quoting from Wikipedia, Hexachlorocyclohexane (HCH), $\ce{C6H6Cl6}$, is any of several polyhalogenated organic compounds consisting of a six-carbon ring with one chlorine and one hydrogen attached to ...
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How to determine if the ring compound has optical isomers?

The first column and fourth column of the table below says that the compound has the plane of symmetry and is not optically active. However, I noticed that each side has different arrangement of the H ...
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How to depict small molecules such as D-glucose based on isomeric SMILES

The isomeric SMILES for D-glucose is C([C@@H]1[C@H]([C@@H]([C@H](C(O1)O)O)O)O)O. The Haworth projection looks like this: I can parse the SMILES and draw the ...
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How does bis(glycinato) Nickle exhibit optical isomerism?

I'm a medical practitioner but sometimes I find time to discuss few topics of chemistry with my son who has just passed out his 12th standard exams. Regarding optical isomerism I have learned that a ...
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Why are the products of Grignard reaction on an alpha-chiral ketone diastereomers rather than a racemate?

Comment on stereochemistry of products. This is a Grignard reaction and the product has two chiral carbons. I think it should be a racemic mixture. However, my teacher says the correct answer is ...
2 votes
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stable conformation of 2,3-dimethylsuccinic acid

I was researching for answering this question on Kolbe's electrolysis of 2,3-butanedicarboxylic acid (succinic acid). Turns out, this compound is not very well researched in particular, and shows few ...
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Is hydroxylamine monodentate or ambidentate ligand?

What is the total number of geometric isomers of the complex $\ce{[Pt(Cl)(py)(NH3)(NH2OH)]+}$? If $\ce{NH2OH}$ acts as an ambidentate ligand, then there should be six geometric isomers. Or is it ...
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Does no optical rotation always implies optical inactivity? [duplicate]

This question popped up in my mind in reference to this question, Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles? Suppose that I give a chemistry ...
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Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles? [closed]

Is a compound optically active if plane polarised light is deflected by an angle of n*(2π) angles(like 360°); as there won't be any deflection in the analyser of the polarimeter?
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Does the 3D structure generated with MolView violate the wedge-dash rules of "above/below the plane"?

I've been taught that in a wedge-dash diagram, the wedge represents a bond above the plane of the paper, and the dash represents a bond below the plane. Accordingly, I expected the structure of this ...
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Why is diequatorial trans-1,2-dimethylcyclohexane more stable than diaxial trans-1,2-dimethylcyclohexane?

Consider diequatorial trans-1,2-dimethylcyclohexane and diaxial trans-1,2-dimethylcyclohexane as shown in the figure below [1, p. 178]. In both compounds, the ring is free of angle strain. trans-1,2-...
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How does Entropy influence the racemization of an optically active compound?

We were doing the topic "Isomerism" in our Organic Chem class and there's a question in our worksheet whose answer I haven't really understood, the question is as follows: The racemization ...
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Stereochemistry of nitrosyl chloride addition to an alkene

My book states addition of $\ce{NOCl}$ to propylene results in 2‐chloro‐1‐nitrosopropane: Would it follow syn or anti addition? According to Mallya and Nagendrappa [1], the reaction would follow syn ...
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Monochlorination of (R)-2-chlorohexane: Number of possible chiral dichloro products

How many possible chiral dichloro products can be formed when (R)-2-chlorohexane reacted with one equivelent of $\ce{Cl2}$ in the presence of UV radiation (monochlorination only)? $$\ce{C6H11Cl + Cl2 -...
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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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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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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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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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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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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 ...
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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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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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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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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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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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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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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