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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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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How to identify chiral carbon in rings [closed]

Chiral carbons are tetravalent and are bonded to 4 different groups, easy to see when we are dealing with carbons in a chain however, this is difficult when dealing with a ring. Consider the following ...
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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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Is there a way, formula, to calculate the possible amount of enantiomers and diastereomers in molecule?

So I have to calculate the max. possible number of enantiomers and diastereomers from a molecule(in my case beta-D-glucopyranose). I know that the stereoisomers are calculated using 2^n, where n is ...
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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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79 views

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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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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67 views

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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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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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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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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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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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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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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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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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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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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Of 2-bromobutan-2-ol and trans-1,2-dimethylcyclobutane which is chiral as well as dissymmetric?

In an examination I was asked to determine the molecules which are chiral as well as dissymmetric. There were four options, and among them, two were achiral, as they had an improper axis of symmetry. ...
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Confusion in D/L nomenclature [duplicate]

With regard to carbohydrates, it is known that in a Fischer projection, if the $-OH$ group is on the right side of the lowest priority asymmetrical (chiral) carbon, then we name it as D and if it is ...
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Chirality of conformations of butane

I have read that the conformations of butane are as follows: I came across a question about number of chiral conformations of butane. My Attempt : The total or fully eclipsed is achiral because it ...
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Confusion in R/S Nomenclature and Chirality [closed]

I have many confusions regarding optical isomerism: What is the use of the R/S nomenclature? I understand that it is used to distinguish between the different spacial arrangements that are possible ...
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How many stereogenic centers exist in the atropine?

I'm pretty sure that both C bonded to N are stereogenic centers. I don't know about the others, any help? Is this correct?
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How do molecules with opposite rotational photoisomerization bonds behave? [closed]

If a molecules bond change upon isomerization with the respective bonds straining the molecules as they orient themselves opposite from each other, would the molecule undergo some kind of ...
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Does 1,4-dimethylcyclohexane have a chiral center?

My textbook says that 1,4-dimethylcyclohexane (cis or trans) does not have a chiral centre, since two groups on the tertiary carbon (that are the part of the ring) are identical, and thus the compound ...
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Why is [M(AB)2] a geometrical isomer?

Our teacher told us that for coordination number 4 and tetrahedral shape $\ce{[M(AB)2]}$ doesn't have a plane of symmetry, so it shows optical isomerism. What if we take a plane passing through the ...
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How many conformations are possible for ethane?

I am talking on the basis of observations made on the Newman projection of ethane. According, to the various sources, that I found on many websites, the number of conformational isomers are 2. They ...
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Is the SN1 reactions stereospecific or stereoselective? [duplicate]

In the SN1 reaction, the product show retention and inversion. Since one of them is major unless it forms a racemic mixture, does it mean that the SN1 reaction is stereospecific?
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Determining if the product would be cis or trans after an anti elimination on fischer projections

I find these kind of problems really confusing for some reason, but I saw a way on the web and tried doing it that way: I considered the basic Fischer operations (Vertical: Below the plane of paper, ...
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Could Gaussian or Spartan software determine stereoisomers from conformational landscape of a molecule alone?

I read that, on some papers, conformers were generated by stereoconfiguration of the molecules and from there, they evaluated stability of each stereoisomer in terms of free energy differences between ...
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How do I label stereogenic centers R or S when there are 3 bonds in the plane and 1 bond coming out?

I need help with question (d). I labeled the O the first priority, then the C that's bonded to an O the 2nd, and the C above that is attached to 3 other C's the 3rd priority. So, I ended up getting S, ...
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Labelling of molecular motor isomeric forms as trans and cis

I am reading Koumura et al. (2002), a paper about molecular motors. It contains this figure: Being an absolute layman when it comes to naming my molecules I'm a little confused as to why the left ...
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How do you know if a compound with only one stereogenic center is trans or cis? [closed]

I understand that both of these compounds are R but I do not understand why A is trans and C is cis.

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