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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Are all geometrical isomers are diastereomers? [closed]

Till now I knew that all geometrical isomers are diastereomers. Is there any example of Geometrical isomers which are not diastereomers ?
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Is syn addition possible with Br2?

How is this reaction correct? I have studied until now that with $\ce{Br2}$ only anti-addition takes place.
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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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Difference between enantiomers diastereomers meso and achiral compunds [closed]

I am currently doing high school organic chemistry but whenever i come across a reaction asking me to identify whether the product is enantiomer , diastereomer ,meso ,racemic ,optically active or ...
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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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Cis and Trans isomers of a cyclic compound

I am supposed to check whether or not 2-ethylidene-1,1-dimethylcyclopentane shows cis and trans isomerism and if so I must show them. My Attempt The carbon towards the right has two bonds, one with a ...
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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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E Z configurations of alkenes where one of the substituents is same (a ring) [duplicate]

[I dont understand how we assign priority to the c=c group which has both of its valencies satisfied with the same substituent. Should I open the ring? Even then wouldn't it be the same?]
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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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1answer
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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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1answer
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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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2answers
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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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1answer
389 views

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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1answer
199 views

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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1answer
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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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1answer
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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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1answer
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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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D and L configuration of monosaccharides

I got this question in the last week's test from Organic Chemistry. I am a bit confused in assigning D and L configuration. Help me understand the topic of D and L configuration and help with this ...
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Why do Enantiomers have different chemical properties with optically active reagents?

As I understand Enantiomers have similiar physical properties but they do show different chemical properties with optically active reagents. This point is something which I am not able to logically ...
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3answers
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Chiral center or not? Similar substituents, but still two possible structures!

As far as I know, the central carbon shouldn't be a chiral center because it has two identical substituents. And yet, these two compounds should be different from each other.. Is it possible to denote ...
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Does this molecule show cis-trans isomerism? [duplicate]

I want to find if the above molecule shows cis-trans isomerism, per an assignment. I am assuming that such isomerism, if present, will be shown by the substituted chlorines. It seems clear to me that ...
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How does optical activity work? [duplicate]

I have learnt that chiral molecules are able to show optical activity; that is, they are able to rotate plane polarized light by some angle. But how does it actually happen? Won't the orientation of ...
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1answer
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Why is the A-value of methoxy group lower than that of the hydroxyl group?

I am studying conformational analysis of monosubstituted cyclohexane. "A-value" refers to the energy difference between conformers with substitutent in equatorial (more favored) and axial ...
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Stereoisomers of 1,3,4,6-tetramethylcyclohex-1,4-diene

How many stereoisomers are possible for following compound (1,3,4,6-tetramethylcyclohex-1,4-diene)? My Approach the 1,4 methyl groups lie in the plane, whereas 3,6 are possible chiral centers. ...
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Odd/Even swap rule for chiral compounds in stereochemistry

I had this question asked in my exam, where I was supposed to find if this pair is a diastereomer: Now, I have learnt this rule where: Making odd number of swaps in a molecule means they both are ...
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1answer
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R or S configuration?

The respective configutations of a and b are...? I tried to find the answer for a (for me is: 2S, 3S) but I'm not sure of my results, can someone help me?
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Does PubChem have stereocenter location data?

I have spent the last couple of days learning to navigate, find useful information and use the download service on the PubChem website. One of the pieces of information you can find is a stereocenter ...
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Diastereomers - cyclic compounds [closed]

Why in this problem there isn't a diastereomer with the $\ce{-CH3}$ in the back (dash) and the $\ce{-CH2CH3}$ in front (wedge)?
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Enantiomers and diastereomers [closed]

I don't understand why on the problem a. B and C are enantiomers, while on the problem b. B is identical to the last molecule.
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Determining priority for a cyclic compound [duplicate]

I have problem in determining the CIP priorities in (S)-ketamine. What is the order of priorities for esketamine? Does the carbon bonded to the ring with chlorine have higher priority compared to the ...
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1answer
216 views

Assigning E–Z configuration for alkenes with cyclic substituent groups [duplicate]

I was taught that according to CIP rules, we must check the priority order for the substituents. But how can we do the same for molecules with cyclic groups as substituents? How do we compare the ...
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How can a compound having a plane of symmetry be Chiral?

The compound( Given in the image below) is treated with $\ce{excess H2 in Pt}$. Here, (a) - The given compound. (b) - What the answer should be according to me. (c) - What the actual answer is: Q1 - ...
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How do electrostatic effects effect facial selectivity in addition to cyclic oxo-carbeniums?

I was reviewing Dave Evans' notes for stereochemistry of C=X electrophile additions, and found this slide detailing differences in additions to cyclic oxo-carbenium electrophiles, but I don't ...
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How is chirality center defined for an atom with 5 substituents?

I understand that carbon atoms normally only have up to 4 substituents and the R and S chirality centers are defined for 4 substituents. Is there a similar convention of 'chirality' for an atom with 5 ...
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Ramachandran plot Phi(ϕ) Psi(ψ) dihedral angle Convention for Zero, Positive and Negative value- old and new

Update: possible duplicate: What is the precise definition of Ramachandran angles?. Question modified. G.N. Ramachandran et al, in their own work (PMC) (DOI), did not used phi(ϕ) and psi(ψ) as we use ...
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Does syn-dihydroxylation form racemic mixture?

I have been asked to determine the nature of the product for the following reaction: And as I recognized this reaction to be a case of syn-dihydroxylation, my obvious response was that the product ...
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Does optical isomerism fall under the category of stereoisomerism?

I have been asked to find the total number of dichlorination products (including stereoisomers) for the following reaction: I have figured out nine possible structures out of which two are optically ...
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Enantiomers or identical structures?

What is the relationship between the following pair of molecules? Is the underlined answer correct? Explain. I'm getting mixed answers. Some say these are identical molecules. Other say these are ...

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