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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 alkene geometrical isomers achiral?

I was reading a book and it tells that alkene geometrical isomers are achiral. I wanted to know that is it applicable for alkene geometrical isomers? Thanks in advance.
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What do D and L stand for in the Fischer-Rosanoff convention?

In R and S configuration, the R stands for rectus and the S stands for sinister. Similarly, do the D and L descriptors in the Fischer-Rosanoff convention stand for something?
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number of optical isomers of a cyclic molecule

What is the number of optical isomers for this compound? Also, there seems to be no clear-cut boundary between geometrical isomers and optical isomers. Referring to a post in StackExchange, is (RS)- ...
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Number of products on dehydrobromination

Question: The total number of alkene products possible from the dehydrobromination of 3-bromo-3-cyclopentylhexane using alcohol KOH is : This question was asked here before but I am getting more ...
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Depicting molecules by Natta projection

Does anyone know the meaning of these two bonds in stereochemistry? These bonds are provided by the $\mathrm{\LaTeX}$ chemfig package. The creator of the ...
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1answer
72 views

Can anyone tell me what reaction is this?

I came across this reaction, but I have no idea what reaction is this. Can anyone please tell me? What will be the products? My first guess is that a carbene will be formed which will attack on the ...
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1answer
58 views

Total number of stereoisomers of 1,2-dimethyl-4-(propan-2-ylidene)cyclopentane [duplicate]

I don't think there is any change of showing geometrical isomerism across the double bond because the two groups on the right side (two $\ce{-CH_3}$) are the same. Also I don't think there should be ...
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How many stereoisomers are possible for 1,2-dimethyl-4-(propan-2-ylidene)cyclopentane?

How many stereoisomers (not counting different conformers) does 1,2-dimethyl-4-(propan-2-ylidene)cyclopentane have? I think the answer should be 3. There are two geometrical isomers (cis and ...
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Diels Alder stereoselectivity

I'm familiar with the endo rule as well as the regioselectivity of the reaction. However, what I fail to understand is the stereoselectivity of the product in relation to the diene. For example, in ...
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How many stereo isomers of 1-{3-chloro-2-[2-methyl-6-(prop-1-en-1-yl)phenyl]cyclohexyl}ethan-1-ol?

There is this problem that bugged me in a test: Find the number of stereoisomers of this compound. So far I have been able to identify only one chiral center and I'm stuck. Edit: The answer ...
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Optical activity of organic compunds

Why are the molecules which are superimposable on their mirror images optically inactive? For example 1-bromo-2-methylpropane.
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Total number of stereoisomers of 2,3,5,6-tetrachlorooctane

I tried the following combinations: RRRR, SSSS, RRRS, SSSR, RRSS, RSRS, SRRS, RSSR, RSRR, SRSS, RRSR, SSRS, SSRR, SRSR. So total stereoisomers which I got is 12 but my teacher says it's 16. I don't ...
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Carrying on a stereospecific 1,4 conjugate addition on a terminal alkyne

I am looking for a way to attack a propiolate ester with a triazole and get the Z isomer of the resulting acrylate selectively. All literature survey can come up with is big nitrogen containing ...
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Endo/Exo for same length bridges

I'm looking at a cycloaddition that produces a bicyclic intermediate, there are two different ways of doing the addition which can be described as endo/exo. However, all three bridges are the same ...
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Enantioselective alkylation of Aldehydes by Dialkylzinc reagents

Enantioselective catalysis is one of the important reactions in Organic chemistry which has huge applications in practical basis for synthesis of optically pure natural compounds. In this respect, I ...
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Optical Isomerism in Coordination Compounds of type MA₂B₂(CC)

I was asked the following question: How many optical isomers are there for $\ce{[Cr(NH3)2Cl2(en)]^+}$ ? First of all I figured out the following four geometrical isomers of the above complex: Out ...
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2answers
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Is there absolotely no relation between R/S configurations and d/l optical rotations?

Is there such a relation between R/S configurations and d/l optical rotation that, if we experimentally know that R configuration of a fixed compound gives 'l' rotation then can we infer that the S ...
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1answer
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Enantiomers and couple of enantiomers

I ask myself a question for some time but it's impossible to me to find the answer! I can't understand the difference when we say " that molecule has a enantiomer " and when we say " has a couple of ...
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X-ray structure analysis mirrored coordinates?

How to ensure, that X-ray crystallography structure analysis was done right to provide correct, non-mirrored atomic coordinates? Example: Following Wikipedia image, is generated from data taken from ...
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3answers
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Is there a thermodynamic driving force for racemisation?

Why does racemisation occur? My doubts are: Is it due to entropy? If it is due to entropy, how is the reduction of optical activity by racemisation a consequence of increased thermodynamic ...
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1answer
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What is the configuration of dimethyl[tris(trifluoromethyl)]-λ⁵-phosphane?

I know that $\ce{(CH3)2P(CF3)3}$ is geometry of trigonal bipyramid and according to Bent's rule $\ce{CH3}$ goes to axial positions and $\ce{CF3}$s remains on equatorial positions. However, as per ...
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Does 3,6-di-X-cyclohexa-1,4-diene have stereo centers?

The following question has multiple correct answers: The book out of which the question is taken shows that a, b and d are correct answers. According to me c should also be correct, as it shows ...
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2answers
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Are the stereoisomers of nucleosides actually anomers?

An anomer is an epimer at an (hemi)-acetal carbon like $\ce{R2C(OR')2}$. Why is the 1'-position of a nucleoside referred to as the anomeric center despite the lack of acetal functional groups?
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According to the Cahn-Ingold-Prelog system assign a priority to each of the following groups. (Highest priority is 1) [closed]

1-CH(CH3)CH2F 2-CHCl2 3-CH2Br 4-C(CH3)3 this is the order i did using the system but i am having a hard time understanding it and was wondering if anyone could tell me if my answer is correct, and if ...
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1answer
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Classification in Stereoisomerism [closed]

I was trying to understand stereoisomerism. I am having trouble creating a 'flow chart' of Stereoisomerism. While there are many sources available over the internet and books, I don't find a standard ...
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What compound has the strongest optical rotation of polarised light?

A question recently asked here whether compounds know to be chiral can have non-measurable optical rotations: Are there chiral compounds that don't rotate plane-polarized light?. Apparently they ...
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1answer
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Are there chiral compounds that don't rotate plane-polarized light?

I know that meso compounds have chiral centers but don't rotate plane-polarized light, and I know that there can be non-traditionally chiral compounds (e.g. ones with large substituents that prohibit ...
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1answer
56 views

Assign stereodiscriptor to 4th carbon of 3-ethyl-2,4-dimethly-5-(propan-2-yl)heptane-1,7-diol

Here is the molecule. Clearly the 4th carbon is chiral. I have drawn the diagraph for it, but the exploratory pathways of the left and right chains are the same. So, the problem is that the two chains ...
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2answers
146 views

Why does 1,3-dichloropropane not show stereoisomerism?

It is a multiple choice question: Which compound does not show stereoisomerism? A 1,2-dichloroprop-1-ene B 1,2-dichloropropane C 1,3-dichloroprop-1-ene D 1,3-dichloropropane I ...
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1answer
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Determining R and S configuration for a cyclic compound when the lowest priority group is on the plane of the paper

I am struggling with determining R and S configuration for the following compound I know how to give R and S configuration for a cyclic compound like the compound above if the lowest priority group ...
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2answers
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What is the most stable conformation (Newman Projection) of CF3CH3?

Is a totally eclipsed Newman projection the most stable conformation for a 2 carbon compound, with one carbone bonded to more electronegative atoms (making them partial negative), and the other carbon ...
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Why atropisomers are called conformers?

Changing one atropisomer to another requires bond breaking (in some cases the removal and reattachement of steric groups, according to my understanding) so how it is possible that according to IUPAC ...
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1answer
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what is superimposability of mirror images of this molecule? [closed]

I don't get why (a) and (d) are achiral when we cant superimpose their respective mirror images?Or can we superimpose them?
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Fischer projections

Can somebody tell me how why they changed/choose the groups for vertical and horizontal lines. As far as I know the vertical lines represent group going away from us and horizontal depicts coming ...
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R/S descriptors in long carbon chain

I'm trying to figure out how to assign R/S descriptors using a Fischer model without transforming it into a spacial one. What I learned so far is the method to assign it for 'terminal' (I'm gonna use ...
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2answers
233 views

Stability of geometrical isomers in cycloalkanes

Among the following, which should be the most stable compound? 1)Cis-cyclohexane-1,2-diol 2)Trans-cyclohexane-1,2-diol 3)Cis-cyclohexane-1,3-diol 4)Trans-cyclohexane-1,3-diol My thought process is-...
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Which of the following molecules are enantiomers? [closed]

My book says that only molecule 7 is enantiomer of molecule 1. Why is this? Why can't molecule 1 and 2 be enantiomers?
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Are Anomers Epimers?

epimers are the class of stereoisomers which differ along configuration at any carbon in a carbohydrate(generally), And anomers are the kind of stereo isomers that differ at the carbonylic carbon, ...
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1answer
166 views

Stereochemistry of 1,4 disubstituted cyclohexane [closed]

How are these cyclohexanes identical?
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2answers
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Can chiral atoms have same substituents but with different orientations?

So consider this molecule. We have to determine whether nitrogen atom is chiral or not. MY IDEAS: Now going by all I have read, for chiral atoms only criteria is substituents to be different. Here ...
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If a chiral molecule reacts with an achiral molecule will the product be chiral or achiral?

My book says that a pair of enantiomers will react the same way with an achiral substance. How is this possible? Does this imply that the product is achiral, even though the enantiomers are chiral? ...
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Number of spatial arrangements of tetrasubstituted biphenyl

According to my book 2-bromo-2'-(1-chloroethyl)-6'-iodo-6-(prop-1-en-1-yl)-1,1'-biphenyl has eight possible spatial arrangements. How can this be so? I can think of only four – left two groups being ...
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1answer
185 views

Cahn–Ingold–Prelog priority of CN vs CH2NH2

Why does $\ce{CH2NH2}$ have lower priority than $\ce{CN}$? The carbon on the first molecule is bonded to (N,H,H) while the carbon on the second molecule is just bonded to (N). I can't seem to find ...
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What compounds give two products on reacting with NH2OH?

This is a question from the chapter stereochemistry of my coaching module. The answer options include CH3CHO, DCHO, etc. How do I do this? I have an idea that if we take a racemic mixture of D and L ...
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Do you assume undrawn hydrogens are pointing away from you when determining R/S?

When determining R/S of stereoisomers, the group with the smallest atomic number needs to be in the back (dashed line). But if no group attached to a chiral center is drawn in dashed line, do we ...
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Twisting stereoisomers with rings to determine R/S [closed]

I know that if the smallest atomic number group is not in the back, we can twist the molecule so that it is in the back and then determine if it is R/S (Left image). But if the chiral center is ...
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1answer
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Stereogenic Center Question

In cholesterol, I don't understand why the two points I circled are stereogenic centers. Isn't the left carbon attached to an OH, H, CH2, and CH2? And isn't the right carbon attached to CH, CH2, CH, ...
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469 views

Explain optical activity in Biphenyl compounds

How is optical activity explained in biphenyl compounds using atropisomerism. NOTE: I was taught that if vertical symmetry exists then optical activity is not shown by any substituted biphenyl ...
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1answer
315 views

H-NMR Equivalent Protons and Coupling of Glycerol

I've been searching for explanations to understand why the labeled protons on carbons 1 and 3 are not equivalent in the below figure. Another figure that shows the same results: SDBS confirms the ...
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96 views

Systematic Approach to Finding Number of Isomers [duplicate]

I have this compound I want to know how many isomers (including stereoisomers) may have this constitution. Is there a systematic approach towards solving such types of problems related to the total ...