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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1answer
75 views

Can someone explain 3‐(propan‐2‐yl)cyclohex‐1‐ene forming a carbocation?

Can someone explain this one, especially the formation of the secondary carbocation (in the solution)? Solution: After the electrophilic attack by $\ce{H+}$ on the π bond, I had expected the ...
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1answer
2k views

How many dipeptides are possible by the reaction of glycine and alanine?

How many dipeptides are possible by the reaction of glycine and alanine? Glycine has no chiral centre. Alanine has one chiral centre. The products are alanylglycine and glycinylalanine (I not sure ...
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1answer
2k views

What are the isomers of a complex having a structure of M(AB)2C2?

Our instructor have us answer an isomerism problem of a crystal structure that has a form of $\ce{M(AB)2C2}$. I keep getting 9 isomers, which includes the optically inactive isomer, and my peers and I ...
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2answers
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What is the mechanism of the reaction of ethyl prop-2-ynoate to ethyl (2Z)-2,3-dibromoprop-2-enoate?

It's really weird for the product is 99% Z-comformation? Please tell me why? This reaction can be found in scifinder.
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1answer
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Posible Pair of Enantiomers

What is the number of possible enantiomers in monochlorination of 2-methybutane? My approach When $\ce{Cl2}$ is added to any alkane it prefers $3^\circ > 2^\circ > 1^\circ$. When it is being ...
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2answers
640 views

Cahn–Ingold–Prelog Rules, cyclic structures, and breaking ties

(3S,5R)-3-ethyl-5-methylcyclohex-1-ene Does anyone know how one reaches the conclusion that the 5C is R? I tried using the Cahn–Ingold–Prelog priority rules but kept getting confused. From chem....
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1answer
161 views

Why don't ionic compounds show stereoisomerism?

When I was reading about crystalline nature of ionic compounds, I came across the statement that ionic compound doesn't show stereoisomerism. What does that mean and can anybody explain the reason ...
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2answers
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Optical activity of (1r,3R,5S)-3,5-dimethyl-4-methylidenecyclohexan-1-ol

Could anyone explain why compound L is not optically active?
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1answer
271 views

Reactivity of Grignard reagent

I had the following question at an exam: What is the fastest reacting compound towards nucleophilic addition with Grignard reagent? (a) Acyl chloride (b) Aldehyde (c) Ester It is obvious that ester ...
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1answer
233 views

FMO analysis of the [3,3] Sigmatropic reaction regarding geometry. Is it accurate?

While studying the reasons behind the stereospecificity of [3,3] Sigmatropic reactions, I ran into an image portraying both possible transition states for the reaction: The Chair TS and Boat TS. The ...
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2answers
12k views

How to convert wedge–dash structure into Fischer projection? [closed]

I am very confused when a compound with more than one chiral centre is given. How to find whether the two compounds are enantiomers or diasteromers? Please also explain how to convert more than one ...
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1answer
971 views

The maximum no. of isomers (including stereoisomers) that are possible on mono-chlorination of the compound: 3,3-dimethylpentane is?

The maximum no. of isomers (including stereoisomers) that are possible on mono-chlorination of the compound: 3,3-dimethylpentane is? The answer given is 5. My working: The fourth carbon is chiral ...
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1answer
48 views

Stereochemical dichloride treatment [duplicate]

In this question there is no inversion in A to B, but there is one in C to D. I feel like this must be due to the lone pairs on the $\ce{S}$ (in A) being able to open the ring, whereas this isn't ...
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0answers
680 views

Retention of configuration in Hofmann rearrangement

Why is there a retention of configuration in Hofmann bromamide degradation/Hofmann rearrangement? I would think that there should be an inversion of configuration due to the migration of alkyl group ...
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1answer
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Is the -OCH3 group bulky?

Our teacher told us that $\ce{OCH3}$ is a less bulky group when compared to other bulky groups like $\ce{CH3}$, $\ce{NO2}$ etc. Is this true? If yes, why?
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1answer
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Cyclohexane derivative formation of carambolaflavone using a Lewis acid catalyst

The scheme below summarizes the results from a study into the optimum conditions needed for a key step in the synthesis of the proposed structure of carambolaflavone, a natural product that has ...
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2answers
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Path to take when labeling R/S

I'm trying to find the R/S for the carbon marked with the asterisk. As I branched out to from the asterisk carbon to the red carbons, the methyl group has the 3rd priority (with the hidden hydrogen ...
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1answer
731 views

Planarity of given molecules in all conformations

Which of these have all its atoms in one plane in all the possible conformations (if any): A) buta-1,3-diene B) but-1-en-3-yne C) $\ce{CH2=C=O}$ D) $\ce{CH2=C=CH2}$ While I was attempting this ...
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1answer
390 views

Would Z and E isomers show different optical activity?

Consider this compound, which is in E-configuration and that red asterisk denotes the chiral carbon. If I were to somehow cause the E-configuration of the alkene part to Z-configuration keeping the ...
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2answers
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Which of the following compounds is NOT an isomer? [closed]

Which of the following compunds is not an isomer? I cant figure out how the answer is d
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1answer
887 views

Can a double bond extend beyond the plane and if so, how would it be drawn?

Can double and triple bonds, etc., extend beyond the plane in a Lewis structure, and if so, how are they represented? I.e., how would 1 and 2 in this image be drawn if they were doubles or triples?
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0answers
154 views

Why do tetrahedral organic molecules show stereo-isomerism, but not tetrahedral transition metal complexes?

Both types of molecules show different arrangements of the molecule in space, so they should qualify for optical isomerism right?
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method to certify the number of chiral carbons in fischer and haworth projection of glucose

While reading some notes about Glucose and its various projections: Fischer Projection: 4 chiral centres Haworth Projection: 5 chiral centres My doubt is that is there any (specific) method (...
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1answer
719 views

Confused between structural isomers versus stereoisomerism

So this question wanted me to find two cyclical compounds that are 'structural' isomers of the molecular formula given in the question. The two isomers I came up with are: 1,2-dichlorocyclopropane ...
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1answer
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Cis and Trans Isomerism given three different groups around the reference plane

In the following problem I am meant to deduce the molecules that are cis-trans isomers of each other. This question does not make much sense in my head because I thought that cis/trans isomerism was ...
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1answer
823 views

What is the name of "cis/trans" isomerism when all four groups are different?

How would you call a pair of isomers on the picture below? They look a lot like regular cis/trans isomers, except all four groups are different. I can tell they are spacial isomers (stereoisomers) ...
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2answers
2k views

How are these two molecules identical?

I can see that these compounds are identical as we have basically just done a 180 degree rotation of the molecules. But if we go by the concepts of chirality, the carbons 2 and 4 are chiral centers ...
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0answers
218 views

The van't Hoff rule for stereoisomers with planes of symmetry

We know that the maximum possible numbers of stereoisomers of a molecule is given by the van't Hoff rule, which says that: $$Total \space stereoisomers = 2^{n}$$ Where $n$ is the number of ...
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1answer
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Does the Location of Line-Dash-Wedge Notations Matter?

In Line-Dash-Wedge notation, when illustrating that an atom or bond is directed towards or away from the viewer (solid triangle for coming forward, dotted lines for going back), does the location of ...
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0answers
103 views

What does the dissociative mechanism for cis/trans interconversion of [Mo(CO)4(PPh3)2] look like?

All I can find in the literature is that the cis→trans interconversion proceeds via dissociation of one of the PPh3 ligands resulting in a square-pyramidal Cs intermediate, with the remaining PPh3 in ...
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1answer
603 views

Why does the 31P{1H} NMR spectrum of cis-[Mo(CO)2(dppe)2] show two signals?

I've tried searching for literature references that explain this, finding only a single reference which refers to the two signals as originating from phosphine environments cis/trans to carbonyls, ...
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3answers
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Why are carbons of Inositol chiral centers?

I was asked to draw all possible stereoisomers of inositol (1,2,3,4,5,6-cyclohexanehexol). To obtain the answer I had to assume that all six carbons of the molecule are asymmetric, which (bearing in ...
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2answers
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Can we rotate a mirror image by any angle to check if it is superimposable? [closed]

A molecule is chiral when it is different from its mirror image, and achiral if it is identical to its mirror image. To check if the mirror image is identical to the original object, we have to check ...
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1answer
40 views

Creating a Battery using azobenzene in High School [closed]

I’m doing a project on isomerization in high school and have stumbled across the studies involving azobenzene in energy storage using its photoisomeric properties and sunlight . Do you think that this ...
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2answers
3k views

Which one has higher priority according to Cahn–Ingold–Prelog rules?

Which one has higher priority according to Cahn–Ingold–Prelog rules? (1) $\ce{-CH2OH}$ and $\ce{-CH=CH2}$ (2) $\ce{-CH2OH}$ and $\ce{-C(CH3)3}$ The answer says $\ce{-CH=CH2}$ has higher priority, but ...
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1answer
182 views

What is the correct number of stereo isomers in case of 3,6-dimethylpiperazine-2,5-dione?

What is the correct number of stereo isomers in case of the following compound, i.e. 3,6-dimethylpiperazine-2,5-dione? The answer key gives three, but I think there should be four. I recognised the ...
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1answer
349 views

Predict stereochemistry of product [closed]

When 3-methyl(1,1-2H2)pent-1-ene reacts with HCl, why do we obtain a racemic mixture? The given reactant is optically pure.
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1answer
293 views

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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1answer
324 views

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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1answer
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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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0answers
94 views

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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1answer
357 views

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
149 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
98 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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1answer
820 views

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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0answers
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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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1answer
58 views

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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4answers
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Total number of stereoisomers of 2,3,5,6-tetrachlorooctane

Total number of stereoisomers for: I tried the following combinations: RRRR, SSSS, RRRS, SSSR, RRSS, RSRS, SRRS, RSSR, RSRR, SRSS, RRSR, SSRS, SSRR, SRSR. So, total number of stereoisomers I got is ...
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0answers
98 views

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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0answers
175 views

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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