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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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1 answer
90 views

Can you have a diastereomer with one chiral center? If yes, give me example

If we say yes, how? Because if the compound have 1 chiral carbon, thus if it is S and another compound is R thus is mirror imagested
-3 votes
0 answers
17 views

What happen when the angle decrease than standard angle 109.5°? [duplicate]

I know when become less than 109.5° angle will cause angle strain that will reduce the stability of compound but why? ( I mean what is the reason decrease the stability of compound or what is the ...
-3 votes
0 answers
19 views

What happen when the angle become less than standard angle 109.5°? [closed]

I know when become less than 109.5° angle will cause angle strain that will reduce the stability of compound but why? Is it because steric hindrance?
-1 votes
0 answers
42 views

Confused with CIP Rules

I really tried very hard to understand what the highlighted text means, but I didn't find anything. I also tried very hard myself, but I cannot understand what the author is trying to say. And one ...
3 votes
3 answers
476 views

Diastereotopic methylene protons in achiral molecules

Are the protons in methylene groups of achiral molecules such as propane-1,2,3-triol or 3-hydroxypentanedioic acid diastereotopic? Consider propane-1,2,3-triol. To me, replacing one of the protons in ...
3 votes
2 answers
76 views

Does 1-chloro-4-(chloromethylidene)cyclohexane show geometrical isomerism?

Would this compound show geometrical isomerism, or GI for short? There certainly wouldn't be any restricted rotation for any atoms in the ring, as for the chiral carbon having chlorine and hydrogen (...
0 votes
1 answer
84 views

Are these stereoisomers considered geometrical isomers?

I came across this compound in the Black Book of Organic Chemistry by Ashish Mishra. The question asked whether this compound could show geometrical isomers. Now, I know the compound has the ...
8 votes
2 answers
534 views

Can O-alkyl sulphoxides be chiral?

Consider the two molecules below. A chemical drawing software that I won't name says that the one on the left is chiral with configuration R at sulphur, whereas the one on the right isn't. I checked ...
0 votes
1 answer
84 views

Why do we use cis/trans for 1,4-dichlorocyclohexane, but R/S nomenclature for its 1,3 isomers?

1,4-dichlorocyclohexane has two isomers, and 1,3-dichlorocyclohexane has three: Looking at the substituted carbon, the reason for the isomers is the same: either the chlorine points up or it points ...
5 votes
1 answer
86 views

Optical activity in tritiated cyclobutane

How would we determine the optical activity in a compound as such: The biggest difficulty I'm having is determining the R-S configuration as that will determine whether the pair are enantiomers or ...
5 votes
1 answer
179 views

Does the chlorination of 4-methylcyclopentene generate two enantiomers or two diastereomers?

Does the chlorination of 4-methylcyclopentene generate two enantiomers or two diastereomers? I think it makes two enantiomers (or one pair of enantiomer) since the starting compound is achiral, but ...
1 vote
2 answers
741 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 ...
5 votes
2 answers
564 views

Geometrical isomerism in 1-(chloromethylidene)-3,5-dimethylcyclohexane

Will this compound exhibit geometrical isomerism? This question was asked in JEE (Mains) 2020, which is an entrance exam held in India annually. The official answer given for this question was "...
0 votes
2 answers
800 views

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 ...
-1 votes
1 answer
57 views

How exactly are mirror images of molecules rotated to determine enantiomeric pair?

I know there are many similar questions to this but none could clear my confusion over how exactly the mirrored molecules is rotated i.e on which axis it is rotated to superpose with the original ...
1 vote
1 answer
4k views

Enantiomers of 1,2-dichlorocyclohexane

The other day in class we were discussing the enantiomers of 1,2-dichlorocyclohexane and my teacher told us that (R,R) and (S,S) are different isomers while (R,S) and (S,R) are the same. I understand ...
2 votes
1 answer
75 views

How to determine the value of the NOE from the NOESY spectrum?

I have 1D NOESY spectra from which I need to find out the value of the NOE (%). Is it enough to simply measure the intensity of the resulting peaks or is it necessary to subtract it from the ...
7 votes
2 answers
679 views

Is there a plane of symmetry in [Ma3b2c]?

We have been taught to look for plane of symmetries in inorganic complexes. If there is a plane of symmetry then the complex is optically inactive, otherwise it is optically active. In this particular ...
8 votes
2 answers
1k views

Why does this compound only have one pair of enantiomers?

I've been doing some reading about enantiomers, which are apparently chiral molecules that are non-superimposable mirror images of each other. An example I found of this in some problems that I've ...
0 votes
0 answers
34 views

Is the compound optically active? [duplicate]

My work - The compound seems to have a plane of symmetry(POS)(The plane of the compound itself seems to be the POS) Because- all carbon atoms in the benzene ring, the - COOH, the C=C, are all SP2 ...
0 votes
1 answer
60 views

Which of these molecules have stereoisomers?

Problem: Which of these molecules have stereoisomers? Solution: (The molecules with a red X beside them are the ones with stereoisomers.) Question: What is the method used to identify which molecules ...
5 votes
3 answers
5k views

R and S Configuration Understanding

So I have been trying to understand how to draw R and S configurations. I feel like I have understood how to draw them, but every time I do a question, I get a wrong answer. So here is what I have ...
5 votes
3 answers
479 views

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 ...
1 vote
1 answer
152 views

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 ...
8 votes
2 answers
32k views

Is there a formula to determine the total number of constitutional isomers?

Is there a trick or a formula that given a molecular formula, allows you to know exactly how many constitutional isomers can be formed with that many atoms? Or is it more of a trial-and-error ...
6 votes
1 answer
285 views

What is the number of different compounds formed from the monochlorination of cis-1,2-dimethyl cyclopentane?

I encountered this question in the Black Book of Organic Chemistry by Ashish Mishra while preparing for a college entrance exam. According to the answer key the answer is 12. I have only managed to ...
4 votes
1 answer
244 views

Why is cyclooctene the smallest cycloalkene to have cis-trans isomerism?

What prevents cis and trans isomers from existing in smaller cycloalkenes, for example, cyclohexenes for more than a short period of time?
2 votes
1 answer
111 views

How the tertiary carbons of cyclohexane are assigned the stereo-descriptors (r)?

We assign the stereodescriptors R and S for chiral centres - carbons and other atoms, as per the set of sequence rules (CIP rules). The pseudochiral centres are given the descriptors (r) & (s) ...
3 votes
2 answers
2k views

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) ...
-1 votes
1 answer
47 views

Optical rotation and chirality

I had the same question as in Molecular chirality and optical rotation In the answer, it says that there can't be such a mirror position where the effect of one molecule be cancelled by other. But I'm ...
2 votes
2 answers
125 views

Point group of trimethyl borate $\ce{B(OCH_3)3}$

What's the point group of trimethyl borate $\ce{B(OCH_3)3}$. The answer that my teacher gave is $D_{3h}$ but I'm struggling to see the n perpendicular $C_2$ axes and the horizontal plane of reflection....
6 votes
2 answers
5k views

Is trans-1,2-dimethylcyclopropane optically active or not?

According to my book it is optically active, but no valid reason is given. But what I found is there exists an alternating axis of symmetry, and so my conclusion is the compound would be inactive or ...
3 votes
1 answer
147 views

If the substituents are distinguishable, is it possible to prioritize them using the CIP rules?

In the R/S stereochemical nomenclature, when we try to determine the priority of substituents around a chiral carbon, are there specific examples where the ranking cannot be definie under the CIP ...
4 votes
3 answers
1k views

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) ...
1 vote
1 answer
61 views

Stereochemical relationship of molecules including double bond configuration and absolute configuration

Are (S,E)-4-isopropoxypent-3-en-2-ol and (R,Z)-4-isopropoxypent-3-en-2-ol both enantiomers and diastereomers? I am a bit confused because they would be diastereomers when only looking at the ...
3 votes
0 answers
37 views

Systematic method to determine D/L notation of substances other than amino acids and glyceraldehyde

The fundamental rules of D/L notation, as I understand it, are as follows; In D/L notation, a molecule is named by mapping it to glyceraldehyde. The D/L notation is based on the stereo configuration ...
2 votes
2 answers
399 views

Does a chiral allene have stereogenic centres?

This a picture of what my professor taught in class. According the the definition of a stereogenic centre, allene should have two of them. So I don't understand what I am interpreting wrong.
0 votes
4 answers
327 views

Do conformations arise from vibrations?

I was wondering how a molecule transforms from one conformation to another. Surely, since the conformations are separated by a potential barrier, some activation energy must be required. The energies ...
0 votes
0 answers
192 views

Which enantiomer of 3-Chloro-2-pentanol is this?

I think that there is a chiral centers at $C_2$ and at $C_3$ (Numbering starting such that the carbon with hydroxy attached is number 2. Then, for $C_2$: Priority would be: OH > $C_3$ > $C_1$ &...
2 votes
1 answer
164 views

Explain the mechanism of the following reaction, which involves a 1,2-alkyl migration with double inversion of configuration

I came across the following reaction, whose mechanism is said to involve a 1,2-alkyl migration with a double inversion in configuration. The reagents used were nitrous acid (generated in situ) ...
1 vote
1 answer
1k views

What determines the higher priority in CIP rules, if both groups have the same atoms?

Which of the following groups has the highest priority in the Cahn-Ingold-Prelog sequence rules? a) CH2CH3 b) CH=CH2 c) C≡CH d) C(CH3)3 I narrowed it down to either C or D. The carbon in answer C is ...
4 votes
1 answer
2k views

Confusion on enantiomers and meso compounds

Question: Are these compounds enantiomers? Attempt: The compounds given are mirror images. But if I rotated the three bonds in the third carbon (configuration will not change), I will get a meso ...
1 vote
1 answer
4k views

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?
3 votes
0 answers
100 views

How to apply the parvo/amplo akamptisomeric stereodescriptors to this bicyclic system?

I'm looking for examples of akamptisomerism[1]. I'm try to find simple molecules able to (theoretically) show this kind of isomerism. I thought about the isomers of (2R)-2-methyl-9-oxabicyclo[3.3.1]...
0 votes
0 answers
45 views

Why the C4 in this 1,3,4,5-substituted Cyclohexanes has a R/S configuration?

(1S,3S,4S,5S)-3,5-dimethoxy-1-phenylcyclohexane-1,4-dithiol. ChemDraw21 shows the C4 is S configuration. However I think C4 has two same function groups(C3 and C5 are both S configuration; C2-1-6 and ...
3 votes
1 answer
521 views

Are conformational isomers diasteromers?

I am currently struggling on seeing where exactly conformational isomers fit within stereochemistry & how (and whether) they are a subset of diasteromers. I've seen potentially conflicting ...
1 vote
1 answer
67 views

Fischer Projection for Different Compounds

Which of the following Fischer projections is different from the other? Just by looking at the R-S configuration, figure C is the odd one out. But when I look at D I see that both methyl and hydrogen ...
-1 votes
1 answer
27 views

9,10-dihydro-9,10-ethanoanthracene derivatives. Stereoisomers or different compounds? What are their chemical names?

What is the relationship between these compounds? Are they stereoisomers or some of them are different compounds? Additionally, what would be their names? (For position 9, with the methyl substituent) ...
6 votes
2 answers
46k views

How do we assign alpha/beta status in polysaccharides?

In polysachharides like sucrose or any other disachhaharides, how is it that we assign whether the glycosidic bond is alpha/beta ? For example the images here: http://forums.studentdoctor.net/...
-3 votes
1 answer
282 views

How many aldehydes and ketones can be formed from molecular formula C5H10O? [closed]

Question: What are the possible aldehydes and ketones with molecular formula $\ce{C5H10O$ (including the stereoisomers)? Answer: 5 aldehydes and 3 ketones The degree of unsaturation of the compound ...

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