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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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3 votes
2 answers
197 views

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)?
1 vote
0 answers
80 views

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 ...
4 votes
1 answer
1k 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 ...
-1 votes
1 answer
127 views

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.
4 votes
1 answer
2k views

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 - ...
5 votes
2 answers
3k views

When is rotation around double bonds to form cis-trans isomers allowed?

Textbook Question: The rhodopsin molecules in the retina contain a derivative of vitamin A called cis-retinal (Figure 6). On exposure to light, cis-retinal becomes an isomer called trans-retinal. ...
0 votes
1 answer
211 views

stereochem of epoxide opening

Here I have an epoxide opening reaction, but I was wondering that when a nucleophile attacks, How would the stereochemistry work? I have 2 products I predicted and I'm not sure which one would be ...
1 vote
0 answers
36 views

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 ...
4 votes
1 answer
98 views

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 ...
0 votes
0 answers
1k views

What are the limitations of the D, L system and the (+), (-) system for naming organic compounds

In organic chemistry, both the D, L system and the (+), (-) system are widely used, in conjunction with the modern (R, S) system. The D, L system names an organic molecule based on the direction that ...
4 votes
2 answers
245 views

Is there any mathematical or logical proof that carbon with 4 different groups would be chiral?

In chemistry; chirality is generally defined in 2 ways. Lord Kelvin's definition: "I call any geometrical figure, or group of points, chiral, and say it has chirality, if its image in a plane ...
44 votes
2 answers
108k views

How to derive these general formulae for number of stereoisomers of a compound with a possible plane of symmetry?

These formulae are used if the molecule has a possible plane of symmetry. One such example would be: Here the carbons marked with an asterisk are stereogenic centres (the asterisk is not used to mark ...
4 votes
1 answer
417 views

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 ...
3 votes
0 answers
71 views

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 ...
-3 votes
2 answers
928 views

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 ...
6 votes
1 answer
72 views

Does the mechanism of AChE inhibition by Isoparathion depend on chirality?

It is known that the inhibition of acetylcholinesterase by isomalathion can proceed either with diethyl succinate as the leaving group or thiomethyl, depending on the specific stereoisomer of ...
0 votes
3 answers
309 views

What exactly is a 'chiral centre' in a carbon compound? [duplicate]

The typical progression (in books, YouTube videos) of explanation of chiral carbons in a compound is as follows: Chiral compounds are non-superimposable by their mirror-image; It is easily seen that ...
1 vote
0 answers
134 views

In a pair of diastereomers, which of the following is true?

While going through my book, I came across this question and got really confused. Here's what the problem was: In a pair of diastereomers, Both can be laevo-rotatory or both can be dextro-rotatory ...
3 votes
0 answers
216 views

Fischer's projection, enantiomers and diastereomers

Given Fischer's projections of a few stereoisomers of some compound, how can we find out if they are enantiomers, diastereomers, etc.? From what I understand, we can rotate the projections to have the ...
10 votes
1 answer
20k views

What is the difference between absolute and relative configuration in stereochemistry?

Can you help me understand the difference between absolute and relative configuration?
1 vote
1 answer
334 views

Does anyone know what program was used to make this molecular structure picture? [closed]

I am a quantum chemistry beginer, and this picture color scheme is classic. I wonder how to make such pictures by myself.
3 votes
0 answers
114 views

What happens when tran-2-butene reacts with aqueous bromine in the presence of chloride?

$\ce{Br2-H2O}$, containing some $\ce{NaCl,AlCl3}$ ? I initially though that there would be anti addition of Br and OH to give 3-Bromobutan-2-ol but then I also got the intuition that NaCl might ...
10 votes
3 answers
634 views

Can cis-trans isomers interconvert?

Can cis-trans isomers interconvert via tunneling ?
2 votes
1 answer
5k 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 ...
2 votes
2 answers
974 views

How to draw chair-form for trans-decalin (with slight variation)?

I understand how to draw chair form for trans-decalin (figure 1) for the usual structure, but I am having difficulty if taken as shown in figure 2 wherein the hydrogens at bridge-head carbons are in ...
1 vote
0 answers
18 views

Why does hydrogenation of this compound not result in a diastereomeric mixture? [duplicate]

In a question, this compound was given and it was asked: "Hydrogenation of the above compound in the presence of poisoned Palladium catalyst gives?" When I was answering it, I thought that ...
3 votes
2 answers
774 views

Is it correct to look at plane of symmetry in substituted cyclohexane for determining a meso compound?

I read this question and it's answer by @orthocresol. Now, he has written that the compound in question is meso not because there is a plane of symmetry but because of the rapid flipping of the ...
8 votes
1 answer
6k views

Why are complexes of type MA3B3 not optical active?

Complexes of type $\ce{MA3B3}$ have two geometrical isomers, namely: fac-isomer mer-isomer If we look closely at the mer-isomer, it has a plane of symmetry, so it is optically inactive. But the fac-...
3 votes
0 answers
133 views

Stereochemistry of the product of crotonic acid with bromine

Is there a a simple rule for determining the stereochemistry for the product of a reaction between an unsymmetrical alkene like (2E)-but-2-enoic acid and bromine (anti reaction)? If it's an anti ...
0 votes
1 answer
170 views

Stability of Gauche and Anti form in conformational Isomerism

I came through this question: Which form is stable Gauche or Anti in F-CH2-CH2-F? My answer: Due to lone pair repulsion Anti form should be more stable but the answer is given Gauche form. Please tell ...
1 vote
0 answers
36 views

Hydroboration, steroselectivity and anti-markovnikov product [duplicate]

My first question has to do with the fact that Hydroboration produces an anti-markovnikov product, why?. I don't see how that happens. A wikipedia artical says that B has a partial positive charge ...
0 votes
0 answers
83 views

Does 3‐ethyl‐1,1‐dimethylcyclohexane have a stereocenter?

I knew that we have a stereocenter if the carbon is bonded to four different groups. According to the stereocenter rules, I should have $\ce{CH2}$ bonded to the carbon of the stereocenter (marked with ...
-1 votes
1 answer
2k views

Why these compounds don't show and show Geometrical isomerism? [closed]

I was recently studying organic chemistry related to Isomerism. I have doubt based on an example that is, Why Cumulenes show GI? Why 1-chloro cyclohexene don't show GI?
1 vote
1 answer
289 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 ...
1 vote
1 answer
3k views

Correct way of drawing D-configuration with this stereochemistry?

Hello! I have completely memorized how to draw all 20 amino acids in the way seen in the picture (middle, between the "ball-and-stick" and fisher projection) By my understanding this is in the L ...
5 votes
0 answers
162 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 ...
1 vote
2 answers
874 views

How many structural isomers does 1,2-dimethyl-cyclohexane have?

Can someone tell me how many structural isomers exist for 1,2-dimethyl cyclohexane? My teacher said there is one structural isomer but I believe there aren't any because there is no other way to ...
-1 votes
1 answer
182 views

Why is ephedrine optically active? [closed]

Acyclic amine in which three groups are different with a lone pair of electron is optically inactive and nitrogen is achiral because of the rapid pyramidal inversion. Does similar inversion happen in ...
14 votes
1 answer
2k views

What are the criteria for a molecule to be chiral?

What are the criteria for a molecule to be chiral? (We frequently get questions of this type, so this is an attempt to construct a suitable general answer for duping.)
1 vote
0 answers
66 views

Squiggly line in chemical bond notation [duplicate]

In general is there a convention as to how one interprets squiggly lines in chemical structure notation? e.g. see the below sketch. I suppose it has something to do with cis / trans isomerism. But e.g....
3 votes
2 answers
194 views

Chirality and Optical activity

Do all chiral objects rotate the plane of polarization of EM waves? For example my hand is chiral, will it rotate the plane of polarization of EM waves of suitable wavelength?
1 vote
1 answer
57 views

Stereochemistry + isomer check

We start with compound M: [Please imagine green bonds as dotted bonds going into the plane] From compound M, we are told that the 3 membered ring is opened u using sodium azide yielding a mix of ...
0 votes
3 answers
197 views

A question about rotational symmetry of organic molecules and in particular, the cyclic Isomers of C3H4X2

I was thinking about an organic chemistry problem a few days ago but reached a dead end. There were 2 parts to this question. The first was thinking about the isomers of 'C3H4X2' [where X could be ...
4 votes
1 answer
6k views

Determining absolute configuration when the lowest priority group is not facing backwards

I have learnt that the absolute configuration of a chiral centre can be labelled as (R) or (S) according to the Cahn–Ingold–Prelog rules, when the hydrogen (or other lowest priority group) is facing ...
4 votes
1 answer
250 views

Chiral centres with stereoisomeric substituents

The structure of one particular isomer of 4-chlorohepta-2,5-diene is shown here. I am confused about how two of the propenyl groups attached to the central carbon have the same atoms with different ...
11 votes
2 answers
3k views

Effect of periodic acid on cyclohexane derivatives

Periodic acid (per-iodic acid, $\ce{HIO4}$ ) cleaves vicinal diols(to carbonyls) via a cyclic intermediate. Due to the cyclic intermediate, it needs a syn configuration for the $\ce{-OH}$ groups for ...
6 votes
1 answer
228 views

Is (1R,3aR,4S,6aS)‐1,4‐dibromo‐octahydropentalene chiral or achiral?

Is this molecule on the left chiral or achiral? I believe it is achiral because its mirror image (on the right) is essentially the same molecule. But I was told that it is chiral because it doesn't ...
1 vote
1 answer
6k views

How are these molecules chiral and achiral?

I always thought that a molecule couldn't be chiral if it had a plane of symmetry. Doesn't the chiral molecule here have symmetry diagonally across the OHs? The achiral one doesn't look symmetrical ...
2 votes
2 answers
31k views

Stereo Isomerism - syn/anti

I was studying the types of stereo-isomerism E-Z, Cis-Trans and then I come across syn-anti stereo-isomerism this one is giving me a bit of fight in understanding, especially where lone pairs are ...
0 votes
1 answer
2k views

Which are the Geometrical isomers of the complex [Cr(NH3)2Cl2(en)]+?Is it one or two?

I was recently studying coordination compounds and i came across optical isomerism shown by complexes.I think that the complex i gave above have 4 geometrical isomers(I think this is where I am wrong, ...

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