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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Tables/database/literature of specific or optical rotation

I'm looking for a comprehensive reference of experimental specific rotation or optical rotation data. It can be a published literature review, a free web database with API access or one that permits ...
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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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In the Haworth projections of D and L glucose, is the stereochemistry at every carbon except the anomeric carbon just inverted?

I'm having a bit of trouble grasping sugar stereochemistry. Using glucose as an example, if you cyclize D and L glucose, is the stereochemistry at every carbon just inverted from the other form? ...
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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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Type of chirality in polycyclic compounds

Ignoring whether or not this molecule could exist, is there a name for this type of chirality? This molecule's mirror image cannot be superimposed on itself but there are no chiral centres. Even ...
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Is it possible to estimate the abundance of conformers from J values?

I have a system of two disubstituted cyclohexanes and I want to estimate the abundance/ratio of the two based on the J values and if possible, roughly estimate the difference in free energy. To get ...
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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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Asymmetric Suzuki coupling - saturated alkyl chain

9-BBN is applied for Suzuki coupling of a saturated alkyl chain with some alkenyl,alkynyl or even secondary alkyl halide like the modification attached: (Saito, B.; Fu, G. C. Alkyl−Alkyl Suzuki Cross-...
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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 ...
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49 views

Is optical activity of a given compound a statistical picture?

When optical activity is taught it is done in terms of single molecules. But when it is actually measured it is done on a large collection of such molecules. So, how does the asymmetry manifest itself ...
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[3+1]-Cycloadditions of Sulfur Ylides and 1,3-Dipoles(?)

My question is basically regarding the stereoselectivity of the situation. I am not being able to decide on the positioning of the sulfur ylide with proper justification. In the attached hand-drawn ...
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Examples of intramolecular hydrogen bonding closing bond angles

Okay, we've established that intramolecular hydrogen bonding can exist in molecules, and doesn't always serve the purpose of closing the bond angle at least relative to other stereoisomers of the same ...
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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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779 views

Determining the stereochemistry of the product(s) when an alkyl shift in a carbocation generates a chiral carbon

Consider this carbocation: We know that this carbocation would immediately rearrange - by a methyl shift - to form the more stable carbocation. Now, notice that the migration will produce a chiral ...
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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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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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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 ...
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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 ...
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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 ...
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What do γ (gamma) and λ (lambda) mean in organic chemistry?

From the Wikipedia entry on Cyhalothrin: Pyrethroids such as cyhalothrin are often preferred as an active ingredient in agricultural insecticides because they are more cost-effective and longer ...
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Chemical shift difference methyl groups in 4-hydroxy-2,5-dimethyl-3-hexanone

Can someone explain why the NMR Spectrum of 4-hydroxy-2,5-dimethyl-3-hexanone shows a chemical shift difference for the methyl groups at the end? Why aren't the other carbons have a difference? Below ...
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Why does Pubchem show cis-1,3-cyclohexanediol with the hydroxyls in the equatorial position?

I am a beginning organic chemistry student and trying to reason about something based on information in my book, but seeing that Pubchem gives a different structure than I'd expect. In considering a ...
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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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153 views

effect of different groups on Amine inversion

I know different groups attached to the nitrogen atom affect the amine inversion barrier, but is it due to steric factors or orbital interaction factors, eg. $\ce{(i-Pr)2NMe}$ vs $\ce{NCl3}$.
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In an electrocyclic reaction with two pi bonds that result in a trans product, is a mix of products seen?

When I look at the highest occupied molecular orbital, the two methyl groups will end up being trans to each other. I realized based on which conrotation direction both methyl groups take that two ...
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What symmetry elements mustn't a molecule possess to be considered achiral?

Undergraduate textbooks say that a molecule mustn't posses a reflection plane and an inversion center to be considered achiral. As mentioned by Ron in his answer to this question, molecules that don't ...
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610 views

Using CIP rules in a bicyclic compound with carbonyl subsituent

In bicyclo[2.2.1]heptan-2-one, arrange the numbered groups according to CIP rules: Group 1 will have highest priority because oxygen atom is attached to 1. (It can be considered as two oxygen atoms). ...
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Assigning R/S stereochemistry of a cyclic molecule

I've been dealing with assigning stereochemistry and I seem to be doing okay, but I've come across a molecule that I've found a little tricky to deal with. I've identified three stereocentres, ...
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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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(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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Solvent shell collapse

In "advanced organic chemistry part A" book page:306&307 , the author uses the term 'solvent shell collapse' when talking about the reason for retention of conformation in tertiary ...
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Strains in conformations of cyclohexane

I know some the basic kind of strains that can exist in molecules namely Torsional strain (Vanderwaals' strain), steric strain and angle strain. Is it possible to associate a particular type of ...
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Differences in efficacy of oxime reactivators in organophosphate poisoning

Compounds containing an oxime functional group, such as 2-PAM and obidoxime, are used in the treatment of poisoning with organophosphorus compounds. These oximes reactivate the enzyme ...
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Shortcuts for finding geometrical isomers

Our teacher provides us extra questions for pratice, so one of the questions was :- Find number of products if following are reacted with excess $\ce{NH2OH}$ (hydroxyl amine): Cyclohex - (i) 1,4-...
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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]...
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Finding out more stable conformer via molecular orbital interaction

Out of these two, which one is more stable? I'm unable to imagine the orientation of the lone pairs of O and ABMO of C and Cl bond. Any tips to tackle these kind of problems?
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Name of the intermediate in between phosphono and phosphonato group

$\ce{R-PO3^2-}$ is called a phoshonato group (https://www.ebi.ac.uk/chebi/searchId.do?chebiId=30931) $\ce{R-PO3H2}$ is called a phosphono group (https://www.ebi.ac.uk/chebi/searchId.do?chebiId=48108) ...
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153 views

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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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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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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Does dihydroimidazole show geometrical isomerism?

Does dihydroimidazole (above) exhibit geometrical isomerism? Does the fact that the lone pair is involved in conjugation with a double bond affect anything? As far as I know, it does not exhibit ...
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Geometric isomers of substituted methylidenecyclohexane?

My thoughts on the problem: I am sort compound of sure C and D will not show geometric isomerism because of the same groups (H and H) attached. In compound A and B, suppose I swap the positions of H ...
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Can anomers be destinguished based on Fischer projection?

I would like to ask if it is possible to tell an anomer using Fischer projection (e.g. glucose). In high school we learned only Haworth and Tollens are hepful in this case. However, I'm not exactly ...
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Draw a structure for each of the following isomers of unsaturated amine 1

My ochem professor has several practice exams as resources but does not include answers, I believe I understand the concepts but once I apply them I'm not sure whether I'm right or clueless. Can ...
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Are these two structures of 1,3-dichlorocyclobutane enantiomers?

According to me they are not enantiomers because the mirror image can be rotated by $180^\circ$ to get the same compound. Giving it a little more 3-D look: But the book says they are enantiomers. I ...
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How to interpret the rate constants of in-vivo racemization of thalidomide?

The article by Eriksson et. al. found that thalidomide undergoes chiral inversion in vivo. It found the mean rate constants too, $0.17~\mathrm{h^{-1}}$ (R to S) and $0.12~\mathrm{h^{-1}}$ (S to R). ...
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Mathematical model of isomerism

Does there exist a mathematical model of isomerism? (a model which is capable of predicting, for given circumstances, the re-arrangement that is going to occur, e.g. Demjanov, Wagner-Meerwein etc.). ...
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Entropy and racemization?

The process of racemization of an optically compound is entropy driven and hence nature prefers a racemic mixture to an optically active one, which is consistent with the idea of the intuitive ...
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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 ...