Refers to the spatial arrangement of atoms in a chemical entity.

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Determining chirality after considering conformational interconversion in a cyclohexane

Basically I want to know what does the question mean when it says "taking into consideration conformational interconversions." I assume it means, when I draw the mirror image of the given compound, ...
1
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1answer
36 views

R configuration for cysteine

I think my prof made a mistake. Shouldn't the answer be 1, 4 and 5 instead of 2 and 3?
7
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1answer
88 views

Mark all stereocenters in ampicillin

Shouldn't the N pointed to by the red arrow also be a stereocenter? I am asking this because I think it's lone pair cannot take part in nitrogen inversion.
0
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1answer
39 views

What are all the stereoisomers of 1-ethyl-3-methylcyclohexane?

What are all the stereoisomers of 1-ethyl-3-methylcyclohexane? The following image shows my attempt to answer the question. But I am not sure if I am correct. Note: I am treating this cyclohexane ...
4
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1answer
48 views

Stereoisomers of compounds named tribromocyclobutane

Here is the link to the page in which I don't understand the answer to the last question (Question 13). The question states: Draw all of the constitutional isomers and stereoisomers of compounds ...
2
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1answer
34 views

Does the addition of base to 3-pentanone give the cis or trans enolate?

I've spent several hours searching the WWW with entries like "stereoselective enolate formation" and similar ones, but I find almost only entries for Li-amide bases (LDA, LMTP) and no other bases like ...
4
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0answers
31 views

Effect of enatiomers in pharmaceuticals

Often (or always?) one enantiomer of a certain drug will be effective and the other ineffective or harmful. The famous example is of course Thalidomide where one enantiomer caused mutilation of the ...
6
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1answer
107 views

Stereoselective enolate formation with different bases: Does the addition of a base NR3 to a ketone affords the cis or the trans enolate?

I'm wondering if the addition of a base of type $\ce{NR_3}$ (R: alkyl) to a ketone (e.g. 3-Pentanone or 4-Heptanone) results in the cis or trans-enolate. I didn't find any internet page which ...
3
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1answer
56 views

Carbohydrate conformations

I have to questions regarding the conformations of carbohydrates. There are 38 different conformations for an aldohexose or ketohexose, including $\alpha$ and $\beta$ anomers, namely 2 chairs, 6 ...
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0answers
23 views

Stereoselectivity of 1,3 dipolar additions

How do the 1,3 dipolar additions follow the endo rule as in the reaction below where the anti diastereoisomer is formed predominantly?
6
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67 views

Why does acetate aldol with Evans auxiliary give almost no diasteroselectivity?

Following acetate aldol gives no diasteroselectivity: Because I don't know what the basis of above statement is (I heard it in a lecture and read it on some internet web pages). I expect the two ...
4
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0answers
25 views

How does the stereochemistry of the enolate affect the stereochemistry of the aldol product?

Cis enolates usually produce syn aldols and trans enolates produce anti aldols. How do exemptions from this "rule" arise?
3
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0answers
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Ziegler-Natta polymerization regioselectivity

Why does the Ziegler-Natta polymerization display the regioselectivity shown in the image? Internal (coordinated to the metal) nucleophiles should attack the alkene on the less substituted end like in ...
5
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1answer
33 views

Stereochemistry of epoxide hydrolysis under acidic conditions

The epoxide on the top of the picture, in aqueous acid hydrolyzes to the compound below. What is the mechanism of this reaction? Standard epoxide opening in acidic conditions would happen at the more ...
4
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1answer
93 views

Cis-trans isomers internal energy

Whilst reading about stereochemistry, I came to know that the stability and melting point of cis isomers is lower than trans isomers. By searching on net I've found the reason behind that. But one ...
4
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2answers
63 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 ...
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2answers
50 views

Resolution of enantiomers? How to determine chiral compounds apart from each other? [closed]

How exactly is the interaction between two chiral compounds so they can tell the difference between S or R?
5
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1answer
159 views

Conformations of Cyclohexane

Is there any such thing as a twist chair conformation? Also, the boat and the chair conformations are achiral, while the twist boat conformation of cyclohexane is chiral and dissymetric. What about ...
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1answer
71 views

What is the difference between threo/erythro ephedrine? [closed]

I want to know how to easily make the difference or just understand the importance of stereocenters of ephedrine ?
10
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1answer
92 views

Maximum observed optical rotation through a polarimeter

Is there a maximum optical rotation of plane polarized light that can be observed using a polarimeter? I understand that in a polarimeter, light passes through a filter that converts it into plane ...
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0answers
38 views

How can the stereo selectivity in the hydrogenation of alkenes and alkynes be explained dependent on the used catalyst system?

I'm having great trouble in figuring out syn and anti hydrogenation of alkenes and alkynes. My textbooks are scattered with numerous reagents for hydrogenation but I cannot understand the ...
2
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2answers
45 views

N(delta)-acetyl… vs N(alpha)-acetyl

Can anyone tell me what the difference between these two compounds is: N(alpha)-acetyl-ornithine N(delta)-acetyl-ornithine The only difference I can think of is the chiral properties of the ...
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0answers
41 views

What are different methods to draw/depict stereochemistry with this alkene?

The following molecule in the picture is reacting with meta -Chloropeoxybenzoic acid. My teacher flips the molecule before the reaction in such a way that only certain bonds are sticking behind or in ...
6
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2answers
177 views

Reactions between enantiomers in a racemic mixture

As a follow up to this question I started thinking about another question. During racemization, enantiomers are mixed in a equal ratios to form an optically inactive mixture. What type of reactions ...
13
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3answers
225 views

How to assign E/Z configuration according to the Cahn-Ingold-Prelog rules when subsituents differ only by stereochemistry

I stumbled-upon this compound: CC=C1C(C)CCC1(C) I'm wondering how to determine the configuration of the double bond. Is it E or Z? How do I decide on the ...
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0answers
20 views

Stereoselectivity solvolysis of cyclohexenyl halides

When a functionalized cyclohexenyl halide undergoes $\ce{S_{N}1}$, does a racemic product form (due to ring flipping) ?
0
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1answer
79 views

How to calculate the number of geometrical isomers in allenes?

Can someone explain how to calculate the number of geometrical isomers in allenes like $\ce{CH3-(CH=CH)4-CH3}$ or $\ce{CH3-(CH=CH)5-CH3}$
2
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1answer
47 views

Configurations of Reactants in Second Order Nucleophilic Substitutions

The question asks me to draw the product for the reactions. However, I am stuck and do not understand how to draw the reactants with configurations correctly. (a) (S)-2-Chloropentane and NaSH I ...
6
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1answer
105 views

Planes of Symmetry and Chirality

I am trying to identify whether the following objects possess planes of symmetry or not, but my answers seem different, from the textbook solutions (Klein Organic Chemistry 2e, Page 220, Question 23). ...
5
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2answers
106 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 ...
3
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3answers
62 views

Chirality Centers

The compound below is fexofenadine and the only chirality center, as identified by the textbook is, the one circled in red. I do not understand why the carbon attached to the O by a double bond and ...
3
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3answers
88 views

Ability to Form Stereoisomers

I am asked to identify the number of stereoisomers that are possible for $\ce{H_2C=CHCH_2CH_2CH_2CH=CH_2}$ I drew the bond-line structure as follows, and I think that there can be cis and trans ...
4
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1answer
129 views

Are the circled hydrogens homotopic, enantiotopic, diastereotopic or unrelated?

I'm very confused. According to the answer key, the circled hydrogens are diastereotopic. I thought they were enantiotopic. My thought process is the following. They aren't homotopic because ...
5
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1answer
70 views

Torquoselectivity: Disrotatory ring opening

In organic chemistry lecture we discussed the beginning of the Woodward Hoffmann Rules with a key step of the vitamin B12 synthesis. (The initial paper from their work can be found here: ...
3
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1answer
55 views

Stereochemistry: R and S notation

How do we number the carbon atoms in symmetrical molecules while giving R and S notation. For instance, in 2,3-Dibromobutane, there is an ambiguity over which is carbon C2 and carbon C3. Will we call ...
3
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3answers
85 views

Can a meso compund be rotated in ANY sort of way in order to show its achirality?

Are there any limits to rotating a compound in order to prove that its chirality or achirality? (assuming that you're rotating about a single bond)
2
votes
1answer
59 views

Can pseudochirality be considered when 3 or 4 groups on the C atom are the same?

When for example the C atom is bonded to one H, and then three more structurally identical groups with 2 chiral C each - in configurations R,R and S,S and R,S respectively - then by assigning each of ...
2
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2answers
114 views

Stereochemical aspect of heating of cyclohexane-1,2-diol

Does stereochemistry play any role in the heating of Cyclohexane-1,2-diol? If I remember correctly, different products are formed depending on whether the diol is cis or trans. (I think the products ...
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23 views

Stable conformers of piperazine

which conformer stable of piperazine, when hydrogen of N in axial or in equatorial, or lone pair? why?
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1answer
22 views

Is the correct configuration assigned to the given pair of geometrical isomers?

I suppose that the configurations assigned are opposite as in the left isomer, the left chlorine atom is coming out of the plane of the paper while the other is going into the plane of paper. So it ...
3
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1answer
50 views

Oxymercuration Demercuration Mechanism doubt

I'm having a doubt on the mechanism of oxymercuration Demercuration reaction. How does the reaction, initially heading towards anti addition(after cyclic transition state formation) ,get spoiled by ...
2
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0answers
41 views

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, ...
2
votes
1answer
72 views

How to get a protein's dihedral angles ordered by variance?

The setting: I want to simulate protein docking and let some dihedral angles vary, but in order to keep it low-dimensional I have to select those which are most likely to change. What I've thought of ...
2
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1answer
48 views

what are possible isomers of (meso-stilbenediamine)(isobutylenediamine) palladium (II)?

It can form a square planar and a tetrahedral complex but within square planar or within tetrahedral can there be isomers possible?
6
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2answers
490 views

Is 2-bromobutane chiral?

My textbook says 2-bromobutane is chiral, but it look like it will form superimposition mirror image
3
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1answer
53 views

Enantioselective organic reaction not working

I'm performing the reaction between acetone and 2-nitrobenzaldehyde catalysed by (L)-Proline, as answered to one of my questions a while ago: Simple experiments involving enantiomer synthesis ...
4
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1answer
805 views

Boiling and melting point of trans- and cis-but-2-ene

The boiling point of trans-but-2-ene is lower than that of its cis isomer but the melting point of the former is higher than the later. Why is it not following the same order? Is there any factor of ...
3
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1answer
32 views

Bipyridyl complex isomers

What type of stereoisomers do these two complex compounds represent?
10
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1answer
261 views

Do molecules with axial chirality have “stereogenic units”?

This question is a follow-up to a recent question on discodermolide stereochemistry that I answered here. In the course of reading IUPAC's definition of "stereogenic center", I wondered if axially ...
2
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1answer
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How many stereogenic centres are there in discodermolide? [closed]

It is generally said that carbon-carbon double bonds cannot behave as stereogenic centres but the above molecule contains three such centres. Can somebody please point out all the stereogenic centres ...