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

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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?
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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 ...
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31 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 ...
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67 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 ...
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1answer
37 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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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?
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129 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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62 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 ?
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70 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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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 ...
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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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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 ...
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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 ...
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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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Stereoselectivity solvolysis of cyclohexenyl halides

When a functionalized cyclohexenyl halide undergoes $\ce{S_{N}1}$, does a racemic product form (due to ring flipping) ?
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48 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 $\ce{CH3-(CH=CH)5-CH3}$
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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 ...
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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). ...
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101 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 ...
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3answers
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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 ...
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80 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 ...
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1answer
71 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 ...
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1answer
63 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: ...
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51 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 ...
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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)
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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 ...
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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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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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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 ...
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1answer
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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 ...
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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, ...
2
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1answer
62 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 ...
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1answer
42 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?
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453 views

Is 2-bromobutane chiral?

My textbook says 2-bromobutane is chiral, but it look like it will form superimposition mirror image
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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 ...
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1answer
620 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 ...
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1answer
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Bipyridyl complex isomers

What type of stereoisomers do these two complex compounds represent?
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235 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 ...
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1answer
116 views

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 ...
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Is tetraammine dichloro cobalt (III) an optically active compound?

Is $$ \text{Co}[{(\text{N}{\text{H}}_{3})}_{4}{\text{Cl}}_{2}]$$ optically active? If so, write its stereo-isomers. I know that for a compound to be optically active, it should ...
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Enantiomerism and Diasteriomerism

I am really confused between them. I know that an enantiomer is an isomer having optical activity, non super-imposability of image on original configuration, same molecular formula(Correct me if I am ...
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90 views

Catenane optical activity

Would a [2]catenate whose each ring consist of a different number of methylene groups only, be optically active if one hydrogen atom of a random methylene group is replaced with e.g. chlorine? I think ...
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639 views

Are all amino acids except glycine chiral compounds?

Specifically, I was thinking of the case where the R group is a carboxylic acid functional group or an amine group. Then there would not be a chiral carbon atom. Is there a restriction on what can be ...
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2answers
422 views

Whats the H-C-H bond angle in ethene?

The carbon is $sp^2$ hybridised and is therefore planar and should also, theoretically be 120$^o$. However, VSEPR theory suggests that the pi bond would "need more space" due to greater electron ...
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532 views

Why six C atoms are usually seen in cyclic compounds?

When it gets to Carbon-based molecules, one very possible structure when there are more than six C atoms is the hexagon; though not mostly perfect, it emphasizes that six Carbon atoms tend to bond ...
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817 views

Endo rule for the Diels Alder stereoselectivity

Do you agree with the stereocenter with the CF3/CN in the product? source I would have expected that CF3 is a better electron withdrawing group than CN, and therefore placed opposite the diene and ...
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139 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 ...
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108 views

Lactone vs Ester

With regard to stereoelectronic effects in esters and corresponding s-trans lactones why does donation into the $\sigma _{CO}^*$ orbital from an anti lone pair on the sp3 oxygen cause the lactone to ...
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234 views

Why is nitration of veratrole specific in these positions?

Why do we not need $\ce{H2SO4}$ as an acid catalyst for the di-nitration of veratrole? Why does the 2nd nitro group go to positions 4 or 5, following the directing effects of the methoxy-group? ...
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“Asymmetric molecules are necessarily polar”

Is a molecule with no symmetry necessarily polar? Can a polar molecule still have some elements of symmetry (i.e. mirror image is the same as itself)? I think so ... because we can have achiral ...