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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What is there in this 3D representation of organic molecules I fail to grasp?

I think there's a basic idea I'm missing about 3 Dimensional representation of molecules. I think it may be about converting to Fischer representation. Consider the following two products of ...
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Enantiomer of Amphetamine

I saw this graphic in Organic Chemistry by Klein (2nd edition too!) and this has to be wrong, correct? The mirror images should have the double bond on the far side of the ring in both images, right?...
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Constitutional Isomers or Stereoisomers?

With regard to a trigonal bipyramidal molecule, such as $\ce{PIBrClF_2}$, can there be any constituional isomers? I'm thinking no, because constitutional isomers differ in the connectivity of their ...
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Why unsaturated fats are usually cis?

I've been studying organic chemistry and I think trans fats are actually more stable than cis fats. This is because the steric hindrance (for trans) would be lower and the molecule energy would be ...
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651 views

Cis and Trans Isomerism in Resonance-Stabilized Compounds

Would it be valid to describe $N_2O_5$ isomers as cis or trans? As a matter of fact, does this molecule even have isomers, given that all its outer N-O bonds are resonance stabilized and therefore ...
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Is there a mathematical generalization for the number of isomers (structural and configurational) of a given compound?

The original question was: How do I find the number of structural and configurational isomers of a given compound? is there any formula? For a specific example, how would I find the number of ...
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Which compound can exist as stereoisomers?

I'm having trouble in understanding how to identify chemical compounds as stereoisomers. In the question below, D is the correct answer according to the markscheme. I've drawn out the chemical ...
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2answers
122 views

What is the canonical reference for studying stereochemistry? [closed]

I am well versed with all the named reactions and all of organic chemistry. I am quite weak in stereochemistry. What canonical text can I use to study this topic and connect with other parts of the ...
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Is this analogy explaining the difference between enantiomers and diastereomers correct?

I tried writing an analogy to explain the difference between enantiomers and diastereomers. However, I'm not entirely sure if it's actually a correct representation of the differences. It might also ...
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How does Walter White make pure crystal meth using a non-stereospecific reaction?

In the fantastic TV series Breaking Bad, Walter White, the dying chemistry teacher, takes to making crystal meth (d-methamphetamine) by several routes. Initially, he uses the common small-scale route ...
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Nomenclature for stereoisomer example possible wrong?

I understand the principal of the Cis-Trans naming system (at least I think so), until I saw this example in my learning material. My teacher doesn't know either so I thought I would post it here. ...
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Covalent bond deformation

When do covalent bonds of a molecule $M$ extend or compress while no bonds in $M$ are broken? I can conceive of some possibilities but I don't know how common they are: Temperature changes Inter-...
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What's the difference between alpha-glucose and beta-glucose?

What's the difference between $\alpha$-D-glucose and $\beta$-D-glucose? Are they isomers? Or do they differ in their elemental composition?
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How do you draw (E)-1-phenyl-1,3-butadiene?

I'm having trouble drawing this molecule because I don't understand how the functional group Phenyl (by -ene suffix) can also be a substituent (by 1-phenyl). Also, what does the 1,3-butadiene mean?
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Equilibrium between R and S configuration?

We have learnt that the energy evel of both R and S optical isomer of a compoud is same, just as well the entropy of each isomer is also same. If we consider the conversion of R form of a compound to ...
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Why are allenes chiral?

How is 1-bromo-3-chloropropa-1,2-diene ($\ce{BrHC=C=CHCl}$) chiral? It doesn't have any carbon that is connected to four different groups.
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Why do only chiral molecules rotate the plane of polarized light and how do they rotate it?

I have learnt that only chiral or unsymmetrical molecules can rotate the plane of linearly polarized light. But, why is it so? And how can molecules rotate the plane or what does it actually mean by ...
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1answer
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What are identical molecules?

I don't know what identical molecules are but these are by thoughts. Since from the word identical the molecules should have the same number and kind of atoms attached in the same way. Since in ...
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Molecular chirality and optical rotation

Why does having molecular chirality result in optical rotation? The dissymetry or chirality of molecules translates to the rotation of plane polarized light, the magnitude and direction depending on ...
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How can geometric isomerism arise due to steric factors?

I can see how a double bond and a ring structure can lead to geometric isomerism but can't see the same for steric factors. Could you help? Thank you!
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Finding chiral carbons in aromatic or cyclic compounds

I know that for a carbon to be chiral four different groups should be attached to that particular carbon. But, what about in the case of cyclic compounds? What's the method to check chirality if the ...
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Optical isomerism in Co-ordination Compounds

Optical isomerism in normal organic molecules can be found out by looking for chiral carbon, and the number of isomers can be found out by drawing different spacial orientations of the same. But, I ...
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What does lowercase r-s notation mean?

I came across a naming convention which I haven't seen before. I let ChemDraw name the following compound for me and got a name containing lowercase "r" and "s" configurations. Can someone tell me ...
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Racemization of biphenyl compounds

How does the effect of heat and effect of substituents affect racemization of biphenyl compounds?
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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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Geometrical isomerism in cycloalkenes

Why doesn't cyclohexene have a cis-trans isomer whereas cyclodecene has one? Is strain a factor?
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acyclically stereocontrolled reaction: organolithium and 2-chiral compound

Aoyagi et al. (J. Am. Chem. Soc., Vol. 115, No. 24, p 11393) reported that the addition of 2-lithio-1,3-dithiane to the alpha-chiral (S)-2-Acetylpiperidine gives the (2 S,3 S)-configured product. It ...
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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/...
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What Could Formations of Linkage Isomers of [Co(NH₃)₅NO₂]²⁺ be like?

I am trying to draw the structure of this complex $\ce{[Co(NH3)5NO2]^{2+}},$ however I am not sure if the linkage isomers of this complex like this:
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How do you change the cis-trans isomerism of compounds?

I would like to know a general procedure for the synthesising cis isomers from their trans counterparts and vice versa.
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Is it possible, chemically, to change a dextrorotatory compound to its levorotatory counterpart?

Is it possible, chemically, to change a dextrorotatory compound to its levorotatory counterpart? E.g., is it possible to change dextrodopa to levodopa?
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Why don't trigonal S and P compounds undergo inversion at room temperature?

Most molecules containing nitrogen atoms in trigonal pyramid configuration undergo a relatively fast process of inversion at room temperature. On the other hand, the free energy barrier for phosphines,...
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Is circularly polarized light ever used to isolate particular chiralities?

Chiral molecules tend to absorb one circular polarization of light more than the other. Is this ever used to isolate a particular enantiomer?
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How are non-carbon stereogenic centers named (S/R)?

The R/S naming system for stereocenters relies on the Cahn–Ingold–Prelog priority rules to rank the four substituents of a stereocenter; the R or S name is then attributed depending on the spatial ...
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What is the difference between an angular and linear skeletal formula?

When drawing a skeletal formula, what is the difference between an angular version and a linear version? I was asked to draw the Z isomer of Resveratrol: For which I drew: However the markscheme ...
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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 ...
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How do I determine the absolute configuration experimentally?

Let's say I synthesized or isolated a chiral molecule and want to know the absolute configuration (R or S) of that molecule. I could obviously solve the structure by X-Ray crystallography, but that's ...
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How do you separate enantiomers?

There are some stereochemical reactions that result in the presence of enantiomers. When moving forward with a practical organic synthesis, how does one usually separate them in order to continue with ...
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What are known examples of drugs that racemize/stereoconvert in vivo, and how are they converted?

It is known that although only the (S)-enantiomer of the infamous sedative thalidomide possesses teratogenic properties, it is not very useful to administer the pure (R)-enantiomer since it is ...

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