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31 votes
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What is the perfect definition for chirality?

The correct definition of chirality is given in the IUPAC gold book as follows: chirality The geometric property of a rigid object (or spatial arrangement of points or atoms) of being non-...
Martin - マーチン's user avatar
27 votes

What is the perfect definition for chirality?

I think Martin has provided an excellent answer, and I would like to supplement it with a few additional details and examples that might prove insightful. So as I already mentioned in the comments, ...
getafix's user avatar
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26 votes
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How is exact racemization possible?

Racemization isn't "exact," but rather very very close to equality. It is just simple probability. Think of flipping a coin, p=probability for heads, and q=probability of tails. Now for a fair flip ...
MaxW's user avatar
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17 votes

Why are conformational isomers considered as isomers?

Gaurang's answer deals well with the theory part I just wanted to give a visual aid. (Taken from Atropisomerism of naphthyl alcohol) Let's call the rotating substituent on the naphtahlene a fan. The ...
Avyansh Katiyar's user avatar
15 votes

Why are conformational isomers considered as isomers?

I was taught that geometric (cis-trans) isomers are considered isomers because there is a high energy barrier to breaking the double bond... There's a problem here. Geometrical isomers are isomers ...
Gaurang Tandon's user avatar
14 votes

Is light a reactant in photochemical reactions?

It is neither reactant nor catalyst, and equilibrium concepts do not apply There are processes other than photochemistry that to go in a direction away from equilibrium. They require mechanical or ...
Karsten's user avatar
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13 votes

Difference between Epimers and Diastereomers

This scheme I just drew up specifically for you should answer your question. Diastereomers are stereoisomers that are not enantiomers of each other. That includes conformers (geometric isomers that ...
Jan's user avatar
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13 votes

Number of stereoisomers of tetramethylspirononane

Here is another approach to @loong's solution to the seven stereoisomers of this tetramethyl spiro[4.4.0]nonane. [This question is akin to one recently asked about tetramethylspiropentanes]. Using ...
user55119's user avatar
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13 votes

How is plane polarized light rotated by chiral compounds?

Circularly polarized light is like a helix that twists through space. The two components are mirror images of each other. Now, every molecule interacts with both the left-handed twisting light and the ...
Osal Thuduwage's user avatar
12 votes
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Difference between Epimers and Diastereomers

epimers as compounds which differ by configuration at only one carbon Yes, at only one centre. However isn't that the same thing as diastereomers? No, not completely. Diastereomers differ at ...
Klaus-Dieter Warzecha's user avatar
12 votes
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What is the reason of the color difference for the cis/trans isomers of tetraamminedichloridocobalt(III) chloride?

If you search a library for a copy of Inorganic Chemistry by Miessler and Tarr, they have an excellent diagram showing which explains the phenomenon. $\ce{Cl-}$ ligands have lone electrons that can ...
Xahoc's user avatar
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12 votes
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What is the error in the number of aromatic isomers of C7H8O?

You are completely correct - the furan derivatives you've drawn display unquestionable aromatic character, though the "strength" of their aromaticity is somewhat lower than various other ...
Nicolau Saker Neto's user avatar
11 votes

Isomers with molecular formula C₄H₇Cl

There are 12 different constitutional isomers: There is also the further possibility of stereoisomerism in some of the compounds above. 3: Two diastereomers (cis- and trans-) are possible. 7, 8, 9: ...
gilleain's user avatar
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11 votes
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For molecules to be enantiomers, do the groups have to be non-superimposable mirror images even when rotated around C-C single bonds?

Real molecules surely do rotate around their single C-C bonds all the time(*). So yes, if two models can be superimposed after an internal rotation of such sort, this means they represent the same ...
Ivan Neretin's user avatar
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10 votes
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Polymerization Isomerism In Transition-Metal Complexes Not True Isomerism?

I’m pretty sure that polymerisation isomerism should mainly be considered a historical term nowadays. Going back in the history of science, all people knew at some point was which elements a specific ...
Jan's user avatar
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10 votes

What is the seventh plane of symmetry in benzene?

Have a look at this picture which shows some of the symmetry axes and planes. You should be able to see other similar ones. Taken from www.molecule-viewer.com.(You can also use this site to practice ...
porphyrin's user avatar
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10 votes
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If a chiral molecule reacts with an achiral molecule will the product be chiral or achiral?

The key here is to look at the transition state through which the reaction proceeds. The short answer is that the transition states are enantiomeric, i.e., also mirror images of each other, and in ...
Zhe's user avatar
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9 votes
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Number of cyclic isomers of C4H6

You can answer such questions using D.U. (Degree of unsaturation) The formula is $\mathrm{C + 1 - }\frac{H + X - N}{2}$ ...
Mesentery's user avatar
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9 votes

What is metamerism

The terms metamerism, or metamer, in a sense of chemical isomerism (there are other meanings in zoology and colorimetry), are very old. Presently, they are not used nor mentioned in authoritative ...
mykhal's user avatar
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9 votes
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Stability of 4-pyridone vs 4-pyridinol

I don't think this is an either this or that situation. As with most of the equilibria we know it depends very much on the circumstances we look at it. Many examples of keto-enol-tautomerism are ...
Martin - マーチン's user avatar
9 votes

Why doesn't 2,3-pentadiene show geometrical/cis-trans isomerism?

The (cis)/(trans) nomenclature (or, more universally applicable, (E)/(Z) nomenclature) works fine for isolated and conjugated double bonds. In the case of 2,3-pentadiene, however, where double bonds ...
Buttonwood's user avatar
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9 votes

How can I find all possible isomers of a given molecule?

As drawn, there are 8 positions where the OH could replace an H, but only 3 structurally unique arrangements: Two positions: on the centre-C (above or below are a symmetric reflection). Two positions:...
Ray Butterworth's user avatar
8 votes
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Is peroxynitrous acid an isomer of nitric acid?

Keeping aside its stability and considering only their structure and structural formula, is peroxynitrous acid an isomer of nitric acid? Yes. It seems that peroxynitrous acid is a very, very ...
hBy2Py's user avatar
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8 votes
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Why does having identical groups on either side of the pi bond lead to no geometrical isomerism?

Hmm, you seem to be having a problem visualizing the structures in the case of 2 identical groups on one carbon. But never fear, 3D molecules are here. Check out chloroethene: It has two identical ...
Pritt says Reinstate Monica's user avatar
8 votes
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Reactivity of different isomers of N2F2

According to Dinitrogen Difluoride Chemistry Inorg. Chem., 2010, 49 (15), pp 6823–6833: This increased reactivity of the cis-isomer can be readily explained. In both $\ce{N2F2}$ isomers, each ...
DavePhD's user avatar
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8 votes

Why are carbons of Inositol chiral centers?

Consider 2,3-butanediol. This compound has 2 stereocenters. The meso version of this compound is achiral. However, there are still two stereo centers. As drawn, the left one is (R) and the right one ...
Zhe's user avatar
  • 17.4k

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