Are compounds that contain asymmetric carbons ALWAYS optically active?

1 Answer
anor277
Aug 29, 2017

Just to retire this question, the simple answer is no.......

Explanation:

Asymmetric synthesis is a huge subject, and it is made difficult by the fact that we have to represent a 3-dimensional molecule on a 2-dimensional page. Models are USED LESS widely than they should be, even tho they are allowed examination materials.

Now consider lactic acid.....

HO(O=)C-dotCH(OH)dotCH(OH)C(=O)OH

Now I think you will twig that the dotted carbons are potential chiral carbons in that they are both bound to 4 different substituents. And since there are 2 chiral centres, we might suggest that lactic acid has 2^2, i.e. 4 stereoisomers: "RR; SS; RS; SR". Now "RR" and "SS" are indeed stereoisomeric; however, "SR" and "RS" are SUPERPOSABLE, by virtue of an INTERNAL centre of symmetry.

The "RS" and "SR" isomers are THUS NON-OPTICALLY ACTIVE MESO compounds, even despite the fact that it contains 2 stereogenic centres.

And so, to answer your question, not all compounds with asymmetric carbons are chiral.

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