Does citric acid show any form of stereoisomerism?
I realise that citric acid is not chiral, and that is has no geometrical isomerism, though I am unsure of the term conformational isomerism. Can you help?
Citric acid shows no stereoisomerism at all beyond conformational isomers, which are interconverted by rotating about carbon-carbon single bonds. It contains no chiral carbons whatsoever. However, other compounds in the citric acid cycle, notably isocitric acid and malic acid, do show stereoisomerism.
What you are groping toward is the situation found in, for example, meso-2,3,4-pentanetriol. Here, the central carbon atom is not formally chiral but nevertheless shows stereoisomerism, as shown by the Fisher projections below--which are not superimposable:
| Dan Berger |
| Bluffton College |
| http://www.bluffton.edu/~bergerd |