Tartaric Acid Isomers & Isomer Numbers

From WikidChem

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Slide 25

In 1830, Berzelius identified two compounds, tartaric acid and racemic acid, with the same chemical composition. However, -boiling- melting (they are solids of low volatility) point analysis suggests that there may be more than two isomers of the compound. These results were a part of Pastuer's larger puzzle: why do some compounds bend light to the left, why do some bend light to the right, and why do some not bend light at all? By understanding the optical properties of compound, Pasteur could more accurately identify how many isomers a certain compound should have.

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Slide 26

Isomerism was not yet fully understood. Some scientists predicted too many isomers for certain chemical compositions, while others predicted to few isomers; often when they failed to consider the left and right-handed nature of some molecules. Louis Pasteur set out to understand "rotary polarization" and how it had caused previous scientists to over/underpredict the number of isomers for a chemical composition.

NOTE: racemic acid is a 50:50 mixture of L and D tartaric acid