Racemic

In chemistry, a racemic mixture consists of equal amounts of left and right-handed isomers. Because the two isomers rotate plane-polarised light in opposite directions, a racemic mixture does not rotate plane-polarised light. The first known racemic mixture was 'racemic acid', which Pasteur found to be a mixture of the two enantiomeric isomers of tartaric acid.

The reagents of, and the reactions that produces, racemic mixtures are said to be "not stereospecific" or "not stereoselective", for their indecision in a particular stereoisomerism.

See also:

• optical isomerism
• chirality
• Compounds with Two Chiral Centers (http://www.uis.edu/~trammell/organic/stereochemistry/tartaricAcid.htm)