RACEMIC MIXTURES

RACEMIC MIXTURES

• A racemic mixture is a 50:50 mixture of the 2 enantiomers of a chiral compound.
• Because the two enantiomers have equal and opposite specific rotations, a racemic mixture has a specific rotation of zero, i.e., it is optically inactive
• In nature, most naturally occurring compounds occur as a single enantiomer, not as racemic mixtures. The importance of racemic mixtures is that ordinary laboratory synthesis which generate a stereogenic center produce a racemic mixture. For example,if 1-butene is converted to 2-butanol by the addition of water catalyzed by acid, a stereogenic center is created in a molecule where none previously existed. Since both enantiomers have equal energy, and since there is nothing in the catalyst or solvent or reactant that is chiral, both enantiomers are formed in equal amounts(for a mechanistic explanation, see later).
• Whereas racemic mixtures are not particularly desirable, they are not problematic in many labaoratory organic syntheses. However, in the manufacture of drugs, usually only a single enantiomer is effective, so that it is desirable to synthesize only a single enaniomer. Nevertheless, racemic drugs are often used anyway because the other enaniomer is harmless, and racemic mixtrues are easier(read, cheaper) to synthesize. 
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