Mosher's acid

Mosher's acid, or α-methoxytrifluorophenylacetic acid is a carboxylic acid which was first by Harry S. Mosher used as a chiral derivitizing agent. It is a chiral molecule, consisting of R and S enantiomers.

Applications
As a chiral derivitizing agent, it reacts with an alcohol or amine of unknown stereochemistry to form an ester or amide. The configuration of the ester or amide is then determined by proton NMR spectroscopy.

Mosher's acid chloride, the acid chloride form, is sometimes used because it has better reactivity.