sand·mey·er reaction \ˈsan(d)ˌmī(ə)r-\noun Usage: usually capitalized S Etymology: after Traugott Sandmeyer died 1922 Swiss chemist : a reaction for preparing aromatic halides or cyanides from a salt with a cuprous halide or cyanide as catalyst < ortho-bromo-toluene can be made from ortho-toluene-diazonium bromide by the Sandmeyer reaction >