Preparation of Cyanides

Four routes give alkyl cyanides. (1) FROM ALKYL HALIDES: treating an alkyl halide with NaCN or KCN in solution gives the alkyl cyanide, forming a NEW carbon-carbon bond (e.g. ethyl bromide + KCN gives propanenitrile + KBr); aryl cyanides CANNOT be made this way, since aryl halides resist nucleophilic substitution -- they are instead made via the Sandmeyer reaction on a diazonium salt (CuCN/KCN, already covered under diazonium chemistry). (2) DEHYDRATION OF PRIMARY AMIDES OR ALDOXIMES with P2O5: acetamide loses water to give ethanenitrile; acetaldoxime similarly loses water to give ethanenitrile. (3) DEHYDRATION OF AMMONIUM CARBOXYLATES with P2O5: ammonium acetate gives ethanenitrile + 2H2O -- this route is well suited to LARGE-SCALE preparat …