The hydrogenation of mandelonitrile over a Pd/C catalyst: towards a mechanistic understanding.

A carbon supported Pd catalyst is used in the liquid phase hydrogenation of the aromatic cyanohydrin mandelonitrile (C 6 H 5 CH(OH)CH 2 CN) to afford the primary amine phenethylamine (C 6 H 5 CH 2 CH 2 NH 2 ). Employing a batch reactor, the desired primary amine is produced in 87% selectivity at reaction completion. Detection of the by-product 2-amino-1-phenylethanol (C 6 H 5 CH(OH)CH 2 NH 2 ) accounts for the remaining 13% and closes the mass balance. The reaction mechanism is investigated, with a role for both hydrogenation and hydrogenolysis processes established.