Manufacture of organic nitriles

A process for the conversion of butadiene or isoprene to 3-pentenenitrile or 4-methyl-3-pentenenitrile respectively which comprises reacting the butadiene or isoprene with hydrogen cyanide in the molar ratio of said butadiene or isoprene to hydrogen cyanide of 2:1 to 1:10 at -25.degree. to 200.degree.C and pressures up to 50 atmospheres in presence of from 0.0005 to 0.1 mole per mole of butadiene or isoprene of anhydrous cuprous chloride or anhydrous cuprous bromide and, for each part by weight of said cuprous chloride or cuprous bromide, of from 0.5 to 5 parts by weight of a thiol or sulphide of the formula

• R.sub.1 SH or R.sub.1 SR.sub.2
• in which R.sub.1 and R.sub.2 represent alkyl groups having from 1 to 6 carbon atoms, said alkyl being unsubstituted or substituted by hydroxyl, alkoxyl, carboxylic ester or halogen, or represent cyclohexyl, phenyl, tolyl or benzyl groups, or together with the S atom represent a heterocyclic ring having 5, 6 or 7 atoms, which ring may contain carbon-carbon unsaturation.