THIS INTENTION relates to the manufacture of organic nitriles and more particularly to the conversion of olefinically unsaturated mo ^ή onitriles to dinitriles. Our invention provides a process for the disproportionation of a Cj- mono-olefinically unsaturated mononitrile into a mixture of Cr saturated dinitrile and butadiene which comprises heating the said mononitrile, in the absence of added hydrogen cyanide, with a zerovalent nickel catalyst. The C_- mono-olefinically unsaturated mononitrile is preferably one in which the nitrile and olefinic group are unconjugated. Particularly suitable mononitriles are 3-ρentenenitrile, 4-pentεnenitrile and 2-methyl-3-butenenitrile. The zerovalent nickel catalyst is preferably of the formula NiL, where L represents a suitable ligand. Suitable ligands include organic phosphines, arsines, stibines, phosphites, arsenites, stibites, phosphinites and phosphonites. Particularly suitable ligands are those phosphorus compounds of the formula P(XYZ) where X and Y represent R or OR and Z represents OR, where the R's, which may be the same or different, represent alkyl or aryl groups. Preferably the alkyl or aryl groups contain up to 18 carbon atoms. More preferably the alkyl groups contain from 1 to 6 carbon atoms, and the aryl groups are phenyl, tolyl, xylyl or substituted phenyl groups. As examples of such ligands

there nay be mentioned tri ethyl phosphite, triethyl phosphite, triphenyl phosphite, tri(m-tolyl) phosphite, tri-(p-tolyl) phosphite, tri-(p-chloro-phenyl) phosphite tri-(p-methoxyphenyl) phosphite. The disproportionation process is effected by heating the said mononitrile -with the zerovalent nickel catalyst. The temperature of heating is, for example, within the range 50° to 200°C and is preferably within th range 100° to 150°C. The disproportionation process is preferably effected in the presence of a Lewis acid. Suitable Lewis acids are, for example, the salts of various metals, especially zinc, aluminium, titanium, tin and iron. The anion of the salt may be inorganic, for example, fluoride chloride, bromide or iodide, sulphate or phosphate and ma be the anion of an organic carboxylic acid, ^' especially a lower aliphatic acid having up to 6 carbon atoms, for example, the acetate.

It may also be advantageous to add ligand in ex of that required to form the zerovalent nickel complex.

If desired the disproportionation process may b carried out in the presence of a solvent. Suitable solve are, for example, hydrocarbon solvents, e.g. benzene, toluene and xylene, .or nitrile solvents, e.g. acetonitril propionitrile, benzonitrile and adiponitrile.

The zerovalent nickel catalyst is used in catalytically effective amount, for example in the range 0.005 to 0.2 moles per mole of mononitrile. The Lewis ac may be used, for example, in the proportion of from 0.5 t 50 moles per mole of catalyst and preferably in the range 1 to 5 moles.

The disproportionation process may be effected, for example, by heating the said mononitrile with the catalyst and optionally Lewis acid, excess ligand and solvent, in a closed vessel under autogeneous pressure. period of heating may be varied, for example, according t the degree of conversion of starting material desired, an may vary, for example, from 0.5 to 50 hours. At the end

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the process the reaction mixture comprises, in addition to catalyst, unconverted mononitrile and possibly its isomers formed during the process, butadiene and Cg saturated dinitriles. The C saturated dinitriles are principally

5 " adiponitrile and 2-methylgluta onitrile. Any conversion of the starting mononitrile to an iso er during the process, for example of 3-pentenenitrile to 4-pentenenitrile or vice versa is immaterial since the isomers are also converted to the dinitriles. The principal components of the 0 reaction mixture may be separated from each other by any convenient means, for example by fractional distillation, desirably in part under reduced pressure. If desired the butadiene may alternatively be bled from the reaction vessel as the process proceeds. 5 The process of our invention may be used in the manufacture of adiponitrile from butadiene. Thus butadiene may be converted to 3-pentenenitrile by methods known in themselves, for example by reaction with hydrogen cyanide

__, ^' in the presence of a copper catalyst as described, for 0 example, in British Patent Specification No. 1,429,651. The 3-pen.tenenitrile may then be disproportionated to adiponitrile and butadiene according to the* process of our invention and the butadiene recycled for further conversion to 3-pentenenitrile. 5 Adiponitrile may be converted by hydrogenation to hexamethylene diamine a valuable intermediate for the manufacture of polyamides and polyurethanes, especially of polyhexamethylene adipamide (nylon 6,6) useful in the manufacture of fibres, films and mouldings. 0 The invention is illustrated but not limited by the following Examples in which the parts and percentages are by weight. EXAMPLES 1 to 4

3-ρentenenitrile (5 parts), nickel tetrakis- 5 (tri-p-tolylphosphite) (0.5 part) and anhydrous zinc chloride (0.2 part, 2 moles/mole of catalyst) were heated at 120°C for 9 hours. After cooling, butadiene was removed by evaporation and the residue was found to contain

1.2% of adiponitrile and 2Λ% cf glutaronitrile by gas/ liquid chromatography.

The experiment was repeated under varied conditions which are set out in the following-table together with the results.

EXAMPLE 5

4-pentenenitrile (5 parts), nickel tetrakis- ^" (tri-p-tolylphosphite) (0.5 part) and anhydrous zinc _ chloride (0.1 part) were heated at 120°C for 18 hours. After cooling and evaporating butadiene the residue was found to contain 4.396 of adiponitrile and 3.8% of 2-methylglutaronitrile.