Res. Chem. Intermed.
, Vol. 34, No. 1, pp. 93–101 (2008)
Also available online - www.brill.nl/rci
Hydrogenation of nitrobenzonitriles using Raney nickel
KLARA KOPRIVOVA and LIBOR CERVENY
Institute of Chemical Technology Prague, Technicka 5, 166 28 Prague 6, Czech Republic
Received 18 July 2007; accepted 10 September 2007
Abstract—2-, 3-, 4-Nitrobenzonitriles were hydrogenated using Raney nickel catalyst in the environ-
ment of two different solvents (methanol and dioxane). The position of the nitro group relative to the
nitrile group plays the dominant role in the course of hydrogenation. The nearer the substituent to
the nitrile group is, the larger is its effect. 3- and 4-nitrobenzonitriles were hydrogenated to their pri-
mary amines, in contrast to 2-nitrobenzonitrile, which was transformed via intramolecular oxidation
to 2-aminobenzamide. During hydrogenation, numerous intermediates were formed. The choice of
the solvent is another signiﬁcant parameter affecting the course of hydrogenation.
Keywords: Hydrogenation; nitrobenzonitrile; Raney nickel.
The catalytic hydrogenation of aromatic nitriles is an important process in the
production of primary amines. It is carried out using metallic catalysts mostly in
the liquid phase at an elevated hydrogen pressure. Industrially preferred catalysts
are Raney nickel or Raney cobalt; however, Pd and Pt catalysts are also suitable.
Functionalized benzylamines are signiﬁcant intermediates for the manufacturing
of various agrochemicals, pharmaceuticals, dyes and pigments. Hydrogenation of
aromatic, compared to aliphatic, nitriles is much more difﬁcult as the aromatic ring
is also susceptible to hydrogenation and thus secondary products are frequently
produced in a relative abundance. Hydrogenation of nitriles occurs as a set of
consecutive and parallel reactions, whose reaction products are usually difﬁcult
to separate due to small differences in their boiling points. The speciﬁcations
for amines are often strict from the point of view of purity. For this reason,
controlling the selectivity is the crucial requirement and, thus, it is necessary to be
well acquainted with the reaction mechanism and the way by-products are produced.
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