Adams catalyst halogens

The hydrogenation of 4-chloro-CO-dibutylamino-l-propionaphthone hydrochloride over Adams catalyst was accompanied by a large proportion of cleavage of the nuclear halogen. Hydrogenation of the Mannich-type base derived from phenylacetone, 17, R = Me, as the hydrochloride in an aqueous solution over Pd-C failed to take place. However, the hydrogenation of the free bases 17, R = Me and R2 = (CH2)5 was successful over Raney Ni in ethanol at 0.34 MPa H2.143 Freifelder has reviewed the hydrogenation of various amino ketones.144... 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

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