1,2-Dichloro-4-nitrobenzene → 3,4-Dichloroaniline

Participants

Reaction Conditions

Reaction Steps

A titanium autoclave equipped with a jacket for heating, coils for circulating temperature controlled water and an efficient agitator was charged with 300 parts of 3,4-dichloronitrobenzene, 0.30 part of phosphorous acid and 0.006 part of platinum (the actual charge consisting of an aqueous paste of platinum deposited on a carbon support, the quantity of platinum on the support being 5.0 weight % on a dry basis). Air in the autoclave and lines was displaced by pressuring with nitrogen and releasing the pressure through a vent system. The nitrogen was then displaced by pressurizing with hydrogen to 300 p.s.i.g. and releasing the pressure as before. The temperature of the mixture was then raised to 90° C., the agitator was started and the hydrogen pressure was increased to about 500 p.s.i.g. Absorption of hydrogen was rapid with evolution of heat; the temperature of the reaction mass was held at 115° ± 5° C. by circulating low pressure steam through the coils. The autoclave was repressured with hydrogen to 500 p.s.i.g. after each 100 lb. drop in pressure. When no further hydrogen absorption occurred, the mass was held at the operating temperature and 500 p.s.i.g. hydrogen pressure for 15-30 minutes. The total hydrogenation time was 1.25-1.50 hours. The hot reduction mass was cooled to below 100° C., removed from the autoclave, treated with ammonium hydroxide (to a pH above 7.0) and then filtered. The filtrate was allowed to settle at 70°-85° C. and the layers were separated. Analysis of the organic layer by gas chromatography showed the presence of 0.04 mole % of dechlorination products. If desired, the dichloroaniline product can be distilled in the presence of 2 weight % soda ash and 0.25 weight % tetraethylenepentamine, for example, as described in U.S. Pat. No. 2,911,340, to give 3,4-dichloroaniline of greater than 98% purity in greater than 90% yield.

Provenance & Evidence