Amines, acetylation from nitro compounds

Reduction of a nitro compound to a primary amine. In a 50 ml. round-bottomed or conical flask fitted with a reflux condenser, place 1 g. of the nitro compound and 2 g. of granulated tin. Measure out 10 ml. of concentrated hydrochloric acid and add it in three equal portions to the mixtiue shake thoroughly after each addition. When the vigorous reaction subsides, heat under reflux on a water bath until the nitro compound has completely reacted (20-30 minutes). Shake the reaction mixture from time to time if the nitro compound appears to be very insoluble, add 5 ml. of alcohol. Cool the reaction mixture, and add 20-40 per cent, sodium hydroxide solution imtil the precipitate of tin hydroxide dissolves. Extract the resulting amine from the cooled solution with ether, and remove the ether by distillation. Examine the residue with regard to its solubility in 5 per cent, hydrochloric acid and its reaction with acetyl chloride or benzene-sulphonyl chloride. 

Aromatic amines, like phenols, are very easily nitrated. However, primary and secondary amines in particular readily undergo oxidative side reactions, so that it is advisable to protect the amino group by acylation or by conversion by an aldehyde into the Schiff base. Even using a large excess of sulfuric acid protects the amino group to a considerable extent, owing to formation of the ammonium salt, but then entry of the nitro group is directed to a considerable extent into the meta-position. The usual A-acyl derivative is the acetyl compound, but benzoyl, /7-toluenesulfonyl, oxalyl, ethoxycarbonyl (from chloro-formic ester), and phthaloyl derivatives are also used. 

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