Preparation of primary amines


The most industrially significant amines are prepared from ammonia by alkylation with alcohols:

ROH + NH3 → RNH2 + H2O

These reactions require catalysts, specialized apparatus, and additional purification measures since the selectivity can be problematic. Treatment of haloalkanes with amines give the corresponding alkyl-substituted amine, with the release of a halogen acid, which in turn reacts with the amine product or precursor:

RX + 2 R'NH2 → RR'NH + [RR'NH2]X

Such reactions, which are most useful for alkyl iodides and bromides, are rarely employed because the degree of alkylation is difficult to control.

Reductive routes

Via the process of hydrogenation, nitriles are reduced to amines using hydrogen in the presence of a nickel catalyst. Reactions are sensitive acidic or alkaline conditions, which can cause hydrolysis of -CN group. LiAlH4 is more commonly employed for the reduction of nitriles on the laboratory scale. Similarly, LiAlH4 reduces amides to amines. Many amines are produced from aldehydes and ketones via reductive amination, which can use either catalytic hydrogenation or stoichiometric reagents.

Aniline and its derivatives are prepared by reduction of the nitroaromatics. In industry, hydrogen is the preferred reductant, whereas in the laboratory, tin and iron are often employed.

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