Organic Compounds containing Nitrogen (original) (raw)

ut of the two nitration techniques, Vapour-phase nitration is more satisfactory than liquid-phase nitration. General rules of vapour phase nitration of alkanes (and cycloalkanes), as given by Hass and Shechter (1947): i. Polynitro compounds are formed only from alkanes of fairly high molecular weight. Smaller alkanes give mainly mono-nitro alkanes. ii. The ease of replacement of the hydrogen atom by nitro group is: tertiary hydrogen > secondary hydrogen > primary hydrogen. At higher temperature, however, the ease of replacement is almost equal. iii. An alkyl group present in the alkane can also be replaced by a nitro-group, i.e, chain fission takes place. For example, isopentane yields nine nitroparaffins. The fission reaction increases as the temperature rises. iv. Oxidation always accompanies nitration, resulting in the formation of nitro-compounds and a mixture of acids, aldehydes, ketones, alcohols, nitrites, nitroso-compounds, nitroolefins, polymers, carbon monoxide and carbon dioxide. Catalysts such as copper, iron, platinum oxide, etc., accelerate oxidation rather than nitration. Mechanism: Proceeds by a free radical mechanism. 2 2 3 2 3 3 HNO CH CH NO CH CH + • − ⎯→ ⎯ • + − ONO CH CH NO CH CH NO CH CH 2 3 2 2 3 2 2 3 2 3 2 3 O CH CH O CH CH 2 3 2 3 In this reaction, the active hydrogen atom is replaced by an amino-methyl group or substituted amino-methyl group: This reaction provides a means of preparing a large variety of compounds, e.g., nitro-amines, diamines, etc.