Nitro derivatives of polyhydric phenols

Among polyhydric phenols, only the nitro derivatives of resorcinol have gained considerable practical importance. The nitro derivatives of phloroglucinol may also be of some value. Both phenols have hydroxyl groups in the meta position to each other, thus enabling the introduction of three nitro groups. Among dinitro derivatives, those of pyrocatechol have found some uses. 

The presence of a large number of hydroxyl groups in the ring increases the reactivity of phenol very considerably. That is why these compounds are very easy to nitrate, and in the nitration process by the conventional method for phenols, 

A compound is nitrated which in addition to phenolic groups contains some other which inhibits the introduction of nitro groups and after the nitration becomes so mobile that it can readily be removed. A carboxylic group may serve the purpose. For example, by the nitration of resorcylic acid, dinitroresorcinol may be obtained as an end product (for more details see p. 537). 

Among all the possible nitro derivatives of resorcinol only di- and tri-nitroresorci-nols are of practical value. Both are used as initiating explosives in the form of lead salts (Vol. III). The lead salt (Pb2+) of dinitroresorcinol is also of some practical value and in this connection some data characteristic of the compound will be given. 

They are yellow substances, readily soluble in hot water, which dye animal fibres and leather. 

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