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Isocyanates

Isocyanates can be prepared by nucleophilic substitution with CYANATE. This ion is a very good nucleophile and a weak base and therefore it leads to typical SN2 reactions, unless the reacting carbon is too sterically hindered.

Preparation of n-butyl isocyanate from 1-bromobutane and sodium cyanate
Hofmann rearrangement of a primary amide with Br₂/HO⁻, via an isocyanate

Isocyanates are intermediate compounds in the Hofmann rearrangement of amides. This rearrangement can be an alternative method of getting isocyanates.

Click here to go to the Hofmann rearrangement of amides.

The isocyanate functional group bears a very electron-deficient carbon:

Resonance forms of the isocyanate group: the central carbon is very electron-deficient

Due to that feature, the main reactions of isocyanates involve the nucleophilic attack on that carbon, yielding a large variety of new functional groups:

Reactions of isocyanates: with water they give carbamic acids, which lose CO₂ to give amines; with amines, ureas; with alcohols, carbamates (urethanes); and with diols, polyurethanes