Cyanide and Isocyanide Properties

Method of Preparation of Cyanide and Isocyanide Preparation and Properties

→ From Alkyl Halides : Alkyl cyanide are prepared by heating an alkyl halide with an aqueous ethanolic solution of KCN.

→ Alkyl halides when heated with small amount of alcohol and treated with AgCN, alkyl isocyanide is formed.

→ But when alkyl halide reacts with AgCN it always form RNC (alkyl isocyanide) because AgCN is a covalent compound which can not ionise easily therefore N atom attack as a nucleophile on the alkyl group (R).

→ From Amides : By dehydration of primary amides by phosphorus pentoxide (P₂O₅ ) or thionyl chloride (SOCl₂), alkyl cyanides are formed.

and CH₃CONH₂ + SOCl₂ → CH₃CN + SO₂↑+ HCl

→ From Aldoximes : Aldoximes are the functional group isomer of amide whose dehydration with phosphorus pentoxide (P₂O₅) gives alkyl cyanides.

→ From Grignards Reagents : Alkyl cyanide can be prepared by the action of Grignard’s reagent on cyanogen chloride.

→ Carbylamine Test : When a primary amine is warmed with alcoholic KOH and chloroform, isocvanide is formed which have obnoxious smell.

→ From Carboxylic acid : To prepare alkyl cyanide on commercial scale relative carboxylic acid and ammonia are mixed and heated at 500°C on alumina.

Chemistry Notes