. CYANIDES AND ISOCYANIDES . . Introduction These are the derivatives of hydrocyanic acid (HCN), and is known to exist in two tautomeric forms Hydrogencyanide Hydrogen isocyanide XII U13-Organic Nitrogen XII U13-Organic Nitrogen - - - - Two types of alkyl derivatives can be obtained.
Those derived by replacement of H – atom of hydrogen cyanide by the alkyl groups are known as alkyl cyanides (R-C N). ≡ and those obtained by the replacement of H – atom of hydrogen isocyanide are known as alkyl isocyanides (R-N C) In IUPAC system, alkyl cyanides are named as “alkanenitriles” whereas aryl cyanides as “ arenecarbonitrile”. Table : Nomenclature of cyanides Compound (common name, Structural formula, IUPAC Name) IUPAC Name Prefix with position number Root used Primary suffix Secondary Suffix acetonitrile CH -CN Ethane nitrile – Eth ane nitrile Propiononitrile CH CH -CN Propanenitrile – Prop ane nitrile Butyronitrile CH CH CH -CN butanenitrile – But ane nitrile Isobutronitrile CH -CH-CN -methylpropanenitrile -methyl– prop ane nitrile Benzonitrile C H -CN Benzene Carbonitrile – Benzene Carbo nitrile H C CH CN COOH -Cyanobutanoicacid -Cyano but ane / oicacid C H Cl CN Br -Bromo- -chloro- - methyl pentanenitrile. -Bromo- - chloro- - methyl pent ane nitrile XII U13-Organic Nitrogen XII U13-Organic Nitrogen - - - - .
. Methods of preparation of cyanides ) From alkyl halides When alkyl halides are treated in the solution NaCN (or) KCN , alkyl cyanides are obtained. In this reaction a new carbon – carbon bond is formed. Example KCN + CH CH - Br CH CH - CN + KBr Ethyl bromide Propanenitrile Aryl cyanide cannot be prepared in this method because of their less reactivity towards nucleophilic substitution.
Aryl cyanides are prepared using Sandmeyers reactions. . By dehydration of primary amides and aldoximes with P O CH - CONH P O - H O CH - CN Acetamide Ethanenitrile CH - CH=NOH P O -H O CH - CN Acetaldoximes . By dehydration