These are the derivatives of hydrocyanic acid (HCN), and is known to exist in two tautomeric forms
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
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.
Aryl cyanide cannot be prepared in this method because of their less reactivity towards nucleophilic substitution. Aryl cyanides are prepared using Sandmeyers reactions.
This method suitable for large scale preparation of alkyl cyanides.
Methyl magnesium bromide on treatment with cyanogen chloride (Cl - CN) forms ethanenitrile.
The lower members (up to C14 ) are colourless liquids with a strong characteristic sweet smell. The higher members are crystalline solids, They are moderately soluble in water but freely souble in organic solvents. They are poisonous.
They have higher boiling points than analogous acetylenes due to their high dipole moments.
On boiling with alkali (or) a dilute mineral acid, the cyanides are hydrolysed to give carboxylic acids.
On reduction with LiAlH4 (or) Ni / H2 , alkyl cyanides yields primary amines.
a) Thorpe nitrile condensation
Self condensation of two molecules of alkyl nitrile (containing a–H atom) in the presence of sodium to form iminonitrile.
b) The nitriles containing α- hydrogen also undergo condensation with esters in the presence of sodamide in ether to form ketonitriles. This reaction is known as “ Levine and Hauser” acetylation
This reaction involves replacement of ethoxy (OC2 H5 )group by methylnitrile (- CH2CN) group and is called as cyanomethylation reaction.