Aminies and Diazonium Salts

Nitriles

Eg: 

Organic cyanides has a triple bond between the C and N atoms i.e., one sigma and two pi bonds are present. Thus nitrogen here is sp hybridized.

The C-C ≡ N bond angle is 180^o. Bond length of then the triple bond C ≡ N is shorter than the double bond C = N in imines and C - N single bond in amines.

Preparation

From Alkyl Halides

Alkyl halides on treatment with ethanolic solution of sodium cyanide or potassium cyanide give alkyl cyanides.

With secondary halides both substitution and elimination products are formed.

In the case of tertiary halides, elimination is the principal reaction.

aryl halides are less reactive towards nucleophilic substitution reactions and these reactions therefore don’t take place.

From Diazonium Salts

through replacement of diazonium group by cyanide (CN). This is called the sand meyer's reaction.

Dehydration of Amides

The dehydration of primary amides phosphorus pentoxide (P₂O₅) forms corresponding nitrile.

R can also be a phenyl group.

Physical Properties

The lower members of the family are colorless liquids whereas the higher members are crystalline solids. They are stable compounds with pleasant smell.

Boiling points

possess high dipole moment and high melting and boiling points despite lack of hydrogen bonding due to the triple bond.

Solubility

The cyanides with low molecular mass are soluble in water due to hydrogen bonding between molecules.

with increase in molecular mass, solubility in water decreases.

Acetonitrile is miscible with water and propionitrile has low solubility in water.

The cyanides are fairly soluble in organic solvents.

Basic character

Nitriles are very weak bases as its resonance structure is a vinyl cation, which is not very stable.

Acetonitrile is used as a solvent of choice for performing many organic reactions because it is not reactive in mild acidic and basic conditions. Having high polarity it is capable of dissolving a variety of reactants. It has moderate boiling point and can be easily removed. It is miscible with water and a number of organic solvents.

Chemical Properties

Hydrolysis

Nitriles are hydrolyzed to carboxylic acids in presence of acidc or basic medium. The intermediate in both the reactions is the primary amide.

Reaction with Grignard reagent

Nucleophilic Grignard reagent add on to nitriles forming imine salt intermediate which on subsequent hydrolysis give ketones.

Reduction

Nitriles undergo reduction to form primary amines as the products agentts like H₂ in the presence of catalysts like Pt, Ni etc., Na in C₂H₅OH or LiALH₄.

Chemical reduction of alkyl or aryl cyanides using LiAiH₄ or Na/ethanol is referred to as Mendius reaction.