Carbon-carbon bond formation is important as it allows the synthesis of new compounds with longer carbon chains.

The nitrile functional group consists of a carbon-nitrogen triple bond (C≡N).

Nitriles are useful intermediates in the synthesis of other organic compounds such as amines and carboxylic acids.

Nitriles can be formed by heating halogenoalkanes with potassium cyanide in ethanol.

For example, chloroethane reacts with KCN to produce propanenitrile:

CH₃CH₂Cl + KCN ➔ CH₃CH₂CN + KCl 

The mechanism is nucleophilic substitution.

Hydroxynitriles can be formed by heating aldehydes or ketones with sodium cyanide and sulfuric acid to generate hydrogen cyanide in situ.

For example, ethanal reacts with HCN to produce propanenitrile:

CH₃CHO + HCN ➔ CH₃CH(OH)CN

This mechanism is nucleophilic addition.

Nitriles can be reduced to amines by heating with hydrogen in the presence of a nickel catalyst.

For example, ethanenitrile reacts with H₂ to form ethylamine:

CH₃CN + 2H₂ ➔ CH₃CH₂NH₂

Nitriles can be hydrolysed to carboxylic acids by heating with diute aqueous acid e.g. HCl.

For example, ethanenitrile reacts with HCl_(aq) to form ethanoic acid:

CH₃CN + 2H₂O + HCl ➔ CH₃COOH + NH₄Cl

Friedel-Crafts reactions are useful in adding alkyl and acyl adding side chains onto a benzene ring.

The products of Friedel-Crafts reactions can be reacted further to produce other organic compounds.

Alkylarenes can be formed by the Fridel-Crafts alkylation of benzene. Benzene undergoes electrophilic substitution when reacted with a halogenoalkane in the presence of a halogen carrier e.g. AlCl₃.

For example, benzene reacts with chloroethene in the presence of an AlCl₃ catalyst to produce ethylbenzene:

C₆H₆ + C₂H₅Cl ➔ C₆H₅C₂H₅ + HCl

Acylarenes can be formed by the Fridel-Crafts acylation of benzene. Benzene undergoes electrophilic substitution when reacted with an acyl chloride in the presence of a halogen carrier e.g. AlCl₃.

For example, benzene reacts with ethanoyl chloride in the presence of an AlCl₃ catalyst to produce phenylethanone:

C₆H₆ + CH₃COCl ➔ C₆H₅COCH₃ + HCl

1The carbocation, RCO⁺, is generated: 

RCOCl + AlCl₃ ➔ RCO⁺ + AlCl₄^-

2Benzene undergoes electrophilic substitution with the electrophile RCO⁺:

3The catalyst, AlCl₃ is regenerated:                                                            

H⁺ + AlCl₄^- ➔ AlCl₃ + HCl