HCN and CN – in synthesis Increasing carbon chain length.

HCN and CN– in synthesis

Increasing carbon chain length

Reaction of haloalkanes with CN–

• RBr + CN– RCN + Br–

Reaction of carbonyl compounds with HCN:

• Aldehydes: RCHO + HCN RCH(CN)COH

• Ketones: RCOR’ + HCN RCR’(CN)COH

Formation of C–CN

Haloalkane nitrile

Reagents and conditions

•CN– ions, e.g. KCN(aq) in ethanol solvent

Mechanism:

• Nucleophilic substitution

charge

lone pair

C–C bond forms

Carbonyl nitrile

Reagents and conditions

• CN– ions in dilute acid, e.g. KCN(aq)/H2SO4(aq)

Mechanism:

• Nucleophilic addition

charge

lone pair

C–C bond forms

Nitriles in synthesis

Reduction amines

• H2 and Ni catalyst

Acid hydrolysis carboxylic acids

• Aqueous acid, H+/H2O, e.g. HCl(aq)

aminenitrile

carboxylic acidnitrile