hcn and cn – in synthesis increasing carbon chain length
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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
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