Question

Page No.:
Arrange the following carbonyl compounds in the
order of their favourability for formation of
nitriles
CH₂ CH₂ CHO , CH 3 CO CH3, HCOH and PhCOCH3,
aur answer?​

Answer 1

The decreasing ease of  order of formation of nitriles is :

HCOH , CH₂ CH₂ CHO , CH 3 CO CH3, and PhCOCH3

• Formation of nitriles is a nucleophilic addition reaction.
• Reaction of Aldehydes and ketones with HCN or NaCN, KCN leads to addition of nitrile into the compound.
• We know, Ketones are less reactive towards nucleophilic addition reaction than aldehydes because of    i) Steric hinderance  ii)Electronic reasons.
• The presence of two bulky groups on the ketonic Carbonyl carbon, hinders the approach of nucleophile towards it.
• Also, the aromatic aldehyde has even lesser reactivity towards nucleophilic addition reaction because of positive charge of carbonyl carbon here is stabilized by electrons of benzene ring.
• So, Formaldehyde is very easy to form Nitrile, than Propanal than Propanone than Benzyl methylaldehyde.