Question

What is the action of following reagents on pent-3-enal?

1. H₂/Ni
2. LiAlH₄/H₃O⁺

Answer 1

Pent-3-enal contains an isolated > C = C < and an aldehyde group. H₂/Ni can reduce both these functional groups while LiAlH₄ can reduce only –CHO of the two.

1. H₂/Ni:
   \[\ce{\underset{\text{Pent-3-enal}}{CH3 - CH = CH - CH2 - CHO} ->[H2/Ni]\underset{\text{Pentan-1-ol}}{CH3 - CH2 - CH2 - CH2 - CH2 - OH}}\]
2. LiAlH₄/H₃O⁺:
   \[\ce{\underset{\text{Pent-3-enal}}{CH3 - CH = CH - CH2 - CHO} ->[(i)LiAIH4][(ii)H3O+] \underset{\text{Pent-3-en-1-ol}}{CH3 - CH = CH - CH2 - CH2 - OH}}\]