Question

The order of reactivity of (a), (b) and (c) for the catalytic hydrogenation is

• A. a > b > c
• B. b > a > c
• C. a > c > b
• D. c > a > b

Answer 1

The correct option is D c > a > b

The unsaturated compound undergoes catalytic hydrogenation to form saturated compound.
Alkynes and alkenes undergo catalytic hydrogenation readily.
Alkynes are sp hybridised so they are linear in shape so the hydrogenation takes place easily compare to alkene.
Comapring (a) and (c), (c) is more reactive to hydrogenation since it is terminal alkyne it it less hindered. So the order of rate of hydrogenation is
(c) > (a) > (b)