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Question: $$CH_3-C \equiv C-CH_3 \xrightarrow{Na/liq. NH_3} (A);$$ $$CH_3-C \equiv C-CH_3 \xrightarrow[\left(C...

CH3−C≡C−CH3→Na/liq.NH3(A);CH_3-C \equiv C-CH_3 \xrightarrow{Na/liq. NH_3} (A); CH3−C≡C−CH3→(CH3COO)2PbPd/CaCO3(B);CH_3-C \equiv C-CH_3 \xrightarrow[\left(CH_3COO\right)_2Pb]{Pd/CaCO_3} (B); The minimum heat of hydrogenation is in

A

(A)

B

(B)

C

Both have equal

D

Cannot predict

Answer

A

Explanation

Solution

(A) is trans-but-2-ene, and (B) is cis-but-2-ene.Trans-but-2-ene is more stable than cis-but-2-ene. More stable isomers have lower energy and thus release less heat upon hydrogenation to the same product (butane). Therefore, (A) will have the minimum heat of hydrogenation.