Pent-2-yne is reduced with sodium in liquid ammonia. The major product is

A(E)-pent-2-ene
Bpent-1-ene
C(Z)-pent-2-ene
Dpentane

Answer: A

Na/liq.

NH X_{3}

reduces an internal alkyne through a radical anion and a vinyl anion; the more stable trans vinyl anion is protonated, giving net anti addition. The product is (E)-pent-2-ene.

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