`Aoverset(H_(2)//"Lindlar's catalyst")larrCH_3C-=C CH_(3)overset(Na//Liq" "NH_(3))toB` A and B, respectively, are

Options

A. cis, trans-but-2-ene
B. both trans-but-2-ene
C. trans, cis-but-2-ene
D. both cis-but-2-ene

Answer

A

Explanation

The reduction of internal alkynes in the presence of lindlar's catalyst leads to the syn addition of hydrogen on account of the attachment of two H's to the same side of an alkyne sitting on the catalyst surface. Reduction in the presence of Na/liq. `NH_3` leads to the anti addition of hydrogen on account of the formation of vinylic radical anion.