In the reactionR - C equiv C - R xrightarrow{ | vedclass

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(B) The reduction of an alkyne with $Na$ in liquid $NH_3$ (Birch reduction) proceeds via anti-addition of hydrogen,resulting in the formation of a $tr

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$A$ is trans and $B$ is cis

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(B) The reduction of an alkyne with $Na$ in liquid $NH_3$ (Birch reduction) proceeds via anti-addition of hydrogen,resulting in the formation of a $trans$-alkene $(A)$.The reduction of an alkyne with $H_2$ in the presence of Lindlar's catalyst ($Pd + CaCO_3$ or $Pd + BaSO_4$) proceeds via syn-addition of hydrogen,resulting in the formation of a $cis$-alkene $(B)$.

In the reaction
$R - C \equiv C - R \xrightarrow{Pd + CaCO_3} B$
$R - C \equiv C - R \xrightarrow{Na + liq. NH_3} A$
$A$ and $B$ are geometrical isomers. Then:

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In the reaction$R - C \equiv C - R \xrightarrow{Pd + CaCO_3} B$$R - C \equiv C - R \xrightarrow{Na + liq. NH_3} A$$A$ and $B$ are geometrical isomers. Then: