Question

When but$-2-$yne is treated with $Na$ in liquid ammonia :

• A. cis$-2-$butene is obtained
• B. trans$-2-$butene is formed
• C. $n-$butane is the major product
• D. it rearranges to but$-1-$yne
• E. there is no reaction

Answer 1

The correct option is B trans$-2-$butene is formed

When but$-2-$yne is treated with $Na$ in liquid ammonia, addition of two $H-$atoms takes place at the triple bonded carbon atoms in trans manner.

$C{H}_{3}C\equiv CC{H}_3\underset{Liq.N{H}_3}{\overset{Na}{\to }}\underset{Trans-2-butene}{C{H}_3-\stackrel{H}{\stackrel{|}{C}}=\underset{H}{\underset{|}{C}}-C{H}_3}$