Which of the following alkynes is not normally reduced to alkene by sodium in liquid ammonia?

Options

A. pent-1-yne
B. pen-2-yne
C. but-2-yne
D. 4-methypent-2-yne

Answer

A

Explanation

Pent-1-yne `(CH_2CH_2CH_2C-=CH)` is a terminal alkyne with an acidic hydrogen atom. Thus, it reacts with sodium in liquid ammonia to form sodium alkynide:
`CH_3CH_2CH_2C-=CH+Naoverset(NH_2)toCH_2CH_2CH_2C-=overset(-)(C)overset(+)(N)a+(1)/(2)H_2`