Which bases can deprotonate acetylene? The pKa values of the conjugate acids are given in parentheses.

Removal of a proton from acid during an acid-base reaction is deprotonation.

Species formed from acid after deprotonation is called the conjugate base of the acid. For a deprotonation reaction to occur, the value of conjugate acid of the base should be higher than the value of the base.

Acetylene is a Bronsted-Lowry acid with value of 25.

Acetylene undergoes deprotonation to form acetylide.

Therefore, any base having conjugate acid with value above 25 can deprotonate acetylene.

a.

value is above 25. Therefore, it can deprotonate acetylene.

b.

value is less than 25. Therefore, it cannot deprotonate acetylene.

c.

value is above 25. Therefore, it can deprotonate acetylene.

d.

value is less than 25. Therefore, it cannot deprotonate acetylene. Hence, and can deprotonate acetylene while and cannot.