Ethyne (Acytylene) is less acidic than water or ethanol. So it reacts with very strong Bases.
C2H2 reacts with sodium amide in liquid ammonia and forms sodium acetylide.
Na NH2 + C2 H2 ----> Na C2 H + NH3
C2H2 also reacts with ButyLithium to form Lithium Acetylide
C2 H2 + Bu Li --> Li C2 H + Bu H
Above two reactions shows the acidic nature of Ethyne