Terminal Alkynes ($R-C\equiv C-H$) exhibit weak acidic character.

• This is due to the $sp$ hybridization of the carbon atoms in the triple bond.
• An $sp$ orbital has 50% $s$-character, making it more electronegative than $s{p}^2$ or $s{p}^3$ orbitals.
• The $sp$ carbon pulls the shared electron pair of the $C-H$ bond closer to itself, making the $H$ atom more easily removable as a proton ($H^{+}$) by a strong base (like $NaN{H}_2$).