Acidity of Alkynes Terminal alkynes,R-C=C-H,are more acidic than other hydrocarbons. ·Acetylene-→acetylide by NH2,but not by OH-or RO. More s character,so pair of electrons in anion is held more closely to the nucleus.Less charge separation,so more stable. > Chapter9 13Chapter 9 13 Acidity of Alkynes • Terminal alkynes, R-CC-H, are more acidic than other hydrocarbons. • Acetylene → acetylide by NH2 - , but not by OH- or RO- . • More s character, so pair of electrons in anion is held more closely to the nucleus. Less charge separation, so more stable. =>