H H Acidity of Alkynes Terminal alkynes, R-C=C-H, are more acidic than other hydrocarbons Acetylene>acetylide by Ni2 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 > Chapter 9 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. =>