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14
CH1012
ALKYNES
• Alkynes generally display very similar reactivity to alkenes with bromination, hydration & hydrohalogenation occurring.
A notable
exception: terminal RCCH alkynes
• The H of terminal
alkynes is weakly acidic pKa » 25 compared with
alkenes pKa » 44.
• Treatment with a
strong base gives an acetylide anion a very useful nucleophile in organic synthesis.
• The strong base here is sodium
amide &
when R = H the product is sodium acetylide.
S.I. sodium ethynide
when R = H the product is sodium acetylide.
S.I. sodium ethynide
