Add too much strong base

mechanism

Both ortho-dihalogen and gedi-halogen can be used

poisoned catalyst

Metal sodium in liquid ammonia (−33°C)

form trans alkenes

mechanism

Summarize

mechanism

For terminal alkynes

Radical addition only occurs with HBr (not with HCl or HI)

mechanism

The reaction rate of alkynes is significantly lower than that of alkenes

Adding mercuric sulfate (HgSO4) significantly speeds up the reaction rate

The resulting enol is isomerized into ketone

aldehyde is formed

Enol is initially formed, but Cannot be separated and rapidly isomerizes to form aldehydes

Alkynes contain two π bonds. To avoid hydroboration of both π bonds, Add some sterically hindered hydroboration reagents to prevent further hydroboration

major antiaddition

subtopic