Alkyne Hydrohalogenation

Question 1

purpose

Answer 1

HX addition (2 moles) to alkynes to form gem dihalides (Markovnikov)

Question 2

X = ?

Answer 2

Br, Cl, I

Question 3

if starting with a terminal alkyne…

Answer 3

1st mol creates a haloalkene, 2nd mol forms the geminal dihalide

hard to stop at single addn of HX

Question 4

if starting with an internal alkyne

Answer 4

carbons will be equally substituted

1st mol creates a mixture of the Markovnikov haloalkene, 2nd mol adds to same carbon creating a gem dihalide

Question 5

HX + peroxide addition

Answer 5

anti-markovnikov free-radical reaction like with alkenes

1st mol creates haloalkene diastereomers (E/Z syn/anti)

2nd mol creates a mixture of geminal and vicinal dihalides; polymerization too so not practical