Alkene Electrophilic Addition Flashcards
1
Q
Regioselectivity of HX addition to alkenes
A
Major product when most stable carbocation formed due to hyper conjugation of filled σ stabilising empty p (3>2>1)
2
Q
Add water to alkenes
A
Oxymercuration: 1. Hg(OAc)2/H2O 2. NaBH4, H2O attacks more substituted C = better able to stabilise positive charge
Hydroboration: 1. BH3 2. H2O2/NaOH, B adds to less hindered = sterics, concerted reaction so B/H both added to same face = syn addition
3
Q
How to improve regioselectivity of hydroboration
A
Sterically hindered boranes eg 9-BBn
4
Q
Add of ammonia to alkenes
A
- B2H6 (syn add) 2. H2NOSO3H (HOSA) 3. NaOH
5
Q
How to remove HgOAc
A
NaBH4
6
Q
How to remove B after hydroboration
A
H2O2, NaOH removes with retention
