CH3 CH3
C
|
H + |
|
|
|
|
|
|
2 1 |
At Position
( 1)
|
CH 3
CH3
|
C CH 3 |
Br |
CH 3
CH
|
C |
CH
3
|
CH2
3 ° more stable cation
3
Br Major Product
H + CH 3 Br CH3
CH CH 2
CH 3
CH3
1 ° less stable cation
At Position( 2)
CH CH2 Br
Minor Product
Peroxide effect or Kharasch( Anti Markownikoff’ s addition):- In 1933 Kharasch and Mayo observed that when HBr is added to an unsymmetrical double bond in the presence of organic peroxide, the reaction take places opposite to the Markovnikov rule.
CH 3 |
CH CH 2 |
HBr
Peroxide
|
CH3 CH2 CH2Br
propyl bromide
|
Noted:- peroxide effect is applicable only to HBr and not to HF, HCl and HI. Addition of HF, HCl and HI takes place according to Markovnikov’ s rule even in the presence of peroxide.