Advices For Studying Organic Chemistry

alternate course.

4.

C the rate of addition dramatically and makes the reaction an easy

Adding silica gel or alumina to the mixture of the alkene and HCl or HBr in

H 2 Cl 2 increases

one to carry out.

5. The regioselectivity of the addition of HX to an unsymmetrical alkenes:
   i) The addition of HBr to propene: the main product is 2-bromopropane.

H 2 CCHCH 3 + HBr CH 3 CHCH 3 (

Br

little BrCH 2 CH 2 CH 3 )

2-Bromopropane 1-Bromopropane

i

i) The addition of HBr to 2-methylpropene: the main product is tert-butyl

bromide.

CCH

3

2 + HBr H C CCH (little H CCHCH

H

H C CH 3

3 2 Br

CH 3

2-Methylpropene

(isobutylene)

tert-Butyl bromide l bromide

)

8.2A M

1. Russian chemist Vladimir Markovnikov in 1870 proposed the following rule:
   
   
   1. “If an unsymmetrical alkene combines with a hydrogen halide, the halide
      ion adds to the carbon atom with fewer hydrogen atoms” (The addition of
      HX to an alkene, the hydrogen atom adds to the carbon atom of the double
      that already has the greater number of hydrogen atoms).
   
   
   
   

3 C

(^33)
Br
Isobuty

ARKOVNIKOV’S RULE:

Carbon atom with the greater

number of hydrogen atoms

CH 2 CHCH 3 CH 2 CHCH 3

H Br H Br

i)

Markovnikov addition: