L1 /
12
CH1012
BROMINATION
Radical
reaction of bromine with propane.
hn
or D
CH3CH2CH3 + Br2 ® CH3CH2CH2Br
+ CH3CH(Br)CH3
• Propane contains 8 H’s (6 x 1o H, 2 x 2oH)
• Substitution of any of the 6 primary H’s gives 1-bromopropane while substitution
of the secondary H’s
gives 2-bromopropane.
• On the basis of random substitution we expect a
ratio of 6:2 or 75% : 25%.
• Experimentally a ratio of 8% : 92% is found
The reaction of Br2 is selective in the
order:
3o H > 2o H > 1o H site selectivity
3o H > 2o H > 1o H site selectivity
