Advices For Studying Organic Chemistry

8.2C MODERN STATEMENT OF MARKOVNIKOV’S RULE:

metrical reagent to a double bond, the positive

ing reagent attac es itself to a carbon atom of the double

bond so as to yield the more stable carbocation as an intermediate.

1) This is the step that occurs first (before the addition of the negative portion of

the adding reagen it is the step that determines the overall orientation of the

reaction.

1. In the ionic addition of an unsym
   portion of the add h

t) ⇒

CCH 2

H 3 C

H 3 C δ+ δ−

CC

H 3 C

+ I Cl + H 2

H 3 C

I H 3 C C

CH 3

CH 2

Cl

I
Cl −
2-methylpropene 2-Chloro-1-iodo-2-methylpropane

8.2D REGIOSELECTIVE REACTIONS:

1. When a reaction that can potentially yield two or more constitutional isomers
   actually produces only one (or a predominance of one), the reaction is said to be

8.2E AN EXCEPTION TO MARKOVNIKOV’S RULE:

1. When alkenes are treated with HBr in the presence of peroxides (i.e., compounds

regioselective.

with the general formula ROOR) the addition occurs in an anti-Markovnikov

manner in the sense that the hydrogen atom becomes attached to the carbon atom

with fewer hydrogen atoms.

CH 3 CH CH 2 +HBr ROOR CH 3 CH 2 CH 2 Br

1) This anti-Markovnikov addition occurs only when HBr is used in the presence

of peroxides and does not occur significantly with HF, HCl, and HI even when

peroxides are present.