Advices For Studying Organic Chemistry

Br 2 3

Br −

6 1 2 at C 1

Bromonium ion

Br+

123

inversion

Cyclohexene

Br

Br

Diaxia formation

Diequatorial conformation

rans-1,2-Dibromocyclohexane

6

Br

Br

trans-1,2-

Dibromo-

cyclohexane

inversion at C 2

Br

Br

Br

Br

1) The product is a racemate of the trans-1,2-dibromocyclohexane.

2) The initial product of the reaction is the diaxial conformer.

i) They rapidly converts to the diequatorial form, and when equilibrium is

reached the diequatorial form predominates.

ii) When cyclohexane derivatives undergo elim ation

is the diaxial one.

8.7A STEREOSPECIFIC REACTIONS

1. A reaction is stereospecific when a particular stereoisomeric form of the starting
   material reacts gives a specific st.
   product is (2R,3S)-2,3-dibromobutane,
   the meso compound.

Reaction 1

l con

t

ination, the required conform

ereoisomeric form of the product

2. When bromine adds to trans-2-butene, the

C

C

H 3 CH

HCH 3

Br 2

CCl 4

C

C

Br H

Br H

CH 3

CH 3

trans-2-Butene (2R,3S)-2,3-Dibromobutane

(a meso compound)