Advices For Studying Organic Chemistry

1. E2 reaction


2. E1 reaction

6.17 THE E2 REACTION

1. Rate equation
   Rate = k [CH 3 CHBrCH 3 ] [C 2 H 5 O–]

A Mechanism for the E2 Reaction

Reaction:
C 2 H 5 O– + CH 3 CHBrCH 3 CH 2 =CHCH 3 + C 2 H 5 OH + Br–

Mechanism:

CH 3 CH 2 O−

CH 3 CH 2 O

δ−

CH 3 CH 2 O

CC

H

Br

HCH 3

HH

β α CC

H

Br

HCH 3

HH

β α δ−

Transition state

++

The basic ethoxide ion begins to remove

a proton from the β-carbon using its

electron pair to form a bond to it. At the

same tim, the electron pair of the β

C−H bond begins to move in to become

the π bond of a double bond, and the

bromide begins to depart with the

electrons that bonded it to the α carbon.

Partial bonds now exist between the

oxygen and the β hydrogen and

between the α carbonand the

bromine. The carbon-carbon bond is

developing double bond character.

CC

H

CH 3

H

H

+ H + Br −

Now the double bond of the alkene is fully formed

and the alkene has a trigonal plannar geometry at

each carbon atom. The other products are a

moleculeofethanolanda bromide ion.

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