Page 376 - Mechanism and Theory in Organic Chemistry

1.2-Elimination Reactions

Increasing C-X distance
Figure 7.2 Projection in the horizontal plane of the E, reaction path. A poorer leaving
group will facilitate motions R2 and I,, causing shift of the transition state to *
and change of the reaction path from the solid curve to the dashed curve.
t t
B B B B
J. 4
t t
H H H H
L L
C-C C-C C-C C-C
K K
X X X X
L L
Motion R1 R2 11 12

than C-X bond breaking (39) to one similar to that of the E, reaction, 41.84
Intermediate would be the fully concerted transition state 40.

84 See note 64, p. 355.