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Unformatted text preview: 6-26 I t is i mportant to analyze the structure of carbocations to consider if migration of any groups from adjacent carbons w i l l lead to a more stable carbocation . As a general rule, if rearrangement would lead to a more stable carbocation , a carbocation w i l l rearrange. (Beginning with this problem, only those unshared electons pairs involved in a partic ular step w i l l be shown. ) CH3
(a) C H 3-C I CH3 I - CH3
CH-CH3 I� 1\ 1- + CH3- - -CH3 CH3 H yy
+ n ucleophilic attack on unrearranged carbocation CH3 :O-CH3 CH3- - -CH3 CH3 H
n ucleophilic attack after carbocation rearrangement ??
! I c�� .. HRCH3 CH3 :O-CH3 CH3- C - C-CH3 CH3 H
u nrearranged product .. -----l� I I I I CH3 CH3 -C-C-CH 3 CH3 H
M ethyl shift to the I + � I�I 2 ° c arbocation forms a more stable 3° c arbocation. n ucleophilic attack on unrearranged carbocation cj:
u nrearranged product
106 rl<- -;: � ",H
C H3 H
I H CH2CH3 :R - CH,CH ; ...
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This note was uploaded on 02/27/2010 for the course CHEM 140 taught by Professor Wade during the Spring '10 term at Whitman.
- Spring '10