Portmess Homework Q&S 114

Portmess Homework Q&S 114 - Br 2 CHCHBr 2...

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( e ) The alkyl bromide must be primary in order for the desired alkene to be the only product of E2 elimination. If 1-cyclopentylethyl bromide were used, a mixture of regioisomeric alkenes would be formed, with the desired vinylcyclopentane being the minor component of the mixture. ( f ) Either cis - or trans -1-bromo-3-isopropylcyclobutane would be appropriate here. ( g ) The desired alkene is the exclusive product formed on E2 elimination from 1-bromo-1- tert - butylcyclopropane. 5.33 ( a ) Both 1-bromopropane and 2-bromopropane yield propene as the exclusive product of E2 elimination. ( b ) Isobutene is formed on dehydrobromination of either tert -butyl bromide or isobutyl bromide. ( c ) A tetrabromoalkane is required as the starting material to form a tribromoalkene under E2 elimination conditions. Either 1,1,2,2-tetrabromoethane or 1,1,1,2-tetrabromoethane is satisfactory.
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Unformatted text preview: Br 2 CHCHBr 2 1,1,2,2-Tetrabromoethane 1,1,1,2-Tetrabromoethane 1,1,2-Tribromoethene BrCH 2 CBr 3 BrCH CBr 2 or E2 base (CH 3 ) 3 CBr tert-Butyl bromide Isobutyl bromide 2-Methylpropene (CH 3 ) 2 CHCH 2 Br (CH 3 ) 2 C CH 2 or E2 base base E2 CH 3 CH 2 CH 2 Br or CH 3 CHCH 3 Br 1-Bromopropane 2-Bromopropane Propene CH 3 CH CH 2 base E2 H H H Br H C(CH 3 ) 3 C(CH 3 ) 3 1-Bromo-1-tert-butylcyclopropane 1-tert-Butylcyclopropene base E2 H H H Br H CH(CH 3 ) 2 CH(CH 3 ) 2 cis- or trans-1-Bromo-3-isopropylcyclobutane 3-Isopropylcyclobutene base E2 CHCH 3 CHCH 3 CH CH 2 1 Br 1-Cyclopentylethyl bromide Ethylidenecyclopentane (major product) Vinylcyclopentane (minor product) base E2 CH 2 CH 2 Br CH 2-Cyclopentylethyl bromide Vinylcyclopentane CH 2 108 STRUCTURE AND PREPARATION OF ALKENES: ELIMINATION REACTIONS...
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