Portmess Homework Q&S 111

Portmess Homework Q&S 111 - 105 STRUCTURE AND...

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Stereoisomeric 3-methyl-2-pentenes are formed by proton abstraction from C-2. ( h ) Only 3,3-dimethyl-1-butene may be formed under conditions of E2 elimination from 3-bromo-2,2-dimethylbutane. 5.31 ( a ) The reaction that takes place with 1-bromo-3,3-dimethylbutane is an E2 elimination involving loss of the bromine at C-1 and abstraction of the proton at C-2 by the strong base potassium tert -butoxide, yielding a single alkene. ( b ) Two alkenes are capable of being formed in this b -elimination reaction. The more highly substituted alkene is 1-methylcyclopentene; it is the major product of this reaction. According to Zaitsev s rule, the major alkene is formed by proton removal from the b carbon that has the fewest hydrogens. ( c ) Acid-catalyzed dehydration of 3-methyl-3-pentanol can lead either to 2-ethyl-1-butene or to a mixture of ( E )- and ( Z )-3-methyl-2-pentene. The major product is a mixture of the trisubstituted alkenes, ( E )- and ( Z )-3-methyl-2-
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