What is the major alkene produced from dehydrohalogenation of 1-bromo-2-methylpropane with a strong base?

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Multiple Choice

What is the major alkene produced from dehydrohalogenation of 1-bromo-2-methylpropane with a strong base?

E2 dehydrohalogenation with a strong base favors the more substituted alkene. Here the bromine is on a terminal carbon, and the adjacent carbon is secondary and bears a methyl substituent. The base removes a beta-hydrogen from that secondary carbon and the bromide leaves, forming a double bond between the brominated carbon and that adjacent carbon. The resulting alkene is 2-methylpropene (isobutylene), CH2=C(CH3)2, which is more substituted and thus the major product. Other possible eliminations would lead to less substituted alkenes or aren’t accessible from this substrate under these conditions, so they’re not formed preferentially.

E2 dehydrohalogenation with a strong base favors the more substituted alkene. Here the bromine is on a terminal carbon, and the adjacent carbon is secondary and bears a methyl substituent. The base removes a beta-hydrogen from that secondary carbon and the bromide leaves, forming a double bond between the brominated carbon and that adjacent carbon. The resulting alkene is 2-methylpropene (isobutylene), CH2=C(CH3)2, which is more substituted and thus the major product. Other possible eliminations would lead to less substituted alkenes or aren’t accessible from this substrate under these conditions, so they’re not formed preferentially.

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