Write the structures of all the alkenes that can be formed by dehydrohalogenation of each...

Write the structures of all the alkenes that can be formed by dehydrohalogenation of each of the following alkyl halides with sodium ethoxide. Apply the Zaitsev rule to predict the alkene formed in the greatest amount in each case.

(a) 2-Bromo-2,3-dimethylbutane

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(b) tert-Butyl chloride

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(c) 3-Bromo-3-ethylpentane

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(d) 2-Bromo-3-methylbutane

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(e) 1-Bromo-3-methylbutane

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(f) 1-lodo-1-methylcyclohexane

Sample Solution (a) First analyze the structure of 2-bromo-2,3-dimethylbutane with respect to the number of possible β elimination pathways.

The major product, predicted on the basis of Zaitsev’s rule, is 2,3-dimethyl-2-butene. It has a tetrasubstituted double bond. The minor alkene has a disubstituted double bond.