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JEE Advanced levelNumerical answerDifficulty 3 of 3o4256

The alcohol shown is heated with acid. Assume that the secondary cation undergoes a single 1,2-methyl shift to a tertiary cation and that both the unrearranged and the rearranged cations lose a proton. Counting E and Z isomers as different compounds, how many distinct alkenes can form? Give the answer as an integer.

Numerical answer type, tolerance 0.5.

Answer: 5

The alcohol is 3,3-dimethylpentan-2-ol. The unrearranged secondary cation loses only a C-1 hydrogen, giving 3,3-dimethylpent-1-ene (1). The methyl shift gives the tertiary 2,3-dimethylpent-3-yl cation, which gives 2,3-dimethylpent-2-ene (1), (E)- and (Z)-3,4-dimethylpent-2-ene (2) and 2,3-dimethylpent-1-ene (1). The total is 1 + 1 + 2 + 1 = 5.
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