Question

Be sure to answer all parts you have available 2,2−dimethylcyclopentanol (a) and 2−bromo−1,1−dimethylcyclopentane (b) and wish to prepare 3,3−dimethylcyclopentene (c). which would you choose as the more suitable reactant, a or b, and with what would you treat it?

Answer 1

The more suitable is 2-bromo-2, 1-dimethylcyclopentane. The reasons are 1) The reaction should be done with a strong base like NaOC_2H_5, CH_3CH_2OH so that the reaction follows the E2 pathway. If it follows the E1 elimination, then rearrangement may occur, leading to a mixture of products. 2) 2,2-dimethylcyclopenthanol is not suitable at all. In presence of H_2SO_4, or KHSO_4, it forms a carbocation. Subsequently, -CH_3 migration would take place leading to a more stable 3 degree carbocation. Therefore, the nature of the product would be changed.