Predict the major organic products of the reaction below.

Question

Quizplus · Accepted Answer

The reaction is an electrophilic addition of HBr to 3-methyl-1-butene. The double bond of 3-methyl-1-butene can accept HBr to form two possible carbocations (I and II). However, a methyl shift can occur to convert carbocation I to the more stable carbocation IV. 
HBr can then add to carbocation I or carbocation IV, resulting in the formation of two major products: 2-bromo-3-methylbutane (I) and 2-bromo-2-methylbutane (IV). The product III is not formed because there is no rearrangement of carbocation II to form a more stable carbocation. Therefore, the best choice is C - I and IV.

Predict the Major Organic Products of the Reaction Below