6. Thermodynamics and Kinetics

Why do $\mathrm{carbocation}$ rearrangements occur? Choose the single best answer.

Which of the following is the most stable carbocation?

Which of the following factors most significantly contribute to the stability of a $\mathrm{carbocation}$?

Which term best describes a carbocation in which the positively charged carbon is attached to three other carbon atoms?

Rank the following carbocations in order of decreasing stability: $C_6{H}_5-C+H{2}_3$ (benzylic), $\mathrm{CH}{3}_{2}C+H$ (tertiary), $\mathrm{CH}{3}_2\mathrm{CH}+$ (secondary), $\mathrm{CH}{3}_3+$ (methyl).

Which of the following carbocations is the most stable?