6. Thermodynamics and Kinetics

Identify the more stable carbocation in each pair.

(b)

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

Which of the carbocations in part a is most stable?

1. the isobutyl cation?

2. the n-butyl cation?

3. the sec-butyl cation?

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).

For each pair of reactions, predict which will happen more quickly. [For (c) and (d), the more substituted carbocation is more stable due to hyperconjugation.]

(c)

Identify the more stable carbocation in each pair.

(c)

Which of the following carbocations is the most stable?

Which of the following structural changes would most increase the stability of a $2^o$ carbocation intermediate?

Which of the following alkyl halides will form the most stable carbocation upon ionization?

Given the following carbocations: (A) ${\mathrm{CH}}_3-C⁺H_2{\mathrm{CH}}_3$ (a tertiary carbocation), (B) ${\mathrm{CH}}_3-\mathrm{CH}⁺{\mathrm{CH}}_3$ (a secondary carbocation), and (C) $\mathrm{CH}⁺{\mathrm{CH}}_3$ (a primary carbocation), rank them from most stable to least stable.

Which of the following carbocations is most likely to undergo a rearrangement to increase its stability?

Which of the following carbocations would be most stable?