11. Radical Reactions

What is the correct order of stability of the following alkyl radicals (from most stable to least stable): $\mathrm{tertiary}$, $\mathrm{secondary}$, $\mathrm{primary}$, $\mathrm{methyl}$?

Which of the following is the most stable radical?

Rank the following carbon radicals in order of decreasing stability: ${\mathrm{CH}}^3\cdot$ (methyl radical), $\mathrm{CH}{3}_2\mathrm{CH}\cdot$ (secondary radical), $\mathrm{CH}{3}_{3}C\cdot$ (tertiary radical), $\mathrm{CH}{3}_1\mathrm{CH}\cdot$ (primary radical).

Which of the following radicals formed by cleavage of a $C–H$ bond is the most stable in isobutane (${\mathrm{(CH}}_3{)}_3\mathrm{CH}$)?

Which of the following radicals is the most stable?

Use the information in Table 4-2 (p. 167) to rank the following radicals in decreasing order of stability.

Use the information in Table 4-2 to explain why toluene (PhCH₃) has a very high octane rating of 111. Write an equation to show how toluene reacts with an alkyl free radical to give a relatively stable radical.

A student adds NBS to a solution of 1-methylcyclohexene and irradiates the mixture with a sunlamp until all the NBS has reacted. After a careful distillation, the product mixture contains two major products of formula C₇H₁₁Br.

b. Rank these three intermediates from most stable to least stable.

Explain the dramatic difference in rotational energy barriers of the following three alkenes. (Hint: Consider what the transition states must look like.)

The following ethers are ranked according to their ability to form explosive peroxides. Explain this ranking based on your knowledge of the reaction mechanism.

Based on the stability of the radicals produced, predict which bond in each pair would have the higher bond-dissociation energy.

(a)

Based on the stability of the radicals produced, predict which bond in each pair would have the higher bond-dissociation energy.

(b)

Based on the stability of the radicals produced, predict which bond in each pair would have the higher bond-dissociation energy.

(c)

Why is a 2° carbon radical more stable than a 1° carbon radical?

The following polyunsaturated fat, which does not exist in nature, is oxidized at a rate similar to oleic acid (Table 11.14), despite having two cis-alkenes. Why?