11. Radical Reactions

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

(d)

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 radicals in decreasing order of stability. Classify each as primary, secondary, or tertiary.

a. The isopentyl radical,

b. The 3-methyl-2-butyl radical,

c. The 2-methyl-2-butyl radical,

d.

Ethers can be converted into radicals, some more easily than others. Which of the following radicals is more stable, and thus, more likely to form?

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).

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

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

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

(c)

Which of the following radicals is the most stable?

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

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

a. Which of the hydrogens in the structure in the margin is the easiest for a chlorine radical to remove?

b. How many secondary hydrogens does the structure have?

Methyl t-butyl ether (MTBE) is used preferentially over diethyl ether because it is less prone to form peroxides. Explain this observation in terms of the two structures.

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