Question

Which of the following free radicals is the most stable ?

• A. primary
• B. methyl
• C. secondary
• D. tertiary

Answer 1

Answer: (D)

tertiary

Electron poor species are stabilized by neighboring atoms that can donate electron density. The most common way to interpret rich neighbors here is the observation that increasing the number of alkyl groups on the carbon bearing the free radical increases its stability.

Radical stability increases in the order methyl < primary < secondary < tertiary.

Hence, option $D$ is correct.