Question

Arrange the following free radicals in the order of decreasing stability: methyl `(I)`, vinyl `(II)`, allyl `(III)`, benzyl `(IV)`
A. `IgtIIgtIIIgtIV`
B. `IIIgtIIgtIgtIV`
C. `IIgtIgtIVgtIII`
D. `IVgtIIIgtIgtII.`

Answer 1

Correct Answer - D
Among the alkyl free radicals, tertiary alkyl radicals are the most stable and methyl radical is least stable. Benzyl and allyl free radicals are resonance stabilized and are more stable than alkyl free radicals. Vinyl radical is least stable since the odd electron is present on `sp^(2)` C atom

Resonance in benzyl radical
`CH_(2)=CH-overset(cdot)CH_(2)harroverset(cdot)CH_(2)-CH=CH_(2)`
Resonance in allyl radical `therefore` order is Benzyl (I)`gt` Allyl (II)`gt` Methyl (Ill)`gt` Vinyl (II).