Which statements about the radical shown are correct? Select all that apply.

AThe two C-C bonds have equal length.
BIt is less stable than the n-propyl radical.
CThe central carbon carries most of the spin density.
DThe unpaired electron is delocalised over the two terminal carbons.

Answer: A, D

The radical shown is the allyl radical, a resonance hybrid of

CH X_{2} = CH - CH X_{2} X^{∙}

and

X_{∙} X_{2}^{2 ∙} CH X_{2} - CH = CH X_{2}

. The spin density sits on the two terminal carbons and the two C-C bonds are equal (bond order 1.5), so statements 1 and 2 are true. The central carbon carries almost no spin density, and resonance makes allyl more stable than a localised primary radical such as n-propyl.

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Which statements about the radical shown are correct? Select all that apply.

Answer: A, D

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