Question

comments on c-c bond length in benzene.

Answer 1

The six-membered ring in benzene is a perfect hexagon (all carbon-carbon bonds have an identical length of 1.40 Å). The cyclohexatriene contributors would be expected to show alternating bond lengths, the double bonds being shorter (1.34 Å) than the single bonds (1.54 Å).

Answer 2

Since in this resonance will ocuur so when resonance occcur then double bond shifts to adjacent carbon atom so b.o will be 1.5