Describe two different types of physical evidence which show that benzene does not contain three double bonds.

Explain how the reaction of benzene with bromine provides chemical evidence that benzene does not contain three double bonds.

the C–C bond lengths are all the same;

IR absorption of C–C bonds in benzene is different to that of both C–C single bonds and C=C double bonds;

chemical shift of protons in benzene is different to that of protons in alkenes;

only one isomer exists for 1,2-disubstituted benzene compounds;

substitution rather than addition occurs / OWTTE;

Many candidates scored marks by describing the physical evidence in part (a) and the chemical evidence in part (b), which shows that benzene does not contain three double bonds.

Many candidates scored marks by describing the physical evidence in part (a) and the chemical evidence in part (b), which shows that benzene does not contain three double bonds.