The structure shown was suggested for benzene by a chemist called Kekulé.
Benzene is now thought to have a delocalised structure.
Evidence for the delocalised structure of benzene includes
• only one structure for 1,2-dichlorobenzene
• analysis of X-ray diffraction images of benzene.
Explain why each of these makes the delocalised structure more likely to be
correct than the Kekulé structure.
Isomers of dichlorobenzene in which one has a single bond between the C atoms bonded to Cl and the other has a double bond have not been found.
Can be shown on a Kekulé diagram. (1)
(X-ray diffraction shows that)
all carbon-carbon bonds are the same (length)
OR intermediate between C=C and C-C (not as in Kekulé )
OR shows that benzene is a regular hexagon
ALLOW
All bonds are same length
(1)
IGNORE
Reference to bond angles
Benzene undergoes substitution reactions rather than additions
