Answer to Question #306292 in Physical Chemistry for Libina k

Question

The hypothetical heats of hydrogenation for 1,3,5-cyclohexatriene is different from the heats of hydrogenation of benzene. Explain this in detail.

Answer 1

Benzene is aromatic and therefore gives off n152kJ/mol less

1,3,5- Cyclohexatriene has one double bond and its heat of hydrogenation is -120kJ/mol.

Benzene has three double bonds so we might expect its heat of hydrogenation to be -360°kJ/mol.

However its measured value is -208kJ/mol

Benzene is more stable than expected by 152 kJ/mol.