What are 3 characteristics of Benzene that go against the proposed Kekule model?

The Kekule model states Benzene consists of 3 pairs of alternating double C=C and single C-C bonds. A typical C=C bond would readily react with bromine to produce a dibromo-alkane and therefore would react with bromine water (bromine gas dissolved in water) to produce a colour change from brown to colourless. Benzene however doesn’t react with bromine water, producing no colour change and require much more forcing conditions, such as heat and UV light or a halogen carrier, to react.

Benzene’s bond lengths are also all equal and have a length of (139pm), thereby being in-between that of a typical C=C double bond’s length (134pm) and a C-C single bond’s length(154pm). The final characteristic of Benzene would be it’s lower than expected hydrogenation enthalpy (enthalpy of reaction with hydrogen gas). A typical C=C bond would have a hydrogenation enthalpy of 120 kJmol-1 and therefore 3x C=C bonds would produce a hydrogenation enthalpy of 360 kJmol-1, whereas benzene’s hydrogenation enthalpy is less at 208 kJmol-1.

CG
Answered by Chris G. Chemistry tutor

4661 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

Calculate the empirical and molecular formula of the molecule giving rise to the molecular ion peak at 148 m/z. The percentage composition by weight is 64.80 % carbon, 13.62 % hydrogen, and 21.58 % oxygen


What is the optical activity of the product formed when propanone is refluxed with HCN with KCN dissolved in ethanol and why?


What is the geometry of a BF3 molecule?


Explain what the rate-determining step in a reaction is with reference to activation energy.


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning