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

4129 Views

See similar Chemistry A Level tutors

Related Chemistry A Level answers

All answers ▸

How do you calculate the equilibrium constant, Kc, of a reaction?


Regarding the first ionisation energies, why do the values shown on the graph go down from magnesium to aluminium and then rise again from aluminium to silicon


24.5g of CH3CH2CH2Br was reacted with ammonia to form CH3CH2CH2NH2 at a 75.0% yield, calculate the mass of the product formed.


Briefly describe the nature of three types of intramolecular bonding and two types of intermolecular bonding (drawings encouraged)


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences