What evidence is there to support the delocalised model of benzene over Kekulé's model?

Bond lengths - a single bond is 0.153nm while a double bond is 0.134nm, making Kekulé's model of alternating single and double bonds asymmetric.  Other evidence shows benzene to be symmetrical so it cannot have this combination.  Instead, all bonds are 0.139nm.

Enthalpy change of hydrogenation - if cyclohexene is hydrogenated, the enthalpy change for adding hydrogen across 1 double bond is -120kJ/mol.  If benzene has 3 double bonds, it should have an enthalpy change of -360kJ/mol (3x120).  However, when benzene is hydrogenated, it releases -208kJ/mol, showing it to be more stable than Kekulé's structure.  This supports the theory of a delocalised electron ring as this electronic structure stabilises the molecule.

Resistance to reaction - benzene will not react with halogens or strong acids, or take part in addition reactions so it does not react like an alkene.  This suggests that C=C double bonds are not present.

Katherine F. A Level Chemistry tutor, A Level Biology tutor, GCSE Fre...

7 months ago

Answered by Katherine, an A Level Chemistry tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


PremiumLouise R. A Level Biology tutor, A Level Chemistry tutor, A Level Mat...
View profile
£24 /hr

Louise R.

Degree: Chemistry (Masters) - Edinburgh University

Subjects offered: Chemistry, Maths+ 1 more


“Hi my name is Louise Roberts and I am a 1st year Chemistry student at the University of Edinburgh.  I am very much looking forward to meeting some of you and hopefully helping you with your studies inBiology, Maths and of course, Chem...”

Parthik P. A Level Biology tutor, GCSE Biology tutor, A Level Chemist...
View profile
£20 /hr

Parthik P.

Degree: Biochemistry and Molecular Medicine (Bachelors) - Nottingham University

Subjects offered: Chemistry, Maths+ 2 more

Extended Project Qualification

“Hey! I am a Biochemistry and Molecular Medicine student at the University of Nottingham. I started tutoring at school when I was 13 and now have built up my skills to specialise inGCSE's and A Levels. I had volunteered abroad to Thail...”

PremiumCharlotte R. GCSE Chemistry tutor, GCSE Geography tutor, Uni Admissio...
View profile
£24 /hr

Charlotte R.

Degree: Natural Sciences (Bachelors) - Durham University

Subjects offered: Chemistry, Geography


“Hi there! I'm Charlie and I'm studying Natural Sciences at Durham University, specialising inChemistry and Earth Sciences. At A Level I got 3 A*s in Chemistry, Geography and Maths from Bedford Modern School andat GSCE I have 12 A* gr...”

About the author

Katherine F. A Level Chemistry tutor, A Level Biology tutor, GCSE Fre...
View profile

Katherine F.

Currently unavailable: for new students

Degree: Biochemistry (Bachelors) - Oxford, Trinity College University

Subjects offered: Chemistry, German+ 2 more


“Hi!  I'm a first-year biochemist at Oxford University and I am very keen to help with biology and chemistry A levels, or with French and German at GCSE.  I love learning and want to pass on this enthusiasm, as well as helping students ...”

MyTutor guarantee

You may also like...

Posts by Katherine

What evidence is there to support the delocalised model of benzene over Kekulé's model?

How can an aldehyde be distinguished from a ketone?

How do auxins bring about positive phototropism in plants?

How do ionic charge and radius affect lattice enthalpy?

Other A Level Chemistry questions

What is the effect of temperature on K(equilibrium constant)?

Which has a lower boiling point chlorine or bromine, and why?

What is a ligand?

What does the term isotope mean?

View A Level Chemistry tutors


We use cookies to improve our service. By continuing to use this website, we'll assume that you're OK with this. Dismiss