MYTUTOR SUBJECT ANSWERS

885 views

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...

1 year ago

Answered by Katherine, an A Level Chemistry tutor with MyTutor


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

98 SUBJECT SPECIALISTS

£20 /hr

Abhinav T.

Degree: Medicine (Other) - University College London University

Subjects offered:Chemistry, Physics+ 2 more

Chemistry
Physics
Maths
Biology

“Confirming understanding by verbal confirmation and communication so as to ensure clarity and confidence during the learning process and progression.”

MyTutor guarantee

£24 /hr

Pooja D.

Degree: Medicine (Bachelors) - Birmingham University

Subjects offered:Chemistry, Science+ 6 more

Chemistry
Science
Physics
Maths
Biology
.UKCAT.
-Personal Statements-
-Medical School Preparation-

“I have tutored for the past 4 years and have gathered many ways of teaching concepts to students in a way that is easily-digestible and understandable. ”

£26 /hr

Martyna S.

Degree: Neurotechnology (Masters) - Imperial College London University

Subjects offered:Chemistry, Science+ 4 more

Chemistry
Science
Maths
Biology
.BMAT (BioMedical Admissions)
-Personal Statements-

“PhD candidate in Bioengineering at Imperial College London. Long experience in effective tutoring!”

About the author

Katherine F.

Currently unavailable: for new students

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

Subjects offered:Chemistry, German+ 2 more

Chemistry
German
French
Biology

“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

0.250 g of a hydrocarbon known to contain carbon, hydrogen and oxygen was subject to complete combustion and produced 0.3664 g of CO2 and 0.1500 g of H2O. What is the empirical formula of this hydrocarbon?

What is the ideal gas equation?

A buffer was made by mixing 20cm3 of 0.05M NaOH and 20cm3 of 0.25M propanoic acid. Calculate the pH. Ka=1.34x10^-5

Providing reasoning, what is the trend in the atomic radius of row 3 elements across the periodic table?

View A Level Chemistry tutors

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

mtw:mercury1:status:ok