3.10 Aromatic chemistry

Question 1

Explain why the structure of Benzene is more stable than the proposed Kekule structure (6)

Answer 1

1. Bond length in Benzene is 139pm this is between the length of single and double C-C bonds so it cannot contain simple C-C or C=C bonds. Stability is due to delocalised electrons
2. Enthalpy of hydrogenation of cyclohex-1-ene was -120kJ/mol (this is for one C=C) so expected value for hydrogenation of Benzene would be 120 X 3 = -360kJ/mol however the actual value is -208kJ/mol so more energy is required to break the bonds in benzene so it must be more stable

Question 1

Formula of Benzene

Answer 1

c6h6

Question 2

What was Kekule’s proposed structure of benzene

Answer 2

Cyclical 6 carbon compound with each carbon attached to 1 H. 3 double CC bonds and 3 single CC bonds which alternate

Question 3

In what orbital are the delocalised electrons in Benzene in?

Answer 3

P

Question 4

What type of reaction do arenes undergo

Answer 4

Electrophilic substitution

Question 5

Name the reaction that produces a strong electrophile for acylation

Answer 5

RCOCl + AlCl3 > RCO+ AlCl4-