Aromatic

Question 1

How does delocalised model prove kekule’s model wrong

Answer 1

Resistant to reaction: Elec. density is lower in Delocalised model as it is less susceptible to electrophilic attack

C-C Bond Lengths are the same in the delocalised model

Enthalpy change of hydrogenation of delocalised model has lower exothermic value than expected

Question 2

Similaries + Differences between Kekule and Delocalised model in terms of orbital overlap?

Answer 2

Similarities: Both have overlap of p-orbitals

Differences: Kekule –> 2elec in Pi bond, ovlerlap in 1 direction. Pi bonds are LOCALISED

Delocalised –> 6 Electrons in Pi bond, overlap in both directions + ALL p-orbitals overlap. Pi bonds are DELOCALISED

Question 3

Why does phenol react more readily than benzene

Answer 3

High electron density due to lone pair of electrons on O in -OH donated to pi ring hence making it more susceptible to electrophilic attack

Question 4

Why does Salicylic Acid react more readily than benzene

Answer 4

Lone pair of elec. on O in OH is partially delocalised in the ring. Br2 is more polarised

Question 5

What are conditions for bromation and reduction for aromatic compounds

Answer 5

Bromation –> AlCl3
Reduction –> Sn

Question 6

What is condition for Fidel Crafts Reaction

Answer 6

AlCl3

Question 7

What are the conditions for the mechanism where the aromatic compounds with OH have H remvoed and replaced with the halogen carrier

Answer 7

H2S04 (acid catalyst)

Question 8

Write equation for catalyst being used up and formed for the nitration of benzenoic acid

Answer 8

HNO3 + H2SO4 -> H20 + HS04- + NO2+

H+ + HSO4 -> H2SO4

Question 9

Write equation for catalyst being used up and formed again for chloronation of phenol

Answer 9

AlCl3 + Cl2 -> AlCl4- + Cl+

H+ + AlCl4 —> AlCl3 + HCl