Question

6. Napthalene undergoes electrophilic aromatic substitution. Predict its reactivity (activating or deactivating) and predict where it will direct addition by drawing the product(s). [10 points] Br2, CC14, A

Answer 1

Answer with explanation

The reaction is given below

Br Br Br2, CCI4, heat 1-Bromo napthalene Major product 2-Bromo napthalene Minor product

Substitution bromination will occurs more readily at the 1 position than at the 2 position because the intermediate for 1-substitution is more stable than that for 2-substitution. Because resonance forms determine that C-1 has higher reactivity

a) C-1 attack has 2 resonance structures with benzene rings as under

H X H X H H

c) C-2 attack has only 1 resonance structure with a benzene ring

H H X X

Conclusion: 1-substitution is more favorable because the positive charge can be distributed over two positions, leaving one aromatic ring unchanged while only one resonance structure is possible for the 2-substitution intermediate with aromatic ring unchanged. Therfore, position 1 if favourable for bromination