5. Benzene and cyclohexene have different reactivity towards addition reaction. i. Explain why do benzene and cyclohexene undergo different type of reaction with bromine.

Question

5. Benzene and cyclohexene have different reactivity towards addition reaction. i. Explain why do benzene and cyclohexene undergo different type of reaction with bromine. ii. State the type of reaction for both compounds. iii. Write the chemical reaction equations of benzene and cyclohexene in (i). (

Answer 1

Benzene and cyclohexene undergo different types of reactions with Bromine because benzene is aromatic, and cyclohexene is not. Aromatic compounds react differently than “free” alkenes. Aromatic compounds are much less reactive, as they do not like to break aromaticity. Therefore, for aromatic compounds, you need a much stronger electrophile than you would for a normal alkene addition reaction. The reaction with benzene is called electrophilic aromatic substitution, while the reaction with cyclohexene is called alkene addition. For the electrophilic aromatic substitution, FeBr3 is used as a catalyst to make the bromine a stronger electrophile.

equations:

Benzene + FeBr3 + Br2 —> Bromobenzene

cyclohexene + Br2 —> 1,2-dibromocyclohexane

Hope this helps!

Cara B