1. The Nature of Double Bonds

* Hexene: Contains a carbon-carbon double bond. This double bond is relatively electron-rich and susceptible to electrophilic attack.

* Benzene: Contains a system of delocalized pi electrons, which create a stable, aromatic ring. This system is much less reactive than a simple double bond.

2. Bromine's Reactivity

* Bromine (Br₂) is an electrophile. It seeks out electron-rich areas to react with.

3. Reaction Mechanisms

* Hexene: Bromine reacts with hexene through an electrophilic addition reaction. The double bond in hexene is attacked by the electrophilic bromine, breaking the double bond and forming a di-bromoalkane.

* Benzene: While benzene can react with bromine under specific conditions (with a catalyst like FeBr₃), it undergoes electrophilic aromatic substitution, not addition. This is a much slower process because it disrupts the stability of the aromatic ring.

In summary:

* The double bond in hexene is more susceptible to attack by electrophiles like bromine, leading to a straightforward addition reaction.

* The aromatic system in benzene is much less reactive, requiring harsh conditions and a catalyst to undergo substitution.