1. Electrophilic Aromatic Substitution (EAS):
* Conditions: In the presence of a Lewis acid catalyst like FeBr3, the reaction proceeds via electrophilic aromatic substitution.
* Product: This reaction forms 1-bromo-2-phenylethane (or 2-bromo-1-phenylethane). The bromine atom adds to the benzylic carbon (the carbon adjacent to the benzene ring).
2. Free Radical Addition:
* Conditions: Under radical conditions (UV light or peroxides), the reaction proceeds via free radical addition.
* Product: This reaction forms a mixture of 1,2-dibromo-1-phenylethane and 1,2-dibromo-2-phenylethane. The bromine atoms add to both carbons of the double bond.
Here's a summary:
| Conditions | Product |
|---|---|
| FeBr3 catalyst (EAS) | 1-bromo-2-phenylethane |
| UV light or peroxides (Free Radical) | Mixture of 1,2-dibromo-1-phenylethane and 1,2-dibromo-2-phenylethane |
Mechanism:
* EAS: The Lewis acid catalyst activates the bromine molecule, making it more electrophilic. This electrophile attacks the aromatic ring of styrene, leading to the formation of a carbocation intermediate. The bromine then attacks the carbocation, leading to the formation of the product.
* Free Radical: The UV light or peroxides initiate the formation of bromine radicals. These radicals attack the double bond of styrene, leading to the formation of a radical intermediate. The intermediate then reacts with another bromine molecule to form the dibromo product.
Let me know if you'd like a more detailed explanation of the reaction mechanisms.
