**Reaction of HBr with 3-methylpent-2-ene in the Presence of Peroxide**

When HBr reacts with 3-methylpent-2-ene in the presence of peroxide, the reaction undergoes a radical mechanism known as free radical addition. This reaction results in the formation of different stereoisomers due to the presence of a chiral center in the reactant molecule.

**Mechanism of the Reaction**

1. Initiation: The reaction is initiated by the homolytic cleavage of the peroxide (ROOR) in the presence of heat or light. This produces two reactive radicals, which are RO• (alkoxy radical) and •R (alkyl radical).

2. Propagation: The alkyl radical (•R) attacks the double bond of 3-methylpent-2-ene, resulting in the formation of a new carbon-carbon bond and the generation of a new radical intermediate. This intermediate is a secondary radical, which can undergo further reactions.

3. Termination: The reaction terminates when two radicals combine to form a stable product. This can occur between two alkyl radicals or between an alkyl radical and a hydrogen atom.

**Formation of Stereoisomers**

The formation of stereoisomers in this reaction is due to the presence of a chiral center in 3-methylpent-2-ene. A chiral center is a carbon atom bonded to four different groups or substituents, resulting in non-superimposable mirror images (enantiomers). In this case, the chiral center is the carbon atom adjacent to the double bond.

When the alkyl radical attacks the double bond, it can approach from either the front or the back side of the molecule, leading to the formation of two different stereoisomers. These stereoisomers are the result of a syn-addition (attack from the same side) and an anti-addition (attack from the opposite side).

Therefore, in the reaction of HBr with 3-methylpent-2-ene in the presence of peroxide, two stereoisomers are formed. These stereoisomers are enantiomers, meaning they are non-superimposable mirror images of each other.

**Conclusion**

In summary, the reaction of HBr with 3-methylpent-2-ene in the presence of peroxide results in the formation of two stereoisomers. This is due to the presence of a chiral center in the reactant molecule, which allows for the formation of enantiomers through syn- and anti-addition during the radical mechanism of the reaction.

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