3 - Methylpent -2- ene `overset(HBr)underset(H_(2)O_(2))rarrZ`.
The number of stereoisomers possible for the product 'Z' is _______.

Answer

To solve the problem, we need to determine the number of stereoisomers for the product 'Z' formed from the reaction of 3-methylpent-2-ene with HBr in the presence of peroxide.

### Step 1: Identify the structure of 3-methylpent-2-ene
3-methylpent-2-ene is an alkene with the following structure:
- It has 5 carbon atoms (pent).
- The double bond is between the second and third carbon atoms.
- There is a methyl group (−CH₃) on the third carbon.

The structure can be drawn as:
```
CH3
|
CH3-CH=CH-CH2-CH3
```

### Step 2: Understand the reaction conditions
The reaction is carried out with HBr in the presence of peroxide. This indicates that the reaction follows the anti-Markovnikov rule due to the presence of peroxide.

### Step 3: Determine the product of the reaction
In anti-Markovnikov addition:
- The bromine (Br) will add to the carbon atom with fewer hydrogen atoms (the carbon at position 2), while the hydrogen (H) will add to the carbon with more hydrogen atoms (the carbon at position 3).

Thus, the product 'Z' will be:
```
CH3
|
CH3-CH-CH2-Br
```
Where the Br is added to the second carbon.

### Step 4: Identify chiral centers
In the product, we need to identify if there are any chiral centers:
- The carbon at position 2 (attached to CH3, H, CH2, and Br) is a chiral center.
- The carbon at position 3 (attached to CH3, H, and CH2) is also a chiral center.

### Step 5: Count the number of stereoisomers
The number of stereoisomers is determined by the formula \(2^n\), where \(n\) is the number of chiral centers.
- Here, we have 2 chiral centers (at positions 2 and 3).

Thus, the total number of stereoisomers is:
\[ 2^2 = 4 \]

### Final Answer
The number of stereoisomers possible for the product 'Z' is **4**.

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