What will be the major product (A)
`CH_3-overset(CH_3)overset(|)(CH)-CH=CH_2overset(HBr)rarr(A)`

Options

A. `CH_3-overset(CH_3)overset(|)(CH)-CH=CH_2`
B. `CH_2-overset(CH_3)overset(|)(CH)-CH_2-CH_2-Br`
C. `CH_3-overset(CH_3)overset(|)(CH)-underset(Br)underset(|)(CH)-CH_3`
D. `CH_3-overset(CH_3)overset(|)underset(Br)underset(|)(CH)-CH_2-CH_3`

Explanation

To determine the major product (A) of the reaction between the given alkene and HBr, we will follow these steps:

### Step 1: Identify the Reactants
The reactant is an alkene, specifically 2-methyl-2-pentene, which can be represented as:
\[ CH_3-CH(CH_3)-CH=CH_2 \]

### Step 2: Apply Markovnikov's Rule
When HBr reacts with an alkene, the addition follows Markovnikov's rule. This means that the hydrogen atom from HBr will add to the carbon atom of the double bond that has the greater number of hydrogen atoms, while the bromine (Br) will add to the carbon with fewer hydrogen atoms.

### Step 3: Protonation of the Alkene
In our case, the double bond is between the second and third carbon atoms:
- The second carbon (C2) has one hydrogen atom.
- The third carbon (C3) has two hydrogen atoms.

According to Markovnikov's rule, the hydrogen will add to C3 (the carbon with more hydrogens), resulting in the formation of a carbocation at C2.

### Step 4: Formation of Carbocation
After the addition of H⁺, we form a carbocation:
\[ CH_3-CH^+(CH_3)-CH_2-CH_3 \]
This is a secondary carbocation because it is attached to two alkyl groups (C1 and C3).

### Step 5: Carbocation Rearrangement
Next, we check if rearrangement is possible. The secondary carbocation can rearrange to a more stable tertiary carbocation by a hydride shift:
- The hydrogen from C3 shifts to C2, and the positive charge moves to C3, forming a tertiary carbocation:
\[ CH_3-CH_2-CH^+(CH_3)-CH_3 \]

### Step 6: Nucleophilic Attack by Bromide Ion
Now, the bromide ion (Br⁻) will attack the more stable tertiary carbocation:
\[ CH_3-CH_2-CH(CH_3)-CH_2Br \]

### Step 7: Identify the Major Product
The major product (A) formed from this reaction is:
\[ CH_3-CH_2-CH(CH_3)-CH_2Br \]
This product is the result of the more stable tertiary carbocation.

### Conclusion
Thus, the major product (A) of the reaction between 2-methyl-2-pentene and HBr is:
\[ \text{Major Product (A)}: CH_3-CH_2-CH(CH_3)-CH_2Br \]

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