`CH_3-underset(CH_3)underset(|)(CH)-CH_3+overset(Br_2)underset(hv)rarr(A)` . (Major) . A will be

Options

A. `CH_3-underset(CH_3)underset(|)(CH)-CH_2Br`
B. `CH_3-underset(CH_3)underset(|)(CH)=CH_2`
C. `CH_3-underset(CH_3)underset(|)overset(Br)overset(|)(CH)-CH_3`
D. `CH_3-overset(CH_2)overset(|)(CH)=H_2Br`

Answer

To determine the major product (A) when the compound \( CH_3-CH(CH_3)-CH_3 \) reacts with bromine (\( Br_2 \)) in the presence of sunlight (hv), we will follow these steps:

### Step 1: Identify the Structure
The compound \( CH_3-CH(CH_3)-CH_3 \) is 2-methylpropane (also known as isobutane). It has a branched structure with a central carbon atom connected to two methyl groups and one ethyl group.

### Step 2: Understand the Reaction Conditions
The reaction involves bromination in the presence of sunlight. Sunlight provides energy that initiates the free radical halogenation mechanism. In this process, the \( Br-Br \) bond will break homolytically to form two bromine radicals.

### Step 3: Formation of Bromine Radicals
When \( Br_2 \) is exposed to sunlight, it dissociates into two bromine radicals:
\[ Br_2 \xrightarrow{hv} 2Br^{\cdot} \]

### Step 4: Free Radical Mechanism
The bromine radicals can abstract hydrogen atoms from the alkane (2-methylpropane) to form free radicals. The abstraction can occur at different positions:
- Primary hydrogen (from the terminal carbon)
- Secondary hydrogen (from the central carbon)

### Step 5: Stability of Free Radicals
The stability of the resulting free radicals is crucial in determining the major product. The stability order is:
- Tertiary (3°) > Secondary (2°) > Primary (1°)

In this case:
- If a bromine radical abstracts a hydrogen from a primary carbon, a primary radical is formed.
- If a bromine radical abstracts a hydrogen from the central carbon (which is secondary), a secondary radical is formed.

Since secondary radicals are more stable than primary radicals, the major product will be formed from the secondary radical.

### Step 6: Product Formation
The secondary radical will react with another bromine radical to form the major product:
- The major product will be 2-bromo-2-methylpropane.

### Conclusion
Thus, the major product \( A \) formed from the reaction of \( CH_3-CH(CH_3)-CH_3 \) with \( Br_2 \) in the presence of sunlight is:
\[ A = 2-bromo-2-methylpropane \]