`H_3C-undersetunderset(CH_3)|CH-CH=CH_2+HBr to A`
A (Predominantly ) is

Options

A. `CH_3-undersetunderset(Br)|CH-undersetunderset(CH_3)|CH-CH_3`
B. `CH_3-undersetunderset(CH_3)|CH-undersetunderset(Br)|CH-CH_3`
C. `CH_3-undersetunderset(CH_3)(|)CH-CH_2-CH_2Br`
D. `CH_3-undersetunderset(CH_3)(|)oversetoverset(Br)(|)C-CH_2CH_3`

Explanation

To solve the problem, we need to analyze the reaction of the compound with HBr and determine the predominant product (A) formed.

### Step-by-Step Solution:

1. **Identify the Reactant**: The given reactant is 2-methylpropene (H3C-CH(CH3)-CH=CH2). It has a double bond between the carbon atoms.

2. **Electrophilic Addition Reaction**: When HBr is added to an alkene, it undergoes an electrophilic addition reaction. The double bond acts as a nucleophile and attacks the electrophile (H+ from HBr).

3. **Formation of Carbocation**: The addition of H+ to the double bond leads to the formation of a carbocation. In this case, the more stable carbocation (due to hyperconjugation and inductive effects) will be formed. The double bond can attack the H+, leading to a secondary carbocation (2°).

4. **Carbocation Rearrangement**: If the carbocation can rearrange to form a more stable tertiary carbocation (3°), it will do so. In this case, the hydrogen from the adjacent carbon can migrate to stabilize the carbocation.

5. **Nucleophilic Attack by Br-**: Once the more stable carbocation is formed, the nucleophile (Br-) will attack the positively charged carbon atom, resulting in the formation of the product.

6. **Final Product (A)**: The final product will be 2-bromopropane (CH3-CHBr-CH3), which is the predominant product formed from this reaction.

### Final Answer:
A (Predominantly) is 2-bromopropane (CH3-CHBr-CH3).

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