`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 of the addition of HBr to the alkene \( H_3C-CH(CH_3)-CH=CH_2 \), we will follow these steps:

### Step 1: Identify the Alkene
The compound given is an alkene with the structure \( H_3C-CH(CH_3)-CH=CH_2 \). The double bond is between the last two carbon atoms.

### Step 2: Mechanism of HBr Addition
When HBr is added to an alkene, the reaction typically follows a carbocation mechanism. The double bond will react with HBr, leading to the formation of a carbocation intermediate.

### Step 3: Formation of Carbocation
The first step in the mechanism is the protonation of the alkene. The double bond attacks the hydrogen of HBr, resulting in the formation of a carbocation. The most stable carbocation will form, which is determined by the stability of the carbocation (more substituted carbocations are more stable).

In this case, the proton can add to the less substituted carbon (the terminal carbon), leading to the formation of a secondary carbocation at the more substituted carbon.

### Step 4: Hydride Shift
To stabilize the carbocation, a hydride shift may occur. In this case, a hydride from the adjacent carbon will shift to the carbocation, resulting in a more stable tertiary carbocation.

### Step 5: Nucleophilic Attack by Bromide Ion
After the formation of the more stable carbocation, the bromide ion (Br⁻) will attack the positively charged carbon, leading to the formation of the final product.

### Step 6: Write the Final Product
The final product after the addition of HBr to the alkene will be \( H_3C-CH(CH_3)-C(Br)-CH_3 \), which is predominantly a brominated alkane.

### Final Answer
The product A (predominantly) is \( H_3C-CH(CH_3)-C(Br)-CH_3 \).

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