In the given reaction `CH_3-underset(C_3H_7)underset(|)overset(C_2H_5)overset(|)C-Broverset(NaI//HOH//"Acetone")rarr[X]`
[X] will be

Options

A. `CH_3-underset(C_3H_7)underset(|)overset(C_2H_5)overset(|)C-I`
B. `I-underset(C_3H_7)underset(|)overset(C_2H_5)overset(|)C-CH_3`
C. Mixture of A and B
D. None of these

Answer

To solve the given reaction involving the tertiary bromide `CH3-C(C2H5)(C3H7)-Br` and sodium iodide in acetone, we need to analyze the mechanism of the reaction step by step.

### Step 1: Identify the Type of Reaction
The compound is a tertiary alkyl bromide, which suggests that the reaction will likely proceed via an SN1 mechanism due to the stability of the tertiary carbocation.

**Hint:** Tertiary alkyl halides favor SN1 reactions because they can form stable carbocations.

### Step 2: Formation of the Carbocation
In the first step of the SN1 mechanism, the bromine atom (Br) leaves, resulting in the formation of a carbocation. The structure of the carbocation will be `CH3-C(C2H5)(C3H7)+`.

**Hint:** The leaving group (Br) departs, creating a positively charged carbocation intermediate.

### Step 3: Nucleophilic Attack
In the second step, the nucleophile (I-) from sodium iodide will attack the carbocation. Since the carbocation is trigonal planar, the nucleophile can attack from either side of the planar structure. This leads to the possibility of two different products.

**Hint:** The nucleophile can attack from either side of the carbocation, leading to different stereochemical outcomes.

### Step 4: Possible Products
The two possible products formed from the nucleophilic attack are:
1. `CH3-C(C2H5)(C3H7)-I` (when I- attacks from one side)
2. `CH3-C(C3H7)(C2H5)-I` (when I- attacks from the opposite side)

Since both products can be formed, we have a mixture of these two products.

**Hint:** The formation of two products indicates that both stereochemical configurations are possible due to the planar nature of the carbocation.

### Conclusion
The final product [X] will be a mixture of both possible products formed by the nucleophilic attack on the carbocation.

**Final Answer:** The correct answer is a mixture of A and B (Option 3).