Assertion: tert-butylbromide undergoes `S_(N)1` nucleophilic substitution readily than n-butyl bromide.
Reason: It proceeds by the formation of stable carbocation.

Options

A. Assertion and reason both are correct statements and reason is correct explanation for assertion.
B. Assertion and reason both are correct statements but reason is not correct explanation for assertion
C. Assertion is correct statement but reason is wrong statement.
D. Assertion is wrong statement but reason is correct statement.

Answer

To solve the question regarding the assertion and reason about tert-butyl bromide and n-butyl bromide undergoing nucleophilic substitution, we will analyze each part step by step.

### Step 1: Understanding the Assertion
The assertion states that tert-butyl bromide undergoes \( S_N1 \) nucleophilic substitution more readily than n-butyl bromide.

- **Tert-butyl bromide** has the structure \( (CH_3)_3CBr \).
- **N-butyl bromide** has the structure \( CH_3CH_2CH_2Br \).

### Step 2: Mechanism of \( S_N1 \) Reaction
The \( S_N1 \) mechanism involves two main steps:
1. Formation of a carbocation by the loss of the leaving group (in this case, bromide ion).
2. Nucleophilic attack on the carbocation.

### Step 3: Carbocation Stability
The stability of the carbocation formed during the \( S_N1 \) reaction is crucial for the reaction rate.

- **Tertiary carbocation** (from tert-butyl bromide) is more stable due to hyperconjugation and inductive effects from the surrounding alkyl groups.
- **Primary carbocation** (from n-butyl bromide) is less stable because it has fewer alkyl groups to stabilize the positive charge.

### Step 4: Comparing Carbocation Formation
- When tert-butyl bromide loses bromide, it forms a tertiary carbocation:
\[ (CH_3)_3C^+ \]
- When n-butyl bromide loses bromide, it forms a primary carbocation:
\[ CH_3CH_2CH_2^+ \]

### Step 5: Conclusion on Assertion
Since the tertiary carbocation is more stable than the primary carbocation, the assertion is true: tert-butyl bromide undergoes \( S_N1 \) nucleophilic substitution more readily than n-butyl bromide.

### Step 6: Understanding the Reason
The reason states that the reaction proceeds by the formation of a stable carbocation. This is indeed correct because the stability of the carbocation directly influences the rate of the \( S_N1 \) reaction.

### Step 7: Conclusion on Reason
The reason is true and correctly explains why the assertion is true.

### Final Conclusion
Both the assertion and reason are true statements, and the reason correctly explains the assertion. Therefore, the answer is that both the assertion and reason are true, and the reason is the correct explanation for the assertion.