Assertion: tert-Butyl carbanion is less stable than methyl carbanion.
Reason: The `+1`-effect of the `CH_(3)` groups tends to stablize the tert-butyl carbanion.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true and the reason is the correct explanations of the assertion
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that "tert-Butyl carbanion is less stable than methyl carbanion."

- **Tert-Butyl Carbanion Structure**: The tert-butyl carbanion has the structure (CH₃)₃C⁻. It has three methyl groups attached to a central carbon atom that carries a negative charge.
- **Methyl Carbanion Structure**: The methyl carbanion has the structure CH₃⁻, which consists of a single carbon atom with a negative charge and three hydrogen atoms.

### Step 2: Analyze Carbanion Stability
To determine the stability of carbanions, we consider the effects of substituents on the carbon atom bearing the negative charge.

- **Tert-Butyl Carbanion**: The three methyl groups (alkyl groups) are electron-donating through the +I (inductive) effect. This increases the electron density on the negatively charged carbon, making it less stable since carbon cannot effectively stabilize a high electron density due to its electronegativity.

- **Methyl Carbanion**: The methyl carbanion has only one methyl group. The hydrogen atoms do not donate electrons significantly, so there is less electron density around the negatively charged carbon, making it more stable compared to tert-butyl carbanion.

### Step 3: Conclusion on Assertion
Since the tert-butyl carbanion has more electron-donating groups, it is indeed less stable than the methyl carbanion. Thus, the assertion is **true**.

### Step 4: Understand the Reason
The reason states that "the +I effect of the CH₃ groups tends to stabilize the tert-butyl carbanion."

- As discussed, the +I effect of the methyl groups actually increases the electron density on the carbanion, which destabilizes it rather than stabilizing it. Therefore, the reason is **false**.

### Step 5: Final Evaluation
- Assertion: True
- Reason: False

Thus, the correct answer is that the assertion is true, but the reason is false.

### Final Answer
The correct option is C: Assertion is true, Reason is false.

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