(A) : The pKa of the - COOH of alanine is much greater than pKa of -COOH of `CH_(3)COOH`
(R ) : The electron withdrawing inductive effect of `N` stabilises the -COOH.

Options

A. Both (A) and (R ) are true and (R ) is the correct explanation of (A)
B. Both (A) and (R ) are true and (R ) is not the correct explanation of (A)
C. (A) is true but (R ) is false
D. (A) is false but (R ) is true

Answer

To solve the assertion-reason question regarding the pKa values of the -COOH groups in alanine and acetic acid, we will analyze both statements step by step.

### Step 1: Understanding the Assertion
The assertion states that the pKa of the -COOH group of alanine is much greater than the pKa of the -COOH group of acetic acid.

- **pKa** is a measure of the acidity of a compound; a lower pKa indicates a stronger acid.
- In this case, we need to compare the acidity of alanine (NH2-CH(CH3)-COOH) and acetic acid (CH3-COOH).

### Step 2: Analyzing the pKa Values
- The pKa of acetic acid is approximately 4.76.
- The pKa of the -COOH group in alanine is typically around 2.34.

From this information, we can conclude that the pKa of alanine is **not greater** than that of acetic acid. In fact, it is **lower**, indicating that alanine is a stronger acid than acetic acid.

### Conclusion for Assertion
Thus, the assertion is **false**.

### Step 3: Understanding the Reason
The reason states that the electron-withdrawing inductive effect of nitrogen stabilizes the -COOH group.

- The presence of the amino group (-NH2) in alanine exerts a **-I (inductive)** effect, which means it pulls electron density away from the -COOH group.
- This electron withdrawal increases the polarity of the O-H bond in the carboxylic acid, making it easier for the hydrogen ion (H+) to dissociate, thereby increasing acidity.

### Conclusion for Reason
The reason is **true** because the -NH2 group does stabilize the -COOH group through its inductive effect.

### Final Conclusion
- Assertion (A) is **false**.
- Reason (R) is **true**.

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