Which of the following statements is/are correct?

Options

A. Maleic acid is a stronger acid than fumaric acid but maleate monoanion is a weaker acid than fumarate monoanion
B. Maleic acid is a stronger acid than fumaric acid and also maleate monoanion is a stronger acid than fumarate monoanion
C. Maleic acid is a weaker acid than fumaric acid but maleate monoanion is a stronger acid than fumarate monoanion
D. Maleic acid is a weaker acid than Fumaric acid and also maleate monoanion is a weaker acid than fumarate monoanion.

Answer

To determine which statements regarding malic acid, fumaric acid, and their respective conjugate bases are correct, we can analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement 1**: Malic acid is a stronger acid than fumaric acid, but malate monoanion is a weaker acid than formate monoanion.

1. **Understanding Malic and Fumaric Acid**:
- Malic acid (C4H6O5) has a structure that allows for intramolecular hydrogen bonding in its conjugate base (malate monoanion).
- Fumaric acid (C4H4O4) does not have the same capability for intramolecular hydrogen bonding in its conjugate base.

2. **Acidity Comparison**:
- The presence of intramolecular hydrogen bonding in the malate monoanion stabilizes it, making malic acid a stronger acid than fumaric acid.

3. **Conjugate Bases**:
- The malate monoanion is less acidic than the formate monoanion (from formic acid) because the formate monoanion can more easily release a proton due to the absence of stabilizing intramolecular hydrogen bonding.

**Conclusion for Statement 1**: This statement is correct.

### Step 2: Analyze the second statement
**Statement 2**: Malate monoanion is a weaker acid than formate monoanion.

1. **Understanding the Monoanions**:
- The malate monoanion has intramolecular hydrogen bonding, which makes it less likely to release a proton compared to the formate monoanion, which can easily release its proton.

2. **Acidity Comparison**:
- Since the formate monoanion can release its proton more readily, it is a stronger acid than the malate monoanion.

**Conclusion for Statement 2**: This statement is incorrect.

### Step 3: Analyze the third statement
**Statement 3**: Malic acid is a weaker acid than formic acid.

1. **Acidity Comparison**:
- Malic acid is stronger than formic acid because it has a more stable conjugate base due to intramolecular hydrogen bonding.

**Conclusion for Statement 3**: This statement is incorrect.

### Step 4: Analyze the fourth statement
**Statement 4**: Malic acid is a weaker acid than fumaric acid.

1. **Acidity Comparison**:
- As established earlier, malic acid is stronger than fumaric acid.

**Conclusion for Statement 4**: This statement is incorrect.

### Final Conclusion
From the analysis:
- **Correct Statement**: Statement 1
- **Incorrect Statements**: Statements 2, 3, and 4

### Summary of Correct Statements
- The only correct statement is that malic acid is stronger than fumaric acid, but malate monoanion is weaker than formate monoanion.