Which of the following is not true for maleic acid and fumaric acids?

Options

A. Configurational isomers
B. Stereo isomers
C. Z and E isomers
D. Optical isomer

Explanation

To determine which statement is not true for maleic acid and fumaric acid, we first need to understand their structures and properties.

### Step 1: Draw the Structures of Maleic Acid and Fumaric Acid

1. **Maleic Acid**:
- Structure:
- It has a double bond between two carbon atoms (C=C).
- The carboxylic acid group (-COOH) is attached to one of the carbon atoms.
- The structure can be represented as:
```
HOOC-CH=CH-COOH
```
- Configuration: Maleic acid is in the Z-form (cis) because the -COOH groups are on the same side of the double bond.

2. **Fumaric Acid**:
- Structure:
- Similar to maleic acid, it has a double bond between two carbon atoms.
- The carboxylic acid groups are on opposite sides of the double bond.
- The structure can be represented as:
```
HOOC-CH=CH-COOH
```
- Configuration: Fumaric acid is in the E-form (trans) because the -COOH groups are on opposite sides of the double bond.

### Step 2: Analyze Their Properties

- **Configurational Isomers**: Maleic and fumaric acids are configurational isomers because they have the same molecular formula (C4H4O4) but differ in the spatial arrangement of atoms around the double bond.

- **Stereoisomers**: They are also stereoisomers as they exhibit E/Z isomerism due to the different configurations around the double bond.

- **Optical Isomerism**: For a compound to exhibit optical isomerism, it must have a chiral center (a carbon atom attached to four different groups). In the case of maleic and fumaric acids, there are no chiral centers present.

### Step 3: Identify the Incorrect Statement

Now, let's evaluate the options given in the question:

1. **Configurational Isomers**: True
2. **Stereoisomers**: True
3. **E/Z Isomers**: True
4. **Optical Isomers**: Not true (because they lack chiral centers)

### Conclusion

The statement that is **not true** for maleic acid and fumaric acid is that they exhibit **optical isomerism**.

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