There are three isomeric compounds `P,Q,R` with molecular formula `C_(4)H_(6)O_(3)`.Compound `P` is a saturated hydroxy carboxylic acid.Compound `Q` is a symmetrical anhydride while `R` is an aldehydic ester.
Which of the following is `P`?

Options

A.
B.
C.
D.

Answer

To determine which compound is `P`, a saturated hydroxy carboxylic acid with the molecular formula `C4H6O3`, we will analyze the characteristics of the compounds based on the given information.

### Step-by-Step Solution:

1. **Understanding the Molecular Formula**:
- The molecular formula `C4H6O3` indicates that the compound contains 4 carbon atoms, 6 hydrogen atoms, and 3 oxygen atoms.

2. **Identifying Compound P**:
- Compound `P` is described as a saturated hydroxy carboxylic acid. This means it must have a carboxylic acid group (`-COOH`) and a hydroxyl group (`-OH`), and it should not contain any double bonds or rings (saturated).

3. **Drawing the Structure**:
- Start by placing the carboxylic acid group on one end of a 4-carbon chain. The structure can be represented as:
```
HOOC-CH2-CH2-CH3
```
- Now, we need to add the hydroxyl group. Since it is a hydroxy carboxylic acid, the hydroxyl group can be placed on the second or third carbon:
```
HOOC-CH(OH)-CH2-CH3
```
- This structure satisfies the requirement of being saturated and contains both the carboxylic acid and hydroxyl groups.

4. **Checking Stability**:
- The placement of the hydroxyl group on the second carbon is more stable compared to placing it on the carbon adjacent to the carboxylic acid. Therefore, the most stable structure for `P` would be:
```
HOOC-CH(OH)-CH2-CH3
```

5. **Analyzing Other Compounds**:
- For compound `Q`, which is a symmetrical anhydride, it would not fit the description of `P` since it would contain a different functional group.
- For compound `R`, an aldehydic ester, it would also not fit the description of `P` as it involves an aldehyde group.

6. **Identifying the Correct Option**:
- Based on the structures and functional groups, we can identify the correct structure for `P` from the options provided. The option that contains a saturated hydroxy carboxylic acid structure with the correct functional groups is the answer.

### Conclusion:
The correct answer for compound `P`, which is a saturated hydroxy carboxylic acid, is the option that contains the structure `HOOC-CH(OH)-CH2-CH3`.