The most stable form of meso-tartaric acid is

Options

A. Gauche form
B. Anti form
C. Fully eclipsed form
D. Partially eclipsed

Explanation

To determine the most stable form of meso-tartaric acid, we need to analyze its structure and the concept of stability in stereoisomers. Here's a step-by-step solution:

### Step 1: Understand the Structure of Tartaric Acid
Tartaric acid has two carboxylic acid groups (-COOH) and two hydroxyl groups (-OH) attached to a four-carbon chain. The general structure can be represented as:

```
HOOC
|
CH
|
CH
|
COOH
```

### Step 2: Identify Meso Compounds
A meso compound is one that has multiple stereocenters but is superimposable on its mirror image due to an internal plane of symmetry. Meso-tartaric acid has two stereocenters, and due to its symmetrical structure, it is classified as a meso compound.

### Step 3: Analyze the Conformations
Tartaric acid can exist in different conformations. The two main conformations are:
- **Anti-form**: where the hydroxyl groups are positioned opposite to each other.
- **Syn-form**: where the hydroxyl groups are positioned adjacent to each other.

### Step 4: Determine Stability Factors
The stability of these conformations can be influenced by steric hindrance and intramolecular interactions:
- **Anti-form**: This conformation minimizes steric hindrance between the bulky -OH and -COOH groups. Additionally, it allows for potential hydrogen bonding between the hydroxyl groups, which can enhance stability.
- **Syn-form**: This conformation experiences steric hindrance due to the proximity of the hydroxyl groups, making it less stable.

### Step 5: Conclusion
Given that the anti-form of meso-tartaric acid has reduced steric hindrance and the possibility of hydrogen bonding, it is the most stable form of meso-tartaric acid.

### Final Answer
The most stable form of meso-tartaric acid is the **anti-form**.

---