Which one of the following statements regarding the population of different conformers butane -2, 3 - diol is true?

Options

A. The most populated conformer with have the hydroxyl groups of the gauche position.
B. The most populated conformer will have the hydroxyl groups at the anti position.
C. All staggered conformations will be equally populated.
D. Relative populations of different conformers is not predictable

Answer

To determine which statement regarding the population of different conformers of butane-2,3-diol is true, we will analyze the conformers and their stability based on intramolecular hydrogen bonding and steric interactions.

### Step-by-Step Solution:

1. **Identify the Structure of Butane-2,3-diol**:
- Butane-2,3-diol has the structure: CH3-CHOH-CHOH-CH3.
- The two hydroxyl (-OH) groups are located on the second and third carbon atoms.

2. **Draw the Conformers**:
- The conformers can be represented in staggered and eclipsed forms. The staggered conformers are more stable due to reduced steric hindrance.
- The main conformers to consider are the Gauche and Anti conformers.

3. **Analyze the Gauche Conformer**:
- In the Gauche conformer, the two hydroxyl groups can be positioned in such a way that they can participate in intramolecular hydrogen bonding, which stabilizes the structure.
- This conformer has the -OH groups positioned at a dihedral angle of 60° relative to each other.

4. **Analyze the Anti Conformer**:
- In the Anti conformer, the -OH groups are positioned 180° apart. This configuration does not allow for intramolecular hydrogen bonding, making it less stable compared to the Gauche conformer.

5. **Determine Stability and Population**:
- The Gauche conformer is more stable due to the presence of intramolecular hydrogen bonding. Therefore, it will be more populated in a sample of butane-2,3-diol.
- The Anti conformer, while staggered, does not benefit from hydrogen bonding and is thus less populated.

6. **Conclusion**:
- The statement that is true regarding the population of different conformers of butane-2,3-diol is that the most populated conformer will have the hydroxyl groups in the Gauche position due to the stability provided by intramolecular hydrogen bonding.

### Final Answer:
The most populated conformer of butane-2,3-diol will have the hydroxyl groups in the Gauche position.

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