The most stable conformation of meso - 2,3 - dibromobutane is:

To determine the most stable conformation of meso - 2,3 - dibromobutane, we need to consider the various factors that affect stability, such as steric hindrance, torsional strain, and the stability of the conformers.

Factors affecting stability:
1. Steric hindrance: Steric hindrance occurs when bulky groups are close to each other, causing repulsion between them. In the case of meso - 2,3 - dibromobutane, we have two bromine atoms attached to the second and third carbon atoms. These bromine atoms are bulky and will contribute to steric hindrance.

2. Torsional strain: Torsional strain occurs when there is an unfavorable interaction between the electron clouds of adjacent atoms. In the case of meso - 2,3 - dibromobutane, the bromine atoms will cause torsional strain due to their large size and electron density.

3. Stability of conformers: The stability of conformers is influenced by the interactions between the substituents and the surrounding atoms. In the case of meso - 2,3 - dibromobutane, we have two conformers - the anti and gauche conformers.

Conformation analysis:
1. Anti conformer: In this conformation, the two bromine atoms are positioned opposite to each other, minimizing steric hindrance. However, there is still some torsional strain due to the proximity of the bromine atoms.

2. Gauche conformer: In this conformation, the two bromine atoms are positioned closer to each other, resulting in increased steric hindrance. The torsional strain is also present due to the proximity of the bromine atoms.

Most stable conformation:
The most stable conformation of meso - 2,3 - dibromobutane is the anti conformer. Although there is some torsional strain, the anti conformer minimizes steric hindrance between the bulky bromine atoms. This conformation is more stable compared to the gauche conformer, which has increased steric hindrance.

Summary:
The most stable conformation of meso - 2,3 - dibromobutane is the anti conformer. This conformation minimizes steric hindrance between the bulky bromine atoms, although there is some torsional strain present. Considering the factors affecting stability, the anti conformer is the most favorable conformation for meso - 2,3 - dibromobutane.