Which of the following conformations will be the most stable?

The given Newman projections represent different conformations of butane viewed along the C₂-C₃ bond.

The stability of these conformations depends on torsional strain and steric strain.

• Torsional strain is maximum in eclipsed conformations and minimum in staggered conformations.

• Steric strain increases when the two methyl groups come closer to each other.

Option A represents the anti conformation. It is a staggered conformation in which the two methyl groups are separated by $$180^\circ$$. This arrangement minimizes both torsional strain and steric strain, making it the most stable conformation.

Option B represents the fully eclipsed conformation. The two methyl groups are directly eclipsing each other, resulting in maximum torsional and steric strain. Hence, it is the least stable conformation.

Option C represents the gauche conformation. Although it is staggered, the two methyl groups are only $$60^\circ$$ apart, leading to gauche interactions. Therefore, it is less stable than the anti conformation.

Option D represents an eclipsed conformation in which a methyl group eclipses a hydrogen atom. It possesses significant torsional strain and is less stable than the staggered conformations.

The stability order is:

$$\text{Anti} > \text{Gauche} > \text{Eclipsed} > \text{Fully Eclipsed}$$

Hence, the most stable conformation is the anti conformation.

$$\boxed{\text{Option A}}$$