Which configuration has the larger substituents 120° apart?

The configuration in which larger substituents are positioned 120° apart is known as the gauche configuration. This occurs in the context of staggered conformations of a molecule, particularly butane and its isomers.

In a staggered conformation, substituents are positioned further apart compared to an eclipsed conformation, where substituents are aligned with one another. In the gauche conformation, two larger substituents are placed adjacent to each other but at a staggered angle of approximately 60° apart. This position can lead to steric interactions since these larger groups are likely to be closer to one another than in the anti conformation, where they are 180° apart. However, the 120° angle refers broadly to the relative orientation of other substituents present.

Additionally, in the equatorial position of a chair conformation (specifically for cyclohexane derivatives), substituents are also positioned to minimize steric strain, with larger groups ideally taking the equatorial position. However, when comparing the 120° separation, the gauche configuration specifically allows for positioning that can maximize the distance between larger substituents compared to the eclipsed conformation, thus making it favorable.

In summary, the gauche configuration