the ratio of anti/gauche conformation of butane is 4:6 the anti conformation is more stable than gauche conformation at room temperature by

HI

You are correct.

The cause behind it the steric hindrance faced in gauche conformation ofbutane. The gauche is less stable than the anti by 0.9 kcal/mol Energy(And we know that lesser the energy more stable is the product) . This is due to a crowding of the two methyl groups (CH3) in the gauche structure and is calledsteric strainorsteric hindrance.


Look below in the diagram and you can understand that in gauche the CH3 groups are closer and in anti it is away.Closer the bulky or big group more will be the repulsion in it.