Question

is the most stable conformation of butane.

• A. Gauche form
• B. Anti form
• C. Eclipsed form
• D. Fully eclipsed form

Answer 1

The correct option is B Anti form

The lowest energy conformation will be the one, in which the two methyl groups are as far apart as possible i.e., ${180}^{\circ }$ away form each other.

This conformation will be maximum staggered and is called anti conformation. Other conformations can be obtained by rotating one of the $C_{2}or{C}_3$ carbon atoms through an angle of ${60}^{\circ }$ as shown ahead.

The order of stability of these conformations is, Anti $>$ Skew or Gauche $>$ Eclipsed $>$Fully eclipsed.