Question

The dihedral angle between two methyl group in partially eclipsed conformation of n-butane is :

• A. ${180}^{\circ }$
• B. ${120}^{\circ }$
• C. ${90}^{\circ }$
• D. ${109}^{\circ }{28}^{\prime }$

Answer 1

The correct option is B ${120}^{\circ }$

The partially eclipsed structure of n-butane is

the dihedral angle between two methyl group is ${120}^{\circ }$.
The dihedral angle between two methyl group in anti-staggered conformation of n-butane is ${180}^{\circ }$.
The dihedral angle between two methyl group in fully-eclipsed conformation of n-butane is $0^{\circ }$.
The dihedral angle between two methyl group in fully gauche-staggered and partially gauche-staggered in conformation of n-butane is ${60}^{\circ }$ and ${300}^{\circ }$ .