Question

Draw Newman projection, similar to Figure 3-25, down the C1-C6 bond in the equatorial conformation of methylcyclohexane. Show that the equatorial methyl group is also anti toC5. (Using your models will help.)

Short answer

Chair conformation Newman projection

Step-by-step solution

Newman projection

Newman projections are often used in drawing conformations. In Newman projection, one is viewing the C-C bond end on along the axis of connection. The front carbon is represented by the intersection of bonds from it, while the rear carbon appears as a circle.

Anti conformation

Dihedral angle θ gives the identity of any conformation. It may be defined as the angle between C-H bonds on the front carbon atom and the C-H bonds on the back carbon atom in the Newman projection. A staggered conformation takes place at θ =180° ,where the two bulky groups are pointing in opposite direction known as the anti-conformation.

Drawing Newman projection of methylcyclohexane

Chair conformation Newman projection

Looking down C1-C6 bond of the equatorial conformation, it can be seen that the methyl group is anti to C5 (red solid lines).