Organic Chemistry

15 Conformations

Conformers, also calledconformational isomers, orrotational isomers, are ar-
rangements of the same molecule made transiently different by the rotation in space about
one or more single bonds.

Other types of isomer can only be converted from one form to another bybreakingbonds,
but conformational isomers can be made simply byrotatingbonds.

15.1 Newman projections

Newman projections are drawings used to represent different positions of parts of molecules
relative to each other in space. Remember that single bonds can rotate in space if not
impeded. Newman projections represent different positions of rotating molecule parts.

Conformers interconvert readily, normally thousands of times a second as parts

of molecules spin. Figure 26

In the following drawings, methyl groups are on the front and back ends of the

molecule and a circle represents all that lies between. Figure 27

Note:

This is how methyl groups are represented in

Newman projections

Figure 28

Figure 29

Staggered conformation Eclipsed conformation

(front end overlaps the back)