Carbon — carbon Single bonds are free to rotate about the line joining their centers that is , there is freedom of rotation about two carbons sharing a single bond .
This results in an alkane molecule that can assume many different forms depending on the angle of rotation of one carbon with respect to another . For example , structures 1, 2 and 3
below are not isomers . Rather , they are identical because they differ only by the rotation of one or more carbon atoms.