The propyl radical is the simplest example of a secondary radical. A secondary radical has two non-H groups attached to the radical center.As with the ethyl radical, the methyl groups stabilize the radical and two methyl groups are more efficient than one. Thus, in general secondary radicals are more stable than primary radicals. Note that the central carbon is not completely planar anymore. There is a small tendency toward pyramidalization of the radical C-atom. Note that the methyl groups both assume conformation that allow the C-H bonds to align with the orbital that contains the unpaired electron.