The ubiquitous appearance of repulsive geminal interactions in the BEBOP analysis invites some explanation. The transition state for the reaction of H 2 with a hydrogen atom provides a convenient prototype. Since the singly occupied 1σ u orbital must be orthogonal to the 1σ g orbital, the 1σ u orbital will necessarily introduce a 1, 3-antibonding interaction. This repulsive germinal interaction is responsible for the linearity of the H 3 transition state, and is a recurrent theme in hundreds of molecules we have examined. as the H 3 structure below (Figure ).