passed away on 9 January 1998. Fukui was awarded a Nobel Prize in Chemistry ( 1 ) in 1981, jointly with Roald Hoffmann, for their independently developed theories concerning the course o f chemical reactions. Fukui conceived the theory of frontier orbitals, which are the outermost orbitals in a molecule, similar to valence orbitals in , atoms. In the early 1950s, he proposed that HOMO (the highest occupied molecular orbital) and LUMO (the lowest unoccupied molecular or-