Kenichi Fukui (1918-1998)

K enichi Fukui, director of the Institute of Fundamental Chemistry in Kyoto, Japan, passed away on 9 January 1998. Fukui was awarded a Nobel Prize in Chemistry ([1][1]) in 1981, jointly with Roald Hoffmann, for their independently developed theories concerning the course of 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 orbital) play a dominat role in reactions, and he called these the frontier orbitals. Fukui discovered that the symmetry of the frontier orbital itself governs chemical reactions, finding that chemical reactions involved neither a square of the frontier orbital, nor an electron density. Based on a solid quantum-mechanical foundation, Fukui was able to naturally incorporate the idea of orbital and orbital phase into his theory. At that time, chemists had tried in vain to solve the challenge of chemical reactions. Once awakened by this insight, chemists around the world were able to explain and predict the course of organic reactions, as if solving a jigsaw puzzle. His theory is now a permanent part of chemistry. The Woodward-Hoffmann rules ([2][2]) came about as a result of collaborative work between a genius of organic chemistry and an excellent theoretical chemist. Fukui's background and expertise encompassed both these fields, and his huge commitment to science is self-evident. However, it must be remembered that he was interested in a great number of pursuits, including leisure activities such as walking and reading. Moreover, he had a passion for nature and was deeply concerned about environmental issues. Fukui will be greatly missed; for so many years, scientists have relied on his knowledge and sound reasoning. ![Figure][3] YOMIURI SHIMBUN 1. [↵][4]For more on Fukui and the 1981 Nobel Prize, see . 2. [↵][5]The Woodward-Hoffmann rules state that a reaction is forbidden if the symmetry of the orbitals is not conserved during the reaction. [1]: #ref-1 [2]: #ref-2 [3]: pending:yes [4]: #xref-ref-1-1 View reference 1 in text [5]: #xref-ref-2-1 View reference 2 in text