News and Views

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Obituary In the very next year our lives were Kenichi Fukui (1918–98) inextricably bound together, when R. B. Woodward and I developed the concept of Theoretical chemist who orbital symmetry control of organic reactions. Ours was a primitive frontier had fundamental insights orbital approach, developed intuitively and into chemical reactivity graphically, and buttressed by simple molecular orbital calculations. Our idea of 8 Kenichi Fukui, the first Japanese Nobel a controlling orbital was in the spirit of laureate in chemistry, died on 9 January Fukui. And indeed Fukui could right away this year. When Fukui was born, the derive all of our conclusions. What electronic theory of chemical bonding was happened next was interesting, in that the in its infancy. Oh, chemists did have a very success of the orbital symmetry ideas very well-grounded chemical notion of a bond naturally heightened, retrospectively, the and a symbolism for it. But the electron respect of the world community for itself had barely reached maturity, and Fukui’s frontier orbitals. Lewis and Langmuir were just For Kenichi Fukui and me, science for assimilating the then new Bohr quantum once worked the way it should on the theory of the atom into chemistry. human level — instead of a competition By the time Fukui completed his there developed a friendship. Part of our education in 1941, things were different. bond was formed by the four talented The first textbook of quantum chemistry Fukui graduate students who then were had been written six years before by a postdocs with me. Kenichi and I were German in exile, Hans Hellmann. And brought together not by the accident of American and British chemists had shared external recognition, but by a real secured a place for quantum mechanics in kinship in spirit — yes, across cultures, chemistry, through the charismatic between exploding American bombs. After and respectful of the cultural differences expositions of Linus Pauling, the quieter the war, he gathered around himself a that enrich life — and by a shared and deep reflections of Robert Mulliken, talented group of theoretical students, and philosophical outlook and scientific style. and the elegant, perceptive teaching of in 1952 published in the Journal of In time he and I were awarded the Charles Coulson. Chemical Physics the paper that defined Nobel prize in chemistry. The event had Fukui wrote that chemistry was not his the idea of frontier orbitals. more serious consequences for Kenichi favourite subject in high school. His father Erich Hückel’s seminal ideas on the than for me. In the United States the eye of (the family is an old Nara one), however, stability of Ț-electron systems were finally the public is on rock stars, and Nobel prize enquired of Gen-itsu Kita, a professor at receiving their due in just those years, and winners are relatively many. So — thank Kyoto Imperial University, what his bright simple molecular orbital theory was in the God — we are left alone. In Japan, Fukui, son might study. Kita suggested that ascendancy. Chemistry is reactivity; so it as the country’s first chemistry laureate, Kenichi should enter the department of was natural to think of reducing the surfeit had a tremendous burden of committees, industrial chemistry. In those days of information in the wavefunctions (how official obligations and public children listened to the advice of their much worse it is now!) to a few pithy appearances. It was not easy for this shy elders, and Fukui graduated from that numbers, indicators of reactivity. intellectual gentleman of the old school to department in 1941. Various reactivity indices were devised, face his duty. But he did so, with style. Some important work on synthetic most emphasizing the charge distribution Kenichi Fukui was impelled by the aviation fuels during the Second World in the molecule as a whole. Fukui, Teijiro truest desire to understand this world, and War led to an appointment in the Yonezawa, Chikayoshi Nagata and Haruo especially our dear chemistry. He strove to department of fuel chemistry, in the Shingu’s brilliant simplifying idea was to do so in pictures of conceptual simplicity faculty of engineering of Kyoto Imperial concentrate on one orbital — the highest and real depth. And he understood so well University. Much productive experimental occupied molecular orbital of the molecule that the nature we have tried to work on reaction engineering and catalysis when the reaction was with an acid; the comprehend (and what our creation has followed. The building of a career in an lowest unoccupied molecular orbital when added to it) is a precious gift, unique, and applied setting was, I believe, crucial — it the reaction was with a base; and the singly worth preserving. sensitized Fukui to problems of real occupied molecular orbital for a radical So I miss him, as does our chemical chemical reactivity. In this he had an reaction. They called these orbitals the community. I remember our first advantage over his ‘purer’ theoretician frontier orbitals of the molecule. encounter on Sanibel Island, precisely 34 colleagues. It is also an interesting This notion, of tracing the essence of years ago. And, among many subsequent counterpoint to the generally assumed basicity or acidity or radical reactivity to a meetings, one shared moment rises vividly inflexibility of Japanese universities and single orbital, was so simple! And, — together we watched a great Kyoto the koza system that Fukui could, in the remarkably, it worked. The underpinnings ceramic master, Miyashita Zenju, his old end, do what elsewhere would be labelled of the idea were easily found by Fukui in hands trembling, then steadying as he put as ‘pure’ chemistry in an applied setting. perturbation theory, the natural language them on the clay turning on his wheel. For this young scientist had all along of quantum mechanics. In time, he and his Roald Hoffmann had theoretical aspirations and talents. He co-workers expanded their ideas into a Roald Hoffmann is in the Department of told me that he read Dirac’s quantum wide-ranging theory of orbital interactions Chemistry, Cornell University, Ithaca, New York theory text in the dull moments (I never and reactivity. 14853-1301, USA. found out if there were many or few) I first met Kenichi Fukui in early 1964. e-mail: [email protected]