Frank H. Westheimer, Morris Loeb Professor of Chemistry Emeritus, at Harvard University and one of the key figures in 20th century chemistry, died at his home in Cambridge, Mass., on April 14. He was 95.

Westheimer was at the forefront of a major revolution in the field of chemistry involving the sophisticated integration of the fields of physical and organic chemistry and the use of this approach to determine in unprecedented detail the way in which chemical reactions take place. These fundamental advances in the theory of chemical reaction mechanisms are the bedrock of modern chemistry and the basis for much of its current success in guiding research on the creation of complex molecules and the invention of new medicines.

Despite his great proficiency in mathematics and physical-organic chemistry, and the dramatic progress that he achieved in mechanistic chemistry, Westheimer turned his attention by 1950 to the study of enzyme reactions and biochemistry. Here too, his pioneering studies had a profound and lasting impact — this time on biological and biochemical processes.

Over a span of four decades, Westheimer repeatedly demonstrated an ability to take up a fundamental scientific problem — one that appeared either insoluble or very difficult — and to solve it in an elegant and completely definitive way. This approach defined a unique style of research and became a recognizable personal style. He enjoyed going on to new challenges more than exploiting the large new areas that he had opened up. On the occasion of receiving the Priestly Medal, the highest recognition of the American Chemical Society, in 1988, Westheimer remarked, “Whether I would have made a larger contribution to chemistry if I had done fewer things and exploited them better, well, no one will ever know.” What is certain is that his research was deeply influential, enormously instructive to his colleagues, and empowering to their science.

Another Westheimer trademark was his inexhaustible supply of wise aphorisms. For example, advice to a research student: “Why spend a day in the library when you can learn the same thing by working in the laboratory for a month?”

Frank Henry Westheimer was born in Baltimore on Jan. 15, 1912. He attended Dartmouth College and graduated summa cum laude in 1932. His father, a successful Baltimore stockbroker, at first questioned his decision to major in science, but became enthusiastic after talking to Dartmouth faculty. Westheimer entered the graduate program at Harvard in 1932 to study under James B. Conant. Shortly afterward, Conant assumed the presidency of Harvard and Westheimer was left without an adviser. Westheimer later recalled presenting an idea to Conant, who advised: “It may not work, but if it does, it will be a footnote to a footnote in the history of chemistry.” This casually imparted wisdom was clearly taken to heart.

After receiving his doctorate at Harvard in 1935, Westheimer went to Columbia University as a National Research Fellow in the then-new field of physical-organic chemistry. He accepted a faculty position at the University of Chicago in 1936, and in 1937 married Jeanne Friedmann. During World War II, he was a supervisor at the National Explosives Research Laboratory. After the war, he resumed his post at the University of Chicago, where he remained until moving to Harvard in 1953. At Harvard, he was the Morris Loeb Professor and an admired teacher of both undergraduate and graduate students.

Westheimer was the recipient of numerous honors and honorary degrees, including the U.S. National Medal of Science, the U.S. National Academy Award in Chemical Sciences, the Robert A. Welch Foundation Award in Chemistry, and many awards of the American Chemical Society. His national service extended far beyond his involvement in World War II research. He served as a science adviser to President Lyndon Johnson, and in 1966 he chaired an enormously influential Committee of the U.S. National Academy of Sciences that set a course of action for federal support of the chemical sciences. The recommendations of that report were implemented and are still regarded as comprehensive, definitive, and forward-looking. In 2002 Harvard University established the Frank H. Westheimer Medal for scientific excellence in his honor.

Westheimer and his wife had a very wide circle of friends drawn from around the world but especially from the academic and intellectual community in the Boston area. Weekend dinners at their home were filled with humor and laughter, but also with penetrating analyses and discussions of world events and problems. Westheimer’s command of national issues was extraordinary. He reasoned against war, first in Vietnam and then in Iraq. For four decades, he emphasized the need for strong measures against pollution and global warming and in favor of energy conservation, alternative energy development, and greater support of fundamental research. He encouraged fellow chemists to apply their skills to other disciplines, especially biology and medicine. He pleaded with universities to improve the education of nonscientists by finding new ways to teach science. He viewed the problem as complex, but soluble, if the verticality of scientific subjects with their numerous course prerequisites could be dealt with by a new kind of teaching for nonscientists.

Westheimer was admired and respected as a person by his students and colleagues worldwide. Most would agree on the salient qualities that defined the man throughout his life: a powerful intellect, great personal integrity and courage, extraordinary dedication to scientific discovery, and a deep concern for country and humankind. He was a gregarious and social person with a happy family life. His wife of 64 years, Jeanne, passed away in 2001. He is survived by their daughters, Ruth Susan Westheimer of Worcester, Mass., and Ellen Westheimer of Carlisle, Mass.

— E.J. Corey, Deptartment of Chemistry and Chemical Biology