The California Section lost one of its best known figures with the death of Professor Andrew Streitwieser, Jr. on February 23rd, 2022, at the age of 94. As a graduate student with Professor William von Eggers Doering at Columbia University, Streitwieser studied the mechanisms of organic reactions that occur via reactive carbocation intermediates, and became interested in predicting their stability using a relatively new theoretical approach, molecular orbital theory. Theoretical calculations of any kind were still essentially manual procedures in 1950, as Professor Streitwieser describes in his memoir on the quantum chemistry history web site.
Streitwieser continued this work as a postdoc with Professor John D. Roberts at MIT before joining the faculty at the University of California, Berkeley, in 1953, where he taught and advised students continuously until just a few years ago. Professor Bergman kindly submitted the following recollections that describe the broad influence of Professor Streitwieser’s work. His 1985 organic chemistry textbook (coauthored with Professor Clayton Heathcock) was an essential reference for me during my career as chemist in the life sciences industry. I finally met Professor Streitwieser in 2007 when the California Section recognized him as 60-year member of the ACS. -Alex Madonik
by Professor Robert Bergman, UC Berkeley
Andrew Streitwieser was a major figure in the field of physical organic chemistry and was one of the earliest contributors to applying and concepts of physical and theoretical chemistry to organic chemistry, A notable area of study of his involved the inspection of organic compound intermediates called carbocations, or “short-lived” compounds that would form as a result of organic reactions. His textbook on Solvolytic Displacement Reactions was purchased and read by most organic chemists with an interest in mechanisms, and his book on Molecular Orbital Theory for Organic Chemists brought understanding and utility to a wide range of workers in the field. Another major contribution was his understanding and application of kinetic isotope effects to the study of reaction mechanisms, which made him a leader in that area of physical organic chemistry as well.
Andy was also a dedicated teacher. He and Clayton Heathcock were well known for their ground-breaking undergraduate organic textbook, and I learned a lot from him during the several years that he and I co-taught the first year graduate physical organic course at Berkeley.
One of Andy’s insights that most impressed me was his prediction and discovery of the sandwich compound uranocene. Once the structure of ferrocene had been elucidated, Andy’s analysis of the molecular orbital structure of that molecule, and his deep understanding of how MO theory could be used, led him to predict that a similar sandwich compound, but in this case using an actinide and eight-membered pi systems (rather than transition metals and five-membered pi systems that formed ferrocene) should be stable. In what I think was a triumph of that way of thinking led him and his group member Ulrich Mueller-Westerhoff to synthesize uranocene and demonstrate that it is, in fact, quite stable. This was a time when most organic chemists paid little attention to molecules that had metals in them.
Later in his life Andy focused his research on the acidity of organic compounds, and developed one of the most often used methods for measuring quantitatively the pKa’s of organic acids that were weaker acids than water, so that their acidity had to be measured in less protic solvents. This required careful experimental work carried out on equipment that was rigorously air- and water-free.
Besides his scientific contributions, Andy was a kind and friendly man personally. He was one of the people who attracted me to Berkeley in the late 1970’s, and he was always available to answer my questions on the many occasions I found myself confronting a thorny mechanistic problem. He was one of my favorite colleagues and I will miss him greatly.