C. Frederick Koelsch

Koelsch was born in Boise, Idaho in 1907 in a family of German descent.[3] He attended the University of Wisconsin and earned his bachelor's degree in 1928 and his Ph.D. from the same institution in 1931, working under the supervision of Samuel M. McElvain.[2][3] After a postdoctoral fellowship at Harvard University with Elmer Peter Kohler, Koelsch was recommended for a position at the University of Minnesota by Lee Irvin Smith.[3] He joined the faculty there as an instructor in 1932 and became an assistant professor in 1934. Koelsch was awarded the ACS Award in Pure Chemistry in 1934.[3][2] He advanced to associate professor in 1937 and full professor in 1946.[1] He remained at the University of Minnesota until his retirement, assuming professor emeritus status, in 1973.[1][3] Through much of his academic career, Koelsch also served as an industry consultant, working first with Smith, Kline & French and later with Sterling Drug and Union Carbide.[3]

Chemical structure of the Koelsch radical

During his work at Harvard, Koelsch attempted to publish a paper describing an unusually stable radical compound, but it was rejected at the time on the grounds that the compound's properties were unlikely to describe a radical. Subsequent experimental evidence and quantum mechanics calculations suggested his interpretation of the original experiment was correct, resulting in the publication of the paper nearly 25 years after the original experiments.[3][4] The compound - 1,3‐bisdiphenylene‐2‐phenylallyl (BDPA) - is now often referred to as the "Koelsch radical".[5][6]

Koelsch married his wife Helen in 1938 and the couple had three children. He was a ham radio enthusiast.[2][3] He died in Rochester, Minnesota in 1999.[2]