Odd Hassel (ôd häs´əl), 1897–1981, Norwegian chemist, b. Christiania (now Oslo), grad. Oslo Univ. (1920), Ph.D. Univ. of Berlin (1924). After pursuing X-ray crystallographic studies in Germany, in 1925 he joined the faculty at Oslo Univ. where he spent the remainder of his career. From 1930 onwards his work was concentrated on problems connected with molecular structure, particularly the structure of cyclohexane and its derivatives and other substances containing six-membered rings related to that of cyclohexane. He shared the 1969 Nobel Prize in Chemistry with Derek H. R. Barton for their separate contributions to the development of conformational analysis, which is the prediction of the chemical and physical properties of organic molecules based upon a preferred conformation of the atoms in the molecule. They showed that the way organic compounds interact is linked to the way they assume certain geometric configurations. Thus, there exists a simple relationship between configuration and conformation, such that configurations can be predicted once the possible conformations for the products of a reaction are analyzed.