Odd Hassel
Hassel, Odd (1897-1981), a Norwegian chemist, won the 1969 Nobel Prize in chemistry for studies relating chemical reactions with the three-dimensional shape of molecules. He shared the prize with Derek Barton, a British chemist who had independently done similar research.
Hassel's work helped develop the science of conformational analysis, the study of the spatial arrangements of atoms in a molecule, and how these arrangements affect chemical behavior. Barton continued Hassel's pioneering work, and today conformational analysis is an important part of the study of chemical structures.
Hassel was born on May 17, 1897, in Christiana (now Oslo) Norway. He had a twin brother, Lars, as well as two other brothers and one sister. Hassel's father, Ernst, a gynecologist, died when Hassel was 8 years old, leaving his mother, Mathilde Klaveness Hassel, to raise the children alone. Hassel had little interest in school subjects except science and mathematics. He became particularly interested in chemistry during high school and decided to pursue that field of study in college.
Hassel graduated from the University of Oslo in 1920 and then toured France and Italy for a year. In 1922, he went to work at a laboratory in Munich, Germany, where he discovered adsorption indicators, organic dyes used in analyzing silver halide chemical compounds.
Hassel earned a doctorate from the University of Berlin in 1924. While in Berlin, Hassel also worked at the Kaiser Wilhelm Institute and learned a method of determining the atomic structure of a substance by striking a pure crystal of the substance with X rays and analyzing the pattern of diffraction, a method known as X-ray crystallography .
In 1925, Hassel joined the faculty of the University of Oslo. He wrote the book Kristallchemie (Crystal Chemistry) in 1934, and it became a standard reference work for chemists. From 1934 to 1964. Hassel was a professor and director of the university's department of chemistry.
Hassel began his investigation of molecular structure in 1930. He focused his attention on substances related to cyclohexane, an organic compound that has six carbon atoms joined in a ring. He used X-ray crystallography in his early experiments, but that method worked only with solids. Hassel also used a technique called electron diffraction, in which he passed a beam of electrons through a substance and then analyzed the atomic structure of the substance from how the beam was affected.
The German chemist Adolf von Baeyer had suggested in 1885 the possibility that molecules with six or more carbon atoms were arranged in a three-dimensional structure. Another German chemist, Ulrich Sachse, had proposed in 1890 that cyclohexane existed in two configurations. One configuration was shaped like a boat, with four carbon atoms laying in the same plane and the other two in the plane above them like the bow and stern of a boat. The other configuration was shaped like a chair, with four atoms in a central plane and the end atoms positioned one above and one below the plane. These chemists were unable to prove their theories, however. Before their theories and even in Hassel's time, most scientists believed that all the ring-shaped carbon molecules lay on a flat plane, like a doughnut on a plate.
Using electron diffraction, Hassel was able to prove von Baeyer's and Sachse's theories correct. He confirmed that both the boat and chair forms of three-dimensional molecules existed, and he found in addition that the molecules rapidly oscillated (sifted back and forth) between the two forms. Hassel thus determined the structure of the substances related to cyclohexane and clarified the possible conformations (spatial arrangements) of their molecules. He concentrated on this work during the 1930's and 1940's. For this work, he received the Nobel Prize in chemistry in 1969.
Working conditions during the course of Hassel's research became difficult after Germany invaded Norway in 1940, during World War II (1939–1945). The German forces closed the University of Oslo in 1943 and sent its faculty and scholars to a concentration camp at Grini, near Oslo. Hassel was imprisoned in the camp with his colleagues. He and the other prisoners were freed from the camp by Allied troops in November 1944.
Hassel retired from the University of Oslo in 1964 but remained active in research and writing until 1971. During his career, he published more than 250 scientific papers and received many awards and honors.