Jacobus Henricus van’t Hoff
Jacobus Henricus van’t Hoff in 1904. Courtesy Edgar Fahs Smith Memorial Collection, Department of Special Collections, University of Pennsylvania Library.
The Dutch scientist Jacobus Henricus van’t Hoff (1852–1911) was a pioneer in the field of stereochemistry, which deals with the spatial arrangements of atoms within molecules. In 1872, as a graduate student, van’t Hoff went to Bonn to study for a year. From August Kekulé, he learned of a possible tetrahedral arrangement of the valence bonds of carbon, proposed by the Russian chemist Alexander Butlerov in 1862. In 1873, after he had moved to Paris to work with Charles Adolphe Wurtz, van’t Hoff realized that the phenomenon of optical activity possessed by some organic molecules—their ability to rotate plane-polarized light—could be explained by the two possible arrangements of four different substituents in the space around a carbon atom. This theory provided substantial indication that the molecular structures being discussed by the chemists of the time had a physical reality in three-dimensional space and were not just aids to conceptualizing molecules. (Another graduate student working in Wurtz’s laboratory, Joseph Achille Le Bel, arrived at the same explanation of optical activity independently.)
Van’t Hoff disseminated his stereochemical ideas to leading chemists of the day by sending them 3-D paper models of tetrahedral molecules, like these now housed in the Leiden Museum. Photograph courtesy O. Bertrand Ramsay.
Van’t Hoff returned to the Netherlands to complete his doctoral degree. He was soon appointed lecturer in theoretical and physical chemistry at the University of Amsterdam, where he stayed for 20 years. There he conducted the studies of reaction rates, chemical equilibrium, chemical affinity, and osmotic pressures that helped found the discipline of physical chemistry. In 1896 he moved to the University of Berlin, and in 1901 he became the first Nobel laureate in chemistry for his work in physical chemistry.