Van't Hoff, Jacobus Henricus (1852-1911)

Dutch physical chemist. He explained the 'asymmetric' carbon atom occurring in optically active compounds. His greatest work - the concept of chemical affinity as the maximum work obtainable from a reaction - was shown with measurements of osmotic and gas pressures, and reversible electrical cells. He was the first recipient of the Nobel Prize for Chemistry, in 1901. Van't Hoff was born in Rotterdam and studied at several universities in Europe. He was professor at Amsterdam 1878-96 and at the Prussian Academy of Sciences in Berlin from 1896. In 1874 van't Hoff postulated that the four valencies of a carbon atom are directed towards the corners of a regular tetrahedron. This allows it to be asymmetric (connected to four different atoms or groups) in certain compounds, and it is these compounds that exhibit optical activity. Van't Hoff ascribed the ability to rotate the plane of polarized light to the asymmetric carbon atom in the molecule, and showed that optical isomers are left- and right-handed forms (mirror images) of the same molecule. Van't Hoff's first ideas about chemical thermodynamics and affinity were published in 1877, and consolidated in his Etudes de dynamique chimique 1884. He applied thermodynamics to chemical equilibria, developing the principles of chemical kinetics and describing a new method of determining the order of a reaction. He deduced the connection between the equilibrium constant and temperature in the form of an equation known as the van't Hoff isochore.