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Hoff, Jacobus Henrikus van 't

chemistry ideas stereochemistry carbon

(1852–1911) Dutch physical chemist: a founder of stereochemistry.

At the age of 17 van ‘t Hoff informed his mother and father, a physician, that he wished to become a chemist; their reaction was very unfavourable. Despite this, he entered Delft Polytechnic, and received his diploma in 2 years rather than the usual 3. He went on to study chemistry in Leiden, Bonn and Paris. He also became intensely interested in the philosophical ideas of Comte and Taine, in Byron’s poetry and in the biographies of scientists.

Back in the Netherlands, aged 22 and ready to begin his doctoral work, he published a paper which founded stereochemistry. It had been known since work that many organic compounds are optically active (ie rotate the plane of polarized light) had been able to relate this property, for crystalline solids, to the dissymmetry of the crystals; but interest in the organic compounds was in their optical activity in solution. Van ‘t Hoff took up an idea of (1867) that the four groups usually linked to a carbon atom can be expected to be equally distributed in the space around it (a ‘tetrahedral’ distribution; see diagram). Van ’t Hoff saw that, if the four groups are all different from each other, they can be arranged about the carbon atom in two ways; and these two variants of a molecule are non-superimposable mirror images of each other (stereoisomers). He proposed that one form would rotate polarized light to the left and the other form to the right. On this basis a general theory of molecular shapes could be developed and, despite some initial doubts, his ideas of stereoisomerism were soon shown to be both correct and fruitful. The same ideas were offered independently by J A Le Bel (1847–1930) soon after, but he did not develop them. They had known one another slightly, in laboratory in Paris.

At 23 van ‘t Hoff tried for a job as a schoolteacher, but was turned down because he appeared to be a ‘daydreamer’. He got a junior post in a veterinary college in 1876 but 2 years later took a professorship in Amsterdam until 1896, when he moved to Berlin. In the 1880s and later, his work on physical chemistry was as valuable as his stereochemistry. He studied reaction rates, mass action, transition points, the phase rule and especially the chemistry of dilute solutions and the application of thermodynamic theory to chemistry. He was awarded the first Nobel Prize in chemistry, in 1901.

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