who spent much of his career at the University of Kazan, where he was educated, and the University of St Petersburg. Building on the earlier work of Archibald Scott Couper (1831–92), Sir Edward Frankland, and Friedrich August Kekulé on valence and structure, Butlerov postulated in 1861 that a chemical structure showing how each atom in a molecule is linked to other atoms in that molecule was essential to understand the physical and chemical properties of matter made up of these molecules.