New horizons in organic chemistry

Abstract

Tercentenary Lecture delivered by Sir Alexander Todd, F.R.S., at 2.30 p.m.on Wednesday 20 July at the Royal There have been two definitions of organic chemistry. The original definition, due to Berzelius ( ca . 1800), was ‘the chemistry of substances found in living matter.’ The second, commonly ascribed to Gmelin, appeared first about fifty years later, when more was known about the peculiarities of the substances found in living matter—the ‘organic’ substances as distinct from the ‘inorganic’ substances—and was simply ‘the chemistry of the carbon compounds. ’ Each of these definitions is defensible, but neither is wholly satisfactory, since the first is too restricted and the second is, in certain respects, too general. A very large number of known carbon compounds are of purely synthetic origin and do not, as far as we are aware, occur in living matter, but it is undoubtedly true that the study of substances which are found in living organisms has provided most of the major stimuli to the advance of organic chemistry for almost a hundred years, and there is little reason to believe that this will not continue to be the case in the future. After all, it was Pasteur’s work on the tartaric acids from wine that led to the van’t Hoff-Le Bel theory of the tetrahedral carbon atom, the anthraquinone dyestuffs stem from Graebe and Liebermann’s work on alizarin from madder root, and work on polymerization and plastics goes back to the studies of Harries on natural rubber. Many other examples could be quoted, but I shall mention only one more because it is less well known than it should be. It was the work of Windaus on the natural sterols which caused Hiickel to develop his theoretical studies on stereoisomerism in fused ring systems; through these studies, important enough in themselves, developed in due course the modern concept of dynamic stereochemistry of cyclic structures which has had such a profound influence over a very large area of organic chemistry.