COUPER, A. - S.(ARCHIBALD SCOTT). - INTRODUCING A NEW ERA IN ORGANIC CHEMISTRY.

Sur une nouvelle Théorie cimique. (Note présentée par M.Dumas).

(Paris, Mallet-Bachelier), 1858. 4to. No wrappers. In: "Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences", Tome 46, No 24. Pp. (1121-) 1173 (entire issue offered). Couper's paper: pp. 1157-1160. A faint dampstain to right margins.

First appearance of this milestone announcement in organic chemistry - a longer memoir was published in "Annales de Chimie et de Physique" later in the same year, 1858 - in which, independently of Kekulé, Couper introduces the CONCEPT OF BONDS (represented as a dash or a dotted line) in chemistry and also observes the very importent fact, that carbon atoms forms the backbone of organic compounds.

"It was not till 1858 that a satisfactory theory of molecular constitution was advanced, simultaneously and endependently, by thwo young chemists, Friedrich August Kekulé and Archibald Scott Couper. The theory of molecular constitution put foreward....by Couper and Kekulé rested on two main postulates, the quadriivalency of carbon,....and the capacity of the carbon atom for mutual linking or combining together to form a carbon "chain". By this hypothesis of the mutual linking together of carbon atoms - which waslater confirmed by experiment - it was possible to explain the formation of organic compounds containing a large number of carbon atoms. On the foundation of their postulates two postulates, moreover, (they) showed how the molecular constitution or mutual linking together of the atoms of a compound could be represented diagrammatically and the relstions between different compounds made readily intelligible. In his classic paper "On a New Chemical Theory" (the paper offered here in its first appearance) advanced beyond Kekulé by representing the constitutions of the compounds by means of GRAPHIC FORMULA in which, as at the present day, the valencies pf the atoms are represented by lines....his formulae are similar to those at present in use..."(Findlay pp. 34 ff)

"The theory of Kekulé and Couper gave the chemists the maeans of solving the problems of chemical constitution; and by means of the graphic or constitutional formulae it became possible to represent the molecular constitution of known compounds and to foresee the possible existence of isomeric compounds."(Findlay).

Parkinson "Breakthroughs" 1858 C.

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