Crum-Brown studies

Faraday, in 1834, was the first to encounter Kolbe-electrolysis, when he studied the electrolysis of an aqueous acetate solution [1], However, it was Kolbe, in 1849, who recognized the reaction and applied it to the synthesis of a number of hydrocarbons [2]. Thereby the name of the reaction originated. Later on Wurtz demonstrated that unsymmetrical coupling products could be prepared by coelectrolysis of two different alkanoates [3]. Difficulties in the coupling of dicarboxylic acids were overcome by Crum-Brown and Walker, when they electrolysed the half esters of the diacids instead [4]. This way a simple route to useful long chain l,n-dicarboxylic acids was developed. In some cases the Kolbe dimerization failed and alkenes, alcohols or esters became the main products. The formation of alcohols by anodic oxidation of carboxylates in water was called the Hofer-Moest reaction [5]. Further applications and limitations were afterwards foimd by Fichter [6]. Weedon extensively applied the Kolbe reaction to the synthesis of rare fatty acids and similar natural products [7]. Later on key features of the mechanism were worked out by Eberson [8] and Utley [9] from the point of view of organic chemists and by Conway [10] from the point of view of a physical chemist. In Germany [11], Russia [12], and Japan [13] Kolbe electrolysis of adipic halfesters has been scaled up to a technical process. 

In 1868 two Scottish scientists, Crum Brown and Fraser [4] recognized that a relation exists between the physiological action of a substance and its chemical composition and constitution. That recognition was in effect the birth of the science that has come to be known as quantitative structure-activity relationship (QSAR) studies a QSAR is a mathematical equation that relates a biological or other property to structural and/or physicochemical properties of a series of (usually) related compounds. Shortly afterwards, Richardson [5] showed that the narcotic effect of primary aliphatic alcohols varied with their molecular weight, and in 1893 Richet [6] observed that the toxicities of a variety of simple polar chemicals such as alcohols, ethers, and ketones were inversely correlated with their aqueous solubilities. Probably the best known of the very early work in the field was that of Overton [7] and Meyer [8], who found that the narcotic effect of simple chemicals increased with their oil-water partition coefficient and postulated that this reflected the partitioning of a chemical between the aqueous exobiophase and a lipophilic receptor. This, as it turned out, was most prescient, for about 70% of published QSARs contain a term relating to partition coefficient [9]. 

Sir James Dewar was born in Kincardine, Scotland, on September 20, 1842, the son of an innkeeper. He attended local schools until he was ten when he suffered a serious case of rheumatic fever lasting two years. During this period he built a violin, and music remained a lifelong interest of his. In 1858 he entered the University of Edinburgh. There he studied physics and chemistry. Dewar, in an early display of his dexterity, developed a mechanical model of Alexander Crum Brown s graphic notation for organic compounds. This was sent to Friedrich Kekule in Ghent who then invited Dewar to spend some time in his laboratory. 

The goals of QSAR studies were first proposed about 186.5 to 1870 by Crum-Brown and Fraser, who showed that thc grudual chemical modification in the molecular structure of a scries of poisons produced some important differences in their action, They postulated that the physiological action, , of a molecule is a function of its chemical constitution. C. This con be expressed in Equation 2-15 ... 

In 1864, he published an important study on the Theory of isomeric compounds in which, using his graphical formulae, he discussed various types of isomerism [Crum-Brown, 1864] guessing the link between mathematics and chemistry [Crum-Brown, 1867]. 

Methylation of the nitrogen atom in atropine, on the other hand, increases intrinsic activity. Crum Brown and Fraser (26) were the first to study the pharmacology of atropine metho-salts they found that the peripheral atropine-like effects were retained in atropine methiodide and... 

Crum Brown wrote (18 February 1869, AKS), "Although I have never studied in your laboratory I have always considered myself as, in a sense, your disciple, so many of my ideas being derived, directly or indirectly from you."... 

Sir) James Dewar (Kincardine on Forth, 2 September 1842-London, 27 March 1923) studied (1858) in Edinburgh under Playfair and later Crum Brown. His model of the carbon atom (see p. 755) was sent by Playfair to... 

For a full quote, see Appendix 7. It is clear that, at that time and for the following almost 200 years, chemistry was generally perceived to be beyond mathematics. But less that 100 years later, A. Crum Brown (1838-1922), who, after finishing study of medicine in Edinburgh, went to visit Bunsen in Heidelberg and continued with his interest in chemistry, came with a more optimistic reference, stating [35],... 

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