On the classification of chemical substances by means of generic radicals / by Alexander Crum Brown.

Date:
1866
Catalogue details

Licence: Public Domain Mark

Credit: On the classification of chemical substances by means of generic radicals / by Alexander Crum Brown. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    cate it by a single symbol, and I shall use the Greek letter H for this purpose* The relation of H to CN, or of the acid to the nitrile, is seen not only in the mono- basic acids (monocarbonsiiuren), but also in the di- and tri-basic acids (di- and tri- carbonsauren), so that these contain the radical S, two and three times respectively. The investigation sketched above also shows that COH and CH.,(HO), are the radicals of the aldehydes and the true alcohols. Pursuing this method further, we arrive at a system of classification for the various groups of pseudo- alcohols, the number of which has recently increased so much. One of these groups is formed by the hydrogenation of the acetones. The acetones have the general formula COR.^ (in which may represent either two atoms of the same 0-0Z0 or of two different radicals); taking the graphic formula, we have ^ (-©-© being the generic radical), by the addition of we get Y the reaction being similar to that by which the aldehydes are converted into true alco- hols, one of the two pairs of equivalents by which the 0 atom is united to the C, being separated, and hydrogen added to each of the equivalents (one of 0 and one of C), thus rendered free. The generic radical here is obviously {(CH(HO)}and the subgenera and individual substances are determined by the radicals saturating the two free equivalents of this generic radical. This genus, besides the universal character of the alcohol family (the formation of ethers) has the property of form- ing aldehydic bodies (acetones) by the loss of two atoms of H, [CH(HO)} be- coming (CO); and in that subgenus which contains the radical {CH2(H0)}' (or in which one of the R's is H), this aldehydic body is a true aldehyde, capable of forming an acid by further oxidation. When none of the equivalents of the carbon atom in the generic radical are directly saturated with H, the alcohol is incapable of producing an aldehyde or acetone; and, in this case, we have the characteristic radical reduced to {G(HO)}', as in Butlerow's trimethyl alcohol. We thus see that the most generalform of alcohol is C(HO) R3 (whereR3 represents one triatomic. or one diatomic and one monatomic, or three monatomic radicals); and the genera, sub-genera, and individuals of this family are determined by the nature of the radical or radicals, combined with the family radical {C(HO)]For con- venience let us, in the meantime, represent this radical by the symbol The different subdivisions of the family will then be R'0, RR'$, and R'gO) If * I had proposed to express the radical (COHO)' by the symbol S, before I was aware that BuTLERow had already used the symbol A to represent the same radical. While fully acknowledging the priority of Butlerow's recognition of this radical, I prefer to retain tlie symbol 3. By using such of the Greek capitals as differ from the Roman in form, to represent generic radicals, we avoid the danger of confounding them with elementary atoms.