Journal of the chemical society 1922/I. [antikvár]

JOURNALOFTHE CHEMICAL SOCIETY.ABSTRACTS OF CHEMICAL PAPERS PUBLISHED IN BRITISH AND FOREIGN JOURNALS.PART I.rt!Ofganie Chemistry.The Oscillation of Physical Constants in Honaologous Series, Hermann Paxjly (Z. anorg. Chem., 1921, 119, 271 291).The theories put forward by Tammann (A., 1920, ii, 285) and Cuy (A., 1921, ii, 429) to explain the oscillation in the numerical values of different physical properties in homologous series are criticised and an alternative explanation is suggested. A review of the existing data leads to the conclusion that the end groups of the carbon chain and their relationship to each other, especially in the spatial sense, have an important influence on the physical properties. In the fatty acid series, the odd members have proportionately lower molecular volumes and at the same time lower melting points than the even members. It is probable that in the open straight chain compounds the carbon atoms form a zigzag chain, and it follows that when the number of carbon atoms is even the end atoms are relatively farther apart than when the number is odd. The difference is of the " syn " and " anti " type, the odd members having a " syn " structure with low molecular volume and low melting point, the even members the " anti " structure with higher molecular volume and melting point. The odd members, however, have the higher boiHng points. Similarly, the solubihties and molecular heats in the fatty acid series oscillate in the opposite direction to the molecular volume.A special type of oscillation is exhibited by the dissociationVOL. cxxii, i.bI;,1 t*i. 2absteacts of chemical papees./C-C..COOHH3C/ \CC/+ - +constants of the fatty acids and by the optical rotations of the acyl-Z-menthols. When these properties are plotted against the number of carbon atoms in the aliphatic chain, two closely similar curves are obtained showing a kind of double oscillation. When the points corresponding with odd numbers of carbon atoms are joined, a zigzag line is obtained, and the points corresponding vsdth even numbers of carbon atoms lie alternately above and below this hne. This type of oscillation appears to be peculiar to the fatty acids and some of their derivatives, and in these series to be conftned to dissociation constants and optical rotations. Itis suggested that the phenomenon may be due to the influence of the methyl group on the carboxy-group in, for example, the fatty acid series, when the carbon chain has the form indicated in the annexed diagram.E. H. R.The Structure of Carbon Chains. Johannes Staek {Z. anorg. Chem., 1921, 119, 292298).An elaboration of the hypothesis put forward by Pauly (preceding abstract) to account for the difference between the physical properties of the odd and even members of an ahphatic homologous series. Generally, when the numerical value of the physical property is plotted against the number of carbon atoms, the points corresponding with the even members of the series fall on one curve and those of the odd members on another, roughly parallel, curve. The difference must be due to a difference in structure of the carbon chain when the number of carbon atoms is even from the structure when the number is odd. The suggestion is made that the difference hes in the curvature of the zigzag chain. A molecule with a straighter chain would be expected to form a more stable space lattice structure than one with a more curved chain, and hence to have a higher melting point. The compounds of the even series have the higher melting points, and it is concluded that these have the straighter chain and the compounds of the odd series the more curved chain. The molecular volumes and boihng points of the two series are consistent with this conclusion.E. H. R.Preparation of Alumini\iin Carbide and of Marsh Gas. 0. Ohmann {Z. 'physihal. Chem. Unterr., 1921, 34, 7677).A mixture of aluminium fihngs, potassium chlorate, and iron, when ignited in a stream of carbon dioxide, results in the formation of aluminium carbide, Al^Cg. When the powder is finely ground and then gently warmed with water, methane is hberated : AI4C3+ 6H20=3CIl4+2Al203. Four grams of aluminium yield 70 c.c. of methane.Chemical Absteacts.The Formation of Hexachloroethane from Chloropicrin. OsvTALD Silbeeead (Chem. News, 1921,123, 271).When hydrogen chloride is passed through chloropicrin at 100° and the resulting mixed vapours are passed over pumice at 400°, the main products are carbonyl chloride, nitrosyl chloride, and nitric oxide. A smaU amount of hexachloroethane is also formed, and may be collected