LXIX 24 674 H . 1. MII Hertog, J. C. M. Schogt, J. dt: B r u p arid Miss A. d e Klerk, _____-__.._____. ~ ~~ . ----___ .~1934"), 16 chloropyridines of known structure were described; three of the 19 possible chloropyridines, viz. the trichloroderivatives substituted in the 2,3,4-. 2.3.6-and 2,4,5-positions, were missing. Maier-Bode mentions along with the chloropyridines of known structure, three other substances belonging to this group, which are mentioned in the literature but of which the structure had not been established, viz. a trichloropyridine. m.p. 71-72", obtained by Kciser by the action of chlorine on pyridines); a compound meiting a t 64-65", which was obtained in small quantity by Seyfferth by the action of phosphorus pentachloride on nicotinic acid followed by treatment with 80 yo sulphuric acid and which he considered to be a trichloropyridine 4, ; a trichloro-Fyridine, m.p. 6 7 -4 8 " , obtained by Sell and Dootson by chlorinating pyridine with phosphorus pentachloride 5 ) .Keiser's trichloropyridine was identified in 1905 as 3,4,5-trichloropyridine by Sell and Dootson 'j). Maier-Bode apparently missed this. Nicolai' 7 ) has already mentioned this fact when he was handling the chloropyridines in connection with an investigation which he carried out in collaboration with Wibaut on the chlorination of pyridine in the gas phase 8).Nicolai also indicated that the properties of the trichloropyridine, m.p. 67--68", prepared by Sell and Dootson, made it probable that the chlorine atoms in this substance were in the 2, 3 and 6-positions'). In the meantime, this conclusion has been confirmed by Crouch and Lochte, who have synthesised this trichloropyridine by reacting glutarimide with phosphorus pentachloride @) .W e have repeated the$ chlorination of nicotinic acid described by Scyffeerth. Instead of a small quantity of a trichloropyridine, we have obtained a complex mixture of chloropyridines in which the presence of 2,3,5.6-tetrachloropyridine could be detected. We assume now that Seyfferfh had a little 2.3,6-trichloropyridine in his hands on the basis of the melting point of his product and the fact that substitution in nicotinic acid occurs apparently in both a-and &positions l o ) .While Maier-Bode's book was being printed, Graf prepared 2,3,4-trichloropyridine From 4.5.6-trichloropyridine-2-carbonyl chloride j l ) . ) H. Maier-Bodeand 7. Alfpefcr, "Das Pyridin und seine Derivate in Wissen-3) E. H. Keiser, Am. Chem.

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The velocity of the ozonisation of benzene in chloroform is proportional to the concentration of benzene and that of ozone. The reaction constant was determined a t eight temperatures between -25 and -40" C.The reaction takes place about three times more rapidly in nitroinethane than in chloroform. Aluminium chloride and ferric chloride catalyse the reaction; the velocity increases directly with the concentration of aluminium chloride. mechanism suggested in a previous publication.T h e results of our measurements are in agreement with the reaction 4 1. Introduction.Working within the framework of the researches of Wibauf and his collaborators 1 ) on the action of ozone on aromatic compounds, we have initiated an investigation into the mechanism of this reaction.In a previous paper 2 ) we have given a short description of a number of experiments, which show that the velocity of the reaction between several aromatic compounds and ozone decreases in the same order as their reactivity in electrophilic substitution reactions. Moreover boron trifluoride and aluminium chloride have a definite accelerating effect on the ozonisation of benzene derivatives. On the basis of these experiments it was concluded that the addition of ozone to these compounds takes place according to an electrophilic mechanism. Further arguments in favour of this hypothesis have been obtained by a kinetic examination of a number of ozonisation reactions. T h e results of this investigation in so far as they relate to the ozonisation of benzene are described in this communication.

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The isomer shift values of 133Cs implanted in graphite, diamond, Te, Si, Ge, Cu, Zn, Mo, and W are found in a larger interval than those found in Cs and Cs-compounds. The extension to larger values are explained by the increase of electron densities due to the compression of the oversized implanted atom