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.
