CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 

 HARVARD COLLEGE. 



SYMMETRICAL TRIIODBENZOL. 



By C. Loking Jackson and G. E. Behr. 



Presented December 12, 1900. Received December 20, 1900. 



So far as we can find, three triiodbenzols have been described in the 

 chemical literature, but the constitution of only one has been established 

 thoroughly; this is the unsymmetrical (1.2.4) isomere melting at 76° 

 obtained by Kekule * from the action of iodine and iodic acid on benzol. 

 More recently Plantzsch f has also made it from the diioddiazobeuzol 

 iodide prepared from diiodaniline and found that it melts at 77°. 



The other two isomeric triiodbenzols were made by Istrati and 

 Georgescu t by heating together benzol iodine and concentrated sulphuric 

 acid. Unfortunately their original paper is not at our disposal, so that we 

 know their work only from the abstracts of it in the " Jahresbericht liber 

 die Fortschritte der Ch'emie " and Beilstein's Ilandbuch (third edition). 

 From these it appears that they ascribed the unsymmetrical constitution 

 (1 . 2 . 4) to their compound melting at 85°, and the adjacent structure 

 (I . 2 . 3) to that melting at 182° to 184°, but there is no statement that 

 they determined these constitutions experimentally. The experiments 

 of Kekule and Hantzsch just cited prove that the unsymmetrical isomere 

 melts at 77° (or 76°), and, therefore, their compound melting at 85° 

 cannot have this structure. 



Under these circumstances it seemed worth while to prepare the symmet- 

 rical triiodbenzol and to prove its constitution by experiment ; accordingly 

 we made the triiodaniline by the method of Michael and Norton, § that 

 is, treating chloride of aniline with monochloride of iodine ; and replaced 

 the amido group in this body by hydrogen by means of the diazo reaction. 



* Ann. Chem. (Liebig), CXXXVII. 164 (1866). 

 t Ber. (1. chem. Ges., XXVIIL 684 (1895). 



t Buletinul d. Soc. d. Sciinte Fiz. d. Bucuresci, I. 62. Jarhresb. Chem. 1892, 

 1063. Beilstein's Handbuch (3d Edition), III. 73. 

 § Ber. d. chem. Gee., XI. Ill (1878). 



