3476-01-5Relevant academic research and scientific papers
Aromatic sulfonation 85. Halogen directing and steric effects in the sulfonation of the twelve halogenotoluenes and some related compounds
Cerfontain, Hans,Koeberg-Telder, Ankie,Laali, Khosrow,Lambrechts, Hans J. A.,Wit, Peter de
, p. 390 - 392 (2007/10/02)
The isomer distributions for the sulfonation of the twelve halogenotoluenes and some trisubstituted halogenomethylbenzenes, with both 98.4 percent H2SO4 at 25 deg C and sulfur trioxide in nitromethane at 0 deg C, have been determined and found to be very similar.The predominantly para-directing effect of the halogen substituent dominates over that of the methyl substituent: with the 2-halogenotoluenes, the degree of 5-substitution decreases from >/= 90 percent for the fluoro to 50 percent for the iodo compound.The 2- to 3-sulfonation ratio of the 4-halogenotoluenes strongly increases on going from fluorine (0.5) to iodine (7).The ratio of the partial rate factors for the sulfonation of a halogenobenzene ortho and meta to halogen varies from 17 +/- 1 for the fluoro to 1.5 +/- 0.4 for the iodo substituent.In competition to the sulfonation, 2- and 4-iodotoluene undergo deiodination, The latter process is more important with the 4-isomer and with the protic sulfonating reagent.With the aprotic reagent, the reaction proceeds by direct sulfodeiodination, whereas with the sulfuric acid reagent, it proceeds by initial protiodeiodination and sulfodeprotonation.
