Oxidation by Iron(III) Complexes. VIII. The Reactions of Iron(III) Chloride with Toluene and Substituted Toluenes

Abstract

Abstract The thermal and photochemical reactions of toluene with anhydrous iron(III) chloride in the solid state result in nuclear chlorination. In a homogeneous system, a side-chain reaction occurs under irradiation with light, although no product is obtained in the thermal reaction. The addition of water to the iron(III) chloride–toluene system in the range of the molar ratio of 1–5 changes the course of the photochemical reaction; in the water/iron(III) chloride molar ratios of 1–1.7, 3, and 4–5, the main products are the diphenylmethane-type compound, o- or p-chlorotoluene (o>p), and benzyl chloride respectively. Pyridine as a ligand acts to give benzyl chloride selectively. The Mössbauer data of the FeCl3/nH2O solid show that the arrangement of the Cl− ion around the Fe(III) ion changes upon the addition of water. The thermal and photochemical reactions of p-methoxytoluene with anhydrous iron(III) chloride give 2,2′-dimethoxy-4,4′-dimethylbiphenyl by oxidative aryl coupling. Water inhibits the aryl coupling reaction.