Revised Mechanism of Boyland−Sims Oxidation

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2011-04, Vol.115 (15), p.3536-3550
• Main Authors: Marjanović, Budimir, Juranić, Ivan, Ćirić-Marjanović, Gordana
• Format: Article
• Language: English
• Subjects: A: Molecular Structure, Quantum Chemistry, General Theory; Amines - chemical synthesis; Amines - chemistry; Molecular Structure; Oxidation-Reduction; Sodium Compounds - chemistry; Stereoisomerism; Sulfates - chemistry
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp111129t

New computational insights into the mechanism of the Boyland−Sims oxidation of arylamines with peroxydisulfate (S2O8 2−) in an alkaline aqueous solution are presented. The key role of arylnitrenium cations, in the case of primary and secondary arylamines, and arylamine dications and immonium cations, in the case of tertiary arylamines, in the formation of corresponding o-aminoaryl sulfates, as prevalent soluble products, and oligoarylamines, as prevalent insoluble products, is proposed on the basis of the AM1 and RM1 computational study of the Boyland−Sims oxidation of aniline, ring-substituted (2-methylaniline, 3-methylaniline, 4-methylaniline, 2,6-dimethylaniline, anthranilic acid, 4-aminobenzoic acid, sulfanilic acid, sulfanilamide, 4-phenylaniline, 4-bromoaniline, 3-chloroaniline, and 2-nitroaniline) and N-substituted anilines (N-methylaniline, diphenylamine, and N,N-dimethylaniline). Arylnitrenium cations and sulfate anions (SO4 2−) are generated by rate-determining two-electron oxidation of primary and secondary arylamines with S2O8 2−, while arylamine dications/immonium cations and SO4 2− are initially formed by two-electron oxidation of tertiary arylamines with S2O8 2−. The subsequent regioselectivity-determining reaction of arylnitrenium cations/arylamine dications/immonium cations and SO4 2−, within the solvent cage, is computationally found to lead to the prevalent formation of o-aminoaryl sulfates. The formation of insoluble precipitates during the Boyland−Sims oxidation of arylamines was also computationally studied.