Revised Mechanism of Boyland−Sims Oxidation

Abstract

New computational insights into the mechanism of the Boyland-Sims oxidation of arylamines with peroxydisulfate (S(2)O(8)(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 (SO(4)(2-)) are generated by rate-determining two-electron oxidation of primary and secondary arylamines with S(2)O(8)(2-), while arylamine dications/immonium cations and SO(4)(2-) are initially formed by two-electron oxidation of tertiary arylamines with S(2)O(8)(2-). The subsequent regioselectivity-determining reaction of arylnitrenium cations/arylamine dications/immonium cations and SO(4)(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.

Enzymatic oligomerization and polymerization of arylamines: state of the art and perspectives

“…This is because the oxidation of arylamines is quite a complex process, which leads to the formation of a highly reactive arylamine radical as the first intermediate in many cases. The formation of other reactive species, e.g., arylnitrenium cations, is also possible (Marjanović et al 2011; Ćirić-Marjanović 2013b). Templates can suppress certain unwanted reaction pathways of the formed radicals and/or other reactive species, leading to the formation of the desired product in high yield, e.g., the formation of conducting polyaniline (PANI) emeraldine salt in the case of the template-assisted enzymatic oxidation of aniline (Samuelson et al 1998).…”

Aniline oligomers versus polyaniline

“…In addition to the oxidative coupling of aniline molecules to short aniline oligomers, the reaction route to longer aniline oligomers in alkaline media includes the conversion of aniline to p ‐benzoquinone monoimine (semiquinoneimine, Fig. 6(a)) and p ‐benzoquinone 35, 78–80. The former compound is known to be responsible for the brown colour of stored aniline, while the latter is produced by the oxidation of aniline on the industrial scale81 (Fig.…”

Electronic descriptors for analytical use of the benzidine‐based compounds and the mechanism of oxidative coupling of anilines

“…[5] This method is based on the well-known reaction of electrochemical [1][2][3][4]6] or chemical oxidation of the amines with different oxidants. Among them, the naphthalene-1,8-diylbis (diphenylmethylium) ion, [7] atomic chlorine, [8] and such ions as ClO 4 À , [9,10] Cu 2+ , [9,11] Cr 2 O 7 2À , [10,12] S 2 O 8 2À , [12][13][14] Ti 3+ , [15] Ce 4+ , MnO 4 À -anion [12] were effectively utilized to obtain singly and doubly ionized forms of the aforementioned amines. Overall, the latter dications are rather stable-colored species that were comprehensively studied by UV-Vis spectroscopic techniques.…”