Evidence for Radical Cations in Linked Mechanisms of N,N-Dialkyl Aromatic Amine Nitration and Nitrosative Dealkylation

Abstract

N,N-Dialkyl aromatic amines react rapidly with nitrous acid to competitively produce a nitrosamine and a nitro compound. The mechanism of nitro compound formation involves a reaction of an amine radical cation with NO2, while the nitrosamine is produced by two competing pathways, one of which involves N-α-CH deprotonation of a radical cation with subsequent oxidative generation of an imminium ion, and the other of which occurs through NOH elimination of a nitrosammonium ion (R3N−NO+). All three pathways are linked through the reversible homolysis of R3N−NO+ to NO and a radical cation.

Synthesis, Characterization, and Structures of a Persistent Aniline Radical Cation

“…We have described the first example of an aniline radical cation in the solid state, which may be used as a stable intermediate for model studies. [2][3][4][5][6][7][8][9] Experimental Section…”

“…Xiaoyu Chen, Xingyong Wang, Yunxia Sui, Yizhi Li, Jing Ma,* Jinglin Zuo, and Xinping Wang* In contrast to p-phenyldiamine radical cations (Würsters salts), [1] aniline radical cations (ArNR 2 C + , R = H or alkyl) are highly reactive and often exist as short-lived intermediates occurring in dimerization, [2] cationic polymerization, [3] azo compound formation, [4] benzidine rearrangement, [5] protontransfer reactions, [6,7] and various nucleophilic substitutions such as nitration, [7] methoxylation, [8] cyanation, [9] and halogenation. [2b] Because of their importance, aniline radical cations have been the subject of numerous theoretical [10] and experimental studies in the gas phase [10] and in solution.…”

“…[2b] Because of their importance, aniline radical cations have been the subject of numerous theoretical [10] and experimental studies in the gas phase [10] and in solution. [6][7][8][9]11] Calculations have predicted that a discrete aniline radical cation in the gas phase adopts a planar quinoidal-type structure with a partial double C À N bond and the unpaired electron is delocalized in the phenyl ring. [10] However, isolation of salts with an aniline radical cation remains a challenge.…”

Synthesis, Characterization, and Structures of a Persistent Aniline Radical Cation

“…In contrast to p ‐phenyldiamine radical cations (Würster’s salts),1 aniline radical cations (ArNR 2 .+ , R=H or alkyl) are highly reactive and often exist as short‐lived intermediates occurring in dimerization,2 cationic polymerization,3 azo compound formation,4 benzidine rearrangement,5 proton‐transfer reactions,6, 7 and various nucleophilic substitutions such as nitration,7 methoxylation,8 cyanation,9 and halogenation 2b. Because of their importance, aniline radical cations have been the subject of numerous theoretical10 and experimental studies in the gas phase10 and in solution 6–9.…”

Cuso4 -amine redox-initiated radical polymerization of methyl methacrylate mediated by a CuCl2 complex: Homogeneous reverse ATRP

“…NMA and DPA, play a role as efficient inhibitors in parallel experiments. There have been a large number of reports on subsequent transformation of the ET intermediate, DMA radical cations, including oxidative demethylation to NMA (and further to ANi) and formaldehyde, PH/HT to C alpha ‐H leading to C alpha and PH/HT to para ‐C sp2 ‐H leading to para ‐C sp2 , as summarized in Scheme . For ANi, it is generally accepted that ANi cation radicals undergo HT or PT to para ‐C sp2 ‐H, forming para ‐C sp2 ·radicals to initiate radical polymerization of MMA, as the ET derivative of 2,4,6‐triisobutylaniline appears as a persistent cation radical, instead of PT to N‐H.…”