Mechanisms of oxidation of aniline and related compounds in basic solution

Konaka, Ryusei; Kuruma, Kazuo; Terabe, Shigeru

doi:10.1021/ja01009a022

Cited by 38 publications

(32 citation statements)

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“…An alternate mechanism that involves nucleophilic addition of 4-ATP to 4-nitrosobenzenethiol (the latter being formed by oxidation of 4-ATP by O 2 or singlet oxygen2324 in the SPAC reaction, see Fig. S9), is analogous to the oxidation of anilines in solution2125. However, we favor the mechanism involving the hydrazine intermediate on the basis of our experimental results.…”

Section: Resultsmentioning

confidence: 77%

“…In this mechanism, O 2 acts as an electron acceptor (oxidant) while H 2 O serves as a base to deprotonate the intermediates. The entire reaction is initiated by optical energy absorption (plasmonic heating20) of the 4ATP molecules bound to the metal surface, wherein they undergo electron transfer from the –NH 2 groups to give –NH 2 + radical cations (O 2 is an electron acceptor), which then dimerize into a diphenylhydrazine intermediate, Ar–NH-NH–Ar, following deprotonation by H 2 O2122. H 2 O may also increase the local concentration of O 2 at the metal surface for this oxidation reaction.…”

Section: Resultsmentioning

confidence: 99%

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Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

Kang

Mack

et al. 2013

Sci Rep

214

182

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Surface plasmon assisted catalysis (SPAC) reactions of 4-aminothiophenol (4ATP) to and back from 4,4′-dimercaptoazobenzene (DMAB) have been investigated by single particle surface enhanced Raman spectroscopy, using a self-designed gas flow cell to control the reductive/oxidative environment over the reactions. Conversion of 4ATP into DMAB is induced by energy transfer (plasmonic heating) from surface plasmon resonance to 4ATP, where O2 (as an electron acceptor) is essential and H2O (as a base) can accelerate the reaction. In contrast, hot electron (from surface plasmon decay) induction drives the reverse reaction of DMAB to 4ATP, where H2O (or H2) acts as the hydrogen source. More interestingly, the cyclic redox between 4ATP and DMAB by SPAC approach has been demonstrated. This SPAC methodology presents a unique platform for studying chemical reactions that are not possible under standard synthetic conditions.

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Section: Resultsmentioning

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

Kang

Mack

et al. 2013

Sci Rep

214

182

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“…They form mainly due to the head‐to‐tail (C–N) coupling of aniline units, but in alkaline and neutral environments hydrazobenzene and azobenzene are found as a result of head‐to‐head coupling (N–N) . According to various spectroscopies, mass spectroscopy, 1 H NMR, 13 C NMR, 15 N NMR and XRD analyses, aniline oxidation products prepared under alkaline conditions are chemically heterogeneous and contain linear and cyclic fragments with amino and imino groups, as well as oxygen‐containing groups . Such products have molecular weights up to 3000 g mol −1 , are amorphous and are partially soluble in aqueous and organic solvents.…”

Section: Oxidative Polymerization Of Anilinementioning

confidence: 99%

Conjugated polyaniline as a result of the benzidine rearrangement

Sapurina

Теньковцев

Stejskal

2015

Polymer International

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Abstract:The mechanism of the oxidative polymerization of aniline is reviewed on the basis of the experimental evidence and reaction schemes proposed in the literature. It is demonstrated that the balance between the non-protonated and protonated forms of the monomer and the growing chain is responsible for the diversity of the molecular structure, morphology and properties of aniline oxidation products. Various forms are oxidized by two oxidation mechanisms: (1) chain reaction of electrophilic substitution and (2) coupling of cation-radical centres. At pH > 2.5, the non-protonated reagents are oxidized with a chain reaction controlled by electrophilic substitution of the aromatic ring. The reaction leads to the formation of non-conducting aniline oligomers with heterogeneous molecular structures. At pH = 2.5-4, the electrophilic substitution is reduced because of the protonation of the aniline, and the cyclic dimer, phenazine, becomes the main product of the oxidation. The growth of the conjugated chain proceeds at pH < 2.5, when the reactants are protonated. The reaction proceeds through coupling between the terminal cation radical and the monomer cation radical with formation of a -complex. The transformation of the -complex into a para-substituted monomer unit is thermodynamically controlled and is produced through an intramolecular benzidine (semidine) rearrangement. The regular structure of the growing chains is a result of the high regioselectivity of the sigmatropic rearrangements and significant energy gain attained by the formation of protonated polyconjugated chains in the agglomerated state.

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“…À medida que o pH do sistema aumenta, tornando-se neutro, observam-se evidên-cias da formação de ligações N-N, sugerindo o acoplamento cabeça-cabeça 23 . De fato, compostos do tipo hidrazobenzeno e azobenzeno podem ser obtidos da oxidação da anilina em meio básico 24 . Em pH fortemente ácido, produtos associados ao acoplamento cauda-cauda, como a benzidina, são observados e a sua proporção em relação ao ADPA tende a aumentar com a diminuição do pH 14,25,26 .…”

Section: Introductionunclassified

Tratamento dos resíduos gerados na síntese de polianilina em escala pré-piloto

Sousa¹,

Araújo²,

Freitas³

et al. 2003

Quím. Nova

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Recebido em 6/1/03; aceito em 29/4/03 TREATMENT OF THE RESIDUES GENERATED BY POLYANILINE SYNTHESIS IN PRE-PILOT SCALE. Polyaniline (PAni) is one of the most studied conducting polymer. It can be synthesized by two methods: electrochemical or chemical oxidation. The chemical oxidation is more adequate to produce large quantities of polymer. Regardless of the synthesis scale, the treatment of the residues before its final destination is very important and necessary because it contains toxic aniline derivatives (carcinogens in some cases), acids and inorganic salts, both with low toxicity. In this work we discuss the methods used to treat these residues and to eliminate and discard the toxic substances. These were extracted from the reaction residues by using activated coal and the pH of the residue was neutralized.Keywords: polyaniline; residues; coal. INTRODUÇÃOO tratamento de resíduos químicos gerados nos laboratórios das instituições de ensino e pesquisa no Brasil é um assunto cada vez mais discutido entre a comunidade acadêmica 1 . Nas universidades, não são raros os casos em que os alunos de graduação (dos diversos cursos que se utilizam da Química), em suas práticas laboratoriais, não são devidamente instruídos sobre a geração de resíduos e seu devido tratamento antes do descarte. Assim, os resíduos provenientes de sínteses químicas e testes analíticos acabam sendo descartados diretamente no sistema de esgoto sanitário, resultando em contaminação ambiental. Em outros casos, diferentes resíduos são armazenados em um mesmo recipiente sem identificação, o que dificulta sua caracterização 1 , e não são tomadas iniciativas quanto ao seu tratamento e destino final. Felizmente, a crescente preocupação com o meio ambiente tem despertado o interesse de alguns Institutos de Química em criar programas de gerenciamento dos resíduos gerados nos laboratórios de ensino e pesquisa 1-3 , que podem servir de modelo para aqueles que ainda não dispõem destes programas. Dentre as medidas tomadas estão: minimização dos resíduos produzidos, cadastramento e segregação dos diferentes resíduos a serem estocados, tratamento antes da destinação final, e a recuperação daqueles que possam ser reutilizados 1-3 . Tradicionalmente, sempre que se deseja traçar uma estratégia de síntese em laboratório ou em escala piloto, seja nas universidades ou indústrias, a maior parte dos esforços são concentrados em se obter uma rota sintética que vise minimizar os custos e maximizar o rendimento do produto desejado. Assim, os subprodutos das reações, ou resíduos, só recebem a devida atenção depois de constatados os danos ambientais. Portanto, quando se pretende desenvolver um novo experimento, que envolva substâncias químicas, é fundamental que no seu planejamento sejam avaliadas a toxicidade e a reatividade dos reagentes e de todos os possíveis subprodutos da síntese. Deve-se considerar também, se estes reagentes e subprodutos não atuam como precursores de substâncias potencialmente tóxicas quando expostos no meio ambiente. Desta maneira, é desejável ...

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Mechanisms of oxidation of aniline and related compounds in basic solution

Cited by 38 publications

References 1 publication

Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

Mechanistic understanding of surface plasmon assisted catalysis on a single particle: cyclic redox of 4-aminothiophenol

Conjugated polyaniline as a result of the benzidine rearrangement

Tratamento dos resíduos gerados na síntese de polianilina em escala pré-piloto

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