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Abstract
The mechanism of aromatic nitration is critically reviewed with particular emphasis on the paradox of the high positional selectivity of substitution in spite of low substrate selectivity. Early quantum chemical computations in the gas phase have suggested that the retention of positional selectivity at encounter-limited rates could be ascribed to the formation of a radical pair via an electron transfer step occurring before the formation of the Wheland intermediate, but calculations which account for the effects of solvent polarization and the presence of counterion do not support that point of view. Here we report a brief survey of the available experimental and theoretical data, adding a few more computations for better clarifying the role of electron transfer for regioselectivity.
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Vidović K, Lašič Jurković D, Šala M, Kroflič A, Grgić I. Nighttime Aqueous-Phase Formation of Nitrocatechols in the Atmospheric Condensed Phase. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:9722-9730. [PMID: 29944831 DOI: 10.1021/acs.est.8b01161] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Yellow-colored methylnitrocatechols (MNC) contribute to the total organic aerosol mass and significantly alter absorption properties of the atmosphere. To date, their formation mechanisms are still not understood. In this work, the intriguing role of HNO2 (catalytic and oxidative) in the dark transformation of 3-methylcatechol (3MC) under atmospherically relevant aqueous-phase conditions is emphasized. Three possible pathways of dark 3-methyl-5-nitrocatechol and 3-methyl-4-nitrocatechol formation, markedly dependent on reaction conditions, were considered. In the dominant pathway, HNO2 is directly involved in the transformation of 3MC via consecutive oxidation and conjugated addition reactions (nonradical reaction mechanism). The two-step nitration dominates at a pH around the p Ka of HNO2, which is typical for atmospheric aerosols, and is moderately dependent on temperature. Under very acidic conditions, the other two nitration pathways, oxidative aromatic nitration (electrophilic) and recombination of radical species, gain in importance. The predicted atmospheric lifetime of 3MC according to the dominant mechanism at these conditions (2.4 days at pH 4.5 and 25 °C) is more than 3-times shorter than that via the other two competitive pathways. Our results highlight the significance of a catechol oxidation-conjugated addition reaction in a nighttime secondary nitroaromatic chromophore formation in the atmosphere, especially in polluted environments with high NO x concentrations and relatively acidic particles (pH around 3).
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Affiliation(s)
- Kristijan Vidović
- Department of Analytical Chemistry , National Institute of Chemistry , Hajdrihova 19 , SI-1000 Ljubljana , Slovenia
| | - Damjan Lašič Jurković
- Department of Catalysis and Chemical Reaction Engineering , National Institute of Chemistry , Hajdrihova 19 , SI-1000 Ljubljana , Slovenia
| | - Martin Šala
- Department of Analytical Chemistry , National Institute of Chemistry , Hajdrihova 19 , SI-1000 Ljubljana , Slovenia
| | - Ana Kroflič
- Department of Analytical Chemistry , National Institute of Chemistry , Hajdrihova 19 , SI-1000 Ljubljana , Slovenia
| | - Irena Grgić
- Department of Analytical Chemistry , National Institute of Chemistry , Hajdrihova 19 , SI-1000 Ljubljana , Slovenia
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Shopsowitz K, Lelj F, MacLachlan MJ. Regioselectivity in the Nitration of Dialkoxybenzenes. J Org Chem 2011; 76:1285-94. [DOI: 10.1021/jo102113t] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Kevin Shopsowitz
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Francesco Lelj
- La.M.I. and LaSCAMM INSTM Sezione Basilicata, Dipartimento di Chimica, Università della Basilicata, Via dellʼAteneo Lucano 10, 85100 Potenza, Italy
| | - Mark J. MacLachlan
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
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Shiri M, Zolfigol MA, Kruger HG, Tanbakouchian Z. Advances in the application of N2O4/NO2 in organic reactions. Tetrahedron 2010. [DOI: 10.1016/j.tet.2010.09.057] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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The chemistry of electrogenerated acids (EGA); How to generate EGA and how to utilize it? Top Curr Chem (Cham) 2005. [DOI: 10.1007/3-540-17871-6_15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2023]
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Esteves PM, De M Carneiro JW, Cardoso SP, Barbosa AGH, Laali KK, Rasul G, Prakash GKS, Olah GA. Unified mechanistic concept of electrophilic aromatic nitration: convergence of computational results and experimental data. J Am Chem Soc 2003; 125:4836-49. [PMID: 12696903 DOI: 10.1021/ja021307w] [Citation(s) in RCA: 126] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mechanism of electrophilic aromatic nitration was revisited. Based on the available experimental data and new high-level quantum chemical calculations, a modification of the previous reaction mechanism is proposed involving three separate intermediates on the potential energy diagram of the reaction. The first, originally considered an unoriented pi-complex or electron donor acceptor complex (EDA), involves high electrostatic and charge-transfer interactions between the nitronium ion and the pi-aromatics. It explains the observed low substrate selectivity in nitration with nitronium salts while maintaining high positional selectivity, as well as observed oxygen transfer reactions in the gas phase. The subsequent second intermediate originally considered an oriented "pi-complex" is now best represented by an intimate radical cation-molecule pair, C(6)H(6)(+)(*)()/NO(2), that is, a SET complex, indicative of single-electron transfer from the aromatic pi-system to NO(2)(+). Subsequently, it collapses to afford the final sigma-complex intermediate, that is, an arenium ion. The proposed three discrete intermediates in electrophilic aromatic nitration unify previous mechanistic proposals and also contribute to a better understanding of this fundamentally important reaction. The previously obtained ICR data of oxygen transfer from NO(2)(+) to the aromatic ring are also accommodated by the proposed mechanism. The most stable intermediate of this reaction on its potential energy surface is a complex between phenol and NO(+). The phenol.NO(+) complex decomposes affording C(6)H(6)O(+)(*)/PhOH(+) and NO, in agreement with the ICR results.
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Affiliation(s)
- Pierre M Esteves
- Loker Hydrocarbon Research Institute, Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, USA
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NO(2)(+) nitration mechanism of aromatic compounds: electrophilic vs charge-transfer process. J Org Chem 2000; 65:2972-8. [PMID: 10814186 DOI: 10.1021/jo991538u] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The nitration of methylnaphthalenes with NO(2)BF(4) and NOBF(4) was examined in order to shed light on the controversial aromatic nitration mechanism, electrophilic vs charge-transfer process. The NO(2)(+) nitration of 1,8-dimethylnaphthalene showed a drastic regioselectivity change depending on the reaction temperature, where ortho-regioselectivity at -78 degrees C and para-regioselectivity at 0 degrees C were considered to reflect the electrophilic and the direct or alternative charge-transfer process, respectively, because the NO(+) nitration through the same reaction intermediates as in the NO(2)(+) nitration via a charge-transfer process resulted in para-regioselectivity regardless of the reaction temperature. The NO(2)(+) nitration of redox potential methylnaphthalenes higher than 1,8-dimethylnaphthalene gave a similar ortho-regioselectivity enhancement to 1,8-dimethylnaphthalene at lower temperature, thus reflecting the electrophilic process. On the other hand, the NO(2)(+) nitration of redox potential methylnaphthalenes lower than 1,8-dimethylnaphthalene showed para-regioselectivity similar to the NO(+) nitration, indicating the direct or alternative charge-transfer process. In the presence of strong acids where the direct charge-transfer process will be suppressed by protonation, the ortho-regioselectivity enhancement was observed in the NO(2)(+) nitration of 1,8-dimethylnaphthalene, suggesting that the direct charge-transfer process could be the main process to show para-regioselectivity. These experimental results imply that the NO(2)(+) nitration proceeds via not only electrophilic but also direct charge-transfer processes, which has been considered to be unlikely because of the high energy demanding process of a bond coordination change between NO(2)(+) and NO(2). Theoretical studies at the MP2/6-31G(d) level predicted ortho- and para-regioselectivity for the NO(2)(+) nitration via electrophilic and charge-transfer processes, respectively, and the preference of the direct charge-transfer process over the alternative one, which support the experimental conclusion
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Cortona MN, Vettorazzi NR, Silber JJ, Sereno LE. Electrochemical nitration of naphthalene in the presence of nitrite ion in aqueous non-ionic surfactant solutions. J Electroanal Chem (Lausanne) 1999. [DOI: 10.1016/s0022-0728(99)00232-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Peluso A, Del Re G. On the Occurrence of an Electron-Transfer Step in Aromatic Nitration. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp9530156] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Cortona MN, Vettorazzi N, Silber JJ, Sereno L. Mechanistic study of the nitration of naphthalene by its electrochemical oxidation in the presence of nitrite ion in acetonitrile solutions. J Electroanal Chem (Lausanne) 1995. [DOI: 10.1016/0022-0728(95)04076-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Elektronen- und Ladungsübertragung: Zur Vereinheitlichung der Mechanismen organischer und metallorganischer Reaktionen. Angew Chem Int Ed Engl 1988. [DOI: 10.1002/ange.19881001008] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Boughriet A, Bremard C, Wartel M. Chemical and electrochemical activation of the nitration of naphthalene by N2O3 in aprotic media. Electrochim Acta 1988. [DOI: 10.1016/0013-4686(88)80070-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Boughriet A, Bremard C, Wartel M. Electrocatalysis of the nitration of naphthalene by N2O4 in aprotic media. J Electroanal Chem (Lausanne) 1987. [DOI: 10.1016/0022-0728(87)80009-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Boughriet A, Coumare A, Fischer J, Wartel M. Influence of the medium on the ionic dissociation of N2O4 and the kinetics of decomposition of N2O3 in aprotic solvents. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/0022-0728(86)90057-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Masclet P, Mouvier G, Nikolaou K. Relative decay index and sources of polycyclic aromatic hydrocarbons. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/0004-6981(86)90083-1] [Citation(s) in RCA: 173] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Pitts JN, Zielinska B, Sweetman JA, Atkinson R, Winer AM. Reactions of adsorbed pyrene and perylene with gaseous N2O5 under simulated atmospheric conditions. ACTA ACUST UNITED AC 1985. [DOI: 10.1016/0004-6981(85)90236-7] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Bloom AJ, Fleischmann M, Mellor JM. Indirect electrochemical methods of nitration: Novel nitroacetamidation of dienes. Tetrahedron Lett 1984. [DOI: 10.1016/s0040-4039(01)91273-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Hammerich O, Parker VD. Kinetics and Mechanisms of Reactions of Organic Cation Radicals in Solution. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 1984. [DOI: 10.1016/s0065-3160(08)60148-3] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
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Eberson L. Electron-Transfer Reactions in Organic Chemistry. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 1982. [DOI: 10.1016/s0065-3160(08)60139-2] [Citation(s) in RCA: 169] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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Belen'kii LI, Gul'tyai VP. Redox transformations of compounds of the thiophene series (review). Chem Heterocycl Compd (N Y) 1981. [DOI: 10.1007/bf00503474] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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