- Interaction between Electron Donor and Acceptor Groups in Some Trisubstituted Benzenes. Part 1. Relative Reactivities of 4-Substituted 1,2-Dinitrobenzenes towards Sodium Methoxide
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In an effort to study the effects of 'through conjugation' on the properties of some 1,2,4-trisubstituted benzenes, the rates of reaction of a series of four 4-substituted 1,2-dinitrobenzenes with sodium methoxide in methanol have been studied.Although reactivities at the 2-position were qualitatively in the order to be expected from inductive effects, those at the 1-position were highly sensitive to the influence of mesomeric donor action of the 4-substituent.Relatively large effects were seen for the 4-alkyl derivatives; and C-H hyperconjugation appeared to be stronger than C-C hyperconjugation.
- Patil, Sampatrao D.,Nair, P. Madhavan
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- ipso-Nitration: Formation of Nitronium Acetate Adducts in the Nitration of p-Acetamido-, p-Halogeno-, and p-Methoxy-toluenes, and α-p-Tolyloxyisobutyric acid
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Low-temperature nitration of the title compounds in acetic anhydride gives 1,2-nitronium acetate adducts, except p-fluorotoluene which gives both 1,2 and 1,4 adducts and α-p-tolyloxyisobutyric acid which gives a spiro adduct.
- Fischer, Alfred,Fyles, Deborah L.,Henderson, George N.
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- Direct Acetoxylation of Arenes
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Acetoxylation of arenes is an important reaction and an unmet need in chemistry. We report a metal-free, direct acetoxylation reaction using sodium nitrate under an anhydrous environment of trifluoroacetic acid, acetic acid, and acetic anhydride. Arenes (31 examples), with oxidation potentials (Eox, in V vs SCE) lower than benzene (2.48 V), were acetoxylated with good yields and regioselectivity. A stepwise, single electron-transfer mechanism is proposed.
- Hong Nguyen, Thi Anh,Hou, Duen-Ren
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supporting information
p. 8127 - 8131
(2021/08/23)
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- Eco-Friendly Methodology for the Formation of Aromatic Carbon–Heteroatom Bonds by Using Green Ionic Liquids
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A new sustainable method is reported for the formation of aromatic carbon–heteroatom bonds under solvent-free and mild conditions (no co-oxidant, no strong acid and no toxic reagents) by using a new type of green ionic liquid. The bromination of methoxy arenes was chosen as a model reaction. The reaction methodology is based on only using natural sodium bromine, which is transformed into an electrophilic brominating reagent within an ionic liquid, easily prepared from the melted salt FeCl3 hexahydrate. Bromination reactions with this in-situ-generated reagent gave good yields and excellent regioselectivity under simple and environmentally friendly conditions. To understand the unusual bromine polarity reversal of sodium bromine without any strong oxidant, the molecular structure of the reaction medium was characterised by Raman and direct infusion electrospray ionisation mass spectroscopy (ESI-MS). An extensive computational investigation using density functional theory methods was performed to describe a mechanism that suggests indirect oxidation of Br? through new iron adducts. The versatility of the methodology was successively applied to nitration and thiocyanation of methoxy arenes using KNO3 and KSCN in melted hexahydrated FeCl3.
- Richards, Kenza,Petit, Eddy,Legrand, Yves-Marie,Grison, Claude
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supporting information
p. 809 - 814
(2020/11/30)
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- Direct nitration method of electron-enriched aromatic hydrocarbons
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The invention discloses a direct nitration method of electron-enriched aromatic hydrocarbons, and belongs to the field of organic synthesis. The direct nitration method is a novel green free radical nitration method; aromatic hydrocarbons are taken as raw materials, acetonitrile, dichloromethane, chloroform, or acetone is taken as a reaction solvent, at room temperature conditions, the raw materials and green nitration reagent tert-butyl nitrite (TBN) are subjected to free radical nitration so as to obtain nitro-aromatic compounds. According to the direct nitration method, no metal is adoptedin reaction, tert-butyl nitrite is directly adopted in nitration reaction. Electron-donating groups such as OMe are introduced, the electron density of aromatic compounds is increased, the nitration reaction possibility is increased. The using amount of tert-butyl nitrite is reduced; only a product and tert-butyl alcohol are generated, environment pollution is reduced. The direct nitration methodis promising in application prospect in the field of nitro-aromatic compound synthesis, green nitration is realized, and a novel idea is provided for large-scale industrialized nitro-aromatic compoundproduction.
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Paragraph 0048-0050
(2018/10/02)
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- 4-METHOXYACRIDINE-1-CARBOXAMIDE DERIVATIVES AND THE PHENAZINE AND OXANTHRENE ANALOGS AS PDE4-INHIBITORS FOR THE TREATMENT OF ASTHMA AND CHRONIC PULMONARY DISEASE (COPD)
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The present invention relates to new Phosphodiesterase type 4 (PDE4) inhibitors of the formula (1) for treatment of asthma: Ar is a substituted or unsubstituted aryl, substituted or unsubstituted arylalkyl, substituted or unsubstituted heterocyclic ring or substituted or unsubstituted heteroaryl ring; each occurrence of L is O, S or NR 3; X and A are independently-CRaRb-,-CRa-,-C(=B)-, O, S(O)m, N or NR3; each occurrence of m is 0, 1, or 2; n is 0-4; p is 0-2; Y is-C(=B)C(=D)NR 4 or-C(=B)NR4 B is O, S or NRa; D is O, S or NRa; The other substituents are defined in the claims.
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Page/Page column 31-32
(2010/11/08)
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- Steroid and nitro phenol esters from Bignonia unguis-cati roots
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Two new esters, β-sitosterol cerotate 1 and 2-(4-hydroxy-3-nitrophenyl)ethyl stearate 2 have been isolated from the roots of Bignonia unguis-cati (Bignoniaceae) and their structures are elucidated by spectroscopic and chemical studies.
- Dinda, Biswanath,De, Utpal Chandra,Achari, Basudev,Arima, Shiho,Sato, Nariko,Harigaya, Yoshihiro
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p. 1514 - 1518
(2007/10/03)
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- Electrophilic nitration of aromatics in ionic liquid solvents
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Potential utility of a series of 1-ethyl-3-methylimidazolium salts [emim][X] with X = OTf-, CF3COO-, and NO3- as well as [HNEtPri2][CF3COO] (protonated Huenig's base) ionic liquids were explored as solvent for electrophilic nitration of aromatics using a variety of nitrating systems, namely NH4NO3/TFAA, isoamyl nitrate/BF3·Et2O, isoamyl nitrate/TfOH, Cu(NO3)/TFAA, and AgNO3/Tf2O. Among these, NH4NO3/TFAA (with [emim][CF3COO], [emim][NO3]) and isoamyl nitrate/BF3·Et2O, isoamyl nitrate/TfOH (with [emim][OTf]) provided the best overall systems both in terms of nitration efficiency and recycling/reuse of the ionic liquids. For [NO2][BF4] nitration, the commonly used ionic liquids [emim][AlCl4] and [emim][Al2Cl7] are unsuitable, as counterion exchange and arene nitration compete. [Emim][BF4] is ring nitrated with [NO2][BF4] producing [NO2-emim][BF4] salt, which is of limited utility due to its increased viscosity. Nitration in ionic liquids is surveyed using a host of aromatic substrates with varied reactivities. The preparative scope of the ionic liquids was also extended. Counterion dependency of the NMR spectra of the [emim][X] liquids can be used to gauge counterion exchange (metathesis) during nitration. Ionic liquid nitration is a useful alternative to classical nitration routes due to easier product isolation and recovery of the ionic liquid solvent, and because it avoids problems associated with neutralization of large quantities of strong acid.
- Laali,Gettwert
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- Nighttime tropospheric chemistry: Kinetics and product studies in the reaction of 4-Alkyl- and 4-Alkoxytoluenes with NO3 in gas phase
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Alkylbenzenes are important constituents of gasoline and industrial solvents and contribute to the formation of tropospheric ozone. The removal of these compounds from the troposphere is due to reaction with OH during the day and with NO3 during the night. Five para-substituted toluenes are reacted with the nitrate radical in gas phase. Samples to be used for product analysis were preconcentrated and analyzed by GC-MSD analysis with the use of a reference curve. The yields of methanol, ethanol, and formaldehyde were determined by FTIR analysis of the reaction mixture in the chamber. Carbonyl compounds, benzyl alcohols, and nitroderivatives were formed. In the case of the alkoxytoluenes, products were also an alkanol, benzyl alcohols, and nitrophenols. Indirect rate constants measurements were performed by comparing by FTIR measurements the decay of the aromatic compound under investigation to that of a reference compound, with a known rate constant for the reaction with NO3 added to the gas mixture. Wall loss constants were evaluated by FTIR. A Hammett correlation with ρ = - 4.3 ± 0.6; r2-= 0.87 was obtained. This and the kinetic isotope effect of 1.5-1.8 suggest a reaction mechanism occurring via an addition-elimination pathway.
- Bolzacchini, Ezio,Meinardi, Simone,Orlandi, Marco,Rindone, Bruno,Hjorth, Jens,Restelli, Gianbattista
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p. 461 - 468
(2007/10/03)
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- Transformations of arylcyclopropanes under the action of dinitrogen tetroxide
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p-Bromophenylcyclopropane, 1- and 2-methylphenylcyclopropanes, and 1,2-di-p-tolyl- and l,2-bis(p-methoxyphenyl)cyclopropanes react with N2O4with opening of the three-membered ring. Reactions of p-methoxyphenylcyclopropane, 6-cyclopropyl-l,4-benzodioxane, and 2-cyclopropylfluorene yield the corresponding nitroaromatic derivatives with conservation of the cyclopropane ring. The nitration of p-methoxyphenylcyclopropane is accompanied by demethylation. 2-Nitro- and 4-nitrophenylcyclopropanes, as well as l-chloro-2-phenylcyclopropane, do not react with N2O4 under the same conditions. The differences in the behavior of arylcyclopropanes in reactions with N2O4 are explained by the different action of nitrosonium ion in the first reaction step: It acts as either electrophilic species capable of initiating opening of the cyclopropane ring or one-electron oxidant converting the initial arylcyclopropanes into the corresponding radical cations which are precursors of Wheland σ complexes responsible for aromatic nitration. copy;1998 MAHK "Hayka/Interperiodica".
- Mochalov,Kuz'min,Fedotov,Trofimova,Gazzaeva,Shabarov,Zefirov
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p. 1322 - 1330
(2007/10/03)
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- Photochemical nitration by tetranitromethane. Part XXVII. Adduct formation in the photochemical reaction of 4-methylanisole. Solvent and temperature effects on the regiochemistry of reaction of the radical cation of 4-methylanisole
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The photolysis of the charge-transfer complex of 4-methylanisole and tetranitroroethane in dichloromethane gives four isomcnc nitro-triniromethyl adducts, including the epimeric 1-methoxy-4-methyl-3-nitro-6-trinitromethylcyclohexa-1,4-dienes 3 and 4 and the epimeric 1-methoxy-4-methyl-6-nitro-3-trinitromethylcyclohexa-1,4-dienes 5 and 6, 4-methyl-2-trinitromethylanisole 1, 4-methyl-2-nitroanisole 2, nitrophenols 7 and 9, and 4-methyl-4-nitrocyclohexa-2,5-dienone 8. Similar reaction in acetonitrile also gives these products, with the exception of two of the adducts (3 and 4). The effect of reaction temperature on the yields of the various products indicates that they are formed either by attack of trinrtromethanide ion on the radical cation of 4-methylanisole vicinal to the methoxy group at C2 (1, 3 and 4), or by attack of trinitromethanide ipso to the methoxy group (2, 5, 6 and 8). By conducting the photolysis in dichloromethane with trifluoroacetic acid present, the trinitromethanide pathway is eliminated, and the products formed are derived from reaction between 4-methylanisole and or its radical cation and NO2. The effects of added salts Bu4N+ClO4- (TBAP) or Bu4N+C(NO2)3- (TBAT) to reactions on dichloromethane are seen as the consequences of changes in the polarity of the solvent and not to competition between ion-pair and radical-pair collapse during the reactions. By analogy with adducts 3 and 4, two adducts 16 and 17 derived from similar photolysis reactions of 4-chloroanisole are shown to be the epimeric 4-chloro-1-methoxy-3-nitro-6-trinitromethyleyclohexa-1,4-dienes It and 17 rather than nitrit(or hydroxy)-trinitromethyl adducts. The X-ray crystal Structure of 1-methoxy-4-methyl-r-3-nitro-c-6-trinitromethylcyclohexa-1,4-. diene 3 is reported. Acta Chemica Scandinavica 1996.
- Butts, Craig P.,Eberson, Lennart,Hartshorn, Michael P.,Robinson, Ward T.
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p. 122 - 131
(2007/10/03)
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- Convenient synthesis of phidolopin and analogs and their biological activities
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A convenient synthesis of phidolopin (7), a marine natural product, 8-bromophidolopin (14) and other analogs (13) has been reported. Antibacterial (in vitro), antifungal (in vitro) and antiallergic (% PCA inhibition, in vivo) activities of compounds 7, 13 and 14 are also reported.
- Avasthi,Chandra,Rawat,Bhakuni
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p. 437 - 440
(2007/10/03)
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- Convenient Nitration of Anisole and its Derivatives using an NO-O2 System
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Anisole and its derivatives are regioselectively nitrated by use of nitrogen monoxide-molecular dioxygen mixed gas under mild conditions.
- Mizuno, Kazuhiko,Tamai, Toshiyuki,Hashida, Isao,Otsuji, Yoshio,Inoue, Hiroo
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p. 284 - 285
(2007/10/03)
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- Direct Nitrosation of Aromatic Hydrocarbons and Ethers with the Electrophilic Nitrosonium Cation
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Various polymethylbenzenes and anisoles are selectively nitrosated with the electrophilic nitrosonium salt NO(1+)BF4(1-) in good conversions and yields under mild conditions in which the conventional procedure (based on nitrile neutralization with strong acid) is ineffective.The reactivity patterns in acetonitrile deduced from the various time/conversions in Tables 2 and 3 indicate that aromatic nitrosation is distinctly different from those previously established for electrophilic aromatic nitration.The contrasting behavior of NO(1+) in aromatic nitrosation is ascribed to a rate-limiting deprotonation of the reversibly formed Wheland intermediate, which in the case of aromatic nitration with NO2(1+) occurs with no deuterium kinetic isotope effect.Aromatic nitroso derivatives (unlike the nitro counterpart) are excellent electron donors that are subject to a reversible one-electron oxidation at positive potentials significantly less than that of the parent polymethylbenzene or anisole.As a result, the series of nitrosobenzenes are also much better Broensted bases than the corresponding nitro derivatives, and this marked distinction, therefore, accounts for the large differentiation in the deprotonation rates of their respective conjugate acids (i.e.Wheland intermediates).
- Bosch, Eric,Kochi, Jay K.
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p. 5573 - 5586
(2007/10/02)
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- Substituted or unsubstituted benzhydryl heteroalkyl-substituted aminophenol compounds and pharmaceutical compositions thereof
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Aminophenol derivatives of the following formula (I) STR1 wherein X is hydrogen atom, lower alkyl or a protecting group for phenolic hydroxy, Y is hydrogen atom or lower alkyl, Z is hydrogen atom, lower alkyl, halogen atom or trifluoromethyl, A is hydrogen atom or lower alkyl, t is an integer of 1 to 5, l and m are respectively an integer of 2 to 4, E and W are nitrogen atoms, F is a direct bond or oxygen atom, P and Q are each hydrogen atom, halogen atom, lower alkyl or lower alkoxy, and R8 is hydrogen atom, hydroxy or a hydroxy-protecting group, and their pharmcologically acceptable salts. Since the aminophenol derivatives (I) of the present invention have excellent antioxidative action and antiinflammatory and antiallergic action in mammalian animals including human, they are extremely useful as pharmaceuticals such as an antiinflammatory or an antiallergic.
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- 13C NMR Spectra of Substituted o-Nitroanisoles and n-Butyl o-Nitrophenyl Ethers
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13C NMR analyses of substituted o-nitroanisoles and n-butyl o-nitrophenyl ethers are reported. Key Words: 13C NMR - o-Nitroanisoles - n-Butyl o-nitrophenyl ethers
- Zeegers, Petrus J.,Thompson, Malcolm J.
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p. 497 - 499
(2007/10/02)
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- Oxidative Aromatic Nitration with Charge-Transfer Complexes of Arenes and Nitrosonium Salts
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Brightly colored solutions are obtained immediately upon the exposure of various arenes (ArH) to nitrosonium (NO+) salts.The colors arise from the charge-transfer transitions of 1:1 complexes +> that are reversibly formed as persistent intermediates.However the yellow-red charge-transfer (CT) colors are readily bleached by dioxygen, and the corresponding nitroarenes (ArNO2) can be isolated in excellent yields from acetonitrile solutions.Such an oxidative aromatic nitration of aromatic donors proceeds via the initial autooxidation of the charge-transfer complex.The collapse of the resulting radical ion pair .+,NO2> to the ?-adduct, followed by the loss of proton, affords ArNO2.Direct evidence for electron transfer in the initial step when anthracene is treated with NO+PF6- stems for the isolation of (a) the anthracene ion radical salt .+PF6-> along with nitric oxide in dichloromethane solution and (b) the formation of 9-nitroanthracene (admixed with anthraquinone) in the more polar acetonitrile.The aromatic products (and isomer distribution) from oxidative aromatic nitration are highly reminiscent of those from electrophilic aromatic nitration.The possibility of common reactive intermediates in these two distinctive pathways for aromatic nitration is discussed.
- Kim, E. K.,Kochi, J. K.
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p. 1692 - 1702
(2007/10/02)
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- ipso NITRATION. XXIX. NITRATION OF SUBSTITUTED 4-METHYLANISOLES AND PHENOLS
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Nitration of 2-chloro-4-methylanisole (1a) in acetic anhydride gives (Z)-4-chloro-3-methoxy-6-methyl-6-nitrocyclohexa-2,4-dienyl acetate (2a), 2-chloro-4-methyl-4-nitrocyclohexa-2,5-dienone (3a), and 2-chloro-4-methyl-6-nitroanisole (4a).Similarly 2-bromo-4-methylanisole (1b) gives (Z)-4-bromo-3-methoxy-6-methyl-6-nitrocyclohexa-2,4-dienyl acetate (2b), 2-bromo-4-methyl-4-nitrocyclohexa-2,5-dienone (3b), and 2-bromo-4-methyl-6-nitroanisole (4b), whereas 4-methyl-2-nitro-anisole (1c) gives (Z)-3-methoxy-6-methyl-4,6-dinitrocyclohexa-2,4-dienyl acetate (2c), (Z)-3-methoxy-6-methyl-2,6-dinitrocyclohexa-2,4-dienyl acetate (7), and 4-methyl-2,6-dinitroanisole (4c).Nitration of 3-chloro-4-methylanisole (9a) gives 3-chloro-4-methyl-4-nitrocyclohexa-2,5-dienone (10a), 3-chloro-4-methyl-2-nitro anisole (11a), and 5-chloro-4-methyl-2-nitroanisole (12a), and 4-methyl-3-nitroanisole (9c) gives (Z)-3-methoxy-6-methyl-5,6-dinitrocyclohexa-2,4-dienyl acetate (13), 4-methyl-2,3-dinitroanisole (11c), and 4-methyl-2,5-dinitroanisole (12c).Nitration of 2-chloro-4-methylphenol (14) in chloroform gives 3a and 2-chloro-4-methyl-6-nitrophenol (5a), and 3-chloro-4-methylphenol (15) gives dienone 10a, 3-chloro-4-methyl-2-nitrophenol (16), and 5-chloro-4-methyl-2-nitrophenol (17).
- Fischer, Alfred,Henderson, George N.,RayMahasay, Sumit
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p. 1233 - 1240
(2007/10/02)
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- ipso Nitration. XXVIII. Nitration of 4-substituted toluenes: 1,2 adducts
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Nitration of 4-acetamido, 4-chloro, and 4-methoxy-toluene in acetic anhydride gives in each case a cis 1,2 nitronium acetate adduct in adition to the nitro substitution product(s).Nitration of 4-fluorotoluene gives a pair of diastereomeric 1,4 nitronium acetate adducts and the cis 1,2 adduct.
- Fisher, Alfred,Fyles, Deborah L.,Henderson, George, N.,Mahasay, Sumit Ray
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p. 1764 - 1770
(2007/10/02)
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- Electrophilic Aromatic Substitution. Part 28. The Mechanism of Nitration of Some 4-Substituted Anisoles and Phenols, and of Rearrangement of the Intermediate 4-Nitro-4-substituted-cyclohexa-2,5-dienones
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The kinetics of nitration in sulphuric acid of 2-chloro-4-methyl-, 4-chloro-, 2,4-dichloro-, and 4-fluoroanisole and of the corresponding phenols have been determined.The reaction products from the anisoles and from 2-chloro-4-methyl- and 4-fluoro-phenol have been determined.Results for 4-methylanisole supplementary to earlier ones are also reported.Generally the anisoles give the 2-nitro-derivatives and the 2-nitrophenols, and from 2-chloro-4-methylanisole, 2-chloro-4-methyl-4-nitrocyclohexa-2,5-dienone was formed as an intermediate.The decomposition of this dienone in sulphuric acid, like those of others, changes from a non-acid-catalysed to an acid-catalysed form with increasing acidity.The first form is regarded as a decomposition into an aryloxyl radical and nitrogen dioxide which can recombine to give the 2-nitrophenol.The formation of a small amount of 2-(4-fluorophenoxy)-4-fluorophenol in the nitration of 4-fluorophenol is seen as support for this view.The acid-catalysed form is regarded as the decomposition of the protonated dienone into a phenol-nitronium ion encounter-pair which can give the nitrophenol.A consequence of the mechanism is that if the phenol were nitrated at less than the encounter rate, the phenol itself would in appropriate conditions be a product of the ipso-nitration of the original anisole. 4-Methyl-, 2-chloro-4-methyl-, and 4-chloro-phenol have been so identified.Quantitative analysis of the results allows evaluation of the partitioning of dienone decomposition between the two modes.The mechanism accounts for the formation from 2,4-dichloro-anisole of both 2,4-dichloro-6- and 2,4-dichloro-5-nitroanisole, but only 2,4-dichloro-6-nitrophenol.
- Bloomfield, Colin,Manglik, Ajay K.,Moodie, Roy B.,Schofield, Kenneth,Tobin, Geoffrey D.
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- Nitration in Aqueous Nitric Acid: the Rate Profile and the Limiting Reaction Rates
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Rate coefficients for the nitration of a series of quaternary ammonium ions have been used to establish a rate profile for reaction in 63.7percent-100percent nitric acid at 25 deg C and to estimate the concentration of nitronium ions in the aqueous media.The kinetics of nitration of a series of reactive aromatic aromatic compounds (mainly phenolic ethers) in aqueous nitric acid have been analysed in terms of a first-order rate coefficient and the zeroth-order rate of formation of the nitronium ion.The first-order rate coefficients approach a limiting value as the reactivity of the aromatic substrate is increased and this value is as expected for the rate-limiting formation of an encounter pair (ArH*NO2+).The lifetime of nitronium ions in 60.4percent nitric acid (t1/2 ca. 5 x 10-8 s) has been calculated from the zeroth-order rate at 25 deg C and used to show that the formation of the encounter pair (ArH*NO2+) occurs by the diffusion together of the components, not by pre-association.The studies on the more reactive aromatic compounds were carried out in the presence of hydrazine since this was shown to prevent the nitrous-acid catalysed reactions previously observed.
- Draper, Mark R.,Ridd, John H. A.
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