- Kinetics and mechanism of the mineral acid catalysed reactions of hydroxamic acids
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There is currently a great deal of interest in the chemistry of hydroxamic acids. In recent years we have been studying the synthesis, structure and nucleophilicities of hydroxamic acids. This paper reports a kinetic study of reactivity of some hydroxamic acids RC(O)·N(OH)R′; R = C 6H5·CH=CH, R′ = 4-CH3· C6H4 [p-tolylcinnamo hydroxamic acid]; R = C 6H5, R′ 4-CH3·C6H 4 [p-tolylbenzo hydroxamic acid]; R = C6H5, R′ = 2-CH3·C6H4 [o-tolylbenzo hydroxamic acid] in aqueous mineral acids (HCl, HClO4 and H 2SO4). The rate data of hydrolysis reaction revealed that the reactivity/stability sequence of the compounds is generally p-TBHA > o-TBHA > p-TCHA. An excess acidity analysis reveals that the reaction proceeds by nucleophilic attack of water molecule on the protonated substrate.
- Ghosh, Kallol K.,Vaidya, Jyoti,Sinha, Daliya
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Read Online
- Promoting effect of ethanol on the synthesis of N-(2-methylphenyl) hydroxylamine from o-nitrotoluene in Zn/H2O/CO2 system
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The promoting effect of ethanol on the synthesis of N-(2-methylphenyl) hydroxylamine from o-nitrotoluene in Zn/H2O/CO2 system was observed. By adding appropriate amount of ethanol, the selectivity of N-(2-methylphenyl)hydroxylamine increased from 71% to 90% when the reduction was carried out at 25 °C under normal pressure of CO2.
- Liu, Shi Juan,Wang, Yan Hua,Hao, Yuan Ping,Jiang, Jing Yang
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Read Online
- Bactericidal composition containing isotianil and osthole
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The invention discloses a bactericidal composition containing isotianil and osthole, and belongs to the technical field of pesticide preparation. The bactericidal composition comprises, by weight, 1-50% of isotianil, 0.1-10% of osthole, 5-10% of a bacteri
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Paragraph 0019; 0029; 0034
(2021/08/11)
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- Tandem selective reduction of nitroarenes catalyzed by palladium nanoclusters
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We report a catalytic tandem reduction of nitroarenes by sodium borohydride (NaBH4) in aqueous solution under ambient conditions, which can selectively produce five categories of nitrogen-containing compounds: anilines, N-aryl hydroxylamines, azoxy-, azo- and hydrazo-compounds. The catalyst is in situ-generated ultrasmall palladium nanoclusters (Pd NCs, diameter of 1.3 ± 0.3 nm) from the reduction of Pd(OAc)2 by NaBH4. These highly active Pd NCs are stabilized by surface-coordinated nitroarenes, which inhibit the further growth and aggregation of Pd NCs. By controlling the concentration of Pd(OAc)2 (0.1-0.5 mol% of nitroarene) and NaBH4, the water/ethanol solvent ratio and the tandem reaction sequence, each of the five categories of N-containing compounds can be obtained with excellent yields (up to 98%) in less than 30 min at room temperature. This tunable catalytic tandem reaction works efficiently with a broad range of nitroarene substrates and offers a green and sustainable method for the rapid and large-scale production of valuable N-containing chemicals.
- Yan, Ziqiang,Xie, Xiaoyu,Song, Qun,Ma, Fulei,Sui, Xinyu,Huo, Ziyu,Ma, Mingming
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supporting information
p. 1301 - 1307
(2020/03/11)
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- Synthesis of sulpha drug based hydroxytriazene derivatives: Anti-diabetic, antioxidant, anti-inflammatory activity and their molecular docking studies
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Herein, we report synthesis, characterization, anti-diabetic, anti-inflammatory and anti-oxidant activities of hydroxytriazenes derived from sulpha drugs, namely sulphanilamide, sulphadiazine, sulphapyridine and sulphamethazine. Before biological screening of the compounds, theoretical prediction using PASS was done which indicates probable activities ranging from Pa (probable activity) values 65–98% for anti-inflammatory activity. As per the predication, experimental validation of some of the predicted activities particularly anti-diabetic, anti-inflammatory and anti-oxidant was done. Anti-diabetic activities have been screened using two methods namely α-amylase and α-glucosidase inhibition method and IC50 values were ranging from 66 to 260 and 148 to 401 μg/mL, while for standard drug acarbose the values were 12 μg/mL and 70 μg/mL, respectively. Docking studies have also been done for antidiabetic target pancreatic alpha amylase. The molecular docking studies in α-amylase enzyme reveal that the middle phenyl ring of all the compounds mainly occupies in the small hydrophobic pocket formed by the Ala198, Trp58, Leu162, Leu165 and Ile235 residues and sulphonamide moiety establish H-bond interaction by two water molecules. Further, anti-inflammatory activity has been evaluated using carrageenan induced paw-edema method and results indicate excellent anti-inflammatory activity by hydroxytriazenes (71 to 97%) and standard drug diclofenac 94% after 4 h of treatment. Moreover, antioxidant effect of the compounds was tested using DPPH and ABTS methods. All the compounds displayed good results (24–488 μg/mL) against ABTS radical and many compounds are more active than ascorbic acid (69 μg/mL) while all other compounds showed moderate activity against DPPH radical (292–774 μg/mL) and ascorbic acid (29 μg/mL). Thus, the studies reveal potential of sulfa drug based hydroxytriazenes as candidates for antidiabetic, anti-inflammatory and antioxidant activities which have been experimentally validated.
- Baroliya, Prabhat K.,Chauhan, R. S.,Dayma, Varsha,Dwivedi, Aparna,Goswami, A. K.,Sharma, Poonam,Tripathi, I. P.,Vanangamudi, Murugesan
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- Synthesis of meta-substituted anilines via copper-catalyzed [1,3]-methoxy rearrangement
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meta-Substituted anilines were efficiently synthesized via copper-catalyzed [1,3]-methoxy rearrangement of N-methoxyanilines followed by Michael addition of nucleophiles to the in situ generated ortho-quinol imine. The present reaction exhibits excellent
- Ishida, Yasuhiro,Nakamura, Itaru,Tashiro, Hiroki,Terada, Masahiro
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supporting information
p. 3794 - 3798
(2020/06/08)
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- A general and scalable synthesis of polysubstituted indoles
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A consecutive 2-step synthesis of N-unprotected polysubstituted indoles bearing an electron-withdrawing group at the C-3 position from readily available nitroarenes is reported. The protocol is based on the [3,3]-sigmatropic rearrangement of N-oxyenamines generated by the DABCO-catalyzed reaction of N-arylhydroxylamines and conjugated terminal alkynes, and delivers indoles endowed with a wide array of substitution patterns and topologies.
- Diana-Rivero, Raquel,García-Tellado, Fernando,Tejedor, David
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- Highly Selective and Solvent-Dependent Reduction of Nitrobenzene to N-Phenylhydroxylamine, Azoxybenzene, and Aniline Catalyzed by Phosphino-Modified Polymer Immobilized Ionic Liquid-Stabilized AuNPs
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Gold nanoparticles stabilized by phosphine-decorated polymer immobilized ionic liquids (AuNP@PPh2-PIILP) is an extremely efficient multiproduct selective catalyst for the sodium borohydride-mediated reduction of nitrobenzene giving N-phenylhydroxylamine, azoxybenzene, or aniline as the sole product under mild conditions and a very low catalyst loading. The use of a single nanoparticle-based catalyst for the partial and complete reduction of nitroarenes to afford three different products with exceptionally high selectivities is unprecedented. Under optimum conditions, thermodynamically unfavorable N-phenylhydroxylamine can be obtained as the sole product in near quantitative yield in water, whereas a change in reaction solvent to ethanol results in a dramatic switch in selectivity to afford azoxybenzene. The key to obtaining such a high selectivity for N-phenylhydroxylamine is the use of a nitrogen atmosphere at room temperature as reactions conducted under an inert atmosphere occur via the direct pathway and are essentially irreversible, while reactions in air afford significant amounts of azoxy-based products by virtue of competing condensation due to reversible formation of N-phenylhydroxylamine. Ultimately, aniline can also be obtained quantitatively and selectively by adjusting the reaction temperature and time accordingly. Introduction of PEG onto the polyionic liquid resulted in a dramatic improvement in catalyst efficiency such that N-phenylhydroxylamine could be obtained with a turnover number (TON) of 100000 (turnover frequency (TOF) of 73000 h-1, with >99% selectivity), azoxybenzene with a TON of 55000 (TOF of 37000 h-1 with 100% selectivity), and aniline with a TON of 500000 (TOF of 62500 h-1, with 100% selectivity). As the combination of ionic liquid and phosphine is required to achieve high activity and selectivity, further studies are currently underway to explore whether interfacial electronic effects influence adsorption and thereby selectivity and whether channeling of the substrate by the electrostatic potential around the AuNPs is responsible for the high activity. This is the first report of a AuNP-based system that can selectively reduce nitroarenes to either of two synthetically important intermediates as well as aniline and, in this regard, is an exciting discovery that will form the basis to develop a continuous flow process enabling facile scale-up.
- Doherty, Simon,Knight, Julian G.,Backhouse, Tom,Summers, Ryan J.,Abood, Einas,Simpson, William,Paget, William,Bourne, Richard A.,Chamberlain, Thomas W.,Stones, Rebecca,Lovelock, Kevin R. J.,Seymour, Jake M.,Isaacs, Mark A.,Hardacre, Christopher,Daly, Helen,Rees, Nicholas H.
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p. 4777 - 4791
(2019/05/17)
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- Regioselective installation of fluorosulfate (-OSO2F) functionality into aromatic C(sp2)-H bonds for the construction of: Para-amino-arylfluorosulfates
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The construction of para-amino-arylfluorosulfates was achieved through installation of fluorosulfate (-OSO2F) functionality into aromatic C(sp2)-H bonds by the reaction of N-arylhydroxylamine with sulfuryl fluoride (SO2Fs
- Fang, Wan-Yin,Zha, Gao-Feng,Zhao, Chuang,Qin, Hua-Li
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supporting information
p. 6273 - 6276
(2019/06/07)
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- A O-methyl phenyl hydroxylamine production method (by machine translation)
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The invention discloses a method for the production of ortho-methyl phenyl hydroxylamine method, steps are as follows: the O-nitro-toluene, solvent and catalyst into reactor, stirring, O-nitro-toluene, solvent and catalyst weight ratio of 35 - 45:80 - 150
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Paragraph 0029; 0030; 0031; 0032; 0033; 0034
(2017/08/25)
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- Hydroxamic Acids as Chemoselective (ortho-Amino)arylation Reagents via Sigmatropic Rearrangement
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The use of readily available hydroxamic acids as reagents for the chemoselective (ortho-amino)arylation of amides is described. This reaction proceeds under metal-free, mild conditions, displays a very broad scope, and constitutes a direct approach for the metal-free attachment of aniline residues to carbonyl derivatives.
- Shaaban, Saad,Tona, Veronica,Peng, Bo,Maulide, Nuno
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supporting information
p. 10938 - 10941
(2017/08/30)
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- Preparation method for N-2-methylphenylhydroxyamine
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The invention discloses a preparation method for N-2-methylphenylhydroxyamine, and belongs to the technical field of compound synthesis. According to the preparation method, the N-2-methylphenylhydroxyamine is synthesized by taking ortho-nitrotoluene as a
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Paragraph 0010; 0011
(2017/02/09)
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- Synthesis technology of pyraclostrobin
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The invention provides a synthesis technology of pyraclostrobin. The method comprises the following steps that1, ortho-nitrotoluene and NH4Cl are subjected to a reduction reaction under the catalytic action of zinc powder and alloy micro-nano powder; 2, hydroxylamine is subjected to an acylation reaction; 3, a methylation reaction is performed; 4, a bromination reaction is performed to obtain N-methoxy-N-2-methyl bromide methyl phenyl carbamate; 5, DMF is used as a solvent for dissolving the N-methoxy-N-2-methyl bromide methyl phenyl carbamate to prepare a solution for use, 1-(4-chlorphenyl)-pyrazol alcohol, K2CO3 and acetone are placed into a reactor together, heating and reflux are performed, the N-methoxy-N-2-methyl bromide methyl phenyl carbamate solution is added into the reactor slowly, and after the reflux reaction is ended, pyraclostrobin is obtained. Compared with the prior art, the preparation method is simple, raw materials are low in cost and easy to obtain, the reaction conditions are mild, and the obtained target product is high in purity and yield.
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Paragraph 0027; 0029
(2017/01/02)
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- An asymmetric pericyclic cascade approach to 3-alkyl-3-aryloxindoles: Generality, applications and mechanistic investigations
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The reaction of L-serine derived N-arylnitrones with alkylarylketenes generates asymmetric 3-alkyl-3-aryloxindoles in good to excellent yields (up to 93%) and excellent enantioselectivity (up to 98% ee) via a pericyclic cascade process. The optimization, scope and applications of this transformation are reported, alongside further synthetic and computational investigations. The preparation of the enantiomer of a Roche anti-cancer agent (RO4999200) 1 (96% ee) in three steps demonstrates the potential utility of this methodology.
- Richmond, Edward,Ling, Kenneth B.,Duguet, Nicolas,Manton, Lois B.,elebi-?lcüm, Nihan,Lam, Yu-Hong,Alsancak, Sezen,Slawin, Alexandra M. Z.,Houk,Smith, Andrew D.
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supporting information
p. 1807 - 1817
(2015/02/19)
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- Asymmetric pericyclic cascade approach to spirocyclic oxindoles
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The reaction of chiral N-arylnitrones with carbocyclic alkylarylketenes generates spirocyclic oxindoles in good yields and with excellent levels of enantioselectivity (90-99% ee) via a pericyclic cascade process.
- Richmond, Edward,Duguet, Nicolas,Slawin, Alexandra M. Z.,Lebl, Tomas,Smith, Andrew D.
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supporting information; experimental part
p. 2762 - 2765
(2012/07/14)
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- Photocatalytic cleavage of hydroxytriazenes: A solidstate synthesis of azo-dyes under sunlight irradiation
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Sunlight-induced decomposition of hydroxytriazenes, and green photochemical synthesis of azo-dyes is described. Three substituted hydroxytriazenes, viz: 3-hydroxy-3-(2-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (o-CFHT), 3-hydroxy-3-(3-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (m-CFHT), and 3-hydroxy-3-(4-methylphenyl)-1-(3-chloro-4-fluorophenyl)triazene (p-CFHT) were co-crystallized with β-naphthol in equimolar ratio and exposed to sunlight for 9-10h. The reaction resulted in formation of azo-dyes which were identified by comparison with the products obtained by the conventional method (standard azodye), by use of HPLC. A probable mechanism has been suggested. This is first ecofriendly synthesis of azo-dyes using hydroxytriazenes. Springer Science+Business Media B.V. 2012.
- Baroliya, Prabhat Kumar,Mehta, Anita,Dashora, Rekha,Chauhan,Goswami
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p. 2149 - 2153
(2013/02/25)
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- Synthesis and biological activity of novel phenyltriazolinone derivatives
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Phenyltriazolinones are one of the most important classes of herbicides targeting the protoporphyrinogen oxidase enzyme. A series of triazolinone derivatives containing a strobilurin pharmacophore were designed and synthesized with the aim of discovering new phenyltriazolinone analogues with high activity. The herbicidal activity of the synthesized compounds was assayed and some of the test compounds displayed moderate herbicidal activity at 150 g ai/ha.
- Wu, Qiongyou,Wang, Guodong,Huang, Shaowei,Lin, Long,Yang, Guangfu
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scheme or table
p. 9024 - 9034
(2011/03/20)
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- Selective synthesis of N-aryl hydroxylamines by the hydrogenation of nitroaromatics using supported platinum catalysts
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Various substituted nitroaromatics were successfully hydrogenated to the corresponding N-aryl hydroxylamines in excellent yields (up to 99%) using supported platinum catalysts such as Pt/SiO2 under a hydrogen atmosphere (1 bar) at room temperature. The key to the fast and highly selective formation of hydroxylamines is the addition of small amounts of amines such as triethylamine and dimethyl sulfoxide; amines promote the conversion of nitroaromatics, while dimethyl sulfoxide inhibits further hydrogenation of hydroxylamines to anilines. The promotive effect depends on which type of amine and primary amine was most effective. The hydrogenation efficiently proceeded in common organic solvents, including isopropanol, diethyl ether, and acetone. This methodology should extend the application range of conventional solid catalysts to fine chemicals synthesis. The Royal Society of Chemistry 2009.
- Takenaka, Yasumasa,Kiyosu, Takahiro,Choi, Jun-Chul,Sakakura, Toshiyasu,Yasuda, Hiroyuki
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supporting information; experimental part
p. 1385 - 1390
(2010/05/18)
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- Effect of substituents on the rate of oxidation of anilines with peroxomonosulfate monoanion (HOOSO3-) in aqueous acetonitrile: A mechanistic study
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Mechanistic studies on the oxidation of 18 meta-, para-, and ortho-substituted anilines (Ans) by HOOSO3- in aqueous acetonitrile medium have been performed. The reaction can be characterized by the experimental rate equation, -d[HSO5-]/dt = k[An][HSO5-] The addition of p-toluenesulfonic acid (TsOH) retards the reaction. The increase in the reactivity of anilines as the medium is made more aqueous is interpreted. The reaction is enhanced by electron-donating groups on the amine in the series consistent with the rate-limiting nucleophilic attack of the amine on the persulfate oxygen. The proposed mechanism involves the conversion of phenylhydroxylamine to nitrosobenzene in a fast step. The ESR study reveals the absence of free radicals in the reaction. Various attempts have been made to analyze the experimental rate constants in terms of LFER plots. Improved correlations are obtained with σ- values and the σ- form of the Yukawa-Tsuno equation.
- Meenakshisundaram, Subbiah,Selvaraju,Made Gowda,Rangappa, Kanchugarakoppal S.
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p. 649 - 657
(2007/10/03)
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- Mechanism and reactivity in perborate oxidation of anilines in acetic acid
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Perborate but not percarbonate in acetic acid generates peracetic acid on standing and the peracetic acid oxidation of anilines is fast. The oxidation with a fresh solution of perborate in acetic acid is smooth and second order but the specific oxidation rate increases with increasing [perborate]0 or [boric acid]. Perborate on dissolution affords hydrogen peroxide and a borate; the latter assists the former in the oxidation. The oxidation rates of anilines under identical conditions do not conform to any of the linear free energy relationships but the reaction rates of molecular anilines do. Perborate oxidation proceeds via two reaction paths but the overall oxidation rates of molecular anilines conform to structure reactivity relationships; the transition states do not differ significantly. Analysis of the oxidation rates of perborate and percarbonate reveals that while perborate oxidation is faster than percarbonate it is at least as selective as the latter.
- Karunakaran, Chockalingam,Kamalam, Ramasamy
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p. 2011 - 2018
(2007/10/03)
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- Method for producing (hetero)aromatic hydroxylamines
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The invention relates to a method for producing N-acylated (hetero)aromatic hydroxylamine derivatives of formula (I), wherein the substituents, the ring atom and the index have the meanings give in the Description, by hydrogenating a (hetero)aromatic nitr
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- Dihydropyridazinones and pyridazinones and their use as fungicides and insecticides
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Compounds with fungicidal and insecticidal properties having formula I wherein W is n is 0 or 1; Y is O, S, NR1, or R6; the ring bond containing R4 and R5 is a single or double bond; X is independently selected from hydrogen, halo, (C1-C4)alkyl, (C1-C4)al
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- Dihydropyridazinones and pyridazinones and their use as fungicides and insecticides
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Compounds with fungicidal and insecticidal properties having formula I wherein W is n is 0 or 1; Y is O, S, NR1, or R6; the ring bond containing R4and R5is a single or double bond; X is independently selected fr
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- Synthesis, characterization, and conformational analysis of DNA adducts from methylated anilines present in tobacco smoke
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The ability of a series of aromatic amines present in tobacco smoke (2-, 3-, and 4-methylaniline, 2,3- and 2,4-dimethylaniline) to bind to DNA has been investigated by reacting N-(acyloxy)arylamines with dG, dG nucleotides, and DNA. The predominant products from reactions with dG and the nucleotides were characterized as N-(deoxyguanosin-8-yl)arylamines by spectroscopic and HPLC methods. HPLC and spectroscopic analyses of the modified DNA indicated the same adducts. Analyses of the 1H and 13C NMR spectra suggested that the adducts containing a methyl substituent ortho to the arylamine nitrogen had a higher percentage of syn conformers. This observation was supported by theoretical simulation studies that indicated substantial percentages of low energy syn conformers, increasing with the substitution pattern in the order para meta ortho ortho,para ortho,meta. The results demonstrate that, although single-ring arylamines are considered weak carcinogens, their electrophilic N-acetoxy derivatives, which are plausible metabolic intermediates, react with DNA to yield covalent adducts structurally identical to those derived from carcinogenic polyarylamines, such as 2- aminofluorene and 4-aminobiphenyl. Furthermore, the conformational perturbation induced in DNA by the formation of the monoarylamine-DNA adducts, especially those with an ortho substituent, may contribute to the biological activities of these compounds.
- Marques, M. Matilde,Mourato, Luisa L. G.,Santos, M. Amelia,Beland, Frederick A.
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- Process for the preparation of a hydroxylamine
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The present invention relates to a process for the preparation of organic hydroxylamines as a result of the corresponding nitroderivative being hydrogenated in the presence of an inert solvent, a platinum catalyst, a nitrogen-containing base (in an amount of less than 10% by weight calculated on the amount of nitro derivative) and a tri- or pentavalent organic phosphorus compound. It has been found that if only use is made of the nitrogen-containing base or the phosphorus compound the yields of isolated hydroxyl amine are significantly reduced in comparison with those obtained with the present process.
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- A facile synthesis of N-aryl-N-hydroxyformamides from N-arylhydroxylamines
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Several N-arylhydroxylamines (2) have been formylated for the first time with acetic formic anhydride to yield N-hydroxyformanilides (3) in better yields than hitherto reported.
- Ayyangar, N. R.,Brahme, K. C.,Shingare, M. S.,Srinivasan, K. V.
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p. 961 - 963
(2007/10/02)
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- 3-(o-Carboxyphenyl)-1-o-tolyltriazene-N-oxide: A New Triazene Derivative for the Spectrophotometric Determination of Titanium(IV)
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3-(o-Carboxyphenyl)-1-o-tolyltriazene-N-oxide is proposed as a new reagent for the spectrophotometric determination of Ti(IV).The reagent forms 1:2 yellow coloured complex with Ti(IV) between pH 1 and 3.5.The complex exhibits maximum absorbance at 410 nm
- Banerjee, N. M.,Roy, B. C.,Lahiri, S.
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- Hetero-Cope Rearrangements, III. - Vinylindoles via Hetero-Cope Rearrangement
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The reaction of N-phenylnitrones 1 with allenes 2 which are substituted with electron acceptor groups gives various products via addition and sigmatropic rearrangement depending on the specific acceptor group.In this manner one obtains 2-substituted indoles 8a, 8b, and 10 from propadienyl trichloromethyl sulfoxide.Using phenyl propadienyl sulfone a derivative 4a of tetrahydro-1-benzazepin-4-one is obtained.Reactions with allenecarbonitril proceed via several steps and yield 2-vinylindoles of type 6.Intermediate products could not be isolated.
- Blechert, Siegfried
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p. 673 - 682
(2007/10/02)
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- Direct Gravimetric Determination of Copper(II) with a New Reagent, 3-(o-Carboxyphenyl)-1-o-tolyl-triazene-N-oxide
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3-(o-Carboxyphenyl)-1-o-tolyl-triazene-N-oxide has been used for the gravimetric determination of 2-30 mg Cu(II).The green complex, Cu(C14O3N3H11) is precipitated in the pH range 3-9 adjusted with aqueous caustic soda and hydrochloric acid, and is weighed
- Banerjee, N.M.,Ray, B.C.,Lahiri, S.
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p. 617 - 618
(2007/10/02)
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- Investigations on the Kinetics and Mechanism of Polarigraphic Reduction of o-, m- and p-Nitrotoluenes and o-, m- and p-Nitrophenols in the presence of Ionic and non-Ionic Surfactants
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Polarographic behaviour of o-, m- and p-nitrotoluenes (4percent, V/V, ethanolic solution) in the presence of ionic and non-ionic surfactants at their concentrations just sufficient to suppress the maxima has been studied as a function of pH of Britton-Robinson (BR) buffer.The present study aims at investigating the kinetics and mechanism of the reduction of these compounds at the d.m.e. which has been found to be diffusion-controlled and irreversible.The potential-dependent rate constant, kf,h has been calculated by Koutecky's method at different pH values of BR buffer and the values of kinetic parameters (αna and kf,h0) have been calculated from log kf,h Vs Ed.e. plots which are linear thereby suggesting that only a single rate-determining step is involved in the reduction of each depolarizer.Based on the values of kinetic parameter, αna and the variation of E1/2 with pH, the stoichiometry of the rate-determinig step, in each case, has been established thereby leading to the postulation of a mechanism for the polarographic reduction of each depolarizer.
- Singh, M.,Chandra, K.
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p. 977 - 989
(2007/10/02)
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- Kinetics and Mechanism of Polarographic Reduction of Aromatic Nitro Compounds in Aqueous Alcoholic Medium
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Polarographic reduction of nitrobenzene, ortho-, meta- and para- chloronitrobenzenes, nitrotoluenes, nitrophenols and nitrobenzaldehydes has been studied in 25percent (v/v) aqueous ethanolic solutions, using Britton-Robinson (BR) buffer of varying pH values.KCl (0.1 M) has been used as the supporting electrolyte and Triton X-100 (0.001percent) as the maxima suppressor.The potential-dependent rate constant, kf,h has been calculated by Koutecky's method at different pH values and the values of kinetic parameters (αna and kf,h) have been calculated from logkf,h versus Ed.e. plots which are linear thereby suggesting that only a single rate-determining step is involved in the electrode process of each depolarizer.Based on the values of kinetic parameter, αna and the variation of E1/2 with pH, the stoichiometry of the rate-determining step has been established.This has led to the postulation of a tentative mechanism for the polarographic reduction of each depolarizer.Besides, the effect of the nature and position of various substituents, viz.Cl, CH3, OH and CHO on the kinetics of the polarographic reduction of NO2 group has been investigated.
- Ratan, Ram,Rani, Rama,Singh, Mukhtar
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p. 664 - 670
(2007/10/02)
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- Novel Reactions: Part I - Facile Synthesis of Substituted ortho-Chloranilines from Nitrobenzene Derivatives
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N-Substituted benzo and acetohydroxamic acids (5), prepared from N-arylhydroxylamines and benzoyl or acetyl chloride, react readily with thionyl chloride at low temperature to give ortho-chloroanilide derivatives (6) in good yield.The latter (6) on hydrolysis give ortho-chloroanilines (10).Since the N-arylhydroxylamines are obtained from nitroarenes by partial reduction, the overall reaction amounts to the preparation of 10 from nitroarenes.
- Ayyangar, N. R.,Kalkote, U. R.,Nikrad, P. V.
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p. 872 - 877
(2007/10/02)
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- Polarographic Studies on the Effect of Some Ionic and Non-ionic Surfactants on Kinetics of Irreversible Electrode Reactions of o-, m- and p-Nitrotoluenes
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Polarographic reduction of o-, m- and p-nitrotoluenes (in 4percent ethanolic solution) has been studied at 25 +/- 0.1 deg C in BR buffer of pH 7 in the presence of increasing amounts of some ionic and non-ionic surfactants.The reduction of all the three depolarizers is diffusion-controlled and irreversible.The kinetic parameters (αna and kfh0) of the electrode reactions have been calculated by Koutecky's method.The irreversible electrode reactions of o-, m- and p-nitrotoluenes tend to become increasingly more irreversible with increasing concentration of ionic and non-ionic surfactants.This is borne out by a decrease in kinetic parameters and id, and a negative shift in E1/2 with increasing concentrations of the surfactants.A tentative mechanism of the polarographic reduction of nitrotoluenes at pH 7 has also been proposed.This stipulates the protonation of the depolarizers in the steps preceding as well as succeeding the electrode reaction.The ease of reduction of three isomers at d.m.e. is in the order: meta > ortho > para.
- Chandra, Kailash,Shakya, Sarnam Singh,Singh, Mukhtar
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p. 254 - 258
(2007/10/02)
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- Polarographic Behaviour of Some ortho-Substituted Nitrobenzenes: Evaluation of Polarographic ortho-Shift
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The polarographic characteristics of thirteen ortho-substituted nitrobenzenes have been studied at 35 deg C +/- 0.1 deg C in a well-buffered medium of 50percent (v/v) aqueous ethanol, having pH 5.8.Reduction process for all the compounds is found to be ir
- Ganapathy, K,Ramanujam, M
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p. 1087 - 1089
(2007/10/02)
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- Kinetics and Mechanism of the Bamberger Rearrangement. Part 4. Rearrangement of Sterically Hindered Phenylhydroxylamines to 4-Aminophenols in Aqueous Sulphuric Acid Solution
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The rates of the Bamberger rearrangement of sterically hindered phenylhydroxylamines have been determined in aqueous sulphuric acid solution and the substituent effects (in particular, the steric effects) are discussed.The rate constants for phenylhydroxylamines with 2-substituents (Me, Cl, I) satisfied the Taft equation: log krel = ρ*?* - δES with ρ*-1.93 and δ-1.16.The result shows that steric hindrance of the substituents, in addition to the electron-donating effect, has an accelerating effect on the rates of the Bamberger rearrangement.The rate constants for 3-substituted 2-methylphenylhydroxylamines were generally greater than those for 5-substituted 2-methylphenylhydroxylamines.The difference was attributed to the 'buttressing effect' of neighbouring 3-substituents.This is the first example of steric acceleration of the Bamberger rearrangement.
- Sone, Takaaki,Hamamoto, Kazuhiro,Seiji, Yoshiyuki,Shinkai, Seiji,Manabe, Osamu
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p. 1596 - 1598
(2007/10/02)
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- Coulometric determination of several water-insoluble aromatic nitro compounds with electrogenerated chromium(II)
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The electrochemical reduction of a series of water-insoluble aromatic nitro compounds with coulometrically generated chromium(II) has been investigated.Samples ranging from 0.2 to 0.5 μmol could be determined for several substances with a precision and accuracy of about 1percent.The number of electrons involved in the reductions corresponded in most cases to the formation of hydroxylamines or amines, but in some instances to dihydrazo products.
- Al-Daher, I. M.,Kratochvil, B.
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p. 3346 - 3349
(2007/10/02)
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