Rate constant for the reaction Br + O3 ? BrO + O2 from 248 to 418 K: Kinetics and mechanism

1988 ◽  
Vol 20 (2) ◽  
pp. 131-144 ◽  
Author(s):  
Darin W. Toohey ◽  
Wm. H. Brune ◽  
J. G. Anderson
Keyword(s):  
Rate Constant ◽  
Kinetics And Mechanism

scholarly journals Synthesis, kinetics and mechanism of nucleophilic substitution in octahedral (cat)2Sn(py)2

2005 ◽  
Vol 70 (12) ◽  
pp. 1389-1393 ◽  
Author(s):  
K.S. Siddiqi ◽  
Shahab Nami
Keyword(s):  
Nucleophilic Substitution ◽  
Rate Constant ◽  
Substitution Reaction ◽  
Molar Conductance ◽  
Chloride Ions ◽  
Kinetics And Mechanism ◽  
Nucleophilic Substitution Reaction ◽  
Nucleophilic Reagents

Dicatecholatodipyridinetin(IV) in nitrobenzene showed an increase in molar conductance with time, suggesting solvation of the complex. In the presence of nucleophilic reagents, such as SOCl2, C6H5COCl and CH3COCl, the conductance increased sharply owing to the substitution of pyridine by chloride ions. The data for the rate constant of solvation (k s) and for nucleophilic substitution (k 1 and k 2) have been calculated and it was found that the solvation is a slower process compared to the substitution by chloride ions, i.e., k1, k 2 > k s. The nucleophilic substitution reaction follows the SN1 mechanism.

Photochemical reaction kinetics and mechanism of bisphenol A with K2S2O8 in aqueous solution: a laser flash photolysis study

2021 ◽  
Vol 99 (1) ◽  
pp. 43-50
Author(s):  
Yongchao Zhu ◽  
Mengyu Zhu ◽  
Jingjing Xie ◽  
Yadong Hu ◽  
Ying Liu ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Rate Constant ◽  
Photochemical Reaction ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Phenoxyl Radical ◽  
Laser Flash ◽  
Kinetics And Mechanism ◽  
Main Reaction ◽  
Specific Rate

The photochemical reaction kinetics and mechanism of bisphenol A (BPA) with potassium persulfate (K2S2O8) were investigated by using 266 nm laser flash photolysis and gas chromatography mass spectrum (GC-MS) technique. Sulfate radical (SO4•−), generated upon K2S2O8 photolysis, reacted with BPA with the overall rate constant of (1.61 ± 0.15) × 109 L mol−1 s−1, and two main reaction mechanisms were involved. One was addition channel to generate BPA–SO4•− adduct with a specific second-order rate constant of (1.09 ± 0.15) × 109 L mol−1 s−1. Molecular oxygen was involved in the decay of the BPA–SO4•− adduct with a rate constant of (1.28 ± 0.14) × 108 L mol−1 s−1. Another channel was the formation of BPA’s phenoxyl radical, likely derived from a deprotonation of the cation radical (BPA•+) generated from single electron transfer reactions. The specific rate constant of BPA’s phenoxyl radical formation was determined to be (6.16 ± 0.08) × 108 L mol−1 s−1. The overall rate constant was in line with the sum of aforementioned two specific rate constants for two main reaction channels. By comparing these rate constants, it was indicated that SO4•− addition channel accounted for ∼65% (1.09/1.61) to the overall reaction, and phenoxyl radical formation accounted for only ∼35% (0.62/1.61). The transformation products of BPA were identified by using GC-MS including 4-isopropylphenol, 4-isopropenylphenol, and 2,4-di-tert-butylphenol, and the reaction mechanism was proposed. These results may provide microscopic kinetics and mechanism information on BPA degradation using SO4•−-based advanced oxidation processes.

Solvent effects on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)-triazene II. Reactions in aprotic solvents

1990 ◽  
Vol 55 (1) ◽  
pp. 156-164 ◽  
Author(s):  
Oldřich Pytela ◽  
Taťjana Nevěčná ◽  
Miroslav Ludwig
Keyword(s):  
Rate Constant ◽  
Acid Catalyst ◽  
Kinetics And Mechanism ◽  
Aprotic Solvents ◽  
Catalytic Rate Constant ◽  
Negative Effect ◽  
Acid Catalyzed ◽  
Catalytic Rate ◽  
Positive Effect ◽  
Solvent Acidity

The effect of aprotic solvents (hexane, cyclohexane, dichloromethane, 1,2-dichloroethane, benzene, acetonitrile, acetone, 1,2-dimethoxyethane, ethyl acetate, dioxane) on kinetics and mechanism of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene has been studied with trichloroacetic acid as the acid catalyst. It has been found that beside the non-dissociated monomer of the acid also its dimer acts as the catalytic species. With regard to the results obtained in protic solvents (the catalysis by proton and general acid) three cases can be encountered of the dependence of observed rate constant on analytical concentration of the acid. The effect of solvents (inclusive of the protic ones) on the catalytic rate constant of the reaction with the non-dissociated monomer of acid is best interpreted by the equation suggested by Koppel and Palm and by the solvent scale suggested by us earlier. The solvent acidity and polarity have positive effect, whereas its basicity has negative effect. The catalytic rate constant of the reaction with the acid dimer decreases with increasing solvent basicity and polarity, due predominantly to the decrease in the equilibrium constant of dimerization.

Kinetics and Mechanism of Acid-Catalyzed Decomposition of 1,3-Bis(4-methylphenyl)triazene in Hexane-Organic Acid Medium

1996 ◽  
Vol 61 (3) ◽  
pp. 355-363 ◽  
Author(s):  
Miroslav Ludwig ◽  
Miriam Kabíčková
Keyword(s):  
Kinetic Model ◽  
Organic Acid ◽  
Acid Medium ◽  
Rate Constant ◽  
Fourth Order ◽  
Kinetics And Mechanism ◽  
Acid Catalyzed ◽  
Kinetics Of

The kinetics of acid-catalyzed decomposition of 1,3-bis(4-methylphenyl)triazene have been studied in mixtures of hexane and organic acid of various ratios using acetic, isovaleric, and pivalic acids as the catalysts. In all the cases, a monotonously increasing dependence of the observed rate constant upon mol fraction of the acid has been found. The results obtained are discussed with the help of the classic third- and fourth-order functions by Margules and the respective kinetic model. The main catalyzing particle appears to be the dimer of the respective acid, the reaction probably going via a complex formed by two molecules of acid and one molecule of the triazene.

Kinetics and mechanism of the oxidation of oxalate ion by tris(acetylacetonato)-manganese(III) and its hydrolytic derivatives in aqueous perchlorate media

1993 ◽  
Vol 71 (12) ◽  
pp. 2155-2159 ◽  
Author(s):  
Subrata Mukhopadhyay ◽  
Swapan Chaudhuri ◽  
Rina Das ◽  
Rupendranath Banerjee
Keyword(s):  
Free Radicals ◽  
Rate Constant ◽  
Decomposition Rate ◽  
Rate Constants ◽  
Kinetics And Mechanism ◽  
Unimolecular Decomposition ◽  
Decomposition Rate Constant ◽  
Mixed Complexes ◽  
Ph Range ◽  
Oxalate Ion

In the pH range 6.6–8.6, [MnL2(H2O)2]+ and [MnL2(H2O)(OH)] (HL = acetylacetone) oxidize oxalate ion (ox2−) to CO2 through the inner-sphere intermediates [MnL2(ox)]− and [MnL2(OH)(ox′)]2−, where ox′ is a half-bonded (unidentate) oxalate ion. Their rate constants of decomposition are 1.0 × 10−4 s−1 and 11.2 × 10−2 M−1 s−1 at 30 °C and at I = 1.0 M (NaClO4). Decomposition of these mixed complexes produces free radicals, presumably CO2−, which is further oxidized to CO2 by another Mn(III) in a fast step. At pH 4.2, [Mn(ox)3]3− is produced quantitatively when [ox]0 ≥ 0.12 M, which has been characterized spectrally, and its unimolecular decomposition rate constant k (= 2.7 × 10−4s−1 at 30 °C and I = 1.0 M) compares well with that reported earlier (2.44 × 10−4 s−1 at 25 °C and I = 1.0 M).

scholarly journals Kinetics and Mechanism of the Redox Reaction Between Pt(IV) Complex Ions and Sodium Thiosulfate in Aqueous Solution. Part II: Neutral and Alkaline Solution/ Kinetyka I Mechanizm Reakcji Redoks Pomiędzy Jonami Kompleksowymi Pt(Iv) I Tiosiarczanem Sodu W Roztworze Wodnym. Część II: Roztwór Obojętny I Zasadowy

2014 ◽  
Vol 59 (4) ◽  
pp. 1421-1426
Author(s):  
K. Pacławski ◽  
J. Piwowonska
Keyword(s):  
Rate Constant ◽  
Redox Reaction ◽  
Sodium Thiosulfate ◽  
Order Rate Constant ◽  
Reduction Reaction ◽  
Kinetics And Mechanism ◽  
Complex Ions ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy ◽  
Mechanism Of The Reaction

Abstract In this work, spectrophotometric studies on the kinetics and mechanism of the reaction between [PtCl6]2- complex ions and sodium thiosulfate, in neutral (pH = 7) and alkaline (p = 12) solution, were carried out. Applying different conditions, the influence of initial concentrations of reductant and platinum(IV) complex ions as well as the influence of temperature and ionic strength on the rate constant, was experimentally determined. From the obtained results, the molecularity, the order and the value of enthalpy and entropy of activation of the reaction, were experimentally determined. It was found that in both cases the reduction reaction is relatively slow and in the studied conditions the second-order rate constant changes from 2.92 : 10-2 to 0.40 M-1:s-1 at pH = 7, and from 3.84 : 10-2 to 1.55 M-1s-1 at pH = 12. Additionally, depending on the pH, different mechanism of the reaction is present. However, regardless on the studied system the only platinum(II) chloride complex ions are the final product of the redox reaction.

Kinetics and mechanism of the aminolysis of thioesters and thiocarbonates in solution

2009 ◽  
Vol 81 (4) ◽  
pp. 685-696 ◽  
Author(s):  
Enrique A. Castro
Keyword(s):  
Experimental Data ◽  
Aqueous Solution ◽  
Rate Constant ◽  
Aqueous Ethanol ◽  
Kinetics And Mechanism ◽  
Kinetic Investigation ◽  
Concerted Mechanism ◽  
Tetrahedral Intermediate ◽  
Leaving Group ◽  
The Stability

The aminolysis reactions of thioesters and thiocarbonates, in either aqueous solution or in 44 wt % aqueous ethanol at 25 °C, are subjected to a kinetic investigation. The Brønsted-type plots (lg kN vs. amine pKa, where kN is the nucleophilic rate constant) obtained for these reactions can be grouped in three categories: linear plots with slopes 0.8-1, biphasic plots (two linear portions and a curve in between), and linear plots with slopes 0.4-0.6. The two former plots are attributed to stepwise reactions through a zwitterionic tetrahedral intermediate. The latter plots are associated with a concerted mechanism. The fact that some reactions are stepwise and others concerted depends on the stability of the zwitterionic tetrahedral intermediate. This work shows how the experimental data allows one to assess the mechanism of these reactions. Also discussed are the factors that affect the stability of this intermediate, which in turn determines the pathway followed by the reaction. The factors analyzed in this work are (i) the leaving group of the substrate, (ii) the nature of the amine, (iii) the non-leaving group of the substrate, (iv) the electrophilic group of the substrate (CS vs. CO), and (v) the solvent.

scholarly journals The kinetics and mechanism of photooxygenation of 4′-diethylamino-3-hydroxyflavone

2016 ◽  
Vol 15 (2) ◽  
pp. 219-227 ◽  
Author(s):  
Zoltán Szakács ◽  
Márton Bojtár ◽  
László Drahos ◽  
Dóra Hessz ◽  
Mihály Kállay ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Quantum Yield ◽  
Acid Derivative ◽  
Rate Constant ◽  
Reaction Path ◽  
Kinetics And Mechanism

4′-Diethylamino-3-hydroxyflavone is oxidized into a salicylic acid derivative under photolysis. The rate constant and the quantum yield of the photooxidation have been determined and – on the basis of PES calculations – the reaction path has been analyzed.

Oxyhalogen-sulfur chemistry — Kinetics and mechanism of the oxidation of cysteamine by acidic iodate and iodine

2006 ◽  
Vol 84 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Alice Chanakira ◽  
Edward Chikwana ◽  
David H Peyton ◽  
Reuben H Simoyi
Keyword(s):  
Acid Concentration ◽  
Rate Constant ◽  
Oxidation Product ◽  
Initial Conditions ◽  
Reaction Dynamics ◽  
Reaction Scheme ◽  
Kinetics And Mechanism ◽  
Sulfur Chemistry ◽  
Bimolecular Rate Constant ◽  
Acidic Conditions

The oxidation of cysteamine by iodate and aqueous iodine has been studied in neutral to mildly acidic conditions. The reaction is relatively slow and is heavily dependent on acid concentration. The reaction dynamics are complex and display clock behavior, transient iodine production, and even oligooscillatory production of iodine, depending upon initial conditions. The oxidation product was the cysteamine dimer (cystamine), with no further oxidation observed past this product. The stoichiometry of the reaction was deduced to be IO3– + 6H2NCH2CH2SH → I– + 3H2NCH2CH2S-SCH2CH2NH2 + 3H2O in excess cysteamine conditions, whereas in excess iodate the stoichiometry of the reaction is 2IO3– + 10H2NCH2CH2SH → I2 + 5H2NCH2CH2S-SCH2CH2NH2 + 6H2O. The stoichiometry of the oxidation of cysteamine by aqueous iodine was deduced to be I2 + 2H2NCH2CH2SH → 2I– + H2NCH2CH2S-SCH2CH2NH2 + 2H+. The bimolecular rate constant for the oxidation of cysteamine by iodine was experimentally evaluated as 2.7 (mol L–1)–1 s–1. The whole reaction scheme was satisfactorily modeled by a network of 14 elementary reactions.Key words: cysteamine, cystamine, Dushman reaction, oligooscillations.

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