The features of the kinetics of radical reactions of quinone imines with 2-mercaptobenzothiazole

Kinetics of the reactions of N-phenyl-1,4-benzoquinone monoimine and N,N′-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole in chlorobenzene at T = 343 K has been studied by using kinetical spectrophotometry method (periodic spectral measurements and/or monitoring the wavelengths of the absorption band of quinone imines in the visible region). Two general features of the reactions, namely, radical mechanism and the existence of two steps were found. Kinetic features depend on the structure of a quinone imine. A reaction between N,N′-diphenyl-1,4-benzoquinone diimine and 2-mercaptobenzothiazole at first (initial) steps proceeds in an autoinhibition mode and has two independent channels, one of which being radical-chain. The addition of an initiator strongly accelerates the reaction only at the initial step, on completion of which the reaction rate decreases significantly and do not depend on the presence of the initiator. This testifies to the proceeding of the reaction by a non-chain mechanism subsequently to the initial step. The interaction involving N-phenyl-1,4-benzoquinone monoimine proceeds by a radical non-chain mechanism from the very beginning up to the end, and at the initial steps it proceeds in the autoaccelerating mode. The initiator has no influence on the reaction rate. For the process of the interaction of N,N′-diphenyl-1,4-benzoquinone monoimine and 2-mercaptobenzothiazole in the presence of 4-hydroxydiphenylamine, a radical mechanism was proposed, that serves to describe the kinetic features of the reaction and to obtain a quantitative estimation of some of its kinetic parameters.     

Kinetic parameters of radical reactions of 2-mercaptobenzothiazole with quinone imines

The chain reaction of N,N′-diphenyl-1,4-benzoquinone diimine with 2-mercaptobenzothiazole was studied by two methods developed earlier for the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole. In the methods used, the kinetic scheme of the reaction is simplified by creating conditions under which the rates of all stages except radical generation and decay can be neglected. One of the methods was updated. For the nonchain reaction of N-phenyl-1,4-benzoquinone monoimine with 2-mercaptobenzothiazole, both methods gave close results; for the chain reaction of N,N′-diphenyl-1,4-phenylenediamine with 2-mercaptobenzothiazole, the results differed by approximately one order of magnitude.     

The Kinetics and Mechanism of the Reversible Chain Reaction of Quinone Imine with Hydroquinone

The kinetics of the reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-di-tert-butyl-1,4-hydroquinone in chlorobenzene was studied at 298.2 and 340 K. The previously proposed chain mechanism was confirmed and discussed. The rate constants and Arrhenius parameters of all elementary steps were determined or reliably estimated. Data on the possibility of radical formation by a termolecular reaction of quinone imine with two 4-hydroxydiphenylamine molecules were obtained, and the rate constant of this reaction was evaluated: k= 0.22 l²mol^–2s^–1at 298 K. The reversibility of all of the most important steps of this chain reaction (chain initiation, propagation, and termination) was demonstrated.     

Kinetics and mechanism of the chain reaction between <Emphasis Type="Italic">N</Emphasis>-phenyl-1,4-benzoquinone monoimine and thiophenol

The kinetics of the reaction between N-phenyl-1,4-benzoquinone monoimine (quinone monoimine) and thiophenol is studied in chlorobenzene at 343 K. The reaction has the same mechanism proposed earlier for a similar reaction involving N,N'-diphenyl-1,4-benzoquinone diimine (quinone diimine). This mechanism has two paths: chain and nonchain. An important difference between the kinetics of the two reactions is the apparent reversible nature of the chain reaction in the quinone monoimine + thiophenol system. This nature reveals itself when the concentrations of thiophenol are comparable to or slightly higher than the concentrations of quinone imine. In light of this, kinetic research is conducted under conditions where the concentrations of thiophenol are significantly higher than those of quinone monoimine, allowing us to simplify the kinetic features and obtain interpretable data. The rate constants of the reaction’s elementary steps are estimated and found to be three to five times lower for the reaction involving quinone monoamine than for the one involving quinone diimine. Both reactions have relatively short chains whose lengths do not exceed several tens of units.     

Kinetics and mechanism of the chain reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-dimethylhydroquinone

The kinetics of the reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-dimethyl-1,4-hydroquinone in chlorobenzene was studied at 298.2 and 340 K. The reaction occurs by a chain mechanism with a chain length of ～10²?10³ units, depending on temperature and reactant concentrations. The orders of reaction with respect to components and the rate constants (or estimated values) were determined for all of the elementary steps at 298.2 and 340 K. The experimental data were compared with the results obtained previously for the reaction of N-phenyl-1,4-benzoquinone monoimine with 2,5-di-tert-butyl-1,4-hydroquinone. The nature of substituents in hydroquinone exerts a strong effect on the kinetic parameters of this new class of chain reactions. The effect of the final product, 2,5-dimethylquinone, on the reaction kinetics at 298.2 and 340 K was studied, and it was found that 2,5-dimethylquinone additives has only a weak inhibiting effect. The rate constant of the reaction of 2,5-dimethylquinone with semiquinone radicals, which were produced from 4-hydroxydipheny-lamine, was estimated: k _?2 ～ 10⁴?10⁵ l mol^?1 s^?1.     

Thiocyanation of N-aryl,N-acetyl,and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine

N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine with alkyl substituents in the quinoid ring have been synthesized and their spectral characteristics were determined. The thiocyanation of N-aryl, N-acetyl, and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine depending on the LUMO energy of the initial quinone monoamine affords derivatives of benzo[d][1,3]oxathiol-2-ones and benzo[d]oxazole-2(3H)-thiones.     

Micellar catalyzed hydrolysis of mono-2,3-dichloroaniline phosphate

The kinetics of micellar catalyzed hydrolysis of mono-2,3-dichloroaniline phosphate in the presence of different surfactants has been studied at 303?K. The rate of reaction has been found to be first order with respect to both [substrate] and [HCl]. The cationic micelles of cetylpyridinium chloride (CPC), anionic micelles of di-octyl sodium sulphosuccinate (AOT), and non-ionic micelles of polyoxyethylene sorbitan monooleate (Tween 80) enhanced the rate of reaction to a maximum value and after that the increase in concentration of surfactant decreased the reaction rate. The applicability of different kinetic models has been tested to explain the observed micellar effects. The various thermodynamic activation parameters (E_a, ΔH^≠, ΔS^≠, ΔG^≠) have been evaluated. The added salts viz. KCl, KNO₃, K₂SO₄ enhanced the rate of reaction in the presence of CPC, AOT, and Tween 80 micelles. The kinetic parameters were determined from the rate (surfactant) profile and a suitable mechanism consistent with the experimental finding has been proposed.     

The influence of different additives on the early-stage hydration of calcium aluminate cement

The thermal decomposition behaviors of 2,4,6-Trinitrotoluene (TNT) and 1-methoxy-2,4-dinitro-benzene (DNAN) were studied by using a NETSCH company accelerating rate calorimetry. Hazard indicators such as onset temperature, adiabatic temperature rise, initial self-heat temperature, maximum self-heating rate, and time-to-maximum temperature rise rate have been determined directly. The kinetic parameters, such as the activation energy (E _a) and the pre-exponential factor (A) were studied from the measured self-heating rate data by assuming order reaction.     

Autoxidation of p-hydroxydiphenylamine

Autoxidation of p-hydroxydiphenylamine (HDPA) gives N-phenyl-p-benzoquinoneimine and hydrogen peroxide as primary products over a wide range of pH and the previously reported formation of N-(4-hydroxyphenyl)-p-benzoquinoneimine in basic media is in error. An induction period which is independent of substrate concentration but decreases with increase in pH is observed. The rate of oxidation is first order with respect to oxygen and half order with respect to HDPA. Oxygen is used in the system at the rate comparable to its rate of dissolution. On the basis of various kinetic parameters, a mechanism involving electron transfer to oxygen from HDPA anion and subsequent formation of HO₂ radical is postulated. The agreement of the experimental results with the derived rate expression is shown to support the mechanism.Singlet oxygen, produced in situ by methylene blue sensitization, leads to oxidation but with different products indicating that this species is not involved in the autoxidation.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-sulfonyl derivatives of 1,4-benzoquinone monoimine with substituted hydrazines

Reaction direction of N-sulfonyl derivatives of 1,4-benzoquinone monoimine with substituted hydrazines depends on the redox potential of the quinone imine and on the basicity of the hydrazine. Aryl (alkyl)hydrazines of high basicity favor the reduction of quinone monoimine. In reactions with less basic aroylhydrazones N'-(4-oxocyclohexa-2,5-dienylidene)aroylhydrazides were obtained only from the alkylsubstituted in the quinoid ring N-sulfonyl derivatives possessing a lower redox potential.     

Kinetic analysis of the oxidative degradation of polyaryl-orthophosphate

Summary Thermogravimetric study of poly-aryl-orthophosphate indicates that in presence of air the decomposition is a two step process. The first step is the chain scission to form quinone and the subsequent step the oxidation of quinone to maleic anhydride. The kinetic parameters were determined for the oxidative thermal degradation process.With 4 figures     

Solvation model in the allylation of 2-mercaptobenzothiazole

The kinetics of the reaction of allyl bromide with 2-mercaptobenzothiazole has been studied in different protic and aprotic solvents conductometrically. The rate data were correlated with solvation parameters using linear multiple regression analysis. From the regression coefficients, which describe the susceptibility towards rate of different solvent parameters, information regarding solvent interactions is obtained and solvation models are proposed. The reaction has also been studied at different temperatures and thermodynamic parameters ∆H^≠, ∆S^≠, ∆G^≠ are computed.     

Total synthesis of eustifolines A-D and glycomaurrol via a divergent Diels-Alder strategy

The Diels-Alder reaction between a quinone monoimine and cyclic diene allows for the construction of substituted carbazoles in a regiospecific manner. This methodology has sucessfully been employed in a divergent strategy, culminating in the synthesis of eustifolines A-D and glycomaurrol.     

Total synthesis of (+/-)-herbindole B and (+/-)-cis-trikentrin B

[reaction: see text] Herbindole B and cis-trikentrin B are naturally occurring indoles having the unusual and synthetically challenging pattern of carbon substitution at the 4-7 and 5-7 positions, respectively, with no substitution at the 1-3 positions. The total syntheses of these polyalkylated indoles have been achieved in 19 and 12 steps, respectively. The synthesis of herbindole B relies on two iterations of a quinine monoimine Diels-Alder reaction, while cis-trikentrin B uses a single cycloaddition of a suitable quinone monoimine. Indolization of the adducts provides suitably substituted benzopyrrole nuclei for elaboration to the natural products.     

Mechanistic aspects of oxidation of dextrose by N-bromophthalimide in acidic medium: a micellar kinetic study

Kinetic investigations of oxidation of dextrose by N-bromophthalimide (NBP) in acidic medium in the presence of mercuric(II) acetate as a scavenger have been studied. In both the absence and presence of surfactants, the oxidation kinetics of dextrose by NBP shows a first-order dependence on NBP, fractional order on dextrose, and negative fractional order dependence on sulfuric acid. The determined stoichiometric ratio was 1:1 (dextrose:NBP). The variation of Hg(OAC)₂ and phthalimide (reaction product) have an insignificant effect on reaction rate. Effects of surfactants, added acrylonitrile, added salts, and solvent composition variation have been studied. Activation parameters for the reaction have been evaluated from Arrhenius plot by studying the reaction at different temperature. The rate law has been derived on the basis of obtained data. A plausible mechanism has been proposed from the results of kinetic studies, reaction stoichiometry and product analysis. The role of anionic and non-ionic micelle was best explained by the Berezin’s model.     

Kinetics of colloidal MnO<Subscript>2</Subscript> reduction by L-arginine in absence and presence of surfactants

The kinetics of the oxidation of L-arginine by water-soluble form of colloidal manganese dioxide has been studied using visible spectrophotometry in aqueous as well as micellar media. To obtain the rate constants as functions of [L-arginine], [MnO₂] and [HClO₄], pseudo-first-order conditions are maintained in each kinetic run. The first-order-rate is observed with respect to [MnO₂], whereas fractional-order-rates are determined in both [L-arginine] and [HClO₄]. Addition of sodium pyrophosphate and sodium fluoride enhanced the rate of the reaction. The effect of externally added manganese(II) sulphate is complex. It is not possible to predict the exact dependence of the rate constant on manganese(II) concentration, which has a series of reactions with other reactants. The anionic surfactant SDS neither catalyzed nor inhibited the oxidation reaction, while in presence of cationic surfactant CTAB the reaction is not possible due to flocculation of reaction mixture. The reaction is catalyzed by the nonionic surfactant TX-100 which is explained in terms of the mathematical model proposed by Tuncay et al. Activation parameters have been evaluated using Arrhenius and Eyring equations. On the basis of observed kinetic results, a probable mechanism for the reaction has been proposed which corresponds to fast adsorption of the reductant and hydrogen ion on the surface of colloidal MnO₂.     

Reaction of (Ac)Co-5,15di(ortho-methyloxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphyrin and its molecular complex with organic peroxides in xylene

The reaction of cobalt porphyrinate with organic peroxides in o-xylene has been studied using spectrophotometric titration, and its kinetic parameters have been determined. Imidazole has been shown to influence the process rate. A comparative analysis of the kinetic parameters of peroxide decomposition involving cobalt(III) porphyrinate and its zinc analogue has been carried out. A PM3 quantum-chemical method was used to optimize discrete molecules of the reagents and reaction intermediates, and their geometric parameters have been derived. Steric hindrances in the cobalt porphyrinate macrocycle and a considerable enhancement of distortion have been noticed to occur upon its reaction with a peroxide molecule.     

Kinetics and mechanism of the complexation and anation of protonated dioxotetracyanomolybdate(IV) with 1,10-phenanthroline

The anation kinetics of the protonated dioxotetracyanomolybdate(IV) ion with 1,10-phenanthroline have been studied spectrophotometrically. The effect of the H+ ion, ionic strength and temperature on the reaction rate has been determined; the rate increases with increasing H+ ion concentration, is independent of ionic strength, and increases with temperature. The reaction follows first order kinetics with respect to [Mo(OH)2- (H2O)2(CN)4]2– and is considered to proceed through the formation of a 1,10-phenanthroline–Mo(OH)2- (H2O)2(CN)4M2– complex (outer sphere) which converts into an inner sphere complex. The formation constant (Kn) for the outer sphere complex has been calculated from the kinetic data by two different methods. Anation of Mo(OH)2-(H2O)2(CN)42– is discussed in terms of an associative interchange (Ia) mechanism. The activation parameters have been calculated using the Arrhenius equation. A substitution mechanism is proposed and the rate equation derived:kobs = kKnKa[H+] [phen] /{1 + KnKa[H+] [phen]}.     

含氧光敏引发体系的研究——II.BP/TEA/O_2引发体系中氧的加速作用

研究了二苯酮(BP)/三乙胺(TEA)/氧体系引发MMA聚合反应中氧的加速作用。体系中保持比较大的TEA/O_2浓度比值,是实现氧加速作用的必要条件。实验结果得出:系统中氧通过光氧化生成过氧化物的速度Vo_2=K[BP][TEA]~(0.8)。由于过氧化物的光敏分解,使初级自由基得到增殖。从测定的K_p/K_t~(1/2)值,说明存在初级自由基的终止作用。测定了光氧化动力学方程的数据并讨论了机理。     

Oxidation of 1,3-Dioxacycloalkanes with Dimethyldioxirane

The kinetic regularities of the reactions of dimethyldioxirane with 1,3-dioxane, 2-propyl-, 2-isopropyl-, 2-phenyl-, 2,2-pentamethylene-, 2,2-dimethyl-, and 4-(hydroxymethyl)-2,2-dimethyl-1,3-dioxolanes, as well as with 2-isopropyl-, 2-phenyl-, 2,2,4-trimethyl-, 2-isopropyl-4-methyl-, 4-methyl-, 4-methyl-2-phenyl-, and 5,5-dimethyl-2-phenyl-1,3-dioxanes in acetone were studied by spectrophotometry. The reaction kinetics are described by a second-order equation (first order in dioxirane and first order in dioxacycloalkane). The reaction rate is independent of the concentration of oxygen in the reaction mixture. The activation parameters of the reactions were determined.