Photophysics and kinetics of naphthopyran derivatives,part 1: General analytical solutions for the kinetics of AB(k,ϕ) and ABC(k,ϕ) systems

A new formalism allowing solution of the differential equations for kinetic systems comprising three species (ABC) linked by first‐order thermal and/or photochemical reactions is proposed. The approach is developed specifically with photochromic materials in mind, but the formalism developed is shown to be applicable to a variety of kinetic systems irradiated with monochromatic light where the photokinetic factor ( F ) is constant. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 162–174, 2005     

Synthesis of polyetherols with purine ring. Kinetics and mechanisms of reactions,part 2: Reactions in the presence of triethylamine

The kinetics and mechanism of reaction between hydroxymethyl derivatives of uric acid and oxiranes in the presence of triethylamine as catalyst was studied. The formation of polyetherols was inhibited in initial steps of the reaction. Two different mechanisms were established for the reactions in which intermediates contained O‐hydroxymethyl and O‐(2‐hydroxyethyl) groups. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 472–482, 2005     

The kinetics of solid‐state reactions toward consensus,Part 2: Fitting kinetics data in dynamic conventional thermal analysis

This paper is the second part of a review of some of the controversial kinetic aspects of conventional thermal analysis (TA). In this part the physico‐geometric kinetics for the solid‐state reactions were examined. The main problems discussed are (1) problems in fitting kinetics data: the identification of the f (α) function, (2) the suitability of conventional dynamic methods of TA, and (3) the complex reactions. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 193–208, 2002; DOI 10.1002/kin.10028     

A kinetic and mechanistic study on the oxidation of indole‐3‐acetic acid by peroxodisulfate

The kinetics of oxidation of indole‐3‐acetic acid (IAA) by peroxodisulfate (PDS) has been carried out in aqueous acetic acid medium. First‐order dependence of rate each with respect to [IAA] and [PDS] was observed. The reaction rate was unaffected by added [H⁺]. Increase of percentage of acetic acid decreased the rate. Variation of ionic strength (μ) had negligible influence on the rate. A suitable kinetic scheme based on these observations involving a nonradical mechanism is proposed. The reactivity of peroxodisulfate toward indole‐3‐acetic acid was found to be lower than that with peroxomonosulfate. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 355–360, 2005     

Classic and multivariate modeling treatment of the kinetics and mechanism of isomerization of 5‐cholesten‐3‐one catalyzed by sodium ethoxide

A classic kinetic methodology including the treatment of the steady‐state method and a multivariate modeling kinetic treatment were applied to the kinetics and mechanism of the isomerization reaction of 5‐cholesten‐3‐one to 4‐cholesten‐3‐one catalyzed by EtO⁻ in ethanol absolute. The rate constants, thermodynamic parameters of activation, equilibrium constant, and the isomerization enthalpy were determined. The multivariate modeling kinetic treatment allows us to calculate the concentrations of the species, in which the 3,5‐dienolate is included as a highly reactive intermediate species and was able to discriminate among several applicable mechanisms validating the one comprising two reversible steps. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 38–47, 2006     

Kinetics and mechanism of formation of polymeric products during the hydroxyalkylation of parabanic acid with oxiranes

The kinetics of the reaction between N‐(2‐hydroxyalkyl) hydroparabanates (HAHP) and N,N′‐bis(2‐hydroxyalkyl) parabanates (HAP) with ethylene and propylene oxides were studied. The addition of oxiranes to imide function of HAHP led to the formation of HAP. Further reaction of HAP with oxiranes resulted in trioxoimidazolidine ring opening and polymeric products. The kinetics of the system was studied in detail. Based on the final kinetic equations, the mechanism of the reactions was postulated. The temperature dependences of kinetic parameters and analytical data provided experimental evidences supporting the mechanism. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 399–406, 2006     

Curing kinetics of boron‐containing phenol–formaldehyde resin formed from paraformaldehyde

A boron‐containing phenol–formaldehyde resin (BPFR) was synthesized from boric acid, phenol, and paraformaldehyde. The curing reaction of BPFR was studied by Fourier‐transform infrared spectrometry and differential scanning calorimetry. According to the heat evolution behavior during the curing process, several influencing factors on isothermal curing reaction were evaluated. The results show that the isothermal kinetic reaction of BPFR follows autocatalytic kinetics mechanism, and kinetic parameters m, n, k₁, and k₂, were derived, respectively. In the latter reaction stage, the curing reaction becomes controlled mainly by diffusion. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 638–644, 2002     

Synthesis of polyetherols with purine ring. Kinetics and mechanisms of reactions,part 1: Reaction of hydroxymethyl derivatives of uric acid with oxiranes

The kinetics and mechanisms of the initial steps of formation of polyetherols from hydroxymethyl derivatives of uric acid and oxiranes were studied. It has been found that initial steps of the reaction of polyetherol formation occur without a catalyst. The NH groups, which are formed upon release of formaldehyde from N‐ and O‐hydroxymethyl derivatives of uric acid, take part in the reaction. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 464–471, 2005     

Influences of product gases on the kinetics of thermal decomposition of synthetic malachite evaluated by controlled rate evolved gas analysis coupled with thermogravimetry

An instrument of controlled rate evolved gas analysis (CREGA) coupled with TG‐DTA was constructed for analyzing the influences of product gases on the kinetics and mechanism of the thermal decomposition of solids that produce more than one gaseous products at the same stage of reaction. The thermal decomposition of synthetic malachite, Cu₂(OH)₂CO₃, was subjected to the measurements of CREGA‐TG under controlled concentrations of H₂O and CO₂ in the reaction atmosphere with taking account of self‐generated H₂O and CO₂ during the course of reaction. By a series of CREGA‐TG measurements carried out under various atmospheric conditions, it was reconfirmed that the reaction is accelerated and decelerated by the effects of atmospheric H₂O and CO₂, respectively. From the kinetic analysis of the CREGA‐TG curves and results of high temperature X‐ray diffraction measurements under various reaction atmospheres, it was revealed that the anomalous effects of atmospheric H₂O on the reactivity and on the reaction rate of the thermal decomposition of synthetic malachite appear at the early stage of the reaction. Usefulness of the CREGA‐TG technique for measuring the kinetic rate data for the thermal decomposition of solids was demonstrated in the present study, by emphasizing the importance of quantitative control of self‐generated reaction atmosphere. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 346–354, 2005     

Ruthenium(III)‐catalyzed oxidation of cyclopentanol and cyclohexanol by N‐bromoacetamide

Kinetic investigations on Ru(III)‐catalyzed oxidation of cyclopentanol and cyclohexanol by acidic solution of N‐bromoacetamide (NBA) in the presence of mercury(II) acetate as a scavenger have been carried out in the temperature range of 30–45°C. Similar kinetics was followed by both the cyclic alcohols. First‐order kinetics in the lower concentration range of NBA was observed to tend to zero order at its higher concentrations. The reaction exhibits a zero‐order rate dependence with respect to each cyclic alcohol, while it is first order in Ru^III. Increase in [H⁺] and [Cl^?] showed positive effect, while successive addition of acetamide exhibited negative effect on the reaction rate. Insignificant effect of sodium perchlorate, D₂O, and mercury(II) acetate on the reaction velocity was observed. Cationic bromine has been proposed as the real oxidizing species. Various thermodynamic parameters have been computed. A suitable mechanism in agreement with the kinetic observations has been proposed. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 275–281, 2005     

Kinetics and mechanism of the reaction of benzyl bromide with copper in hexamethylphosphoramide

The reaction of copper with benzyl bromides in hexamethylphosphoramide has been studied. The kinetic and thermodynamic parameters of the reaction have been obtained. Hammett plots of log (k/k^o) vs the substituent constant σ gave good correlations (ρ = 0.15, S_ρ = 0.02, r = 0.954). The structure of the organic group has little effect on the rate of reaction of benzyl bromide with copper. In the absence of atmospheric oxygen, the oxidative dissolution of copper occurred by the mechanism of single‐electron transfer with the formation of 1,2‐diphenylethane and copper(I) complexes. The stereochemistry and intermediates compound was also investigated. The reaction mechanism is discussed. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 296–305, 2005     

Alkyl substituted phenoxyl decay in a hydrogen transfer equilibrium

The kinetics of radical decay in the equilibrium: 2,4,6‐tri‐tert‐butylphenoxyl radical 1 + 2,6‐di‐tert‐butyl‐4‐methylphenol 2 = 2,4,6‐tri‐tert‐butylphenol 3 + 2,6‐di‐tert‐butyl‐4‐methylphenoxyl radical 4 was studied at 298 and 273 K by means of EPR spectroscopy. At 298 K second order prevails, whereas at 273 K the best fit was order 3/2. The extinction of 4 takes place in two steps: dimerization followed by disproportionation of the dimer, but the stable radical 1 enters in crossed dimerization with 4 to yield nonradical products. The mechanism ensures a constant [ 4 ]/[ 1 ] ratio along the decay. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 37: 1–4, 2005     

Indigo dyes as indicators for oxidation reactions: Competition kinetic studies

The use of indigo dyes as competiters to study the kinetics of oxidation reactions is reported. The kinetic model was theoretically investigated using the kinetic simulation program KinSim under conditions involving very limiting concentrations of the indigo dye relative to both the oxidant and the reductant. Complete kinetic results on the reaction of an oxidant with a reductant can be obtained indirectly from observing the absorbance changes due to the loss in the indigo dye at 600 nm (ε₆₀₀∼2 × 10⁴ M⁻¹cm⁻¹). Experimental data from the oxidation of an olefin (cyclohexene) with m-chloroperoxybenzoic acid in the presence of an indigo dye were used to check the validity of the kinetic model. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 532–537, 2005     

The “dimer nucleophile mechanism” for reactions with rate‐determining first step: Derivation of the whole kinetic law and further treatment of kinetic results

Overwhelming evidence has been previously reported for the existence of the so‐called “dimer nucleophile mechanism” in aromatic nucleophilic substitutions by amines in aprotic solvents, for which the most prominent feature is the fourth‐order kinetics (third order in amine) that has been observed with many different substrate–nucleophile systems, especially those in which departure of the nucleofuge is the rate‐determining step. The mechanism has been confirmed by several other features, although other alternative mechanisms were suggested to explain the fourth‐order kinetics, no one has been able to explain the other above‐mentioned features. The present paper affords additional experimental evidence and derivation of the kinetic expressions for reactions with good nucleofugues, where the first step is rate determining. The work involves studies of the reactions of 2,4‐dinitrofluorobenzene and 2,4‐dinitrochlorobenzene with aniline and with alkyldiamines in toluene. The novelty of this work lies in the selection of substrate–nucleophile systems exhibiting kinetic behavior that allows estimations of the different k's involved. The satisfactory agreement between the quotients of k's calculated from sets of data obtained under different reaction conditions hereby reported indicates that the assumptions made are correct and that the whole treatment applied to the kinetic data is justified. All together, the results fit well with the reaction scheme involving the dimer nucleophile mechanism, adding new evidence to this mechanism that it is well established in the current literature. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 735–742, 2010     

The influence of some steric and electron effects on the mechanism of aromatic nucleophilic substitution (SNAr) reactions in nonpolar solvent

Kinetic studies are reported for the reactions with aniline in benzene of a series of X‐phenyl 2,4,6‐trinitrophenyl ethers [X = H; 2‐, 3‐, 4‐CH₃; 2,4‐, or 2,6‐(CH₃)₂] a–f , and the results compared with those of the corresponding nitro derivatives. In the methyl series, kinetic data show that increasing substitution reduces drastically the rates of reactions indicative of the operation of some kind of steric effect. The unfavorable steric congestion at the reaction center appears to be unimportant in determining the kinetic order of the reactions. In general, the second‐order rate constants k_A depend linearly on the square of nucleophile concentration. The change in the kinetic form observed in the nitro derivatives may be largely due to the electron‐withdrawing effect of the group. With the 2,6‐dinitro derivative, however, the uncatalyzed pathway k₂ takes all the reaction flux. Steric hindrance to intermolecular proton transfer from base to the ethereal oxygen of the intermediate is sufficient to make the base‐catalyzed pathway insignificant relative to the k₂ pathway. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 744–750, 2005     

Thermal dimerization kinetics of 3‐(p‐bromo‐phenyl)‐pyridazinium benzoyl methylid in solutions

3‐(p‐Bromo‐phenyl)‐pyridazinium‐benzoyl methylid (BPPBM) participates in solution at 3 + 3 dipolar thermal dimerization that can be spectrally monitored by the extinction in its visible intramolecular charge transfer (ICT) band. The attenuation of ICT band intensity shows the decrease of the BPPBM concentration with the increasing of dimer concentration. The complex kinetics of light‐assisted dimerization process was studied taking into account that the thermodynamic equilibrium is reached after more than 24 h. On the basis of general order of reaction theory, we found that the dimerization reaction must be described as a multistep mechanism. The rate constants of the dimerization reactions in ethanol (k = 0.00897 s^?1) and benzene (k = 0.00774 s^?1) solutions were correlated with the BPPBM and dimer structural features established by using the HyperChem 5.02 simulation program package. A kinetic mechanism of 3 + 3 dipolar thermal dimerization for the studied ylid is proposed. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 230–239, 2008     

Experimental and modeling study of the oxidation of 1‐butyne and 2‐butyne

Ignition delays were measured behind shock waves in the cases of hydrocarbon–oxygen–argon mixtures containing 1‐butyne or 2‐butyne (1 or 2% of hydrocarbons for equivalence ratios from 0.5 to 2). Reflected shock waves permitted to obtain temperatures from 1100 to 1600 K and pressures from 6.3 to 9.1 atm. A detailed mechanism of the reactions of 1‐butyne and 2‐butyne has been explained in the line of the mechanism developed previously for the reaction of C₃–C₄ unsaturated hydrocarbons (propyne, allene, 1,3‐butadiene) [Int J chem Kin 1999, 31, 361]. It is based on the most recent kinetic data values published in the literature and is consistent with thermochemistry. This mechanism has been validated by comparing the results of our simulations to the experimental results obtained for ignition delays in our shock tube and to measurements of species obtained during thermal decomposition [Int J Chem Kin 1995, 27, 321; J Phys Chem 1993, 97, 10977]. The main reaction pathways have been derived from flow‐rate and sensitivity analyses. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 172–183, 2002; DOI 10.1002/kin.10035     

Kinetics study of propyl acetate synthesis reaction catalyzed by Amberlyst 15

The reaction kinetics of esterification of acetic acid with n‐propanol was investigated. The reaction was catalyzed by the commercial cation‐exchange resin Amberlyst 15, and the kinetic data were obtained in a batch reactor within the temperature range 338–368 K. The chemical equilibrium constant, K_eq, was first determined experimentally; the result shows that K_eq is about 20 and slightly temperature dependent. Altogether 14 sets of kinetic data were then measured. The influences of operating parameters such as temperatures, initial molar ratios, and catalyst concentrations were checked. The pseudo‐homogeneous (PH), Rideal–Eley (RE), and Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were developed to interpret the obtained kinetic data. The parameters of the kinetic models were identified by the software DIVA, and the confidence interval of each parameter was also estimated. Both the chemical equilibrium constant and kinetic models were formulated in terms of the liquid phase activity, which was described by the nonrandom two‐liquid (NRTL) model. The LHHW model gives the best fitting result, followed by the RE model and the PH model, whereas the confidence intervals rank in the reverse order. In addition, an effective solution was proposed to overcome a convergence problem occurring in the LHHW model parameter identification, which has been reported several times in the literature. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 245–253, 2007     

Kinetics of the reaction of carbon dioxide with blends of amines in aqueous media using the stopped‐flow technique

The effect of mixing 2‐amino‐2‐methyl‐1‐propanol (AMP) with a primary amine, monoethanolamine (MEA), and a secondary amine, diethanolamine (DEA), on the kinetics of the reaction with carbon dioxide in aqueous media has been studied at 298, 303, 308, and 313 K over a range of blend composition and concentration. The direct stopped‐flow conductimetric method has been used to measure the kinetics of these reactions. The proposed model representing the reaction of CO₂ with either of the blends studied is found to be satisfactory in determining the kinetics of the involved reactions. This model is based on the zwitterion mechanism for all the amines involved (AMP, MEA, and DEA). Blending AMP with either of the amines results in observed pseudo‐first‐order reaction rate constant values (k_o) that are greater than the sum of the k_o values of the respective pure amines. This is due to the role played by one amine in the deprotonation of the zwitterion of the other amine. Steric factor and basicity of the formed zwitterion and the deprotonating species have a great bearing in determining the rate of the reactions studied. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 391–405, 2005