bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of solvent on the reactions of coordination complexes. Part 10. kinetics of solvolysis of cis(chloro)(1‐amino‐propan‐2‐ol)bis‐(ethylenediamine)cobalt(III) in methanol + water, propan‐2‐ol + water, and t‐butanol + water media
Authors: Dash Anadi C. , Das Prafulla K. 
Published: January 2005

AbstractThe solvolysis of cis(chloro)(1‐amino‐propan‐2‐ol)bis(ethylenediamine)cobalt(III) in aqueous alcoholic media using methanol, propan‐2‐ol, t‐butanol as cosolvents, resulted in the formation of the (N,O) chelated productcis[Co(en)2(NH2CH2CHOHCH3)]3+. The pseudo first order rate constant decreased with increasing molfraction (Xorg) of alcohols, the decrease being less marked as the bulkiness of hydrophobic moiety of alcohol increased. The plots of log 𝓀obs vs. reciprocal of the bulk dielectric constant of the solvents, log 𝓀obs vs. Grunwald‐Winstein solvent parameter and log 𝓀obs, vs. Xobs under isodielectric condition (Ds = 50, at 50°C) for CH3OH/H2O, C2H5OH/H2O, (CH3)2CHOH/H2O, (CH3)3COH/H2O, (CH2)2(OH)2/H2O, and (CH3)2 C  O/H2O in water rich media indicated that both solvent structural effects and presumably the hydrophobic interaction appreciably mediate the reaction. The calculated values of the relative transfer free energy at 25°C[ΔGt(C3−)‐ΔGt(i.s)(s←w)] where C3+ and i.s. denote the dissociative transition state {cis[Co(en)2(NH2CH2CHOHCH3)]3+}* and the initial state, respectively, indicated that the tripositive transition state is more effectively solvated by the mixed solvent media, than the dipositive initial state, the effect appeared to be more significant with increasing Xorg. The plots of activation enthalpy and entropy against Xorg exhibited maxima and minima indicating that enthalpy and entropy changes associated with the solvent shell reorganization of the reactant contribute to the overall activation parameters.
Kinetics and mechanism of the reaction of Ozone with Aliphatic alcohols
Authors: Rakovski S. , Cherneva D. 
Published: January 2005

AbstractKinetic parameters of the reaction of ozone with aliphatic alcohols of different structures are obtained. The ratio between the relative reactivities of the primary: secondary: tertiary alcohols was found to be 1:15:138. The bond energy changes in the same sense as the activation energy. The rate‐controlling step of ozone reaction with alcohols is the abstraction of a hydrogen atom being in α‐position with respect to the OH group. The pre‐exponential factors (A) are calculated by the collision and activated complex methods and compared with the experimentally obtained values. The results from the calculations represent convincing evidence that the mechanism of the rate‐controlling step of the reaction is associated with the formation of an activiated complex which has a linear shape ensuring free rotation of its fragments.
Kinetics of chlorination of some Ortho‐, Meta‐, and Para‐substituted phenols by N‐chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one: A LFER study
Authors: Ganapathy K. , Palaniappan An. 
Published: January 2005

AbstractThe kinetics of chlorination of a number of ortho‐, meta‐, and para‐substituted phenols by N‐chloro‐3‐methyl‐2,6‐diphenylpiperidin‐4‐one (NCP) in acid medium have been investigated. The reaction is of first order with respect to oxidant and the order with respect to the substrate varies depending on the nature of the substituent present in the ring. With cresols and m‐chlorophenol the order is unity, with p‐methoxyphenol, zero and with the other phenols, a fraction. Isokinetic and Exner plots give straight lines with fine correlation coefficients. But the Hammett plot gives a curve that was concave downwards, instead of a straight line. The observed Hammett plot deviation has been accounted for suitably. Regression analyses of the rate data of ortho‐substituted phenols by using Taft and Charton equations to separate steric effects from electronic effects have been carried out. In this reaction, the localized electronic effect plays a major role while steric and resonance effects play a minor role.
Kinetics and mechanism of base‐catalyzed hydrolysis of Cu(II)‐salicylamide complex
Authors: Niaz M. Arif , Khan A. Aziz 
Published: January 2005

AbstractThe kinetics of hydrolysis of Cu(II)‐salicylamide complex have been studied in sodium hydroxide solution (0.5 to 2.5M). The observed pseudo‐first‐order rate constants vary according to the empirical equation 1/𝓀obs = B1 + B2/[ŌH] up to 2.0 M sodium hydroxide concentration. The mechanism of base‐catalyzed hydrolysis has been proposed and it is concluded that the reaction proceeds by the interaction of complex with the nucleophile, forming tetrahedral intermediate which then breaks down to products. The rate equation has been derived. Thermodynamic parameters have also been reported.
A product study of the gas‐phase reaction of Methacrolein with the OH radical in the presence of NOx
Authors: Tuazon Ernesto C. , Atkinson Roger 
Published: January 2005

AbstractThe gas‐phase reaction of methacrolein with the OH radical, in the presence of NOx, was investigated at 298 ± 2 K and atmospheric pressure of air. Hydroxyacetone, methylglyoxal, a peroxyacyl nitrate identified as CH2  C(CH3)C(O)OONO2 (peroxymethacryloyl nitrate), formaldehyde, CO, and CO2 were observed to be the major products. The product yield data for these compounds show that OH radical addition to the >C  C< bond accounts for ca. 50% of the overall reaction, with the remaining ca. 50% proceeding via H—atom abstraction from the CHO group. The data suggest that the alkoxy radical
equation image
formed following the addition of OH to the terminal carbon atom, decomposes primarily to give the formyl radical plus hydroxyacetone. A lower limit ratio of 5: 1 has been estimated for OH radical addition to the terminal carbon atom of the double bond relative to addition on the inner carbon atom.
Thermal decomposition kinetics of polysilanes: Disilane, trisilane, and tetrasilane
Authors: Martin J. G. , O'Neal H. E. , Ring M. A. 
Published: January 2005

AbstractThe decomposition kinetics of disilane with added butadiene, trisilane both neat and with added butadiene, trimethylsilane or H2, and normal and iso‐tetrasilane both neat and in the presence of added butadiene are reported. Arrhenius parameters of the primary dissociation reactions are determined: A‐factors suggest that polysilane decompositions (1) have similar intrinsic activation entropies (ΔS‡ ≈︁ 6.2 ± 5 e.u.) and (2) have activation energies which increase with increasing reaction endothermicities. Relative trapping efficiencies of SiH4, Si2H6, Si3H8, C4H6, Me3SiH, and H2 toward SiH2 and SiH3SiH are also determined. Other results include the heat of formation of silylsilylene, ΔH (SiH3SiH) = 75.3 Kcal/mol, and the activation energy for 1,1‐H2 elimination from disilane (EH2 = 57.8 kcal/mol).
Kinetics of the solvolysis of [Co(3Rpy)4Cl2]+ ions (R = Me or Et) in water and in water + methanol mixtures
Authors: El‐Subruiti Gehan M. , Wells Cecil F. , Sidahmed Ibrahim M. 
Published: January 2005

AbstractRates of solvolysis of ions [Co(3Rpy)4Cl2]+ with R = Me and Et have been measured over a range of temperatures for a series of water‐rich water + methanol mixtures to investigate the effect of changes in solvent structure on the solvolysis of complexes presenting a largely hydrophobic surface to the solvent. The variation of the enthalpies and entropies of activation with solvent composition has been determined. A free energy cycle relating the free energy of activation in water to that in water + methanol is applied using free energies of transfer of individual ionic species from water into water + methanol. Data for the free energy of transfer of chloride ions ΔG(Cl−) from both the spectrophotometric solvent sorting method and the TATB method for separating ΔG(salt) into ΔG(i) for individual ions are used: irrespective of the source of ΔG(Cl−), in general, −ΔG(Co(Rpy)4Cl2+) > −ΔG(Co(Rpy)4Cl2+), where Rpy = py, 4Mepy, 4Etpy, 3Etpy, and 3Mepy, showing that changes in solvent structure in water‐rich water + methanol mixtures generally stabilize the cation in the transition state more than the cation in the initial state for this type of complex ion. A similar result is found when the free energy cycle is applied to the solvolysis of the dichloro (2,2′,2″‐triaminotriethylamine)cobalt(III) ion. The introduction of a Me or Et group on the pyridine ring in [Co(Rpy)4Cl2]+ has little influence on the difference {ΔG(Co(Rpy)4Cl2+)−ΔG(Co(Rpy)4Cl2+)} in water + methanol with the mol fraction of methanol < 0.20.
On finding the rate constants of linear and nonlinear systems
Authors: Liddell G. F. , Evans A. B. , Buckingham D. A. 
Published: January 2005

AbstractIn lowest approximation, a certain chemical reaction is described by a system of first‐order linear differential equations with unknown constant coefficients. One can therefore write down an expression for the state of the system at time t, and from this find the endpoint of the reaction in terms of the initial state and the rate constants. The relative values of some rate constants can then be estimated from experimental data.A better approximation in which the differential equations are nonlinear is also considered, and it turns out that because of symmetry in the reaction, the relationship between the final state and the ratios of the rate constants is unchanged. Although the differential equations now appear much less tractable, the problem of relating the rate constants to the endpoint of the reaction can be formulated and solved in terms of probabilities.The results illustrate an important property of reaction schemes in which some of the steps are reversible. More generally, this is a property of differential equations: provided that they continue to satisfy certain linear constraints, the parameters of a linear system of ordinary differential equations can vary without affecting the asymptotic solution.
Kinetics and mechanism of oxidation of phenylhydrazine and P‐bromophenylhydrazine by hexacyanoferrate(III) in acidic medium
Authors: Al‐Subu M. M. , E‐Halawa R. Abu , Abed H. M. 
Published: January 2005

AbstractKietics of oxidation of phenylhydrazine and p‐bromophenylhydrazine by hexacyanoferrate(III) in acidic medium have been studied. The reactions follow similar kinetics, being first order with respect to both hydrazine and exacyanoferrate(III) and inverse first order with respect to the hydrogen ion. Addition of hexacyanoferrate(II) has no retarding effect on the rate of oxidation. The effects of varying ionic strength, dielectric constant, and temperature on the reaction rates have been investigated. A plausible mechanism has been proposed to account for the experimental results. Benzene and bromobenzene have been identified as the oxidation products.
Kinetics of the oxidation of aliphatic aldehydes by Os(VIII) in alkaline solution
Authors: Sharma Vinita , Chowdhury Kakuli , Banerji Kalyan K. 
Published: January 2005

AbstractKinetics of oxidation of six aliphatic aldehydes by Os(VIII) in alkaline solutions have been studied. The reaction is of first order with respect to each of the aldehyde and Os(VIII). The pseudo‐first order rate constants decreased with an increase in the concentration of hydroxyl ions. The oxidation of deuterioacetaldehyde (MeCDO) exhibited a substantial primary kinetic isotope effect. Separate rate constants for the oxidation of hydrate and free aldehyde forms have been evaluated. The aldehyde hydrate is postulated as the active reductant. Ionic strength has no noticable effect on the rate. The rate‐determining step is, therefore, postulated to be a bimolecular reaction between the aldehyde hydrate and [OsO4(OH)2]−2. The value of the limiting rate constant exhibited an excellent correlation with Taft σ* values; reaction constant being negative. A mechanism involving transfer of a hydride ion from the aldehyde hydrate to Os(VIII) has been proposed.
A simple method for extending the range of pseudo‐order kinetic measurements
Authors: Jensen James L. , Kanner Richard C. , Shaw Gregory R. 
Published: January 2005

AbstractData are presented demonstrating the validity of a new method of measuring pseudo‐order rate constants, based on an iterative computational procedure long in use for kinetic conditions where the “infinity” value is not experimentally accessible. This new method requires that the kinetic order be known for the limiting reagent, but is otherwise general. It allows measurement of the pseudo‐order rate constant even at a ratio of reactants of 1:1 by maximizing the fit of three half‐lives of data to the appropriate pseudo‐order kinetic equation, treating the “infinity” value as a variable.
The elimination kinetics of secondary Alkyl Bromides in the gas phase
Authors: Chuchani Gabriel , Martín Ignacio , Rotinov Alexandra , Domínguez Rosa M. 
Published: January 2005

AbstractElimination kinetics of 2‐bromohexane and 2‐bromo‐4‐methylpentane in the gas phase were examined over the temperature range of 310–360°C and pressure range of 46–213 torr. The reactionsin seasoned, static reaction vessels, and in the presence of the free radical inhibitor cyclohexene, are homogeneous, unimolecular, and follow first order rate laws. The overall rate coefficients are described by the following Arrhenius equations: For 2‐bromohexane, log𝓀1(s−1) = (13.08 ± 0.70) − (185.7 ± 8.2) kJ mol−1 (2.303RT)−1; for 2‐bromo‐4‐methylpentane, log𝓀1(s−1) = (13.08 ± 0.33) − (183.4 ± 3.8) kJ mol−1 (2.303RT)−1. The electron releasing effect of alkyl groups influences the overall elimination rates. The olefin products isomerize in the presence of HBr gas until an equilibrium mixture is reached.
Kinetic studies of the deactivation of O2(1Σg+) and O(1D)
Authors: Shi Jichun , Barker John R. 
Published: January 2005

AbstractThe kinetics of the deactivation of O2(1Σg+) is studied in real time. O2(1Σg+) is generated in this system by the O(1D) + O2 reaction following O3laser flash photolysis in the presence of excess O2, and it is monitored by its characteristic emission band at 762 nm. Quenching rate constants were obtained for O2, O3, N2, CO2, H2O, CF4and the rare gases. Since O(1D) is the precursor for the formation of O2(1Σg+), the addition of an O(1D) quencher effectively lowers the initial concentration of O2(1Σg+). By measuring the initial intensity of the 762 nm fluorescence signal, the relative quenching efficiencies were determined for O(1D) quenching by N2, CO2, Xe, and Kr with respect to O2; the results are in good agreement with literature values.
Kinetics of the esterification of palmitic acid with isobutyl alcohol
Authors: Goto Shigeo , Tagawa Tomohiko , Yusoff Asma 
Published: January 2005

AbstractKinetics of the sulfuric acid catalyzed esterification of palmitic acid with isobutyl alcohol has been studied and reviewed critically. A theoretical rate equation is derived by the following reaction mechanism: (1) The reaction of sulfuric acid and isobutyl alcohol produces isobutyl sulfuric acid which acts as a catalyst; (2) Palmitic acid is protonated by the catalyst to form the reaction intermediate; and (3) The esterification proceeds reversibly. The experimental results are consistent with this rate equation.
Hydrolysis of 3,4‐diphenyl‐1,2,5‐thiadiazole‐1,1‐dioxide. Acid and base catalysis
Authors: Mirifico M. V. , Vasini E. J. , Sicre J. E. 
Published: January 2005

AbstractWe have performed a product and kinetic study of the hydrolysis of 3,4‐diphenyl‐1,2,5‐thiadiazole‐1,1‐dioxide in aqueous solution. Benzil and sulfamide are the only products of hydrolysis and are formed in equimolar yields.The kinetic results indicate that a first order law is followed up to 90% conversion. The observed rate constant is independent of substrate concentration.Ionic strength and buffer concentration do not affect the rate constant, but the reaction is acid‐base catalyzed. The rate‐pH profile has been determined and a mechanism that fits the experimental data satisfactorily is proposed. Corresponding rate constants and equilibrium constants for the protonation of the substrate are reported.
Electron transfer. 102. Some oxidations by bromite (BrO2−)
Authors: Jhanji Amrit K. , Gould E. S. 
Published: January 2005

AbstractBromite, BrO2−, in aqueous carbonate or borate buffers (pH 9–11), reacts rapidly with H3AsO3, with the tartrate complex of Sb(III), and with the EDTA complexes of Sn(II) and U(IV). Each reaction yields Br−, even when BrO2− is taken in excess. Reaction rates with Sb(III) and Sn(II) are independent of pH, but the acidity pattern observed with As(III) points to competing bimolecular reductions by H2AsO3− and H3AsO3 having specific rates 3.4 and 1.2 M−1 s−1 (25°C, μ = 0.5M). Reduction by U(IV) is strongly inhibited by carbonate; data for carbonate buffers are in accord with the operation of two contributing reaction paths (specific rates 0.45 and 6.3 M−1 s−1) with the activated complex for the slower featuring one more carbonate than that for the rapid. Reactions of BrO2− with single electron reductants, or with reagents that can undergo both 1e and 2e changes, are generally complicated by variable induction periods, inhibition by O2, catalyzed decomposition of BrO2−, or combinations of these. The much smoother reductions by 2e− reagents must pass through OBr−, which reacts much more rapidly than BrO2− in each case. An inner‐sphere path, operating through an oxygen‐bridged transition state and culminating in oxygen atom transfer, is proposed for the 2e reductants. Hypophosphite, despite its highly negative formal potential, is not oxidized by BrO2− under our conditions. Here it is likely that the substitution‐inert character of the coordinatively saturated P(I) center rules out formation of the precursor required for redox.
Oxidation of amino acids by peroxomonophosphoric acid—a kinetic study
Authors: Panigrahi Ganesh P. , Paichha Ramesh C. 
Published: January 2005

AbstractAliphatic amino acids are smoothly oxidized by peroxomonophosphoric acid (PMPA) in the pH region 6–10. Kinetic studies reveal second order dependence in the amino acid not observed hitherto in any of the PMPA oxidations. Dependence in PMPA is unity. Rate‐pH profile yields a maximum around pH 8. The reaction path includes oxidation steps due to H2PO5− and HPO52−. Second order dependence in the amino acid has been attributed to participation of two Zwitter‐ionic molecules of the amino acid to form a nucleophile.
The gas phase reaction of CF3 radicals with C6F5H in the temperature range 373–658 K
Authors: Lane S. I. , Oexler E. V. , Staricco E. H. 
Published: January 2005

AbstractCF3 radicals were generated by the photolysis of perfluoroacetic anhydride. In the presence of pentafluorobenzene, the CF3 radicals react according to the following mechanism:
equation image
It was found that the addition reaction (3) becomes reversible above ca. 453 K. The addition rate parameters have been revised and they satisfactorily agree with those reported previously.At temperatures higher than 593 K, only true H‐abstraction occurs. The rate constant kH for reaction (5) is given by:

where θ = 2.303 RT kJmol−1 and kc is the rate constant for combination of CF3 radicals. The reactions of CF3 with benzene and pentafluorobenzene are compared.
The decomposition kinetics of hydrogen peroxide catalyzed by diethylenetriaminepentaacetatoiron(III) complex
Authors: Anis Samy S. , Mansour Mohamed A. 
Published: January 2005

AbstractThe rate of reaction of (Fe(DTPA)) with H2O2 was investigated at various temperatures. The observed rate law is given by the expression.

The rate constants and the related thermodynamic parameters are calculated. Substitution controlled mechanisms are suggested to account for the formation of the violet peroxy intermediate. The results are compared with previously data for Fe EDTA complex.
Disproportionation reactions between alkyl and fluoroalkyl radicals. VI. Difluoromethyl and n‐propyl radicals
Authors: Pritchard G. O. , Abbas S. H. , Piasecki M. L. , Meleason M. A. 
Published: January 2005

AbstractCross‐disproportionation to combination ratios for CF2H and n‐C3H7 radicals have been determined (the hydrogen acceptor radical is given first) to be Δ(n‐C3H7, CF2H) = 0.30 ± 0.01 and Δ(CF2H, n‐C3H7) = 0.057 ± 0.006.
The flash photolysis of di‐μ‐oxo‐bis(oxo‐molybdate(V)) acid aqueous solutions in the presence of excess thiocyanate
Authors: Martire D. O. , González M. C. , Feliz M. R. , Cafferata L. , Capparelli A. L. 
Published: January 2005

AbstractThe flash photolysis of the mono and di‐thiocyanate complexes of μ‐oxo bis(oxo‐molybdenum(V)) (Mo2O4(NCS)x(H2O)6−x(2−x)+ where x = 1, 2) has been studied in the system composed of perchloric acid solutions of Mo2O4(H2O)62+ in the presence of excess thiocyanate.Irradiation with light in the wavelength range 250–340 nm induced the formation of three reaction intermediates identified as μ‐oxo‐bis (oxo‐molybdenum(V)) species: Mo2O3(H2O)84+ (A), Mo2O3(NCS) (H2O)73+ (B), and Mo2O3(NCS)2(H2O)62+ (C). A rapid equilibria between the transient species is established before they decay following a first order kinetics. Intermediate A is the only species effective in promoting the observed decay leading to the end products Mo(VI) and H2.The relative absorption spectrum of species A, B, and C are reported, as well as the measured stability constants for the formation of B and C in the temperature range 20–45°C. An overall mechanism is proposed.
Kinetics and mechanism of silver(I) catalyzed oxidation of tris(1,10‐phenanthroline)iron(II) with peroxodiphosphate in acetate buffers
Authors: Parasher P. , Hussain J. , Sharma P. D. 
Published: January 2005

AbstractA kinetic study of the silver(I)‐catalyzed oxidation of tris(1,10‐phenanthroline)iron(II) with peroxodiphosphate was carried out by estimating tris‐complex at 510 nm. The reaction is found to conform to the rate law (i).
equation image
with K2 and K3 being the acid dissociation constants of H3P2O8− and H2P2O82−, respectively. The silver(I) catalysis in the reaction has been explained on the basis of complex formation between pdp and silver(I).
Rate constants for the reaction of atomic and molecular bromine with gallium arsenide
Authors: Salusbury I. M. , Ogryzlo E. A. 
Published: January 2005

AbstractThe reaction of the (100) face of a gallium arsenide single crystal with atomic and molecular bromine has been studied in a discharge flow system at temperatures between 100 and 225°C and pressures between 0.1 and 40 torr. The reaction with Br2 was found to be first order in Br2 only at pressures below 1 torr. Temperature dependence studies in the linear range gave the activation energy and preexponential factor for the rate controlling reaction in the low pressure regime. The results are summarized in the following Arrhenius equation:

Deviations from linearity at high pressures are discussed in terms of two alternative mechanisms.The reaction of GaAs with atomic bromine was also studied as a function of temperature, and found to have a temperature dependence described by the following Arrhenius equation: