bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and mechanism of acetylacetonate transfer from acetylacetonatomanganese(III) to iron(III) in acetonitrile catalysis and inhibition effects
Authors: Schmid Roland , Sapunov Valentin N. 
Published: January 2005

AbstractThe reaction between tris(acetylacetonato)magnanese(III) and hexa(N,N‐dimethylformamide)iron(III) perchlorate in acetonitrile proceeds in two stages. The first stage corresponds to the reaction of pentacoordinated Fe(DMF) with Mn(acac)3, and the rate‐determining step of the second stage consists mainly in the elimination of a DMF ligand from Fe(DMF) to yield Fe(DMF) which reacts rapidly with the manganese complex. The formation of Fe(DMF) is catalyzed by Mn(acac)3, this catalytic effect being decreased by manganese products. The rate‐determining step for the formation of Fe(acac)3 is the transfer of the first acetylacetonate to yield Fe(acac)2+. The final products of iron depend on the ratio of reactant concentrations. With Mn or Fe in excess, Fe(acac)3 or Fe(acac)2+ are mainly produced.
Neighboring group participation of polar β substituents in the gas‐phase pyrolysis of 2‐substituted ethyl chlorides
Authors: Chuchani Gabriel , Martin Ignacio , Martin Gonzalo , Bigley David B. 
Published: January 2005

AbstractThe pyrolysis of 2‐dimethylaminoethyl chloride in the temperature range of 360–400°C and the pressure range of 60–271 mmHg is a homogeneous, unimolecular, first‐order reaction giving dimethylvinyl amine and hydrogen chloride. 2‐Methoxyethyl chloride pyrolysis in the temperature range of 450–490°C and the pressure range of 53–110 mmHg by a similar unimolecular, first‐order reaction yields methylvinyl ether and hydrogen chloride. These reactions were carried out in a seasoned reaction vessel and in the presence of a propene inhibitor. The methylvinyl ether decomposes slowly into other products at the temperature of pyrolysis. The rate constants are given by the Arrhenius equations(a) 2‐dimethylaminoethyl chloride:

(b) 2‐methoxyethyl chloride:

The effects of polar β substituents in the 2 position of ethyl chloride are discussed in terms of anchimeric assistance and electron‐withdrawing deactivation in these elimination reactions. The present results are consistent with the heterolytic nature of the four‐centered cyclic transition state for the gas‐phase pyrolysis of alkyl halides.
Evaluation of boundary‐layer effects in shock‐tube studies of chemical kinetics
Authors: Fujii Nobuyuki , Koshi Mitsuo , Ando Hiromitsu , Asaba Tetsuro 
Published: January 2005

AbstractParticle times of flight in incident shock flow were determined experimentally by marking several positions of the test gas (mainly Ar) in the shock tube with an infrared emitting gas (NO or CO2). From the local particle velocity, derived from the particle flight times, temperature and pressure changes behind the shock front were evaluated. Several experimental data were found to be correctly described by Mirels's formulations when used properly. The limitations of the formulations are discussed. It is found to be advisable to evaluate boundary‐layer effects on shock‐tube flow by experiments, rather than theory, in carrying out chemical kinetics studies.
Kinetics of cerium (IV) oxidation of mandelic acid. Ionic strength and specific cation effects
Authors: Arcoleo Gioacchina , Calvaruso Giuseppe , Cavasino F. Paolo , Dio Emanuele Di 
Published: January 2005

AbstractThe kinetics of the redox reaction between mandelic acid (MA) and ceric sulfate have been studied in aqueous sulfuric acid solutions and in H2SO4MClO4 (M+ = H+, Li+, Na+) and H2SO4MHSO4 (M+ = Li+, Na+, K+) mixtures under various experimental conditions of total electrolyte concentration (that is, ionic strength) and temperature. The oxidation reaction has been found to occur via two paths according to the following rate law: rate = k[MA] [Ce(IV)], where k = k1 + k2/(1 + a)2[HSO4−]2 = k1 + k2/(1 + 1/a)2[SO42−]2, a being a constant. The cations considered exhibit negative specific effects upon the overall oxidation rate following the order H+ ⩽ Li+ < Na+ < K+. The observed negative cation effects on the rate constant k1 are in the order Na+ < Li+ < H+, whereas the order is in reverse for k2, namely, H+ ⩽ Li+ < Na+. Lithium and hydrogen ions exhibit similar medium effects only when relatively small amounts of electrolytes are replaced. The type of the cation used does not affect significantly the activation parameters.
Mutual combination of ClO radicals
Authors: Basco N. , Hunt J. E. 
Published: January 2005

AbstractThe mutual combination reaction
equation image
is proposed as the rate‐limiting step in the removal of ClO radicals at moderate pressures. The third‐‐order rate constants measured at room temperature were k1(Ar) = 3.51 ± 0.14 × 109 l2/mol2·ec; k1(He) ≈ 2.8 × 109 l2/mol2·sec, and k1(O2) ≈ 7.9 × 109 l2/mol2·sec. There is also an independent second‐order reaction
equation image
for which k3 ≈ 8 × 106 l/mol·sec. A new absorption spectrum has been observed in the ultraviolet and attributed to Cl2O2. The extinction coefficient for Cl2O2 has been measured at six wavelengths, and, between 292 and 232 nm, it increases from 0.4 × 103 to 2.9 × 103 l/mol·cm. In the presence of the chlorine atom scavengers OClO or Cl2O, Cl2O2 exists in equilibrium with ClO. The equilibrium constant Ke1 = 3.1 ± 0.1 × 106 l/mol at 298 K, and, with ΔS10 estimated to be −133 ± 11 J/K·mol, ΔH10 = −69 ± 3 kJ/mol and ΔHf0(Cl2O2) = 136 ± 3 kJ/mol.
Quantum effects and isotope effects in chemical kinetics
Authors: Christov S. G. , Parlapanski M. 
Published: January 2005

AbstractThe relations of quantum and kinetic isotope effects are investigated using the exact quantum corrections to the collision and activated complex theories. The latter are computed for the collinear three‐atomic reaction H2+ H → H + H2and the related isotopic reactions using realistic potential energy surfaces. Taking into account the bent configurations of the collision complex H‐H‐H gives a very good agreement between the quantum collision theory and the experimental data for the absolute values and the isotopic ratios of rate constants. Classical trajectory calculations yield considerably lower results.
The thermal reactions of ethylene at 500°C in the presence and absence of small quantities of oxygen
Authors: Back M. H. , Martin R. 
Published: January 2005

AbstractInitial rates of formation of primary products have been measured in the pyrolysis of ethylene at 500°C, and a mechanism for the reaction is proposed based on the isomerization of the n−hexyl radical. Additions of oxygen in amounts less than 0.1% markedly increased the rate of formation of all products, but oxygen was not completely consumed in the reaction. It is shown that secondary initiation processes are important at very low conversions, and butene‐1 is the most reactive product. Bimolecular reactions between olefins and with oxygen are important steps in the mechanism.
Wall effects in the pyrolysis of diethylether. A case of hetero‐homogeneous pyrolysis at 500°C
Authors: Foucaut J. F. , Martin R. 
Published: January 2005

AbstractThe pyrolysis of diethylether has been studied at 500°C and 50 Torr initial pressure in packed vessels (surface‐to‐volume ratio 11 cm−1). In untreated vessels the reaction appears to be essentially homogeneous as reported before. On the contrary, it is very sensitive to the walls of PbO‐coated or NaOH‐treated vessels. Thus most of the initial rates of product formation are increased in the PbO‐coated vessel and decreased in the NaOH‐treated vessel. The efficiency of the walls has been monitored for several weeks and was shown to decrease slowly with the vessel aging time. These phenomena are interpreted in terms of a free‐radical chain mechanism in which a part of the initiation or termination steps occurs at the walls, the propagating steps being homogeneous. The present work clearly proves the existence of hetero‐homogeneous chain reactions at 500°C. This new class of reaction could be of practical interest in the design of industrial reactors.
Reaction of NO with hypochlorous acid
Authors: Ghibaudi Elena , Barker John R. , Benson Sidney W. 
Published: January 2005

AbstractThe reaction between NO(g) at concentrations between 0.1 and 1.0 Torr in 1‐atm N2 and aqueous solutions of NaClO has been studied over the pH range of 6–12 and hypochlorite concentrations between 0.01 and 1.0M. A very rapid and efficient reaction occurs leading to the production of about 30%–40% of the NO as NO2 and with conversions of NO up to 98% at about 1‐sec contact time. It is shown that a fast chain reaction initiated by the endothermic step
equation image
can account for the data. The very exothermic reaction NO + ClO− → NO2 + Cl− is shown to be at least 30‐fold slower than i. The overall reaction seems very promising as a method of reducing NO and NO2 emissions from the exhausts of industrial plants.
Estimating the positions of transition states from experimental data
Authors: Basilevsky M. V. , Weinberg N. N. , Zhulin V. M. 
Published: January 2005

AbstractA procedure is suggested to estimate the positions of a transition state (TS) along the reaction coordinate in reaction series involving several radical reactions. It is based on the dependence between experimental activation energies U± and heat effects Q. Taking into account the shift of a TS position, the following relation between these quantities is obtained: U± −; U = A (Q ‐ Q0)2 + B(Q ‐ Q0). The subscript 0 indicates the standard reference reaction. For three series, namely, the hydrogen abstraction from hydrocarbon substrates by radicals CH3˙, CF˙3, and Br·, the bond lengths characterizing the TS reaction center are evaluated. The TS positions appear to vary significantly in the reaction series, which accounts for significant changes in the experimentally observed activation volumes. The derivation of the Hammond rule and the range of its validity for the series with polar and steric substituent effects are discussed.
Kinetics of the reactions of cyclopropane derivatives. V. The gas‐phase unimolecular reactions of 1 α‐chloro‐2α,3α‐dimethylcyclopropane and 1α‐chloro‐2α,3β‐dimethylcyclopropane
Authors: Robinson P. J. , Waller M. J. 
Published: January 2005

AbstractThermolysis of the “all‐cis” compound 1α‐chloro‐2α,3α‐dimethylcyclopropane (A) at 550–607 K and 6–115 torr is a first‐order homogeneous non‐radical‐chain process giving penta‐1,3‐diene (PD) and HCl as products. The Arrhenius parameters are log10A(sec−1) = 13.92 ± 0.08 and E = 199.6 ± 0.9 kJ/mol. The isomer with trans‐methyl groups, 1α‐chloro‐2α,3β‐dimethylcyclopropane (B) reacts by two parallel first‐order processes giving as observed products trans‐4‐chloropent‐2‐ene (4CP) and PD + HCl, with log10A(sec−1) = 14.6 and 13.8, respectively, and E = 199.5 and 190.2 kJ/mol, respectively. The 4CP undergoes secondary decomposition to PD + HCl (as investigated previously). Comparison of the results for compounds (A) and (B) with those for other gas‐phase and solution reactions leads to the conclusion that the gas‐phase thermolyses proceed by rate‐determining ring opening to form olefins which may decompose further by thermal or chemically activated reactions, and that the ring opening is a semiionic electrocyclic reaction in which alkyl groups in the 2,3‐positions trans to the migrating chlorine semianion move apart, with appropriate consequences for the rate of reaction and the stereochemistry of the products.
Excited‐state kinetics of azoalkanes some further studies with azoethane, azo‐n‐propane, and azoisopropane
Authors: Pritchard G. O. , Marchant P. E. , Steel C. 
Published: January 2005

AbstractThe photochemistry of azo‐n‐propane is investigated at 366 nm up to 1 atm pressure, and over a range of temperature from 50 to 190°C. Some additional experiments with azoethane at room temperature and azoisopropane at 180 and 190°C are also reported. From a consideration of the pressure dependence of the quantum yields for photodissociation a generalized mechanism is proposed which accounts for the known experimental observations in acyclic azoalkane photochemistry. These observations include the extensive photoisomerization data which were previously obtained for azoisopropane. In the mechanistic scheme dissociation at low pressures is believed to occur mainly from S and T, the vibrationally excited and randomized first excited singlet and triplet states. At high pressures and low temperatures (≤100°C) the major dissociation channel is probably a nonrandom S1 state. In direct or singlet sensitized photolysis isomerization occurs predominatly at high pressure and is postulated to occur by internal conversion from S, the thermalized singlet, to the ground state. During the process partitioning to the cis or trans isomer is equally probable. In triplet sensitized photolysis isomerization occurs via intersystem crossing from T1to the ground state. At elevated temperatures (>150°C) dissociation from S, which has a significant activation energy, can compete with return to the ground state.
Kinetics of cyclodimerization of hexafluoropropene and of its cycloaddition to chlorotrifluoroethene
Authors: Atkinson Bernard , Tsiamis Christos 
Published: January 2005

AbstractThe thermal cyclodimerization of hexafluoropropene and its cycloaddition to chlorotrifluoroethene have been studied at 570–700 K and 8–62 kPa. Both reactions give 1,2‐substituted hexafluorocyclobutanes. For the intercombination product 1‐chloro‐2‐trifluoromethyl‐hexafluorocyclobutane infrared, nuclear magnetic resonance and mass spectra as well as vapor pressure are reported. The rates of reaction can be expressed by the following equations:

The reactions probably proceed by a biradical mechanism.
Combination and disproportionation reactions of allylic radicals with ethyl, propyl, and t‐Butyl Radicals
Authors: Baulch D. L. , Chown P. K. , Montague D. C. 
Published: January 2005

Abstract1‐Methylallyl, 1,1‐dimethylallyl, 1,2‐dimethylallyl, 1,3‐dimethylallyl, 1,1,2‐trimethylallyl, and 1‐ethylallyl radicals have been generated in the gas phase at 20 ± 1°C by addition of H atoms, formed by Hg(63P1) photosensitization of H2, to appropriate dienes. Their combination reactions with ethyl radicals have been studied and the relative reactivities of the reaction centers in each allylic radical determined. Similar measurements have been made for some combination reactions of n‐propyl, i‐propyl, and t‐butyl with 1‐methylallyl and 1,1,2‐trimethylallyl radicals. The more substituted reaction centers are found to be the less reactive. In addition the self‐combination and disproportionation of 1‐methylallyl radicals has been investigated, as has cross disproportionation of each allylic radical with ethyl. The results establish a general pattern of reactivity for these radicals, which is interpreted primarily in terms of the effects of steric interaction during reaction.
Mechanistic details of the Belousov–Zhabotinsky oscillations. III. The induction period
Authors: Edelson D. 
Published: January 2005

AbstractThe oscillating Belousov–Zhabotinsky reaction exhibits an initial quiescent induction period during which the concentrations of various reactants and intermediates adjust to a quasisteady‐state, which eventually switches into oscillation. The duration of this induction period is strongly dependent on the initial bromide ion concentration. The previously reported detailed mechanism for this system is used to calculate this dependence, and the results are shown to agree with recent experimental work. The factors that account for this behavior are discussed.
Addition of trichloromethyl radicals to tetrachloroethylene
Authors: Horowitz A. , Baruch G. 
Published: January 2005

AbstractThe gamma‐radiation‐induced free‐radical chain reactions in liquid CCl4C2Cl4cC6H12 mixtures were studied in the temperature range of 363–448°K. The main products in this system are chloroform, hexachloropropene and chlorocyclohexane. These products are formed via reactions (1)–(5):
equation image
with G values (molec/100 eV) of the order of magnitude of 102 and 103 at the lowest and highest temperatures, respectively. Values of k2/k1 were determined from the product distribution. In turn, these values gave the following Arrhenius expression for k2/k1 (θ = 2.303RT, in kcal/mol):

From this result and the previously determined Arrhenius parameters of reaction (1), k2 is found to be given by

.
Evidence for α‐elimination from neopentyl chloride in the gas phase
Authors: Failes Robert L. , Mollah Yousuf M. A. , Shapiro Jacob S. 
Published: January 2005

AbstractExperimental evidence is presented for a unimolecular gas‐phase Wagner‐Meerwein shift in neopentyl chloride pyrolysis. In the decomposition of α,α‐neopentyl chloride‐d2 at 445°C, maximally inhibited by cyclohexene, the initial products were isotopically pure 2‐methyl‐1‐butene‐d2 and 2‐methyl‐2‐butene‐d1. Rearrangement, accompanied by loss of either α‐ or γ‐hydrogen in the formation of hydrogen chloride, is consistent with an incipient ion‐pair type of transition state. The cyclohexene maximally inhibited pyrolysis of neopentyl chloride was also examined over the temperature range 424–478°C and Arrhenius parameters of E, 258.7 kJ/mole and logA/sec−1, 13.78, were determined.
Evaluation of the rate coefficients and arrhenius parameters of hydrogen atom transfer reactions. I. The method
Authors: Bérces Tibor , Dombi Jóazsef 
Published: January 2005

AbstractA method is presented for the prediction of rate coefficients and Arrhenius parameters for bimolecular hydrogen atom transfer reactions A + BC → AB + C. The treatment sets out from structural considerations of the complex A ⃛ B ⃛ C and calculates the energy of the complex along the reaction path from empirical functions for a bonding energy term and an endgroup contribution. The treatment proceeds by assuming ultrasimple transition state models and assigning the force constants and vibrational frequencies. Finally the rate coefficient and Arrhenius parameters are obtained on the basis of separable activated complex theory. Application of the method requires known properties of reactant and product molecules and does not demand the use of adjustable parameters. The relation and differences between this method and the BEBO treatment as well as Zavitsas' method are dealt with.
Kinetics of oxidation of butane 2,3‐diol by osmium(VIII)
Authors: Anand B. H. , Menghani G. D. 
Published: January 2005

AbstractThe oxidation of butane 2,3‐, propane 1,2‐, ethane diol and 2‐methoxy ethanol in aqueous alkaline medium by Os(VIII) has been studied. The reaction is base catalyzed and shows first‐order kinetics in Os(VIII), whereas the order is less than 1 in butane 2,3‐diol [BD]. The rate of oxidation is BD > propane 1,2 > ethane diol ≈ 2‐methoxy ethanol. The change in ionic strength has no effect on the rate of reaction. Activation parameters ΔE, PZ, and ΔS* have been evaluated.
Kinetics of the diels–alder addition of ethene to cyclohexa‐1,3‐diene and its reverse reaction in the gas phase
Authors: Huybrechts G. , Rigaux D. , Vankeerberghen J. , Van Mele B. 
Published: January 2005

AbstractThe addition of ethene to cyclohexa‐1,3‐diene has been studied between 466 and 591 K at pressures ranging from 27 to 119 torr for ethene and 10 to 74 torr for cyclohexa‐1,3‐diene. The reaction is of the “Diels–Alder” type and leads to the formation of bicyclo[2.2.2]oct‐2‐ene. It is homogeneous and first order with respect to each reagent. The rate constant (in l./mol sec) is given by

The retron‐Diels–Alder pyrolysis of bicyclo[2.2.2]oct‐2‐ene has also been studied. In the ranges of 548–632 K and 4–21 torr the reaction is first order, and its rate constant (in sec−1) is given by

The reaction mechanism is discussed. The heat of formation and the entropy of bicyclo[2.2.2]oct‐2‐ene are estimated.
A modified model of diffusion‐controlled reactions
Authors: Burshtein A. I. , Yakobson B. I. 
Published: January 2005

AbstractThe treatment used for diffusion‐controlled reactions is extended to the case when the final jumplike step of the reagent approach differs essentially from the preceding diffusion. In terms of the model proposed it is possible to take into account, in a simple way, chemical inhomogeneity of the reagents when the in‐cage reaction rate depends on the pair state (for example, on the molecular orientation). In this connection the reaction can be controlled either by the reagent intrusion into the solvation shell of the partner, or by the in‐cage relaxation.
Chain ion molecular mechanism of ascorbic acid oxidation with hydrogen peroxide. Cu3+ ion as a chain carrier
Authors: Skurlatov Yu. 
Published: January 2005

AbstractThe kinetics and mechanism of ascorbic acid (DH2) oxidation have been studied under anaerobic conditions in the presence of Cu2+ ions. At 10−4 ≤ [Cu2+]0 < 10−3M, 10−3 ≤ [DH2]0 < 10−2M, 10−2 ≤ [H2O2] ≤ 0.1M, 3 ≤ pH < 4, the following expression for the initial rate of ascorbic acid oxidation was obtained:
equation image
where χ2 (25°C) = (6.5 ± 0.6) × 10−3 sec−1. The effective activation energy is E2 = 25 ± 1 kcal/mol. The chain mechanism of the reaction was established by addition of Cu+ acceptors (allyl alcohol and acetonitrile). The rate of the catalytic reaction is related to the rate of Cu+ initiation in the Cu2+ reaction with ascorbic acid by the expression
equation image
where C is a function of pH and of H2O2 concentration. The rate equation
equation image
where k1(25°C) = (5.3 ± 1) × 103M−1 sec−1 is true for the steady‐state catalytic reaction. The Cu+ ion and a species, which undergoes acid–base and unimolecular conversions at the chain propagation step, are involved in quadratic chain termination. Ethanol and terbutanol do not affect the rate of the chain reaction at concentrations up to ≈0.3M. When the Cu2+–DH2–H2O2 system is irradiated with UV light (λ = 313 nm), the rate of ascorbic acid oxidation increases by the value of the rate of the photochemical reaction in the absence of the catalyst. Hydroxyl radicals are not formed during the interaction of Cu+ with H2O2, and the chain mechanism of catalytic oxidation of ascorbic acid is quantitatively described by the following scheme.Initiation:
equation image
Propagation:
equation image

equation image
Termination:
equation image
Deactivation of O2(A3Σ) by O2, O, and Ar
Authors: Kenner R. D. , Ogryzlo E. A. 
Published: January 2005

AbstractO2 in the A3Σu+ state has been prepared in a discharge flow system by recombining oxygen atoms on a nickel surface. The decay of this excited state was followed by observing the emission between 280 and 400 nm. The wall deactivation was observed to approach unit efficiency. Rate constants were determined to be 0.9 × 10−11, 2.9 × 10−13, and 8.6 × 10−16 cm3/molecule sec for the quenching of O2(A3Σu+) by O, O2, and Ar, respectively.
Consistency of a set of chemical reactions
Authors: Oliver P. 
Published: January 2005

AbstractIt is a useful feature of many general chemical kinetics programs that the user's reaction scheme is tested as far as possible before a calculation is started. Attempts are made to answer the question: How far can a reaction scheme be tested for consistency, with respect to mass conservation, without knowing the molecular weights of the species involved? It is found that this problem can be transformed so that it is solvable by the standard methods used in linear programming.