bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dipolar aprotic–protic solvent influences in the hydrolysis of diol monoesters
Authors: Balakrishnan M. , Rao G. Venkoba , Venkatasubramanian N. 
Published: January 2005

AbstractThe kinetics of the alkaline hydrolysis of five diol monoesters and related esters in aqueous DMSO, aqueous acetone, and aqueous ethanol are reported. A novel solvent dependency of the reactivity pattern of the various esters is noticed. The results are explained on the basis of an internal stabilization of the transition state and the influences of the various solvent systems on such transition states. It is suggested that such dipolar aprotic–protic solvent influences on reaction rates can be used as a criterion in the assessment of anchimeric assistance in such reactions.
Kinetic isotope effects in the thermal gas phase reactions of 1, 2‐epoxycyclohexane‐3, 3, 6, 6‐d4
Authors: Flowers M. C. , Penny D. E. 
Published: January 2005

AbstractFirst‐order rate constants for formation of cyclohexanone and 2‐cyclohexen‐1‐ol from 1,2‐epoxycyclohexane and 1,2‐epoxycyclohexane‐3,3,6,6‐d4 have been determined over the temperature range of 677–746°K. The observed kinetic isotope effects are used in an attempt to determine the mechanism for formation of products. A distinction between a biradical and a concerted mechanism for the alcohol formation could not be made. However, if a common biradical is the precursor of both cyclohexanone and 2‐cyclohexenl‐ol then the rate of ring closure of this biradical must be much faster than the rates of hydrogen transfer to give the ketone and the alcohol.
Mechanism of the acid hydrolysis of aromatic o‐carboxyamides and relative imides
Authors: Nechaev P. P. , Moiseev Yu. V. , Vygodskii Ya. S. , Zaikov G. E. 
Published: January 2005

AbstractThe kinetics of N‐phenylphthalamic acid and of N‐phenylphthalimide hydrolysis in aqueous solutions of sulfuric acid has been studied. A reaction mechanism is proposed implying that unreactive forms of the reactant appear by protonization of the amide bond at the carbonyl oxygen and by dissociation of the o‐carboxyl group (N‐phenylphthalamic acid). Attack of the nonprotonized amide bond by the hydroxonium ion is suggested to be the rate‐limiting step.
The kinetics of free radical chain reactions in solutions of trichlorofluorethylene in cyclohexane
Authors: Horowitz A. , Mey‐Marom A. , Rajbenbach L. A. 
Published: January 2005

AbstractThe kinetics of the gamma‐radiation‐induced free radical chain reaction in solutions of C2Cl3F in cyclohexane (RH) was investigated over a temperature range of 87.5–200°C. The following rate constants and rate constant ratios were determined for the reactions:

In competitive experiments in ternary solutions of C2Cl4 and C2Cl3F in cyclohexane the rate constant ratio k2c/k2a was determined

By comparing with previous data for the addition of cyclohexyl radicals to other chloroethylenes it is shown that in certain cases the trends in activation energies for cyclohexyl radical addition can be correlated with the CCl bond dissociation energies in the adduct radicals.
Reaction of excited iodine atoms with methyl iodide: Rate constant determinations
Authors: Haaland D. M. , Meyer R. T. 
Published: January 2005

AbstractThe rate constant for the reaction I(2P1/2) + CH3I → I2 + CH3 has been reevaluated taking into account both collisional deactivation of excited iodine atoms and loss of I2 by I2 + CH3 → I + CH3I. The reevaluation is based upon data obtained (R. T. Meyer), J. Chem. Phys., 46, 4146 (1967) from the flash photolysis of CH3I using time‐resolved mass spectrometry to measure the rate of I2 formation. Computer simulations of the complete kinetic system and a closed‐form solution of a simplified set of the differential equations yielded a value of 6(± 4) × 106 1./mole‐sec for the excited iodine atom reaction in the temperature region of 316 to 447 K. A slight temperature dependence was observed, but an activation energy could not be evaluated quantitatively due to the small temperature range studied. An upper limit for the collisional deactivation of I(2P1/2) with CH3I was also determined (2.4 × 107 1./mole‐sec).
Kinetics and mechanism of the reaction between N‐and N,N′‐methyl ethylenediamines and palladium(II) chloro complexes in aqueous acid medium
Authors: De Waal D. J. A. , Robb W. 
Published: January 2005

AbstractThe substitution of N‐alkyl substituted ethylenediamines for chloride ions in the rapidly equilibrating system

has been investigated in aqueous acid medium. The kinetic data can be accommodated by the general rate law

where n = 0, 1, or 2 and m = 0, 1, or 2, depending on whether none, one, or two methyl groups are attached to the two nitrogen atoms of ethylenediamine. Reaction with the most heavily substituted ethylenediamine, namely, N2N2en discloses a change of the mentioned rate law to

on going from a lower to a higher chloride ion concentration range. This change in the mathematical form of the rate law can be explained in terms of an ion‐pair association of N2N2enH+ and free chloride ions.
Very low‐pressure pyrolysis (VLPP) of alkanes: n‐butane, 2,3‐dimethylbutane, 2,2′,3,3′ ‐tetramethylbutane, and isobutane
Authors: Golden D. M. , Alfassi Z. B. , Beadle P. C. 
Published: January 2005

AbstractThe four species in the title were decomposed under VLPP conditions at temperatures in the vicinity of 1100°K. Three model transition states were constructed that fit the low‐pressure data thus obtained and that also yield (1) E298 = ΔE298; (2) E1100 = ΔE1100; (3) log A1100 = 16.4 per C–C bond broken. The predictions of these models as to values of the high‐pressure rate constants for bond scission and the reverse rate constants (radical combination) are compared with existing data.
Reaction of chlorine with bromine
Authors: Olbregts J. 
Published: January 2005

AbstractDifferent possible mechanisms for the gas phase reaction of formation of bromine chloride from bromine and chlorine are discussed. The rate of the reaction has been deduced from photometric measurements in conventional static reactors of surface‐to‐volume ratio ranging between 0.6 and 3 cm−1, at temperatures between 51 and 113°C. Experimental data show that (1) the observed reaction is predominantly heterogeneous, and (2) the homogeneous reaction must proceed by an atomic chain mechanism initiated by Br atoms.
A flash photolysis‐resonance fluorescence study of the reaction of atomic hydrogen with molecular oxygen H + O2 + M → HO2 + M
Authors: Wong W. , Davis D. D. 
Published: January 2005

AbstractUsing the technique of flash photolysis‐resonance fluorescence, absolute rate constants have been measured for the reaction H + O2 + M → HO2+M over a temperature range of 220–360°K. Over this temperature range, the data could be fit to an Arrhenius expression of the following form:

The units for kAr are cm6/mole‐s. At 300°K the relative efficiencies for the third‐body gases Ar:He:H2:N2:CH4 were found to be 1.0:0.93:3.0:2.8:22. Wide variations in the photoflash intensity at several temperatures demonstrated that the reported rate constants were measured in the absence of other complex chemical processes.
The reaction of trichloromethyl radicals with hydrogen chlorid and a new estimation of the rate of combination of trichloromethyl radicals
Authors: Matheson I. A. , Sidebottom H. W. , Tedder J. M. 
Published: January 2005

AbstractThe effect of the addition of hydrogen chloride on the photolysis of carbon tetrachloride in the presence of cyclohexane has been investigated in a companion paper. The data enable the rate constant ratio k8/(k5)1/2 to be determined. Since k−8 is well established, k5 can be estimated from known thermochemical data. The validity of the thermochemical derivation is checked by applying it to trifluoromethyl radicals. The photolysis of bromotrichloromethane and carbon tetrachloride in the presence of hydrogen chloride has been investigated over a range of temperatures. From these results and assuming reaction (5) has no activation energy, Arrhenius parameters for reaction (8) have been determined:

equation image

The activation energies for the reaction of methyl, trichloromethyl, and trifluoromethyl radicals with hydrogen chloride are compared, and at first sight surprising results are rationalized in terms of relative electronegativity.
Kinetics of the addition of propene to cyclohexa‐1,3‐diene in the gas phase
Authors: Debande G. , Huybrechts G. 
Published: January 2005

AbstractThe addition of propene to cyclohexa‐1,3‐diene has been studied between 512 and 638°K at pressures between 70 and 640 torr. The products are endo‐ and exo‐5‐methylbicyclo [2.2.2] oct‐2‐ene, and their formations are second order. The rate constants (in 1./mole‐sec) are given by

The results are discussed in terms of a biradical mechanism.
Rate of the reaction of hydroxyl radical with acetylene
Authors: André Pastrana V. , Carr Robert W. 
Published: January 2005

AbstractThe kinetics of the decay of hydroxyl radicals in the presence of excess acetylene were studied at pressures in the vicinity of 1 torr and at ambient temperature in a tubular discharge‐flow reactor. Hydroxyl radicals were produced by the reaction of atomic hydrogen with nitrogen dioxide, H + NO2 → OH + NO. The concentration of hydroxyl was followed by line absorption photometry at 308.939 nm and 308.328 nm. Second‐order rate coeffcients were determined in two sets of experiments. The initial concentration ratio [C2H2]0/[OH]0 was in the range of 2.3 to 13.2 in the first set, and 14 to 125 (owing to greater hydroxyl detection sensitivity) in the second set. Values of the

equation image

second‐order rate coefficient obtained were nk5 = (2.9 ± 0.3) × 10−13 cm3/molec‐sec in the first set, and nk5 = (2.1 ± 0.6) × 10−13 cm3/molec‐sec in the second set, where n is the stoichiometric coefficient of OH. A value of the bimolecular rate constant k5 = (2.0 ± 0.6) × 10−13 cm/molec‐sec is consistent with both sets of data, as well as an earlier determination.
The reaction of atomic oxygen and hydrogen with nitric acid
Authors: Chapman C. J. , Wayne R. P. 
Published: January 2005

AbstractThe reactions

have been studied in a discharge‐flow system. Kinetic studies were made using resonance fluorescence for the measurement of atom concentrations. Based on the rates of atom loss, the following upper limits were obtained for the rate constants:

Observed reaction in the HHNO3 system is at least partially due to an autocatalytic chain removal of both reactants. Diagnostic tests have suggested that OH, NO2, and NO3 are the chain carriers.
Electron transfer reactions between the superoxide ion and quinones
Authors: Afanas'ev I. B. , Prigoda S. V. , Mal'tseva T. Ya. , Samokhvalov G. I. 
Published: January 2005

AbstractThe electron transfer reactions of the superoxide ion with benzoquinone, trimethylbenzoquinone, and menadione in dimethylformamide were studied. A procedure of the determination of the relative rate constants of these reactions was developed; the reaction of O2 with butyl bromide was chosen as a standard one. The relative rate constants measured at 20,°, 35°, and 50°C were slightly dependent on the quinone structure.The relationship between the free energy ΔF*of the electron transfer reactions and the standard free energy ΔFo was discussed. This relationship is proposed as ΔF* = αΔFo + β, where the proportionality coefficient α is equal to 0.04–0.11 for exothermal reactions and to 0.90–0.96 for endothermal reactions.
The solvent‐jump relaxation method using continuous flow
Authors: Schelly Z. A. , Wong M. M. 
Published: January 2005

AbstractA step perturbation (concentration‐jump or solvent‐jump) relaxation method is described for studying the rates of fast reactions, using nontransient observation in a steadystate flow system. Therelaxation time is determined from a single measurement of an integrated relaxation amplitude. Remeasurement of the rate of dimerization of aqueous rhodamine B is reported.
The homogeneous pyrolysis of 2‐butenes
Authors: Jeffers Peter , Bauer S. H. 
Published: January 2005

AbstractThe homogeneous pyrolysis of 2‐butene subjected to shock heating was studied in the limit of high pressures by a relative rate technique. Over the temperature range of 1150–1325°K nearly equal amounts of methane, propylene, and butadiene were formed starting with either the cis‐ or trans‐2‐butene, while isomerization remained far from equilibrium. The results are consistent with a simple free radical mechanism for which we find

as the initial rate‐limiting step.
The collisional quenching of electronically excited arsenic atoms As(42DJ) and As(42PJ), studied by time‐resolved attenuation of atomic resonance radiation
Authors: Bevan M. J. , Husain D. 
Published: January 2005

AbstractA kinetic investigation of electronically excited arsenic atoms in the low‐lying states, As(4p3 2DJ) and As(4p3 2PJ), ca. 1.33 and 2.28 eV, respectively, above the 44S3/2 ground state, has been carried out by atomic absorption spectroscopy. Atoms in these optically metastable states were generated by the pulsed irradiation of suitable arsenic compounds (AsMe3 for 2D and AsCl3 for 2P) in different spectral regions and monitored photoelectrically by time‐resolved attenuation of atomic resonance radiation. Rate constants for the deactivation of these two states are reported for a range of collision partners. The data are compared with those of the analogous states of lighter atoms in group V, namely, P(32DJ, 32PJ) and N(22DJ, 22PJ), and discussed in terms of spin and orbital symmetry considerations.
The collisional quenching of electronically excited tin atoms Sn(51D2) by time‐resolved atomic absorption spectroscopy
Authors: Brown A. , Husain D. 
Published: January 2005

AbstractElectronically excited tin atoms Sn(51D2), 1.068 eV above the 53P0 ground state, have been generated by the pulsed irradiation of tin tetramethyl and monitored photoelectrically in absorption by time‐resolved attenuation of atomic resonance radiation at λ=285.06 nm [Sn((5d3F20) ← (5p2 1D2))]. Deactivation rate constants are reported for the quenching of Sn(51D2) with a range of collision partners and the resulting data are compared with those for analogous states within group IV, namely, C(21D2) and Pb(61D2). The data are discussed in terms of correlations based on both the weak and strong spin orbit coupling approximations.
Very low‐pressure pyrolysis of cyclobutyl cyanide. The cyano stabilization energy
Authors: King Keith D. , Goddard Richard D. 
Published: January 2005

AbstractA very low‐pressure pyrolysis (VLPP) apparatus has been constructed and shown to yield kinetic data consistent with other VLPP systems. The technique has been applied to the pyrolysis of cyclobutyl cyanide over the temperature range of 833–1203°K. The reaction was found to proceed via a single pathway to yield ethylene and vinyl cyanide. If A∞ is based on previous high‐pressure data for this reaction and for cyclobutane pyrolysis, then RRKM theory calculations show that the experimental unimolecular rate constants are consistent with the high‐pressure Arrhenius parameters given by

where θ=2.303 RT in kcal/mole. If A∞ is adjusted relative to the more recent parameters for cyclobutane pyrolysis suggested by VLPP studies, then the Arrhenius expression becomes

The cyano group reduces the activation energy for cyclobutane pyrolysis by 6±1 kcal/mole, and on the basis of a biradical mechanism this value may be attributed to the cyano stabilization energy.
The mechanism of the H2 + CL2 reaction: Ignition behind reflected shocks
Authors: Lifshitz Assa , Schechner Pinchas 
Published: January 2005

AbstractA detailed shock‐tube investigation of the ignition in H2 + Cl2 + Ar mixtures in a shock tube is presented, and the mechanism of the reaction is discussed. Ignition delay times were determined from pressure and heat flux measurements behind reflected shock waves. The induction times measured ranged between 35 and 2100 μsec over the temperature range of 830–1260°K. The experimental results of close to seventy tests can be correlated by the relationship

where the concentrations are expressed in mole/cm3. The above relationship served as a basis for a computer modeling of the ignition delay times. Ten calculations, simulating typical laboratory experiments, were run by the computer for each reaction scheme and the obtained temperature and composition dependence of the induction times were compared with the ones observed experimentally. A reaction scheme based on a simple exothermal chain propagation could not reproduce the experimental relationship. When the energy branching reaction HCl*(ν) + Cl2 → (HCl3) → HCl + Cl + Cl was added to the reaction scheme, a much better agreement with the experiment was obtained. It is believed that the above reaction does take place and that it is the main supplier of atoms to the system.
Kinetics of the reactions Br2 + HCN, BrCN + I−, S(CN)2 + I− in aqueous acid solution
Authors: Nolan M. F. , Pendlebury J. N. , Smith R. H. 
Published: January 2005

AbstractSpectrophotometric methods have been used to obtain rate laws and rate parameters for the following reactions:
equation image
with ka, kb, Ea, Eb having the values 85±5 l./mole · s, 5.7±0.2 s−1 (both at 298.2°K), and 56±4 and 66±2 kJ/mole, respectively.
equation image
with kc=0.106±0.004 l./mole ·s at 298.2°K and Ec=67±2 kJ/mole.
equation image
with kd=(3.06 ±; 0.15) × 10−3 l./mole ·s at 298.2°K and Ed=66±2 kJ/mole.Mechanisms for these reactions are discussed and compared with previous work.
The kinetics of the thermal bromination of CF3I. Determination of the bond dissociation energy D(CF3−I)
Authors: Okafo Ernest N. , Whittle Eric 
Published: January 2005

AbstractThe kinetics of the thermal bromination reaction

have been studied in the range of 173–321°C. For the step
equation image
we obtain

where θ=2.303RT cal/mole. From the activation energy for reaction (11), we calculate that

This is compared with previously published values of D(CF3−I). The relevance of the result to published work on kc for a combination of CF3 radicals is discussed.
Application of the modified semi‐ion pair model for the evaluation of activation energies for HX (X = F, Cl, Br, I, OH) addition to olefins
Authors: Tschuikow‐Roux E. , Maltman K. R. 
Published: January 2005

AbstractThe modified semi‐ion pair model for four‐center reactions initially developed to treat the addition of hydrogen halides to olefins, including polar olefins, has been extensively applied to these systems. In addition, the restriction that the species added be a hydrogen halide has been relaxed and addition of HOH to olefins is treated within the same frame‐work. Input parameters, transition state properties, and calculated activation energies are presented for 111 such reactions. Calculated activation energies for the elimination reactions agree to better than ±2 kcal/mole, on the average, with experimental values where these areknown.
N2O Dissociation behind reflected shock waves
Authors: Baber S. Charles , Dean Anthony M. 
Published: January 2005

AbstractThe dissociation of N2O/Ar mixtures, with and withoutadded CO, has been studied by monitoring both infrared and ultraviolet emissions behind reflected shock waves. Initial temperatures ranged from 1850 to 2535°K, and the total concentrations were 1.94–2.40 × 1018 molecule/cm3. The infrared emission, corrected if necessary for CO, was observed to decay exponentially, and an apparent rate constant Kapp was obtained. Addition of CO had no effect upon kapp and all the data can be described by the followingArrhenius parameters (in units of cm3/molecule.sec): log A=−9.31±0.12 and EA=219.1±5.2 kJ/mole. Ultraviolet emission data, in runs with added CO, indicate that the atomic oxygen concentration reached a constant value at t < 600 μsec for T0 > 2050°K.Numerical integration of the mechanism
equation image
allowed comparison of calculated and observed parameters relating to both infrared and ultraviolet data. A consistent fit to these data was obtained with k1=1.3×10−9 exp (−238 kJ/RT) and k2=k3=1.91×10−11 exp(−105 kJ/RT).The concentration of atomic oxygen produced by N2O dissociation is shown to be a sensitive function of k1 through k3. Upper limits are also set for the rate constants of the following reactions:
equation image
Hydrogen fluoride vibrational energy distributions for the reactions of fluorine atoms with cyclanes
Authors: Parker John H. 
Published: January 2005

AbstractThe hydrogen fluoride infrared chemiluminescence produced by the reactions of fluorine atoms with cyclopropane, cyclopentane, and cyclohexane have been studied. The emission data were used to determine the vibrational energy distributions for the abstraction of hydrogen from the secondary carbon–hydrogen bonds of these small cyclic hydrocarbons. The fraction of reaction exothermicity going into vibrational excitation of hydrogen fluoride was as follows: c‐C3H6, 45%; c‐C5H10, 53%; c‐C6H12, 49%. The slightly lower fraction for the cyclopropane system may indicate that its radical reorganization energy is not completely available for excitation of product HF.
Aquation of chloropentaamminecobalt(III) Perchlorate in chloride‐ion containing water–nonaqueous solvent mixtures
Authors: Reynolds Warren L. , Barber Elaine S. 
Published: January 2005

AbstractThe equilibrium quotients for the formation of Co(NH3)5Cl2+ from Co(NH3)5OH23+ and Cl− were 3.74±0.25 M−1 and 6.07±0.54 M−1 at 45.0°C in 10:1 mole ratio water: dimethyl sulfoxide and in 25 w/w % aqueous ethanol, respectively, and those forthe formation of the ion pair Co(NH3)5OH23+ . Cl− were 1.21±0.20 M−1 and 1.58±0.17 M−1, respectively, in the same solvents. The aquation and anation rateconstants were determined at 45.0°C for these two solvents over the range of chloride‐ion concentrations 0.0 ≤ [Cl−] ≤ 0.9 M. The aquation rate constant was essentially independent of chloride‐ion concentration in each solvent over this range. The inverse of the pseudo‐first‐order anation rate constant was linearly dependent on the inverse of the chloride‐ion concentration in each solvent. The least squares relationships between (1/kan) and (1/[Cl−]) gave intercepts and ratios of intercept to slope which were analyzed interms of Id and D mechanisms. It was concluded that the data were not satisfied by a D mechanism, but that they were consistent with an Id mechanism.
Effect of olefins on the thermal decomposition of propane part I. The model reaction
Authors: Dombi A. , Huhn P. 
Published: January 2005

AbstractStudy of the thermal decomposition of propane at very low conversions in the temperature range 760–830 K led to refinement of the mechanism of the reaction.The quotient V/V characterizing the two decomposition routes connected with the 1‐ and 2‐propyl radicals proved to depend linearly on the initial propane concentration. This suggested the occurrence of intermolecular radical isomerization:
equation image
in competition with decomposition of the 2‐propyl radical:
equation image
The linearity led to the conclusion that the selectivity of H‐abstraction from the methyl and methylene groups by the methyl radical is practically the same as that by the H atom. The temperature‐dependence of this selectivity ( μ = kCH3/kCH2) was given by

Further evaluation of the dependence gave the Arrhenius representation

for the ratio of the rate coefficients of the above isomerization and decomposition reactions.Steady‐state treatment resulted in the rate equation of the process, comparison of which with measurements gave further Arrhenius dependences.