bluuebunny/crossref_metadata_2025_split huggingface dataset:
The photolysis of SO2 at 3080 Å in the presence of cis‐ and trans‐1,2‐difluoroethylene
Authors: Wampler Fred B. 
Published: January 2005

AbstractThe photolysis of SO2 at 3080 Å, FWHM = 150 Å, and 22°C has been investigated in the presence of cis‐ and trans‐C2F2H2. Quantum yield measurements for the photosensitized isomerization of cis‐C2F2H2 to trans‐C2F2H2 have been made for a variation in the [SO2]/[cis‐C2F2H2] ratio from 0.992 to 253. The results fit a mechanism which is consistent with the SO2(3B1) state being the reactive excited state of sulfur dioxide. A mechanism employing only the SO2(1B1) and SO2(3B1) excited states is quite satisfactory to rationalize the data. A value for the SO2 collisionally induced intersystem crossing efficiency from SO2(1B1) to SO2(3B1) of 0.35 ± 0.14 was estimated while the cis‐C2F2H2 efficiency was found to be 0.030 ± 0.012. The rate constant at 22°C for the removal of SO2(3B1) molecules by cis‐C2F2H2 was found to be (1.43 ± 0.13) × 10101./mole · sec. A photostationary composition, [cis]/[trans] = 1.0 ± 0.1, was found from prolonged irradiations of SO2 in the presence of the cis and trans isomers.
The kinetics of aquation and racemization of some cis‐ chloro‐, hydroxo‐, and aquabis(ethylenediamine)(amine)cobalt(III) complexes
Authors: Fenemor D. R. , House D. A. 
Published: January 2005

AbstractAquation rates forcis‐CoCl(en)2(A)2+ (A = 3,5‐lutidine, imidazole, N‐methylimidazole, benzimidazole) have been determined by halide release titration in 1.0 M HNO3 at 50–80°C. Kinetic parameters are (in the above order of A) 107k298 (sec−1), 7.4, 5.7, 1.3, 9.7; Ea (kJ/mole), 103, 101, 130, 112; log PZ (sec−1), 11.89, 11.53, 16.04, 13.58; ΔS298‡ (J/°K· mole),−26, −32, +54,+7. Rates of racemization for active cis‐Co(en)2(A)‐(OH2)3+ were measured spectropolarimetrically in 0.1 M HClO4, 0.02 M Hg2+ for A = ammonia, cyclohexylamine, 3,5‐lutidine, N‐methylimidazole. Kinetic parameters are (units as above) 109k298 = 1.8, 38.0, 7.7, 1.7; Ea = 150, 135, 152, 157; log PZ = 17.49, 16.18, 18.56, 18.87; ΔS298‡ = +82, +57, +102,+108. Rates of racemization of the active hydroxo complexes cis‐Co(en)2(A)(OH)2+ (A = NH3, CH3NH2, 3,5‐lutidine, imidazole) were measured similarly at pH = 8 (π = 2.0, NaClO4). The racemization of the hydroxo is ca. (3–4) × 103 faster than for the corresponding aqua complex. Kinetic parameters are 106k298 = 2.55, 7.2, 30.1, 7.0; Ea = 138, 123, 122, 128; log PZ = 18.58, 16.39, 16.85, 17.18; ΔS298‡ = +102,+60, +69,+76. Racemization rates for aquahydroxo mixtures (A = CH3NH2, 3,5‐lutidine, imidazole) were also determined in the pH range of 4–8 (θ = 2.0, NaClO4) at 50.6°C, and pKa data calculated from the pH versus k plot are 5.50, 5.65, and 6.40, respectively, for A.
The decarboxylation of methylmalonic acid and n‐octadecylmalonic acid in normal alkanols
Authors: Clark Louis Watts 
Published: January 2005

AbstractRate constants and activation parameters are reported for the decarboxylation of methylmalonic acid and n‐octadecylmalonic acid in three normal alkanols (hexanol‐1, octanol‐1, and decanol‐1). Enthalpies of activation for both substrates in the various solvents are found to be a linear function of the number of carbon atoms or methylene groups in the hydrocarbon chain of the solvent. For both reaction series the isokinetic temperature is found to be equal to the melting point of the substrate. The free energy of activation at the isokinetic temperature in kcal/mole is 29.0 for n‐octadecylmalonic acid and 29.4 for methylmalonic acid. Based on the results of the present investigation as well as on previously reported data in the case of malonic acid and n‐butylmalonic acid, an empirical method of calculating the rate of reaction for the decarboxylation of malonic acid and its n‐alkyl derivatives in normal alkanols is proposed. As a further test of the method of calculation the decarboxylation of n‐dodecylmalonic acid in heptanol‐1 at 110.30°C was studied. The calculated value of the pseudo‐first‐order specific reaction velocity constant of the reaction agreed with the experimental value to within about 0.1 percent.
Radiation‐induced hydrogen fluoride formation in fluorine‐containing ethanes and ethenes
Authors: Chu Chao‐kang , Heckel Edgar 
Published: January 2005

AbstractSeveral fluorine‐containing ethanes (monofluoro, 1,1‐difluoro, 1,1,1‐trifluoro, 1,1,2‐trifluoro, 1,1,2,2‐tetrafluoro, and pentafluoro) and ethenes (1,1‐difluoro and trifluoro) form hydrogen fluoride when irradiated with gamma rays in the gas phase at 25°C. Hydrogen fluoride is apparently formed from fluoroethanes by a mechanism which involves formation of an intermediate semiion pair. We observed identical HF yields both in the absence and presence of molecular oxygen, except for monofluoroethane. A reduction of G(HF) with increasing sample pressure, for example, of 1,1,2,2‐tetrafluoroethane, indicates that collisional stabilization of excited fluoroethane molecules competes with the process of HF elimination. High G values for HF and CO2 in mixtures of CF2CFH and O2 reveal the occurrence of a chain reaction.
Some reactions of the isopropyl radical
Authors: Szirovicza L. , Márta F. 
Published: January 2005

AbstractThe decomposition of ethane sensitized by isopropyl radicals was studied in the temperature range of 496–548°K. The rate of formation of n‐butane, isopentane, and 2,3‐dimethylbutane were measured. The expression k1/k2½ was found to be

where k1 and k2 are rate constants of

equation image
The decomposition of propylene sensitized by isopropyl radicals was studied between 494 and 580°K by determination of the initial rates of formation of the main products. The ratio of k13/k21/2 was evaluated to be

where k13 is the rate constant for

equation image
The isomerization of the isopropyl radical was investigated by studying the decomposition of azoisopropane. The decomposition of the iso‐C3H7 radical into C2H4 and CH3 was followed by measuring the rate of formation of C2H4. On the basis of the experimental data, obtained in the range of 538–666° K, k15/k2½ was found:

where k15 is the rate constant of

equation image
Excited‐state kinetics in the photolysis of azoethane and hexafluoroazomethane at 366 nm, up to one atmosphere pressure, and from room temperature to 150°C
Authors: Pritchard G. O. , Servedio F. M. , Marchant P. E. 
Published: January 2005

AbstractThe photochemistry of azoethane and hexafluoroazomethane at 366 nm has been reinvestigated up to 1 atm pressure, and over a range of temperature from 27 to 150°C. The Stern‐Volmer type quenching plots primarily demonstrate the decomposition of a single electronic and vibrationally excited state for azoethane, but competitive photodissociation from two different electronic and vibrationally excited states, which was previously postulated for hexafluoroazomethane and azoisopropane, is confirmed for hexafluoroazomethane. It is concluded, however, that two different electronic and vibrationally excited photodissociating states are present in azoethane photolysis, but that one of them is difficult to detect, at least by the present approachPhotosensitization with biacetyl at 436 nm also causes the dissociation of azoethane, and this is probably from the vibrationally equilibrated first triplet state. The energy barrier for this process was found to be 5.0 kcal/mol.
Vibration–vibration energy exchange between 15N14NO and CO
Authors: Suitor Jerry W. , Kuby W. C. 
Published: January 2005

AbstractThe temperature dependence of the vibration–vibration energy transfer between the v3 mode of 15N14NO and the first vibrational level of CO was determined over a range of 680 to 1300°K using a shock tube. Several mixtures of 15N14NOCO were tested, diluted in 95% Ar. The resulting exothermic transfer probabilities for the reaction,

are compared to previous work on N2O—CO. The results for 15N14NOCO exhibit a more pronounced direct temperature dependence than for N2O—CO even though the process has a closer resonance (ΔE = 59 cm−1 for 15N14NOCO and ΔE = 81 cm−1 for N2OCO).
The heats of formation of NO3− and NO3− association complexes with HNO3 and HBr
Authors: Davidson J. A. , Fehsenfeld F. C. , Howard Carleton J. 
Published: January 2005

AbstractThe equilibrium constant for the reaction
equation image
has been determined between 331 and 480°K using a variable‐temperature flowing afterglow. These data give ΔH°(1) = ‐1.03 ± 0.21 kcal/mol and ΔS°(1) = —4.6 ± 1.0 cal/mol°K. When combined with the known thermochemical values for HBr, Br−, and HNO3, this yields ΔH(NO3−) = ‐74.81 ± 0.54 kcal/mol and S(NO3−) = 59.4 cal/mol·°K. In addition ΔHn‐1,n and ΔSn‐1,nfor the gas‐phase reactions

were determined for n = 2 and 3. The implications of these measurements to gas‐phase negative ion chemistry are discussed.
Relaxation of DF(v = 1) by various polyatomic molecules
Authors: Bott Jerry F. 
Published: January 2005

AbstractBy means of the technique of laser‐induced fluorescence, the room‐temperature vibrational relaxation of DF(v = 1) has been studied in the presence of several polyatomic chaperones. The rate coefficients obtained [in units of (μ;sec·torr)−1] are CH4, 0.22; C2H6, 0.61; C4H10, 1.26; C2H2, 4.0 × 10−2; C2H2F2, 1.86 × 10−2; C2H4, 0.175; CH3F, 0.36; CF3H, 1.95 × 10−2; CF4, 1.0 × 10−3; CBrF3, 5.6 × 10−4; NF3, 5.1 × 10−4; SO2, 1.27 × 10−2; and BF3, 7.1 × 10−3. Results are also reported for vibrational relaxation rate coefficients for HF(v = 1) in the presence of the following chaperones: CH4, 2.6 × 10−2; C2H6, 5.9 × 10−2; C3H8, 8.4 × 10−2; and C4H10, 0.128. A comparison of DF and HF results indicates that for deactivation by CnHn+2, rate coefficients for DF are approximately an order of magnitude larger than for HF. The deactivation rate coefficient of DF(v = 1) by CH4 was found to decrease with increasing temperature between 300 and 740°K.
Collisional energy transfer in the reactions I + NO + M → INO + M and I + NO2+ M → INO2+ M
Authors: Van Den Bergh H. , Benoit‐Guyot N. , Troe J. 
Published: January 2005

AbstractThe low‐pressure recombination rate constants of the reactions I + NO + M → INO + M (with 14 different M) and I + NO2+ M → INO2+ M (with 26 different M) have been measured at 330°K by laser flash photolysis. The collision efficiencies βcare analyzed and compared with other thermal activation systems. Whereas βcincreases in one reaction with an increasing number of atoms in M, practically no such effect is found when, for the same M, different reactions with varying complexities of the reacting molecules are considered.
Activation energy and nonequilibrium effects in thermal reactions
Authors: Penner Alvin P. , Bhattacharjee Rakhal C. , Forst Wendell 
Published: January 2005

AbstractCalculations of the nonequilibrium rate constant for the model system H2O2 + M → 2 OH + M over the temperature range of 300–1900°K, assuming that only vibrational, or that both vibrational and rotational, energy is transferred in a collision, show that (1) inefficient energy transfer leads to a distinctly non‐Arrhenius temperature dependence, the nonlinearity being in principle different for different M, and (2) despite different activation energies for different M, the order of M efficiencies is preserved throughout the temperature range. A reversal of M efficiencies can occur only if there is a change of mechanism of the reaction over the temperature range investigated.
Energy transfer in unimolecular reactions at high temperatures
Authors: Barnard J. A. , Parrott T. K. 
Published: January 2005

AbstractThe application of modern theories of energy transfer to unimolecular reactions taking place at very high temperatures is discussed. It is shown that the efficiency of energy transfer for both reactant–reactant and reactant–inert diluent collisions may be substantially smaller than the values determined experimentally at lower temperatures. Consequently at high temperatures unimolecular falloff effects, particularly in some shock‐tube measurements, may be greater than has been believed hitherto.The application of these calculations to the unimolecular reactions of cyclopropane, cyclobutane, and cyclohexene at temperatures around 1300°K is discussed, and it is shown that under shock‐tube conditions the apparent first‐order rate coefficient may be at least ten times less than the high‐pressure limiting value.
The triplet state of 4‐nitronaphthylamine
Authors: Capellos C. , Lang F. 
Published: January 2005

AbstractNanosecond spectroscopic and kinetic studies of 4‐nitronaphthylamine (4‐NO2NA) in aerated and deaerated nonpolar solvents at room temperature show a transient species with absorption maxima at 470 and 665 nm. The rate constant for the decay of this species in deaerated benzene is 6.7 × 105 sec−1, while in aerated benzene solutions the species is quenched by oxygen with arate constant k = 2.0 × 109M−1·sec−1. The transient absorption at 470and 665 nm is assigned to the lowest triplet excited state of 4‐NO2NA. In polar solvents, however, electronic excitation of 4‐NO2NA does not lead to any detectable transient absorption between 400 and 800 nm for the temperature range of 25 to −150°C. This is attributed to lack of intersystem crossing of 4‐NO2NA in polar solvents.
BEBO Calculations for hydrogen abstraction by 0(3P)
Authors: Previtali Carlos M. , Neumann Miguel G. 
Published: January 2005

AbstractRate constants for hydrogen transfer reactions from C—H bonds to O(3P) in the gas phase have been calculated by the bond‐energy bond‐order method. The use of a single or double triplet repulsion term is discussed. Computational results indicate that with carefully selected input parameters, it is unnecessary to use a double‐repulsion term. Tunneling corrections were carried out by two different procedures. Results indicate that in this case there is not much difference between the simple Wigner's treatment and more complicated methods.
The gas‐phase pyrolysis of alkyl nitrites. IV. Ethyl nitrite
Authors: Batt L. , Milne R. T. 
Published: January 2005

AbstractThe rate of decomposition of ethyl nitrite (EN) has been studied in a static system over the temperature range of 162‐218°C. The main products are formaldehyde, acetaldehyde, ethanol, and nitrous oxide. For low concentrations of EN (10−5‐10−4M), but with a high total pressure of CF4 (∼0.9 atm) and small extents of reaction (2‐6%), the first‐order homogeneous rates of CH2O formation are a direct measure of reaction (1), since k3bk2(NO):
equation image
Addition of large amounts of NO(∼0.9 atm) completely suppressed CH2O formation in agreement with the observed value for k3b.The rate of reaction (1) is given by k1 = 1016.0‐41.8/θ−1. Since (E1 + RT) and ΔH±1 are identical, both may be equated with D(EtO‐NO) = 42.4 ± 0.9 kcal/mol and E2 = O± 1 kcal/mol. The thermochemistry leads to the result ΔHDelta;f(EN) = ‐24.5 ± 1 kcal/mol. From ΔS1 and A1, k2 is calculated to be 1010.3M−1θ−1. From an independent observation that k6/k2 = 0.3 ± 0.05 independent of temperature

it is concluded that k6 = 109.8M−1Δ−1.The addition of NO has no effect on the AcH yields. Although the yields of AcH are affected by the surface‐to‐volume ratio of different reaction vessels, it is concluded that in a spherical reaction vessel, the AcH arises as the result of an essentially homogeneous elimination of HNO from EN(5):

and reaction (6). The rate of AcH formation is given by kobs = 1013.7‐37.5/θ−1. By using isobutane (t‐BuH) as a radical trap for EtO (4),

a value for k3b was determined to be 1015.0‐21.6/θ s−1.From an independent observation that k2:k2:k6:k6 was 1: 0.4: 0.3: 0.18
equation image
we find k2θ = 109.9M−1→ s−1, k1θ = 1016.0‐40.0/θ s−1, and k6± = 109.6M−1 · s−1.
Fast kinetic studies of chemical reactions using high‐intensity pulse radiolysis reaction of hydrogen peroxide with pentavalent vanadium
Authors: Pucheault J. , Ferradini C. , Gardes M. , Lesigne B. , Gilles L. , Muller J. C. 
Published: January 2005

AbstractHigh‐intensity pulse radiolysis, using a Febetron, has made it possible to obtain in a few microseconds homogeneous H2O2 concentrations of about 10−4 to 10−3M without any other reactive radiolytical product. The kinetics of the reaction of this H2O2 with a solute have been studied as a function of time for periods ranging from tens of microseconds to tens of milliseconds.An analytical model of this method is presented and then compared with the results of experiments in which the H2O2 concentrations are measured. The rate constant for the peroxidation of pentavalent vanadium is determined to be k = (5.7 ± 0.5) × 103M−1 plusmn; s−1.
Esterification of alcohols with acetic acid over ferric oxide
Authors: Kuriacose J. C. , Jewur S. S. 
Published: January 2005

AbstractFerric oxide has been found to promote both the ketonization of acetic acid and its esterification with methyl alcohol, isopropyl alcohol, and benzyl alcohol. The competitive kinetic technique, where the esterification reaction is made to compete with the ketonization of acetic acid, has been used to elucidate the mechanistic model for the ketonization of acetic acid on iron oxide. The ketonization of acetic acid at 375°C is found to be a second‐order reaction which proceeds through a Langmuir‐Hinshelwood mechanism.
Hydrogen abstraction from trichlorosilane by the trichloromethyl and 1,1‐dichlorotrifluoroethyl radicals
Authors: Ormson B. N. , Perrymore W. D. , White M. L. 
Published: January 2005

AbstractThe Arrhenius parameters for the reactions
equation image
and
equation image
have been measured. Reaction (2a) was generated and studied by the photolysis of tetrachloromethane in the presence of trichlorosilane and reaction(2b) by the photolysis of 1,1,1,‐trichlorotrifluoroethane in the presence of trichlorosilane.The measured data are given by the expressions

.
Asymptotic quantum yield of triplet sensitized decomposition
Authors: Oref I. 
Published: January 2005

AbstractThe asymptotic quantum yield of triplet energy transfer is found by calculating the fraction of acceptor molecules with energy above the minimum energy for decomposition. This is done by allowing for a statistical energy distribution among the internal modes in the collision complex. It is found that for a monatomic triplet donor most of the triplet energy is transferred to the acceptor molecule, while for a polyatomic donor molecule only a fraction of it is available for future decomposition of the acceptor.
Thermal decomposition of perfluoro‐di‐t‐butyl peroxide
Authors: Ireton R. , Gordon A. S. , Tardy D. C. 
Published: January 2005

AbstractThe thermal decomposition of perfluoro‐di‐t‐butyl peroxide has been studied for the first time. The reaction was carried out in the gas phase between 5 and 600 torr in the 108‐149°C temperature region. The products consisted solely of C2F6 and CF3COCF3. The decomposition was found to be first order and homogeneous. The rate constant is given by log kdecomp(sec−1) = (16.2 ± 1.2) ‐ (148.7 4.4)/2.3RT where R is 0.008314kJ/mol · °K. These Arrhenius parameters are consistent with those determined for the decomposition of di‐t‐butyl peroxide.
The NO‐ and NO2‐catalyzed decomposition of I2 in shock waves
Authors: Hippler H. , Luther K. , Teitelbaum H. , Troe J. 
Published: January 2005

AbstractMeasurements of the NO‐catalyzed dissociation of I2 in Ar in incident shock waves were carried out in the temperature range of 700°‐1520°K and at total concentrations of 5 × 10−6‐6 × 10−5 mol/cm3, using ultraviolet‐visible absorption techniques to monitor the disappearance of I2. It was shown that the main reaction responsible for the disappearance under these conditions is I2 + NO → INO + I, for which a rate coefficient of (2.9 ± 0.5) × 1013 exp[‐(18.0 ± 0.6 kcal/mol)/RT] cm2/mol·sec was determined. The INO formed dissociates rapidly in a subsequent reaction. The reaction, therefore, constitutes a “chemical model” for a “thermal collisional release mechanism.” Preliminary measurements of the rate coefficient for I2 + NO2 → INO2 + I are also presented. Combined with information on the reverse reactions obtained in earlier room temperature experiments, these results lead to accurate values of ΔH°f for INO and INO2 equal to 29.7 ± 0.5 and 15.9 ± 1 kcal/mol, respectively.
Kinetics of the reaction Cl + CH4 → CH3+ HCl from 200° to 500deg;K
Authors: Zahniser Mark S. , Berquist Bruce M. , Kaufman Frederick 
Published: January 2005

AbstractThe rate constant for the reaction \documentclass{article}\pagestyle{empty}\begin{document}${\rm Cl} + {\rm CH}_4 \mathop {\longrightarrow}\limits^1 {\rm CH}_3 + {\rm HCl}$\end{document} has been determined over the temperature range of 200°–500°K using a discharge flow system with resonance fluorescence detection of atomic chlorine under conditions of large excess CH4. For 300° > T > 200°K the data are best fitted to the expression k1 = (8.2 ± 0.6) × 10−12 exp[−(1320 ± 20)/T] cm3/sec. Curvature is observed in the Arrhenius plot such that the effective activation energy increases from 2.6 kcal/mol at 200° < T < 300°K to 3.5 kcal/mol at 360° < T < 500°K. The data over the entire range may be fitted by the expression k1 = 8.6×10−18 T2.11 exp[−795/T]. These results are compared with other experimental studies and with a semiempirical transition state calculation. Their atmospheric significance is discussed.
Temperature dependence of the reactions of HO2 with NO and NO2
Authors: Simonaitis R. , Heicklen Julian 
Published: January 2005

AbstractMixtures of N2O, H2, O2, and trace amounts of NO and NO2 were photolyzed at 213.9 nm, at 245°–328°K, and at about 1 atm total pressure (mostly H2). HO2 radicals are produced from the photolysis and they react as follows:
equation image
Reaction (1b) is unimportant under all of our reaction conditions. Reaction (1a) was studied in competition with reaction (3) from which it was found that k1a/k31/2 = 6.4 × 10−6 exp { z−(1400 ± 500)/RT} cm3/2/sec1/2. If k3 is taken to be 3.3 × 10−12 cm3/sec independent of temperature, k1a = 1.2 × 10−11 exp {−(1400 ± 500)/RT} cm3/sec. Reaction (2a) is negligible compared to reaction (2b) under all of our reaction conditions. The ratio k2b/k1 = 0.61 ± 0.15 at 245°K. Using the Arrhenius expression for k1a given above leads to k2b = 4.2 × 10−13 cm3/sec, which is assumed to be independent of temperature. The intermediate HO2NO2 is unstable and induces the dark oxidation of NO through reaction (−2b), which was found to have a rate coefficient k−2b = 6 × 1017 exp {−26,000/RT} sec−1 based on the value of k1a given above. The intermediate can also decompose via
equation image
Reaction (10b) is at least partially heterogeneous.
Computer study of the hydrogen atom recombination reaction under high pressure conditions
Authors: Stace A. J. , Murrell J. N. 
Published: January 2005

AbstractThe hydrogen‐atom recombination reaction has been simulated using a molecular dynamics technique recently formulated by the authors [1]. The rate of recombination has been calculated over a range of temperatures and inert gas concentrations (He and Ar) and agrees well with available experimental data. The calculations reproduce the negative activation energy characteristic of an atom recombination process. Over the range of conditions studied recombination was found to proceed via the energy transfer mechanism only, no evidence of bound HAr or HHe species was observed. Recombination was found to occur through an intermediate metastable diatomic molecule which is in equilibrium with its environment and from which there is a bottleneck to the formation of a stable molecule. The initial formation of a metastable species is sensitive to the hydrogen‐inert gas potential, but relaxation of the total energy is primary determined by the mass of the third‐body and the collision frequency.