bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical lasers produced from O(3P) atom reactions. III. 5‐μm CO laser emission from the O + CH reaction
Authors: Lin M. C. 
Published: January 2005

AbstractVery strong laser emission at 5 μm was detected when SO2 and CHBr3 were flash photolyzed in the vacuum ultraviolet (λ ≥ 165 nm) in the presence of a large amount of diluent (SF6, He, or Ar). About 110 vibration–rotation transitions ranging from Δv = 18 → 17 to 3 → 2, except 16 → 15, were identified. The primary reactions leading to the CO stimulated emission are as follows:

equation image

The product analysis results and the variation of laser intensity with flash energy and SO concentration indicate that the following side reactions

equation image

are also occurring. Addition of a small amount of O2 enhances the laser output by both eliminating these side reactions and simultaneously producing vibrationally excited CO via reaction (8),

equation image

which has been previously shown to generate CO stimulated emission. The effects of various reactive (NO and H2) and inert (He, Ar, SF6, CO, N2, N2O, and CO2) gases have been examined. All additives (P ≤ 20 torr), except NO and H2, increase the total laser output. N2O enhances the power most efficiently, whereas CO, N2, and CO2 are less effective and have similar efficiencies. The enhancement of the laser intensity by these near‐resonant gases is ascribed to the depletion of CO population at lower levels which thus increases the rates cascading from higher levels. NO and H2 quench the laser output by chemically reducing the concentration of the CH radical.
Reactions of halogens with hydrogen halides. Studies in the Cl2 + HBr system
Authors: Wen Walter Y. , Noyes Richard M. 
Published: January 2005

AbstractThe following net processes occur in a system containing chlorine and hydrogen bromide:

equation image

These reactions have been followed spectrophotometrically in a gas phase stopped flow apparatus. The first two reactions are strongly surface catalyzed on untreated glass or quartz, but are much slower if the cell surface has been covered with silicone and photochlorinated. Rates in such systems are first order in each reactant, and comparable limiting rate constants have been obtained in cells with different methods of preparing the surfaces and with different surface‐to‐volume ratios. These experimental rate constants must be equal to or greater than those of the homogeneous bimolecular reactions. Then limiting rate constants at 35°C in liters per mole per second are k1 ≤ 0.8, k 2 ≤ 15, and k3 ≤ 0.04. Reactions of HI with Cl2, Br2, and ICl are all much faster than reaction (2). These observations and those of other diatomic molecule reactions can be rationalized if halogen and hydrogen halide molecules react through a transition state in which the hydrogen atom is near the center of a triangle of three halogen atoms.
Flash Photolysis of 2,4,6‐Trinitrotoluene Solutions
Authors: Suryanarayanan K. , Capellos C. 
Published: January 2005

AbstractFlash photolysis of 2,4,6‐trinitrotoluene solutions (TNT) indicates a photochemically induced isomerization leading to the aci‐quinoid isomer magnified image with an absorption maximum at 460 nm in nonpolar solvents, or the conjugate base magnified image of the aci‐quinoid isomer with absorption maxima at 500, 540, and 630 nm in polar solvents. Both species, the quinoid isomer and the conjugate base, have transient existence and their identification was based on detailed spectroscopic and kinetic studies presented here. The magnitude of the negative charge on the transient conjugate base was determined with salt effect experiments and found to be equal to unity.
Kinetic and mechanistic study of the reactions of palladium(II) chlorocomplexes with ethylenediamine in aqueous acid medium
Authors: De Waal D. J. A. , Robb W. 
Published: January 2005

AbstractThe complexes PdCl42−, PdCl3(H2O)−, and PdCl3(Ac)2−, in rapid equilibrium with each other under the adopted experimental conditions, react with ethylenediamine according to the experimental rate law

A reaction scheme is proposed involving the reaction of enH+ with each of the above species, and the specific rate constants are computed. The activation parameters are given.
Initiation process in the system Fe3+ + H2O2
Authors: Kozlov Yu. N. , Nadezhdin A. D. , Pourmal A. P. 
Published: January 2005

AbstractAn inhibitor method for measuring the initiation rate is proposed for the system Fe3+ + H2O2. C(NO2)4 was used as inhibitor. The number of chains terminated by one C(NO2)4 molecule was estimated in specific photochemical experiments and found to be unity. The initiation appeared to involve two processes. The first is proportional to the first power of ferric ion concentration, and the second to the second power. The rate constants and activation energies of these processes are determined. Allowance for the second initiation process permitted qualitative and quantitative description of various reported data on H2O2 decomposition rates over a wide range of Fe3+, H2O2, and H+ concentrations.
Addition–substitution competition in liquid‐phase chlorinations
Authors: Coppens G. , Martens G. J. , Godfroid M. , Delvaux J. , Verbeyst J. 
Published: January 2005

AbstractThe rate constants of liquid‐phase hydrogen abstraction by chlorine atoms from 1,2‐C2H4Cl2 relative to those of addition to C2HCl3 and to C2Cl4 and to that of hydrogen abstraction from cyclohexane have been measured between 250 and 345°K. Assuming a zero activation energy for the addition reactions permits one to calculate the corresponding values for the liquid‐phase hydrogen abstraction from the chlorinated ethanes. These values are discussed and compared with the gas‐phase data.
Arrhenius parameters for reactions of oxygen atoms with the fluorinated ethylenes
Authors: Jones D. S. , Moss S. J. 
Published: January 2005

AbstractCompetitive studies of the reactions of ground‐state oxygen atoms, generated by mercury‐photosensitized decomposition of nitrous oxide, have been carried out with ethylene and all the fluoroethylenes using 2‐(trifluoromethyl)‐propene as reference compound. From measurements at 25°C and 150°C relative rate constants have been determined and used to calculate the Arrhenius parameters shown in the following table:

Olefin

ΔERef

ΔE

CH2CH2
1.10
−1.18
(1.0)
(0)

CH2CHF
1.03
0.84
0.94
2.02

CH2CF2
0.71
1.49
0.65
2.67

CHFCHF (cis‐)
1.23
1.92
1.12
3.10

CHFCHF (trans‐)
1.40
0.79
1.27
1.97

CF2CHF
1.06
0.00
0.96
1.22

CF2CF2
0.86
−3.22
0.78
−2.04

ΔERef = Eolefin − E2TFMP and ΔE = Eolefin − E. Units are kJ/mole.

The results are compared with corresponding data for other atoms and radicals, and discussed in terms of the electronic changes produced in the double bond by fluorine substitution, and in relation to the nature of the transition state.
Rate constants for the bimolecular self‐reactions of ethyl, isopropyl, and tert‐butyl radicals in solution. A direct comparison
Authors: Griller D. , Ingold K. U. 
Published: January 2005

AbstractA competitive method involving the direct measurement of radical concentrations by EPR spectroscopy has been used to show that in solution at 25°C the rate constants for the bimolecular self‐reactions of ethyl, isopropyl, tert‐butyl, cyclopentyl, and trichloromethyl are all approximately equal, as had been indicated previously by direct measurement of the rate constants for decay of these radicals.
The kinetics of nucleophilic substitution processes in the alkyl halides. Part A—theory
Authors: German E. D. , Dogonadze R. R. 
Published: January 2005

AbstractActivation energies for substitution reactions of the type AC + B → A + CB, occurring in polar media and characterized by an abrupt change of the term along two coordinates have been calculated within the framework of the quantum‐mechanical theory of chemical reactions. In the case of nonadiabatic processes, the transmission coefficient and activation energy for these reactions are expressed in terms of characteristic parameters of the medium (reorganization energy, effective frequency of solvent fluctuation polarization) and the potential energy curves for intermolecular interactions between the reactants (AC and B) and between the products (A and BC).
The ferric ion catalyzed decomposition of hydrogen peroxide in perchloric acid solution
Authors: Walling Cheves , Weil Tomas 
Published: January 2005

AbstractPredictions of the “redox” and “complex” schemes for the Fe3+ catalyzed decomposition of H2O2 have been compared with published and new experimental data by numerical integratior of the appropriate complete sets of differential equations. Apparent discrepancies for the redox scheme at high Fe3+/H2O2 ratios are shown to disappear in the complete treatment, and inconsistencies of the complex scheme with both kinetic data and spectroscopic measurements are pointed out.
Photolysis of 1,1,1‐trifluoromethylazomethane as a source of methyl and trifluoromethyl radicals
Authors: Craig N. L. , Setser D. W. 
Published: January 2005

AbstractThe photochemistry of 1,1,1‐trifluoromethylazomethane has been partially characterized. The quantum yield for N2 formation from photolysis at 366 nm and room temperature was unity at low pressure and decreased to 0.5 at 630 torr. At room temperature the principal products were C2H6, C2F6, CH3CF3 (or CH2CF2 + HF at reduced pressures), plus substituted hydrazines, which mainly arise from addition of CF3 to the parent followed by combination of these radicals with CH3 or CF3. These fluorinated methyl hydrazine products detract from the general utility of CF3‐N2‐R compounds as sources for simultaneous study of the chemistry of CF3 and R radicals. At room temperature the hydrazine products accounted for more than 50% of the total yield; however, these products can be reduced by lowering the temperature and at 195°K their yields are negligible. The quantum yield for intramolecular (direct) formation of CH3CF3 + N2 was shown to be ≤0.002.
The correction of rate data for the effects of internal temperature change
Authors: Boddington T. , Gray P. , Tyler B. J. 
Published: January 2005

AbstractThe effect of reactant self‐heating or cooling upon rate data is considered, and three approaches to the problem of obtaining valid kinetic parameters are described in detail. A comparison of these approaches emphasises the need to assess and allow for thermal effects during the initial planning of kinetic experiments if satisfactory results are to be acquired. An integrated rate expression is given for use with nonisothermal data, and is used to provide correction factors for rate constants which have been derived without allowance for thermal effects.
The reaction of O(3P) with C2HCl3
Authors: Sanhueza Eugenio , Heicklen Julian 
Published: January 2005

AbstractThe reaction of O(3P), prepared from the Hg photosensitization of N2O, with C2HCl3 was studied at 25°C. The products of the reaction in the absence of O2 were CO, CHCl3, and polymer (as well as N2 from the N2O). The quantum yields of CO and CHCl3 were 0.23 ± 0.01 and 0.14 ± 0.05, is respectively independent of reaction conditions. The reaction mechanism is

equation image

with k14a/k14 = 0.23, where k14a + k14b. Most of the HCl and CCl2 combine to form CHCl3, but some other products must also be formed to account for the difference in the CO and CHCl3 quantum yields. The C2HCl3O* adduct polymerizes without involving additional C2HCl3 molecules, since the quantum yield of C2HCl3 disappearance, Φ{C2HCl3}, was about 1.0 at high values of [N2O]/[C2HCl3]. The rate coefficient for the reaction of O(3P) with C2HCl3 is 0.10 that for the reaction of O(3P) with C2F4.In the presence of O2 the free radical chain oxidation occurs because of the reaction

equation image

The main product is CHCl2CCl(O) with smaller amounts of CO and CCl2O, and some CO2. The chain lengths were long and values of  Φ {C2HCl3} up to 90 were observed.
Vibrational relaxation of HF(v = 1) by F atoms
Authors: Thommarson Ronald L. , Berend George C. 
Published: January 2005

AbstractThe rate of vibrational relaxation of HF(v = 1) by F atoms has been calculated using quasi‐classical trajectory techniques. An attempt has been made to account for the effects of multiple potential energy surfaces on the vibrational relaxation efficiency within the electronically adiabatic assumption. Toward this end two potential energy surfaces were investigated. The LEPS equation was used to construct a reactive surface for F + HF′ → FH + F′ having a reaction barrier height of 5.4 kcal/mole, which is in agreement with a bond energy‐bond order prediction. A nonreactive interaction potential consisting of atom‐atom Morse functions was calibrated to Noble and Kortzeborn's [J. Chem. Phys. 52, 5375 (1970)] LCAO‐MO‐SCF results for FHF(2II). The results are in qualitative agreement with experiment. However, the nonreactive surface appears to be too repulsive, and consequently, the contribution of collisions on the nonreactive surface to the total vibrational relaxation rate coefficient are overestimated.
Very low‐pressure pyrolysis (VLPP) of t‐butylmethyl ether
Authors: Choo Kwang Yul , Golden David M. , Benson Sidney W. 
Published: January 2005

AbstractThe thermal decomposition of t‐butylmethyl ether has been studied using the VLPP technique. The recommended Arrhenius parameters for the molecular elimination, reaction (1), are A(800°K) = 101 3, 9 sec−1 and Ea (800°K) = 59.0 ± 1.0 kcal/mole. No radical reactions occur under the conditions used.
magnified image
These parameters are in good agreement with earlier experimental work and with theoretical estimates of both A and E.
Kinetics of the reversible reaction between arsenious acid and aqueous iodine
Authors: Pendlebury J. N. , Smith R. H. 
Published: January 2005

AbstractThe kinetics of the reversible reaction

have been studied spectrophotometrically in acid solution under conditions in which both the forward and reverse reactions go to virtual completionand in which the reaction comes to a practical equlibrium. The rates of theforward (Rf) and reverse (Rr) reactions are given by

where f, g, h, u, and v have the values (4 ± 1) × 10−5 mole/1.·s, (4.2 ± 0.2) × 10−5 mole2/1.2·s, (5.0 · 0.3) × 10−7 mole3/1.3·s, (1.1 ± 0.1) × 10−3 1.2/mole2·s, and (3.7 ± 0.2) × 10−3 1.3/mole3·s at 298.2°K and at an ionic strength of 2.00M maintained by adding sodium chloride. The stoichiometric equilibrium constant under similar conditions is 0.022 ± 0.003. Differentvalues of these parameters were obtained when sodium perchlorate and sodiumnitrate were used to control ionic strength.The results are compared with those from previous reports and a mechanism is proposed based upon an initial rapid equilibrium

followed by a rate‐determining attack of water upon H3AsO3I+, H2AsO3I, and HAsO3I−.
The kinetics of the decarboxylation of malonic acid in normal alkanols
Authors: Clark Louis Watts 
Published: January 2005

AbstractRate constants and activation parameters are reported for the decarboxylation of malonic acid in seven normal alkanols (butanol‐l to decanol‐l inclusive). It is found that the enthalpy of activation of the reaction is a linear function of the number of carbon atoms in the hydrocarbon chain of tthe solvent, expressed by the equation: ΔH≠ = –600n + 30,000, where n is thenumber of carbon atoms in the chain. Also an equation is developed relatingthe rate constant for the decarboxylation of malonic acid in normal alkanols to n (the number of carbon atoms in the chain): log K = 10.854283 – 0.3212674n + (131.136876n – 6556.5438)/T + log T. With the aid of this equation rate constants may be calulated for the decarboxylationof malonic acid in any alcohol at any temperature which agree with experimental values to within the limit of error of the experiments. A comparison of the data obtained in the present research for the decarboxylation of malonic acid in normal alkanols with previously reported data for the reaction in amines indicates that for reaction taking place in alcohols the transition state probably contains two molecules of solvent but only one for the reaction in amines.
Determination by the phase shift method of the absolute rate constants of reactions of O(3P) atoms with olefins at 25°C
Authors: Furuyama Shozo , Atkinson Roger , Colussi Agustin J. , Cvetanović R. J. 
Published: January 2005

AbstractTechnical improvements have been made in the application of the phase shift method, recently developed and used in this laboratory to measure the absolute values of the rate constants of the reactions of O(3P) atoms with ethylene, propylene, 1‐butene, and isobutene. More accurate rate constants have now been obtained for these olefins and themeasurements have been also extended to three additional olefins (cis‐2‐butene, trimethylethylene, and tetramethylene).The mean least squares values of the rate constants of the reactions of O(3P) with olefins at 26°C, expressed as k2 × 10−9 (1./mole2·sec), and their standard deviations are ethylene 0.43 ±0.05, propelene 2.02 ± 0.17, 1‐butene 2.40 ± 0.32, isobutene 9.85 ± 1.34, cis‐2‐butene 9.00 ± 1.76, trimethylethylene 31.1 ± 3.0, and tetramethylethylene 44.4 ± 4.1. A Value of (5.78 ± 0.08) × 1010l.2/mole2·sec was obtained for the rate constant of the reaction O(3P) + NO + M, with M = N2O. Where comparison with the absolute rate constants in the literature is possible, agreement is very good, especiallywith some recent absolute values obtained by entirely different experimental techniques. Consistency with the relative rate constant of the O(3P) reactions with olefins previously determined in this laboratory, is excellent.
Vibration–Vibration energy exchange between N2O 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 N2O and the first vibrational level of CO was determined over a range of 780 to 1400°K using a shock tube. Several mixtures of CO‐N2O were tested, diluted in 95% Ar. The Landau–Teller plot of the vibration–vibration relaxation times has a least squares line of

where pτvv is in atm ˙μsec and T in °K. The measured kinetic reaction was determined to be

The transfer probabilities for this process were found to vary directly with temperature.
The rate constant of the reaction HO2 + COCO2 + OH
Authors: Vardanyan I. A. , Sachyan G. A. , Nalbandyan A. B. 
Published: January 2005

AbstractThe high‐temperature oxidation of formaldehyde in the presence of carbon monoxide was investigated to determine the rate constant of the reaction HO2 + CO  CO2 + OH (10). In the temperature range of 878–952°K from the initial parts of the kinetic curves of the HO2 radicals and CO2 accumulation at small extents of the reaction, when the quantity of the reacted formaldehyde does not exceed 10%, it was determined that the rate constant k10 is

A computer program was used to solve the system of differential equations which correspond to the high‐temperature oxidation of formaldehyde in the presence of carbon monoxide. The computation confirmed the experimental results. Also discussed are existing experimental data related to the reaction of HO2 with CO.
Hydrogen abstraction by fluorine atoms under conditions of thermal initiation: Hydrocarbons and fluorinated hydrocarbons
Authors: Manning Ronald G. , Grant Edward R. , Merrill Jerald C. , Parks Norris J. , Root John W. 
Published: January 2005

AbstractModified nuclear recoil techniques have been used to obtain accurate relative bimolecular rate coefficients for thermally induced hydrogen abstraction reactions by atomic fluorine. New results are reported for 12 hydrocarbons and partially fluorinated hydrocarbons studied at 303°K.
The mechanism of the isomerization of cis‐2‐butene photosensitized by sulfur dioxide excited within the first allowed band at 3130Å
Authors: Demerjian Kenneth L. , Calvert Jack G. 
Published: January 2005

AbstractThe mechanism of the electronically excited sulfur‐dioxide sensitized isomerization of cis‐2‐butene has been studied through the measurement of the initial quantum yields of trans‐2‐butene formation in 3130‐A irradiated gaseous binary mixtures of SO2 and cis‐2‐butene and ternary mixtures of SO2, cis‐2‐butene, and CO2. The kinetic treatment of the present data from the SO2C4H8 mixtures and those of recent similar studies of Penzhorn and Güsten [3] and Cox [4] are all consistent with the involvement of only the long‐lived fluorescent 1B1 and phosphorescent 3B1 states of SO2 in the isomerization mechanism. The data give (k2a + k2b)=0.21±0.04; SO2(1B1) + SO2 → SO2(3B1) + SO2(2a); SO2(1B1) + SO2 → (2SO2) (2b). The analogous intersystem crossing ratio for the SO2(1B1)‐cis‐2‐butene quenching collisions is the largest observed among the many quencher molecules studied; the value lies in the range of 0.85 to 0.37, with the extremes representing different choices of alternative data and possible mechanisms. From the present data the ratio of the SO2(3B1) quenching rate constant with SO2 to that with cis‐2‐butene as quencher is estimated to be (2.7±1.2) × 10−3, in good agreement with our directly measured ratio from lifetime studies (2.91±0.23) × 10−3 [30−32], and the value found in isomerization studies by Cox (2.40±0.09) × 10−3 [4]. The simple two‐excited state mechanism, which is seemingly applicable to the relatively low‐pressure binary SO2‐butene mixture results, is not adequate to explain the data obtained in experiments with large quantities of added CO2 gas. Here an “excess” quantum yield of isomerization is observed. Several alternative mechanisms can be used to rationalize these results, but all alternatives must incorporate some other excited SO2 species (X) as well as SO2(3B1) and SO2(1B1). The kinetics suggest that the ill‐defined state is unreactive toward the olefin and decays nonradiatively to SO2 largely in experiments at the lower pressures, X → SO2 (11); it may generate SO2(3B1) in a collisionally induced process at high added inert gas (CO2) pressures, X + CO2 → SO2(3B1) + CO2 (10a) and X + CO2 → SO2 + CO2 (10b). The data give k11/(k10a + k10b)=0.026 mole/l.
The kinetics of the reaction of O(3P) and D atoms with cyclohexane
Authors: Kim Poongzag , Timmons Richard B. 
Published: January 2005

AbstractThe kinetics of the reactions of O(3P) and D atoms with cyclohexane have been investigated using fast‐flow techniques. The rates of reaction were computed by monitoring changes in both atom and cyclohexane concentrations using electron spin resonance and mass spectrometric methods, respectively. The O(3P) + C6H12 reaction was studied over a temperature range of 344 to 513°K and we obtain a specific rate constant of (3.2±0.6) × 1014 exp (−4400±400/RT) cm3/mole˙sec for this reaction. The only reaction product detectable mass spectrometrically under flow conditions of excess oxygen atoms is formaldehyde.The D + C6H12 reaction was studied over a temperature range of 297 to 596°K. A specific rate constant of (4.1±1.0) × 1013 exp (−4000±300/RT) cm3/mole˙sec was obtained for this reaction. On the basis of the results obtained in these studies, the important primary process in both the O(3P) and D atom reactions is concluded to be abstraction of a hydrogen atom from the cyclohexane molecule.