bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of ethylene oligomerization
Authors: Ács G. , Péter A. , Huhn P.
Published: January 2005

A study was made of the oligomerization of ethylene, initiated by the thermal decomposition of azoethane and azo‐isopropane at low temperatures, where the polymerization equilibria are shifted somewhat in the direction of the formation of products with longer carbon chains. The findings supported the picture acquired from a study of the propionaldehyde–ethylene system. Also under these conditions the oligomerization proceeds via addition between the ethylene and radicals, followed by isomerization and decomposition of the longer radicals, with a tendency to yield propylene and longer olefins. At the lower temperatures the decomposition of radicals with shorter carbon chain becomes less important in comparison with their addition reactions and, in spite of the otherwise identical mechanism, this leads to a different product distribution.
Reaction of hydrogen atoms and O2(1Δg)
Authors: Cupitt L. T. , Takacs G. A. , Glass G. P.
Published: January 2005

The reaction of atomic hydrogen with O2(1Δg) has been investigated as a function of temperature, using a fast discharge‐flow apparatus equipped for EPR detection of free radical species. The rate constant for the overall reaction was measured as (1.46 ± 0.49) × 10−11 exp(‐4000 ± 200 cal/mol/RT) cm3/s. Evidence is presented which suggests that the reaction occurs principally via abstraction, H + O2(1Δg) → OH + O, rather than via physical quenching, H + O2(1Δg) → H + O2(X3Σg−).
Rate constants for the reaction of OH radicals with a series of alkanes and alkenes at 299 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. , Winer Arthur M. , Pitts James N.
Published: January 2005

Using methyl nitrite photolysis in air as a source of hydroxyl radicals, relative rate constants for the reaction of OH radicals with a series of alkanes and alkenes have been determined at 299 ± 2 K. The rate constant ratios obtained are: relative to n‐hexane = 1.00, neopentane 0.135 ± 0.007, n‐butane 0.453 ± 0.007, cyclohexane 1.32 ± 0.04; relative to cyclohexane = 1.00, n‐butane 0.341 ± 0.002, cyclopentane 0.704 ± 0.007, 2,3‐dimethylbutane 0.827 ± 0.004, ethene 1.12 ± 0.05; relative to propene = 1.00, 2‐methyl‐2‐butene 3.43 ± 0.13, isoprene 3.81 ± 0.17, 2,3‐dimethyl‐2‐butene 4.28 ± 0.21. These relative rate constants are placed on an absolute basis using previous absolute rate constant data and are compared and discussed with literature data.
Differential method for the determination of the order of reaction and the rate constants
Authors: Ross S. D.
Published: January 2005

A method is proposed whereby the orders and rate constants for processes obeying the rate law −dA/dt = kAn may be determined. The method is illustrated in two ways. First, simulated data for processes of various orders are treated, and the treatment is shown to be capable of reproducing orders and rate constants to a high degree of accuracy. The factors affecting the accuracy with which n and k can be determined are considered. These are inaccuracy in the determination of concentration values, irregularity of the time intevals between concentration determinations, and the length of those time intervals. It is shown that if concentrations are determined at times that are close together, the effect of the other two factors is small, but if the time intervals are made longer, the errors due to the other two factors affect the calculated values of n and k much more seriously. Second, the method was applied to two homogeneous reactions, of which one was first‐order and one was second order, and three heterogeneous reactions, of which one was found by the original workers to be first order, one to be zero order, and one to vary between zero and first order, depending on the initial pressure. The present method gives results in agreement with these conclusions and reproduces the rate constants to within ±5% in all cases.
Quantized RRK theory of unimolecular reaction rates
Authors: Schranz Harold W. , Nordholm Sture , Hamer Norman D.
Published: January 2005

The main difference between the simple RRK theory and the better based but more complex RRKM theory is explained. Starting from the premise that the classical versus quantum mechanical estimation of the density of states is the major source of the difference, earlier attempts to incorporate the quantum effects in an effective value for the number of oscillators s are noted. By examining the expression for the RRKM rate coefficient it is found that a single effective s value will generally not suffice, but a much better representation of the quantum effects can be obtained if it is recognized that the problem inherently contains two different effective s values. A theory based on this analysis is constructed. It reproduces RRKM results to much improved accuracy, removing difficulties found earlier with single‐s‐value theories.
Temperature dependence of the rate constant for the reaction OH + H2S
Authors: Lin C. L.
Published: January 2005

Absolute rate constants for the reaction of OH with H2S have been measured over the temperature range of 239–425 K using the flash photolysis–resonance fluorescence technique. The results showed that the rate constants deviate slightly from Arrhenius behavior but can still be represented adequately by the following Arrhenius equation:

Comparisons with recent literature values are presented.
Laser magnetic resonance spectroscopy of ClO and kinetic studies of the reactions of ClO with NO and NO2
Authors: Lee Yuan‐Pern , Stimpfle Richard M. , Perry Robert A. , Mucha John A. , Evenson Kenneth M. , Jennings Donald A. , Howard Carleton J.
Published: January 2005

Far‐infrared rotational transitions in ClO(X2∏3/2, υ = 0) have been observed using laser magnetic resonance (LMR) with an optically pumped spectrometer. Five observed transitions at wavelengths between 444 and 713 µm have been compared with values predicted with spectroscopic constants from the literature. LMR detection of ClO has been used to study its reactions with NO and NO2 in a discharge flow system under pseudo‐first‐order conditions for ClO. The measured rate constants are k(ClO + NO) = (7.1 ± 1.4) × 10−12 exp[(270 ± 50)/T] cm3/molec·s for the temperature range of 202 < T < 393 K; k(ClO + NO2 + M) = (2.8 ± 0.6) × 10−33 exp[(1090 ± 80)/T] cm6/molec2·s (M = He, 250 < T < 387 K), (3.5 ± 0.6) × 10−33 exp[(1180 ± 80)/T] (M = O2, 250 < T < 416 K), and (2.09 ± 0.3) × 10−31 (M = N2, T = 297 K). All measurements were made at low pressures, between 0.6 and 6.6 torr. These results are compared with those from other studies.
Oscillatory behavior during the oxygen oxidation of ascorbic acid
Authors: Young Jack , Franzus Boris , Huang Thomas T.‐S.
Published: January 2005

The oscillatory phenomenon was observed in aqueous solution during the oxidation of ascorbic acid by oxygen. Even though the exact number and amplitude of the oscillations could not be exactly duplicated for each and every run, such factors as temperature, concentration of ascorbic acid, cupric ions, and pH affecting the oscillatory behavior were studied, and those regions where oscillations occurred were delineated. A mechanism consistent with the oscillatory behavior is proposed and discussed.
New aspects of the mechanism for the thermal hydrocracking of indan and tetralin
Authors: Penninger Johannes M. L.
Published: January 2005

Thermal cracking of indan and tetralin in the gas phase was carried out in a flow reactor at 500°C and 8 MPa pressure in the presence of hydrogen and nitrogen. The primary reactions are ring cracking and dehydrogenation, regardless of the nature of the second component. Ring cracking, however, is strongly enhanced by the presence of hydrogen. This enhancement becomes less significant with increasing concentration of the hydrocarbon in the gaseous reaction mixture and also with a decreasing ratio of hydrogen to hydrocarbon. At hydrocarbon concentrations larger than approximately 0.5 g·mol/L and H2‐to‐HC molar ratios of 1 or lower, conversion rates are almost equal in hydrogen and in nitrogen. Ring cracking exhibits different kinetic behavior in nitrogen than in excess of hydrogen. This illustrates the occurrence of two complementary cracking mechanisms, each of which can dominate in certain concentration ranges. The H2‐initiated ring cracking is gradually transformed into a hydrogen‐donor mechanism as the leading reaction scheme when the concentration of indan or tetralin is increased.
A dual‐frequency Belousov Zhabotinskii oscillating reaction with ethyl acetoacetate as organic substrate
Authors: Salter Leo F. , Sheppard John G.
Published: January 2005

The experimental behavior of the cerium‐ and manganese‐catalyzed Belousov Zhabotinskii oscillating reaction with ethyl acetoacetate as organic substrate has been investigated. Under certain conditions the system displays two types of temporal oscillations. Damped highfrequency oscillations appear immediately after the addition of potassium bromate solution to complete the reaction mixture. These high‐frequency oscillations may be regarded as being superimposed on an induction period of the type found in the reaction using malonic acid. After the induction period, low‐frequency oscillations of the normal type are obtained. Both the high‐frequency and the low‐frequency oscillations can be monitored with a platinum redox or with a bromide specific ion electrode.
Kinetics and mechanism of base‐catalyzed cleavage of some bicyclo[4.2.0.]octa‐1,3,5‐trien‐7‐one (benzocyclobuten‐1(2H)‐one) derivatives
Authors: Sorial Mary A. , Iskander George M. , Bolton R.
Published: January 2005

The kinetics of cleavage of 3‐hydroxybicyclo[4.2.0]octa‐1,3,5‐trien‐7‐ones in aqueous sodium hydroxide, and of the alkoxy and acetoxy analogues in methanolic sodium methoxide solution, were examined under pseudo‐first‐order reaction conditions. The dependence of the rate upon the basicity of the solvent, whether measured by H− or by [OR−], reflects the possible structure of the transition state. The deduced mechanism is also supported by the effects of substituents upon the reaction rate. The relative amounts of the volatile reaction products derived from o‐toluic acid and from phenylacetic acid are understood in terms of the substituent effect upon the relative stabilities of the carbanions.
Ozone–isoprene reactions: Product formation and aerosol potential
Authors: Kamens R. M. , Gery M. W. , Jeffries H. E. , Jackson M. , Cole E. I.
Published: January 2005

Dark‐phase experiments between isoprene and O3 are discussed. UNC outdoor chamber experiments have shown that in high‐concentration systems of isoprene and O3 (5 ppm C and 1 ppm) approximately 75% of the reacted carbon can be observed in the product formation of HCHO, CO, methacrolein, methylvinylketone, methylglyoxal, acetaldehyde, and propylene. Mechanisms were developed which gave reasonable fits to dark‐phase chamber experiments of MACR, MVK, isoprene, and O3. Experimental data and modeling results were used to generate O3 rates of attack on MVK and MACR. An isoprene–O3 rate of 1.67 × 10−2 ppm−1·min−1 was used and is consistent with other rates reported in the literature. Dark isoprene–O3 systems appear to form homogeneously nucleated aerosol. Most of these particles appear and remain at diameters well below the optical cutoff region (0.3–0.5 μm), as opposed to the particles from similar α‐pinene–O3 systems, which also form at smaller sizes but then grow into the optical size range (0.5 μm). Lower concentrations of α‐pinene and O3 (0.2 ppm C and 0.12 ppm) still generated substantial aerosol, but by comparison, rapid CN nucleation was not observed during a similar side‐by‐side system of isoprene and O3.
Self‐ and cross‐disproportionation‐to‐combination rations for cyclopentyl and cyclohexyl radicals and their deuterated analogues
Authors: Fujisaki Noboru , Gäumann Tino
Published: January 2005

Hydrogen, cycloalkene, and bicycloalkyl were found to be the principal products which account for ≈︁97% of all products formed in the gas‐phase radiolysis of water vapor containing low concentrations of cycloalkanes. From the ratios of cycloalkene‐to‐bicycloalkyl yields extrapolated to the zero dose, the self‐ and cross‐disproportionation‐to‐recombination rate constant ratios Δ = kd/kc were determined for the following 12 reactions: Δ(c‐C5H9, c‐C5H9) = 0.73; Δ(c‐C5D9, c‐C5D9) = 0.58; Δ(c‐C6H11, cC6H11) = 0.59; Δ(c‐C6D11, c‐C6D11) = 0.46; Δ(c‐C5H9, c‐C6H11) = 0.28; Δ(c‐C5D9, c‐C6H11) = 0.28; Δ(c‐C5H9, c‐C6D11) = 0.24; Δ(c‐C5D9, c‐C6D11) = 0.24; Δ(c‐C6H11, c‐C5H9) = 0.33; Δ(c‐C6H11, c‐C5D9) = 0.25; Δ(c‐C6D11, c‐C5H9) = 0.35; and Δ(c‐C6D11, c‐C5D9) = 0.28, where in the case of the cross‐disproportionation the symbol Δ(R1,R2) is used to represent kd/kc for the disproportionation in which radical R1 captures a hydrogen (deuterium) atom from radial R2. The geometrical mean rule holds in the cross‐combination reactions of cyclopentyl and cyclohexyl radicals. The kinetic isotope effect in the disproportionation reaction was determined as 1.24 ± 0.06.
Spectra of propylperoxy radicals and rate constants for mutual interaction
Authors: Adachi Hiroyuki , Basco Norman
Published: January 2005

The flash photolyses of azo‐n‐propane and azoisopropane in the presence of oxygen have been studied by kinetic spectroscopy. The transient absorption spectra observed in the region of 210–290 nm are assigned to the n‐propylperoxy and isopropylperoxy radicals. For the n‐propylperoxy radical, εmax = 1148 ± 29 L/mol cm at 242.5 nm and for the isopropylperoxy radical, εmax = 1273 ± 75 L/mol cm at 240 nm. The rate constants for the mutual reactions (7) 2RO2· → products were measured to be k7 = (2.0 ± 0.2) X 108 L/mol s for the n‐propylperoxy radical and k7 = (7.8 ± 2.2) X 105 L/mol s for the isopropylperoxy radical.
A flash photolysis resonance fluorescence investigation of the reaction OH + H2O2 → HO2 + H2O
Authors: Kurylo Michael J. , Murphy Jennifer L. , Haller Geoffrey S. , Cornett Kenneth D.
Published: January 2005

The flash photolysis resonance fluorescence technique has been used to measure the rate constant for the reaction
equation image
over the temperature range of 250–370 K. The present results are in excellent agreement with three very recent studies, and the combined data set can been used to derive the expression
equation image
similar to that currently used in atmospheric modeling applications.

A summary of our computer simulation of this reaction system is presented. The results of the computations indicate the absence of secondary reaction complications in the present work while revealing significant problems in the earlier (pre‐1980) studies of the title reaction.
An ftir study of the reaction between nitrogen dioxide and alcohols
Authors: Niki H. , Maker P. D. , Savage C. M. , Breitenbach L. P.
Published: January 2005

The reaction 2NO2 + ROH = RONO + HNO3 (R = CH3 or C2H5) has been studied using the FTIR method at reactant pressures from 0.1 to 1.0 torr at 25°C. The termolecular rate constant for the forward reaction was determined to be (5.7 ± 0.6) × 10−37 cm6/molec2·s for CH3OH and (5.7 ± 0.8) × 10−37 cm6/molec2·s for C2H5OH, that is, d[RONO]/dt = k[NO2]2[ROH]. The corresponding equilibrium constants were measured as 1.36 ± 0.06 and 0.550 ± 0.025 torr−1, respectively. These results are consistent with those of a previous study based on the NO2 decay measurements at reactant pressures from 1 to 10 torr.
Mechanism of the pyrolysis of C2HCl5, molecular and radical steps
Authors: Benson Sidney W. , Weissman Maia
Published: January 2005

An analysis of the thermochemistry of the kinetic parameters of the elementary reactions involved in the pyrolysis of pentachloroethane has resolved several disputed, unclarified, or inconsistent aspects of the reaction mechanism. The resulting mechanisms for the inhibited and uninhibited pyrolysis account for all reported experimental findings. On the basis of this interpretation, first experimentally based values have been derived for the following: DH0(CCl3–CHCl2) = 79.0 ± 1.0 kcal/mol, ΔH(CHCl2) = 25.7 ± 1.0 kcal/mol, and E1 = 59.7 ± 1.0 kcal/mol C2HCl5 magnified image.
Mechanism of oxidation of triphenylphosphine, triphenylarsine, and triphenylstibine by potassium peroxodisulfate
Authors: Srinivasan C. , Pitchumani K.
Published: January 2005

The kinetics of oxidation of triphenyl derivatives of group V elements Ph3M (M = P, As, Sb) by potassium peroxodisulfate have been investigated spectrophotometrically in 60% acetonitrile–40% water (v/v) mixture. The reaction follows second‐order kinetics, first order in each reactant. Changes in the [H+] and ionic strength have negligible effect on the reaction rate. Addition of acrylonitrile fails to inhibit the rate. The results indicate a rate‐determining nucleophilic displacement of the Ph3M molecule on the peroxide linkage. The relative rate order has been found to be Ph3P > Ph3Sb > Ph3As. This can be attributed to two conflicting trends.
Acid‐catalyzed hydrolysis of some diazoacetophenones in aqueous dioxan
Authors: Thomas C. W. , Leveson L. L.
Published: January 2005

Rate constants and activation parameters for the acid‐catalyzed hydrolysis of eight ring‐substituted diazoacetophenones have been measured in three dioxan–water mixtures. An isokinetic relationship applies to the results obtained using a 50% dioxan–water mixture as solvent. Solvent and substituent effects are discussed together with some mechanistic aspects. Substituent constants are reported for the COCHN2 group.
Rate constants for the gas‐phase reactions of OH radicals with a series of bi‐ and tricycloalkanes at 299 ± 2 K: Effects of ring strain
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L.
Published: January 2005

Relative rate constants for the gas‐phase reactions of OH radicals with a series of bi‐ and tricyclic alkanes have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10−12 cm3/molec·s, the rate constants obtained are (× 1012 cm3/molec·s): bicyclo[2.2.1]heptane, 5.53 ± 0.15; bicyclo[2.2.2]octane, 14.8 ± 1.0; bicyclo[3.3.0]octane, 11.1 ± 0.6; cis‐bicyclo[4.3.0]nonane, 17.3 ± 1.3; trans‐bicyclo[4.3.0]nonane, 17.8 ± 1.3; cis‐bicyclo[4.4.0]decane, 20.1 ± 1.4; trans‐bicyclo[4.4.0]decane, 20.6 ± 1.2; tricyclo[5.2.1.02,6]decane, 11.4 ± 0.4; and tricyclo[3.3.1.13,7]decane, 23.2 ± 2.1. These data show that overall ring strain energies of ≲4–5 kcal mol−1 have no significant effect on the rate constants, but that larger ring strain results in the rate constants being decreased, relative to those expected for the strain‐free molecules, by ratios which increase approximately exponentially with the overall ring strain.
Thermal dehydration kinetics of disaccharides
Authors: Scheer Milton D.
Published: January 2005

The vacuum decomposition of sucrose and cellobiose has been observed in the 150–250°C temperature range. The predominant decomposition product of both sugars is H2O with less than 5% CO, CO2, CH2O, CH3CHO, CH3OH, and C2H5OH formed. The detailed rates and temperature dependences suggest that with the possible exception of C2H5OH, the minor products are formed in secondary reactions of the dehydration products. Further it is shown that the so‐called “melting with decomposition” of a sugar is in reality a high‐temperature dissolution of the disaccharide in the eliminated water.
Relative rate constants for removal of vibrationally excited OH(X2πi)v=9 by some small molecules at room temperature
Authors: Finlayson‐pitts B. J. , Toohey D. W. , Ezell M. J.
Published: January 2005

Vibrationally excited OH in v = 9 [designated OH†(9)] was generated by the reaction of hydrogen atoms with ozone in a fast‐flow discharge system at 300 ± 3 K and a total pressure of 1.1 ± 0.1 torr, with argon as the carrier gas. The addition of a species X, which can deactivate the OH†(9) or react with it, led to a decrease in the Meinel band chemiluminescent emission intensities at both 626 nm (9 → 3 band) and 519 nm (9 → 2 band), which were monitored as a function of the concentration of X. Application of the kinetic scheme developed previously for this chemical system gave the relative rate constant for the removal of OH†(9) by X. The relative rate constants determined in this study, taking O2 as the reference deactivator (k = 1.0), are as follows: He ≤ 0.02; H2 ≤ 0.05; SF6 0.09 ± 0.01; CF4 0.19 ± 0.01; N2O 3.5 ± 0.4; NO 17.7 ± 1.5; H2O 74.3 ± 2.9; D2O 57.6 ± 2.0; NH3 61.3 ± 1.9; ND3 58.7 ± 1.6; SO2 7.1 ± 1.4; COS 8.4 ± 1.7; H2S 33.7 ± 8.4; CH4 1.56 ± 0.03; CD4 1.06 ± 0.06. Application of these relative rate constants to conditions in the upper atmosphere (60–100 km) suggests that OH†(9) is removed primarily by deactivation by O2, and at altitudes ≳90 km, possibly by O(3P). However, since O2 is unusually efficient for a homonuclear diatomic in deactivating OH†(9), it may not be the primary deactivator for the lower (v ≤ 8) vibrational levels. These results are compared to earlier studies of OH†(9), and possible mechanisms of interaction of OH†(9) with these molecules are discussed.
Reaction of pentafluoroethyl radicals with hydrogen cyanide
Authors: Pasteris Leonor , Oexler Elena V. , Staricco Eduardo H.
Published: January 2005

The reaction of C2F5 radicals with HCN has been studied over the range of 533–673 K using the pyrolysis of pentafluoroethyl iodide as the free‐radical source. Arrhenius parameters for the reaction
equation image
relative to C4F10 recombination are given by

where θ = 2.303RT kJ/mol and kH/k is in cm3/2/mol1/2·s1/2.
Intramolecular hydrogen isotope effect in the pyrolysis of diethyl carbonate‐1,1,1,2,2‐d5
Authors: Farneth William E. , Beck Thomas L.
Published: January 2005

The thermal unimolecular decomposition of diethyl carbonate‐1,1,1,2,2‐d5 has been examined in the high‐pressure‐limiting region. The observed chemistry is consistent with a simple, competitive two‐channel model:
equation image
The intramolecular isotope effect kH/kD has been determined, and the relative Arrhenius parameters for the two channels are given by

over the temperature range of 540–620 K. These Arrhenius parameters predict an isotope effect kH/kD = 5.4 at 300 K.
The kinetics of secondary reactions in the iodination of monogermane. The effect of iodine substitution on the GeH bond dissociation energy
Authors: Noble Paul N. , Walsh Robin
Published: January 2005

A study has been made both of secondary reactions occurring during the reaction of I2 with GeH4, and of the direct reaction between I2 and GeH3I. Both these studies show that the abstraction reaction

occurs about 30 times faster than the reaction

in the temperature range of 425–446 K. This information is used to show that iodine substitution weakens Ge–H bonds by 14.4 ± 2.5 kJ/mol and that D(H2IGeH) = 332 ± 10 kJ/mol (79.3 kcal/mol). Possible reasons for the effects of halogen substituents on GeH and SiH bond strengths are discussed.
The gas‐phase reaction of hydrazine and ozone: A nonphotolytic source of OH radicals for measurement of relative OH radical rate constants
Authors: Tuazon Ernesto C. , Carter William P. L. , Atkinson Roger , Pitts James N.
Published: January 2005

The homogeneous gas‐phase reaction of N2H4 with O3 in air atmospheric pressure has been used to generate OH radicals in the dark, allowing the determination of relative OH radical rate constants for compounds which photolyze rapidly. This technique was first validated by determining the OH radical rate constant ratios for n‐butane/cyclohexane and methanol/dimethyl ether, both of which are in excellent agreement with the literature values. The rate constant for the reaction of OH radicals with methyl nitrite at 300 ± 3 K was then determined relative to those for the reaction of OH radicals with n‐hexane and dimethyl ether. The resulting rate constant of 1.8 × 10−13 cm3/molecule·s is about seven times lower than those of previous measurements which employed a different nonphotolytic relative rate method.
Kinetics and mechanism of osmium(VIII)‐catalyzed oxidation of D‐proline and L(–)‐methionine by hexacyanoferrate(III)
Authors: Upadhyay Santosh K.
Published: January 2005

The osmium(VIII)‐catalyzed oxidation of D‐proline and L(–)‐methionine by alkaline hexacyanoferrate(III) has been studied spectrophotometrically. The reactions follow kinetics different from those of the oxidation of many amino acids investigated earlier, being first order in hexacyanoferrate(III) and osmium(VIII). The order in proline or methionine and OH− decreases from unity to zero at higher concentrations of proline or methionine and OH−, respectively. A mechanism consistent with the kinetic data is proposed and discussed.
The kinetics and mechanisms of the gas‐phase pyrolysis of ethyl 4‐bromobutyrate. The ion‐pair mechanism revisited
Authors: Chuchani Gabriel , Dominguez Rosa M.
Published: January 2005

The gas‐phase pyrolysis of ethyl 4‐bromobutyrate has been investigated in a static system over the temperature range of 354.6–374.7°C and the pressure range of 51–126 torr. The elimination reaction in seasoned vessels and in the presence of at least twofold of a chain radical inhibitor is homogeneous, unimolecular, and obeys a first‐order rate law. The rate coefficients are given by the Arrhenius equation log k1(s−1) = (13.31 ± 0.82) – (205.1 ± 8.6)kJ/mol/2.303RT. The partial rates for the parallel eliminations to normal dehydrobromination, lactone formation, and bromobutyric acid product have been estimated and reported. The carboethoxy substituent of the bromoester has been found to assist anchimerically the elimination process, where dihydrobromination and lactone formation arise from an intimate ion‐pair mechanism.
Kinetic and equilibrium study of gas‐phase interconversions of 1,3,6‐cyclooctatriene, 1,3,5‐cyclooctatriene and bicyclo[4.2.0]octa‐2,4‐diene
Authors: Greathead John M. , Orchard S. Walter
Published: January 2005

The gas‐phase equilibrium and rate constants for the isomerizations of 1,3,6‐cyclooctatriene (136COT) to 1,3,5‐cyclooctatriene (135COT) [reaction (1)] and bicyclo[4.2.0]octa‐2,4‐diene (BCO) to 135COT [reaction (‐2)] have been measured between 390 and 490 K and between 330 and 475 K, respectively. The rate constant of reaction (1) obeys the Arrhenius equation

The corresponding equilibrium constant is given by the van′t Hoff equation

The strain energy of the 136COT ring is calculated to be 31.7 kJ/mol, based on the known value of 37.2 kJ/mol for 135COT, and ΔH(298 K) for gaseous 136COT is 196.3 kJ/mol. The rate constant of reaction (‐2) obeys the Arrhenius equation

The equilibrium constant for 135COT ⇆ BCO fits the van′t Hoff equation

The strain energy of the BCO skeleton is calculated to be 108.3 kJ/mol, and ΔH(298 K) for gaseous BCO is 183.3 kJ/mol.
Stopped‐flow determination of carbon dioxide–diethanolamine reaction mechanism: Kinetics of carbamate formation
Authors: Barth D. , Tondre C. , Delpuech J. J.
Published: January 2005

The reaction mechanism of carbon dioxide with diethanolamine (DEA) is investigated using the stopped‐flow method with optical detection in the ranges of concentration [DEA] = 0.111–8.4 × 10−2Mand [CO2] = 2.94–5.6 × 10−3M. The comparison of the fast time‐dependent light transmission change of a pH indicator with theoretical simulations of integrated rate equations requires a kinetic model in which a simple carbamate formation takes place simultaneously with hydration reactions, whose contributions are far from being negligible. A first‐order reaction relative to DEA is thus found with a rate constant for carbamate formation smaller than usually predicted (110 ± 15M−1s−1at 25°C). The equilibrium constant for the same reaction is also determined giving pKR= 5.3 at 25°C, in satisfactory agreement with values assumed so far.
Effects of ring strain on gas‐phase rate constants. 2. OH radical reactions with cycloalkenes
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L.
Published: January 2005

Relative rate constants for the gas‐phase reactions of OH radicals with a series of cycloalkenes have been determined at 298 ± 2 K using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with isoprene of 9.60 × 10−11 cm3 molecule−1 s−1, the rate constants obtained were (X 1011 cm3 molecule−1 s−1): cyclopentene 6.39 ± 0.23, cyclohexene 6.43 ± 0.17, cycloheptene 7.08 ± 0.22, 1,3‐cyclohexadiene 15.6 ± 0.5, 1,4 cyclohexadiene 9.48 ± 0.39, bicyclo[2.2.1]‐2‐heptene 4.68 ± 0.39, bicyclo[2.2.1] 2,5 heptadiene 11.4 ± 1.0, and bicyclo[2.2.2] 2 octene 3.88 ± 0.19. These data show that the rate constants for the nonconjugated cycloalkenes studied depend on the number of double bonds and the degree of substitution per double bond, and indicate that there are no obvious effects of ring strain energy on these OH radical addition rate constants. A predictive technique for the estimation of OH radical rate constants for alkenes and cycloalkenes is presented and discussed.
Energy of activation and temperature for the hydrolysis of sucrose
Authors: Buchanan Susan , Kubler Donald G. , Meigs Cynthia , Owens Michael , Tallman Alan
Published: January 2005

We have reinvestigated temperature effects on the rates of hydrolysis of 0.0585M sucrose in 0.57M HCl solutions over the range of 10–40°C using polarimetry as a physical method to follow the reaction while simultaneously analyzing the solutions by HPLC for the disappearance of sucrose and by GLC for the appearance of glucose. When the polarimetric data are corrected for the mutarotation lag, the energy of activation values are the same by all three analytical methods and are temperature‐independent.
The kinetics of the reactions of i‐C3F7 radicals with BR2 and HBr
Authors: Weeks Ian , Whittle Eric
Published: January 2005

The reactions

have been studied competitively in the vapor phase over the range of 52–204°C. The i‐C3F7 radicals were generated by means of the reaction

It was found that

where θ = 2.303RT J/mol. Absolute Arrhenius parameters are derived for the reactions

where R = CF3, C2F5, and i‐C3F7.
Effect of solvent polarity on the rate of ozone reaction with unsaturated compounds
Authors: Gomes M. , Razumovskii S. D. , Zaikov G. E.
Published: January 2005

The effect of the polarity of seven solvents (ϵ ≈ 2–60) on the rate of ozone reactions with stilbene and allyl chloride has been studied. The data show that the rate of the reaction is insensitive to the medium polarity. The results of earlier publications are revised and are shown to be in agreement with the present data.
The gas‐phase decomposition of methylsilane. Part III. Kinetics
Authors: Sawrey B. A. , O'Neal H. E. , Ring M. A. , Coffey D.
Published: January 2005

The homogeneous gas‐phase decomposition kinetics of methylsilane and methylsilane‐d3 have been investigated by the comparative‐rate‐single‐pulse shock‐tube technique at total pressures of 4700 torr in the 1125–1250 K temperature range. Three primary processes occur: CH3SiH3 → CH3SiH + H2 (1), CH3SiH3 → CH4 + SiH2 (2), and CH3SiH3 → CH2 = SiH2 + H2 (3). The high‐pressure rate constants for the primary processes in CH3SiH3 obtained by RRKM calculations are log (k1 + k3) (s−1) = 15.2 ‐ 64,780 Cal/θ and log k2 (s−) = 14.50 ‐ 67,600 → 2800 Cal/θ. For CH3SiD3 these same rate constants are log k1 (s−) = 14.99 ‐ 64,700 cal/θ log k2 (s−) = 14.68 – 66,700 → 2000 cal/θ, and log k3 (s−) = 14.3 ‒ 64,700 cal/θ.
Shock tube study of cyanogen oxidation kinetics
Authors: Louge Michel Y. , Hanson Ronald K.
Published: January 2005

Mixtures of cyanogen and nitrous oxide diluted in argon were shock‐heated to measure the rate constants of
equation image
A broad‐band mercury lamp was used to measure CN in absorption at 388 nm [B2Σ+(v = 0) ← X2Σ+(v = 0)], and the spectral coincidence of a CO infrared absorption line [v(2 ← 1), J(37 ← 38)] with a CO laser line [v(6 → 5), J(15 → 16)] was exploited to monitor CO in absorption. The CO measurement established that reaction (3) produces CO in excited vibrational states. A computer fit of the experiments near 2000 K led to

An additional measurement of NO via infrared absorption led to an estimate of the ratio k5/k6:
equation image
with k5/k6 ≃ 103.36±0.27 at 2150 K. Mixtures of cyanogen and oxygen diluted in argon were shock heated to measure the rate constant of
equation image
and the ratio k5/k6 by monitoring CN in absorption. We found near 2400 K:

and

The combined measurements of k5/k6 lead to k5/k6 ≃ 10−3.07 exp(+31,800/T) (±60%) for 2150 ≤ T ≤ 2400 K.
Cage reactions in the photolysis of 2,2,4,4‐tetramethyl‐3‐pentanone
Authors: Abuin E. B. , Encinas M. V. , Díaz S. , Lissi E. A.
Published: January 2005

The product quantum yields in the photolysis of 2,2,4,4‐tetramethyl‐3‐pentanone have been measured in homogeneous solvents of different viscosities, in micellar solutions of cetyltrimethylammonium chloride and sodium dodecyl sulfate, and in dioctadecyl ammonium chloride vesicles.

The product quantum yield in n‐heptane was found to be 1. This value decreases to 0.5 in paraffin oil as a consequence of geminate recombination. In the presence of free radical scavengers, the extent of geminate disproportionation can be evaluated from the yields of isobutene and 2,2‐dimethyl propionaldehyde. From these yields and the geminate recombination yields the total amount of geminate processes and the disproportionation‐to‐combination ratio for caged radicals are estimated. It is found that micelles provide the most efficient cages. In these media only about 10% of the radicals avoid cage processes. The disproportionation‐to‐combination ratio of tert‐butyl and pivaloyl radicals was found to be extremely media dependent. The measured values ranged from about 0.2 in paraffin oil to 0.8 in cetyltrimethylammonium chloride micelles.
Kinetics of the reactions of CCl3 with O and O2 and of CCl3O2 with NO at 295 K
Authors: Ryan K. R. , Plumb I. C.
Published: January 2005

The reactions of CCl3 with O(3P) and O2 and those of CCl3O2 with NO have been studied at 295 K using discharge flow methods with helium as the bath gas. The rate coefficient for the reaction of CCl3 with O was found to be (4.2 ± 0.6) × 10−11 cm3/s and that for CCl3O2 with NO was (18.6 ± 2.8) × 10−12 cm3/s with both coefficients independent of [He]. For reaction between CCl3 and O2 the rate coefficient was found to increase from 1.51 7times; 10−14 cm3/s to 7.88 × 10−14 cm3/s as the [He] increased from 3.5 × 1016 cm−3 to 2.7 × 1017 cm−3. There was no evidence for a direct two‐body reaction, and it is concluded that the only product of this reaction is CCl3O2. Examination of these results for CCl3 + O2 in terms of current simplified falloff treatment suggests that the high‐pressure limit for this reaction is ∼ 2.5 × 10−12 cm3/s, which may be compared with a direct measurement of the high‐pressure limit of 5 × 10−12 cm3/s. A value of (5.8 ± 0.6) × 10−31 cm6/s has been obtained for k0, the coefficient in the low‐pressure region. This value is compared with corresponding values found earlier for the (CH3, O2) and (CF3, O2) systems and with estimates based on unimolecular rate theory.
Gas phase reaction of NO2 with alkenes and dialkenes
Authors: Atkinson Roger , Aschmann Sara M. , Winer Arthur M. , Pitts James N.
Published: January 2005

The kinetics of the gas phase reactions of NO2 with a series of organics have been studied at 295 ± 2 K. It was observed that only 2,3‐dimethyl‐2‐butene and the conjugated dialkenes studied reacted at observable rates, with rate constants which ranged from 1.5 × 10−20 cm3 molecule−1 s−1 for 2,3‐dimethyl‐2‐butene to 1.3 × 10−17 cm3 molecule−1 s−1 for α‐phellandrene. These rate constants are compared with the available literature data and the mechanisms of these reactions are discussed.
The reactions of hydrogen atoms with bis(trifluoromethyl)disulfide
Authors: Ekwenchi M. M. , Safarik I. , Strausz O. P.
Published: January 2005

The reactions of hydrogen atoms produced by the mercury‐photosensitized decomposition of H2 with bis(trifluoromethyl)disulfide has been studied. The rate coefficient for the primary reaction, H + CF3SSCF3 → CF3SH + CF3S, was determined in competition with the reaction H + C2H4S → SH + C2H4 to have the value k = (3.0 ± 0.18) × 1014 exp[‐(4560 ± 140)/RT] cm3 mol−1 S−1. The high A factor can be partially accounted for by assuming free rotation for the two CF3 groups and the SCF3 groups about the S—S bond in the transition state. The relatively high activation energy is attributed to inductive and orbital overlap effects. CH3SH, H2S, and CF3SH all react with CF3SSCF3 to yield solid complexes which were not explored further.
Thermal decomposition of azoethane
Authors: Péter A. , Ács G. , Huhn P.
Published: January 2005

The thermal decomposition of azoethane (AE) was studied by detailed product analysis in the temperature and pressure intervals 508–598 K and 2.7–13.3 kPa. Besides the hydrocarbon products, three characteristic and quantitatively important nitrogen‐containing compounds were also determined: ethyl‐2‐butyldiimide, ethanal‐diethylhydrazone, and tetraethyl‐hydrazine. Apart from the predominant termination reactions of the ethyl radical with itself and with the μ2 radical, the decomposition is characterized by a very short chain reaction. The measurements led to determination of the following rate constants and rate constant ratios:

for the following reactions:magnified image
Thermal decomposition of azoisopropane. I. Primary decomposition processes
Authors: Péter A. , Ács G. , Huhn P.
Published: January 2005

The thermal decomposition of azoisopropane (AIP) was studied by detailed product analysis in the temperature and pressure intervals 498–563 K and 0.67–5.33 kPa. Besides the predominant termination and hydrogen‐abstraction reaction of the 2‐propyl radical, the decomposition is characterized by a very short chain process. The following rate constants were determined from the measurements

for the following reactions:magnified image
Kinetics and equilibria of the reaction between bromine and ethyl ether. The CH bond dissociation energy in ethyl ether
Authors: Kondo Osamu , Benson Sidney W.
Published: January 2005

The kinetics and equilibria of the reaction:

have been studied in the temperature range 298–333 K by using the very low pressure reactor (VLPR) technique. Combining the estimated entropy change of reaction (1), ΔS = 8.1 ± 1.0 eu, with the measured ΔG, we find ΔH = 4.2 ± 0.4 kcal/mol; ΔH(CH3CHOC2H5) = −20.2 kcal/mol, and DH° [Et OCH(Me)‐H] = 91.7 ± 0.4 kcal/mol. We find:

where θ = 2.3 RT in kcal/mol. It has been shown that the reaction proceeds via a loose transition state and the “contact TS” model calculation gives a very good agreement with the observed value.
Kinetics of the reactions of O3 and OH radicals with a series of dialkenes and trialkenes at 294 ± 2 K
Authors: Atkinson Roger , Aschmann Sara M. , Carter William P. L.
Published: January 2005

Rate constants for the gas phase reactions of O3 and OH radicals with 1,3‐cycloheptadiene, 1,3,5‐cycloheptatriene, and cis‐ and trans‐1,3,5‐hexatriene and also of O3 with cis‐2,trans‐4‐hexadiene and trans ‐2,trans ‐4‐hexadiene have been determined at 294 ± 2 K. The rate constants determined for reaction with O3 were (in cm3 molecule‐1s−1 units): 1,3‐cycloheptadiene, (1.56 ± 0.21) × 10‐16; 1,3,5‐cycloheptatriene, (5.39 ± 0.78) × 10−17; 1,3,5‐hexatriene, (2.62 ± 0.34) × 10−17; cis−2,trans‐4‐hexadiene, (3.14 ± 0.34) × 10−16; and trans −2, trans ‐4‐hexadiene, (3.74 ± 0.61) × 10−16; with the cis‐ and trans‐1,3,5‐hexatriene isomers reacting with essentially identical rate constants. The rate constants determined for reaction with OH radicals were (in cm3 molecule−1 s−1 units): 1,3‐cycloheptadiene, (1.31 ± 0.04) × 10−10; 1,3,5‐cycloheptatriene, (9.12 × 0.23) × 10−11; cis‐1,3,5‐hexatriene, (1.04 ± 0.07) × 10−10; and trans 1,3,5‐hexatriene, (1.04 ± 0.17) × 10−10. These data, which are the first reported values for these di‐ and tri‐alkenes, are discussed in the context of previously determined O3 and OH radical rate constants for alkenes and cycloalkenes.
Determination of the rate constants for the reactions of CFCl2O2radical with NO and NO2by laser photolysis and time resolved mass spectrometry
Authors: Lesclaux R. , Caralp F.
Published: January 2005

The rate constants for reactions (4) and (5)equation imagewere determined at room temperature by pulsed laser photolysis and time resolved mass spectrometry. A description of the experimental setup is given. CFCl2O2radicals were generated by photolysis of CFCl3at 193 nm in the presence of an excess of oxygen, using an excimer laser. The rate constant for reaction (4), determined under different experimental conditions is:The rate constant of reaction (5) was determined in the pressure range of 1–12 torr, using oxygen as the buffer gas. The reaction is in its fall‐off region and the parameters determined by using the semiempirical method of Troe, takingFc= 0.6 are:The value ofk(∞) is obtained from the low‐pressure measurements and therefore the uncertainty on the actual high‐pressure limit is higher than the error limits quoted above. The results are compared with those reported for similar reactions.
Kinetics and mechanism of diethanolamine degradation in aqueous solutions containing carbon dioxide
Authors: Kim C. J. , Sartori G.
Published: January 2005

The problem of diethanolamine (DEA) degradation in gas‐treating processes was quantified through a detailed kinetic study. This reaction was found to be catalyzed by CO2, and degradation occurs in a successive manner to 3‐(2‐hydroxyethyl)oxazolidone‐2, to N,N,N′‐tris(2‐hydroxyethyl)ethylenediamine and then to N,N′‐bis(2‐hydroxyethyl)piperazine. A reaction mechanism consistent with these observations was proposed and tested through kinetic analyses. A satisfactory kinetic model which can be of practical use was derived.
Linear correlation of polar substituents in the gas‐phase pyrolyses of ethyl α‐substituted acetates
Authors: Rotinov Alexandra , Chuchani Gabriel
Published: January 2005

The pyrolysis kinetics of several ethyl esters with polar substituents at the acyl carbon have been studied in the temperature range of 319.8–400.0°C and pressure range of 50.5–178.0 torr. These eliminations are homogeneous, unimolecular, and follow a first‐order rate law. The rate coefficients are given by the Arrhenius equations: for ethyl glycolate, log k1 (s−1) = (12.75 ± 0.30) – (201.4 ± 3.8) kJ/mol/2.303RT; for ethyl cyanoacetate, log k1 (s−1) = (12.19 ± 0.18) – (191.8 ± 2.1) kJ/mol/2.303RT; for ethyl dichloroacetate, log k1 (s−1) = (12.62 ± 0.36) – (193.9 ± 4.3) kJ/mol/2.303RT; for ethyl trichloroacetate, log k1 (s−1) = (12.27 ± 0.09) – (185.1 ± 1.0) kJ/mol/2.303RT. The results of the present work together with those reported recently in the literature give an approximate linear correlation when plotting log k/k0 vs. σ* values (ρ* = 0.315 ± 0.004, r = 0.976, and intercept = 0.032 ± 0.006 at 400°C). This linear relationship indicates that the polar substituents affect the rate of elimination by electronic factors. The greater the electronegative nature of the polar substituent, the faster is the pyrolysis rate. The alkyl substituents yield, within experimental error, similar values in rates which makes difficult an adequate assessment of their real influence.
The kinetics of the addition of alkyl radicals to carbonyl groups. II. The addition of methyl radicals to trifluoroacetone in the gas phase. The formation reaction of the trifluoro‐t‐butoxy radical
Authors: Kerr J. Alistair , Wright J. Paul
Published: January 2005

By photolyzing azomethane over the temperature range 331–491 K in the presence of trifluoroacetone the kinetics of the addition reaction (1), ĊH3 + CF3COCH3 → CF3C(Ȯ)(CH3)2 have been studied. Detailed analyses have shown that the principal product of the adduct radical, CF3C(Ȯ)(CH3)2, is CH3COCH3 from reaction (−2), CF3C(Ȯ)(CH3)2 → CH3COCH3 + ĊF3. The rate constant of the addition reaction has been determined to be k1(dm3/mol s) = (4.5 ± 1.4) × 107 exp(‐(3370 ± 120)/T) over the temperature range 331–491 K, based on the value k3 = 2.2 × 1010 dm3/mol s for the reaction (3), 2ĊH3 → C2H6. The results are discussed in relation to existing data for radical additions to magnified image groups.
High temperature collisional energy transfer in highly vibrationally excited molecules: Isotope effects in tert‐butyl chloride systems
Authors: Brown Trevor C. , King Keith D. , Gilbert Robert G.
Published: January 2005

The average downward collisional energy transfer (<ΔEdown>) is obtained for highly vibrationally excited tert‐butyl chloride, both undeuterated and per‐deuterated, with Kr, N2, CO2, and C2H4 bath gases, at ca. 760 K. Data are obtained using the technique of pressure‐dependent very low‐pressure pyrolysis. Reactant internal energies to which the data are sensitive are in the range 200–250 kJ mol−1. For C4H9Cl, the <ΔEdown> values (cm−1) are 255 (Kr), 265 (N2), 440 (CO2), and 585 (C2H4), and for C4D9Cl, 245 (N2), 370 (CO2), and 540 (C2H4). The uncertainties in these values are ca. 20% (40% for Kr); the uncertainties in the deuteration ratios are 10–15%. The value for Kr is in agreement with theoretical predictions of a biased random walk model for internal energy change in monatomic/substrate collisions. The effect of deuteration of <ΔEdown> is also in accord with that predicted by a modification of the theory. Extrapolated highpressure rate coefficients for the thermal decomposition of reactant are 1013.6 exp(‐187 kJ mol−1/RT) s−1 (C4H9Cl) and 1014.2 exp(−196 kJ mol−1/RT) s−1 (C4D9Cl), in accord with other studies and the expected isotope effect.
Reactions of trichloromethyl radicals with organosilicon compounds
Authors: Rice J. A. , Treacy J. J. , Sidebottom H. W.
Published: January 2005

The photolysis of carbon tetrachloride in the presence of a number of organosilicon compounds has been investigated in the gas phase. The products obtained from the photolysis experiments were those expected from a chain reaction in which trichloromethyl radicals abstract hydrogen atoms from the organosilane. Arrhenius parameters for hydrogen atom transfer were determined relative to those for trichloromethyl radical combination.
equation image
The activation energies for the reaction of methyl, trifluoromethyl, and trichloromethyl radicals with organosilicon compounds are compared and the results rationalized in terms of polar effects.
Single pulse shock tube study on the thermal stability of ketones
Authors: Tsang Wing
Published: January 2005

5‐Methyl‐hexanone‐2, 3‐methyl‐pentanone‐2, and hexanone‐2 have been decomposed in comparative rate single pulse shock tube experiments. The mechanism of decomposition involves the breaking of carbon‐carbon bonds as well as molecular processes involving 6‐center complexes. The following rate expressions at 1100 K have been obtained:

These results lead to ΔHf(CH3ĊO) = − 13.8 kJ and ΔHf(CH3COCH2·) = − 12.6 kJ at 300 K. They are compared with existing literature values and some generalizations are made with regard to the stability of carbonyl compounds.
The effect of temperature on formaldehyde photooxidation in oxygen‐lean atmospheres
Authors: Carmely Yaakov , Horowitz Abraham
Published: January 2005

The photooxidation of formaldehyde in CH2OO2, oxygen‐lean mixtures was studied in the temperature range 298–378 K. H2 and CO formation and the loss of O2 proceed by a chain mechanism, which between 328 and 378 K follows the previously suggested kinetics [1] with one modification. The reaction HO2 + CH2O ⇄ HO2CH2O (5) is now assumed to be reversible and ΔH is estimated to be between 14 and 19 kcal/mol. The relative yields of the chain formed H2 and CO and of the consumed O2 remained constant over the entire temperature range indicating that the relative efficiencies of the HO reactions: HO + CH2O → H2O HCO† (7), HO + CH2O → H2O + HCO (8) and HO + CH2O → HOCH2O (9) are temperature independent.