bluuebunny/crossref_metadata_2025 huggingface dataset:
A measurement of the rate of the reaction N + H + M → NH + M
Authors: Brown Robert L.
Published: January 2005

The combination reaction between N and H atoms has been studied in a flow system by mixing H atoms produced by thermal dissociation of H2 with active nitrogen produced by a microwave discharge. Relative N atom concentrations were determined from the intensity of the yellow nitrogen afterglow. Absolute N and H atom concentrations were measured by EPR absorption spectroscopy. Absolute N atom concentrations were also determined by titration with NO. Upper and lower limits of 6.4 ± 1.5 × 10−32 and 3.1 ± 1.0 × 10−32 cm6 molecule−2 sec−1 were determined for the rate constant.
The temperature dependence and the mechanism of the SO2 (3B1) quenching reactions
Authors: Wampler Fred B. , Otsuka Kiyoshi , Calvert Jack G. , Damon Edward K.
Published: January 2005

The Arrhenius parameters have been determined for the SO2(3B1) quenching reaction (9), SO2(3B1) + M → (SO2  M), for 21 different molecules as quenching partner M. The rate constants were calculated from phosphorescence lifetime measurements made over a range of reactant pressures and temperatures. Excitation of the SO2 (3B1) molecules was accomplished by two very different methods: (1) a 3829 Å laser pulse generated the triplet directly through absorption within the “forbidden” SO2 (3B1) → SO2 (1A1) band; (2) a broadband Xe‐flash system generated SO2(3B1) molecules and triplets were formed subsequently by intersystem crossing, SO2(1B1) + M → SO2(3B1) + M. The measured rate constants were independent of the method of triplet formation employed. For the atmospheric gases, the activation energies (kcal/mole) were identical within the experimental error: N2, 2.9 ± 0.4; 02, 3.2 ± 0.5; Ar, 2.8 ± 0.6; CO2, 2.8 ± 0.4; CO, 2.7 ± 0.4; CH4, 2.5 ± 0.6. This energy corresponds to the first region of the SO2(3B1) → SO2(1A1) absorption spectra in which Brand and coworkers observe strong perturbations. It is suggested that the quenching in these cases results largely from the physical process involving potential energy surface crossing to another electronic state. Activation energies for SO2(3B1) quenching by the paraffinic hydrocarbons show a regular decrease in the series ethane, neopentane, propane, n‐butane, cyclohexane, and isobutane, which parallels closely the decrease in CH bond energies in these compounds. These and other data are most consistent with the dominance of chemical quenching in these cases. The rate constants for the olefinic and aromatic hydrocarbons and nitric oxide show only very small variations with temperature change, and they are near the kinetic collision number. These data support the hypothesis that quenching in these cases is associated with the formation of a charge‐transfer complex and subsequent chemical interactions between the SO2(3B1) molecule and the π‐system of these compounds.
Time‐resolved fluorescence studies on the formation and decomposition of the aromatic hydrocarbon‐aliphatic amine exciplex in solution
Authors: Nakashima Nobuaki , Mataga Noboru , Yamanaka Chiyoe
Published: January 2005

Fluorescence rise and decay processes were measured and rate parameters were determined for the pyrene‐tri‐n‐butylamine and pyrene‐N,N‐diethylaniline exciplex system in various solvents. An additional activation energy over that for the diffusional motion appears necessary for both exciplex formation and the deactivating quenching processes in the case of the pyrene‐tri‐n‐butylamine system. The rate‐determining step for these processes is electron transfer in the encounter collision leading to the nonrelaxed electron transfer state.
A comparison of the thermal and photochemical oxidation of 2‐propanol by two peroxoanions
Authors: Bida Gerald , Curci Ruggero , Edwards John O.
Published: January 2005

The chain length (i.e., relative quantum yield) for the oxidation of 2‐propanol by peroxodisulfate ion at 25°C has been studied. A number of initial experiments were carried out in order to clarify the influence of dissolved oxygen, light intensity, cupric ion, and acetone absorption. After these problems were understood, conditions satisfactory for evaluation of chain length were chosen. The chain length was found to be 500 (to within ±100). The difference between this value and the thermal oxidation chain length of 1800 at 60° is, in both direction and magnitude, as expected for a common mechanism and a low activation energy for the propagation steps. A remarkable difference is seen for comparable reactions of peroxodisulfate and peroxodiphosphate anions.
The collisional behaviour of the spin orbit states of the lead atom, Pb(63P1,2), studied by time‐resolved attenuation of atomic resonance radiation
Authors: Husain D. , Littler J. G. F.
Published: January 2005

A kinetic study of lead atoms in the spin orbit states, Pb(63P1) and Pb Pb(63P2), 0.969 and 1.320 eV, respectively, above the 63P0 ground state, has been carried out by atomic absorption spectroscopy. The electronically excited lead atoms were generated by the pulsed irradiation of lead tetraethyl and monitored photoelectrically by time‐resolved attenuation of resonance radiation. The decay of the two atomic states has been studied in the presence of He, Ar, H2, D2, N2, O2, CO, NO, CO2, N2O, CH4, C2H4, C2H2 CF4, SF6, and PbEt4, and rate constants for the collisional quenching by these gases are reported. The resulting data are compared with those for the deactivation of other atomic spin orbit states of comparable energy. In general, the higher energy state, Pb(63P2), is found to be deactivated more rapidly. It would appear that the magnitude of the electronic energy to be transferred on collision governs the rates of quenching, at least where a weak interaction potential is involved, and that for most gases, deactivation of Pb(63P2) proceeds via Pb(63P1).
Dipolar aprotic–protic solvent influences in the hydrolysis of diol monoesters
Authors: Balakrishnan M. , Rao G. Venkoba , Venkatasubramanian N.
Published: January 2005

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

equation image

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

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

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

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

equation image

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

The reactions

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

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

The electron transfer reactions of the superoxide ion with benzoquinone, trimethylbenzoquinone, and menadione in dimethylformamide were studied. A procedure of the determination of the relative rate constants of these reactions was developed; the reaction of O2 with butyl bromide was chosen as a standard one. The relative rate constants measured at 20,°, 35°, and 50°C were slightly dependent on the quinone structure.

The relationship between the free energy ΔF*of the electron transfer reactions and the standard free energy ΔFo was discussed. This relationship is proposed as ΔF* = αΔFo + β, where the proportionality coefficient α is equal to 0.04–0.11 for exothermal reactions and to 0.90–0.96 for endothermal reactions.
The solvent‐jump relaxation method using continuous flow
Authors: Schelly Z. A. , Wong M. M.
Published: January 2005

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

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

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

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

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

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

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

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

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

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

Spectrophotometric methods have been used to obtain rate laws and rate parameters for the following reactions:
equation image
with ka, kb, Ea, Eb having the values 85±5 l./mole · s, 5.7±0.2 s−1 (both at 298.2°K), and 56±4 and 66±2 kJ/mole, respectively.

equation image
with kc=0.106±0.004 l./mole ·s at 298.2°K and Ec=67±2 kJ/mole.

equation image
with kd=(3.06 ±; 0.15) × 10−3 l./mole ·s at 298.2°K and Ed=66±2 kJ/mole.

Mechanisms for these reactions are discussed and compared with previous work.
The kinetics of the thermal bromination of CF3I. Determination of the bond dissociation energy D(CF3−I)
Authors: Okafo Ernest N. , Whittle Eric
Published: January 2005

The kinetics of the thermal bromination reaction

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

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

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

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

The dissociation of N2O/Ar mixtures, with and withoutadded CO, has been studied by monitoring both infrared and ultraviolet emissions behind reflected shock waves. Initial temperatures ranged from 1850 to 2535°K, and the total concentrations were 1.94–2.40 × 1018 molecule/cm3. The infrared emission, corrected if necessary for CO, was observed to decay exponentially, and an apparent rate constant Kapp was obtained. Addition of CO had no effect upon kapp and all the data can be described by the followingArrhenius parameters (in units of cm3/molecule.sec): log A=−9.31±0.12 and EA=219.1±5.2 kJ/mole. Ultraviolet emission data, in runs with added CO, indicate that the atomic oxygen concentration reached a constant value at t < 600 μsec for T0 > 2050°K.

Numerical integration of the mechanism
equation image
allowed comparison of calculated and observed parameters relating to both infrared and ultraviolet data. A consistent fit to these data was obtained with k1=1.3×10−9 exp (−238 kJ/RT) and k2=k3=1.91×10−11 exp(−105 kJ/RT).

The concentration of atomic oxygen produced by N2O dissociation is shown to be a sensitive function of k1 through k3. Upper limits are also set for the rate constants of the following reactions:
equation image
Hydrogen fluoride vibrational energy distributions for the reactions of fluorine atoms with cyclanes
Authors: Parker John H.
Published: January 2005

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

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

Study of the thermal decomposition of propane at very low conversions in the temperature range 760–830 K led to refinement of the mechanism of the reaction.

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

Further evaluation of the dependence gave the Arrhenius representation

for the ratio of the rate coefficients of the above isomerization and decomposition reactions.

Steady‐state treatment resulted in the rate equation of the process, comparison of which with measurements gave further Arrhenius dependences.
Gas phase kinetic study of the thermal reactions of t‐butoxy radicals with germane, phosphine, and trimethylsilane
Authors: Lee Yong‐Eun , Choo Kwang Yul
Published: January 2005

The hydrogen abstraction reactions of tert‐butoxyl with germane, phosphine, and trimethylsilane were studied by pyrolyzing di‐t‐butyl peroxide in the temperature range of 403 to 458 K. From the reported rate constant for the tert‐butoxy radical decomposition in the literature, the absolute rate constants were determined from the study of competitive reaction between t‐butoxy radical decomposition

and hydrogen abstraction reaction. (t‐BuO + RH → t‐BuOH + R, where RH = GeH4, PH3, and HSiMe3)

The Arrhenius parameters are found to be as follows:

Ea(kcal mol−1)
Log A(1.mol−1s−1)

t‐BuO + SiHMe3
2.1
8.5

t‐BuO + GeH4
1.9
9.1

t‐BuO + PH3
1.4
9.0
Effects of olefins on the thermal decomposition of propane part V. Effect of butene‐2‐Cis
Authors: Dombi A. , Huhn P.
Published: January 2005

The thermal decomposition of butene‐2‐cis at low conversion and its effect on the pyrolysis of propane have been studied in the temperature range 779‐812 K.

It was established that 2‐butene decomposes in a long‐chain process, with the chain cycle

(Besides the radical path, the molecular reaction
equation image
can also play a role in the formation of the products.)

The thermal decomposition of propane is considerably inhibited by 2‐butene, which can be explained by the fact that the less reactive radicals formed in the reactions between the olefin and the chain‐carrying radicals regenerate the chain cycle more slowly than the original radicals in the above chain cycle or in the reactions

The reactions of the 2‐propyl radical

are further initiation steps. The ratios of the rate coefficients of the elementary steps of the decomposition (Table III) have been determined via the ratios of the products.

Estimation of the radical concentrations indicated that only the methyl, 2‐propyl and methylallyl radicals are of importance in the chain termination.

On the basis of the inhibition‐influenced curves, the role of the bimolecular initiation steps.

could be clarified in the presence of 2‐butene.
Rate constants and kinetic isotope effects for hydrogen/deuterium abstraction by chlorine atoms from the chloromethyl group in CH2ClCH2Cl, CD2ClCD2Cl, CH2ClCHCl2, and CH2ClCDCl2
Authors: Tschuikow‐Roux E. , Faraji F. , Niedzielski Jan
Published: January 2005

The abstraction of hydrogen and deuterium from 1,2‐dichloroethane, 1,1,2‐trichloroethane, and two of their deuterated analogs by photochemically generated ground state chlorine atoms has been investigatedin the temperature range 0–95°C using methane as a competitor. Rate constants and their temperature coefficients are reported for the following reactions
equation image
Over the temperature range of this investigation an Arrhenius law temperature dependence was observed in all cases. Based on the adopted rate coefficient for the chlorination of methane [L.F. Keyser, J. Chem. Phys., 69, 214 (1978)]

which is commensurate with the present temperature range, the following rate constant values (cm3 s−1) are obtained:

The observed pure primary, and mixed primary plus α‐ and β3‐secondary kinetic isotope effects at 298 K are k3/k6 = 2.73 ± 0.08, and k1/k2 = 4.26 ± 0.12, respectively. Both show a normal temperature dependence decreasing to k3/k6 = 2.39 ± 0.06 and k1/k2 = 3.56 ± 0.09 at 370 K. Contrary to some simple theoretical expectations, the kinetic isotope effect for H/D abstraction decreases with increasing number of chlorine substituents in the geminal group in a parallel manner to the trend established previously for C1‐substitution in the adjacent group. The occurrence of a β‐secondary isotope effect, k4/k5, is established; this effect suggests a slight inverse temperature dependence.
Gas phase kinetic and thermochemical data for endo‐ and exo‐5‐monosubstituted bicyclo[2.2.2]Oct‐2‐Enes
Authors: Van Mele B. , Boon G. , Huybrechts G.
Published: January 2005

The thermal reactions of endo‐ and exo‐5‐Y bicyclo[2.2.2]oct‐2‐enes (NYBO and XYBO) where Y = methyl, ethyl, and isopropyl have been studied in the gas phase between 567 and 695 K. For both isomers they are parallel first‐order retro‐Diels‐Alder reactions with elimination of ethene (E) and monosubstituted ethene (YE).The observed Arrhenius parameters are used to discuss the mechanism and to estimate the heats of formation and the entropies of NYBO and XYBO. Group values are proposed for estimation of these thermochemical data for compounds of the same type by means of the methods of Benson.
Estimations of OH radical rate constants from H‐atom abstraction from CH and OH bonds over the temperature range 250‐1000 K
Authors: Atkinson Roger
Published: January 2005

Rate constants for overall H‐atom abstraction by hydroxyl radicals from CH and OH bonds are estimated for alkanes, haloalkanes, aldehydes, ketones, ethers, alcohols, nitriles, and nitrates over thetemperature range 250–1000 K. These estimated rate constants utilize the modified Arrhenius expression K = A'T2e−E'/T in combination with the recommendations given in the recent review and evaluation of OH radical kinetics of Atkinson [1]. This estimation procedure gives good agreement, generally to within better than a factor of 2, of the estimated rate constants with theserecommendations.
High temperature kinetics of the thermal decomposition of the lower alkanoic acids
Authors: Doolan K. R. , Mackie J. C. , Reid C. R.
Published: January 2005

The thermal decomposition of propanoic acid dilute in argon has beenstudied in a single‐pulse shock tube over the temperature range of 1100‐1500 K and over the pressure range of 14‐18 atm. The decomposition kinetics have been satisfactorily computer modelled by means of afree radical mechanism involving H and OH chains.

Recent single‐pulse shock tube product analyses of acetic acid decomposition have been computer modelled using a free radical mechanism for decarboxylation coupled to a unimolecular dehydration reaction.

A comparison between the thermal decomposition kinetics of the C1C3 alkanoic acids is made. The present studies do notprovide evidence for the participation of transition states involving a pentavalent carbon atom in the pyrolyses of the lower alkanoic acids.
The photooxidation of allyl chloride
Authors: Edney Edward O. , Shepson Paul B. , Kleindienst Tadeusz E. , Corse Eric W.
Published: January 2005

The photooxidation of allyl chloride was studied by irradiation either in 100‐L Teflon bags or in a 22.7‐m3 Teflon smog chamber in the presence of added NOx. In the absence of added hydrocarbons, the reaction involves a Cl atom chain, which leads to a highly reactive system. A reaction mechanism is presented to account for the following photooxidation products: chloroacetaldehyde, formaldehyde, 1,3‐dichloroacetone, 3‐chloroacrolein, acrolein, glyoxal, chloroperoxyacetyl nitrate, and peroxypropenyl nitrate. The rate constant for OH reaction with allyl chloride at 298 K was measured by a relative rate method under conditions where the Cl atom chain length was small and was found to be kOH = 1.7 × 10−11 cm3 molecule−1 s−1. The rate constant for O3 reaction with allylchloride at 298 K was found to be kO3 = 1.5 × 10−18 cm3 molecule−1 s−1.
Reaction of the NO3 radical with CO: Determination of an upper limit for the rate constant using FTIR spectroscopy
Authors: Hjorth J. , Ottobrini G. , Restelli G.
Published: January 2005

An upper limit for the reaction rate of CO with the nitrate radical NO3 has been determined equal to 4 × 10−19 cm+3 molec−1 s−1 at 295 ± 2 K. In the experiment the isotopic species C13O16 and C13O18 mixed at 1–2 ppmv level in synthetic air have been reacted with NO3 and the reaction followed using long path infrared absorption FT spectroscopy. The result is of interest in the studies on the role played by NO3 in nighttime tropospheric chemistry.
Kinetics and mechanism of the OH + CIO2reaction
Authors: Poulet G. , Zagogianni H. , Bras G. Le
Published: January 2005

The rate constant k1 for the reaction of OH radicals with CIO2 molecules was measured in a discharge flow system over the temperature range 293 ≤ T ≤ 473 K and at low pressures, 0.5 ≤ P ≤ 1.4 torr, using electron paramagnetic resonance or laser‐induced fluorescence to monitor the pseudo first‐order decay of OH concentrations. At 293 K, the value obtained for k1 was (7.2 ± 0.5) × 10−12 cm3 molecule−1 s−1. Within the temperature range of this study, a negative temperature dependence was observed: k1 = (4.50 ± 0.75) × 10−13 exp[(804 ± 114)/T] cm3 molecule−1 s−1. HOCl was detected by mass spectrometry as a product of the reaction and was titrated using OH + Cl2 as a source in the calibration experiments. A simulation of the mechanism of the OH + ClO2 reaction indicated that HOCl was mainly produced in the first reaction step. Both this result and the observed T dependence of k1 suggest that this reaction proceeds via an intermediate adduct with a cyclic geometry.
Time‐resolved vibrational chemiluminescence: Rate constants for the reactions of F atoms with H2O and HCN, and for the relaxation of HF (v = 1) by H2O and HCN
Authors: Frost Robert J. , Green David S. , Osborn Martin K. , Smith Ian W. M.
Published: January 2005

Rate constants have been determined at (298 ± 4) K for the reactions:
equation image
and the relaxation processes:
equation image
Time‐resolved HF(1,0) emission was observed following the photolysis of F2 with pulses from an excimer laser operating on XeCl (λ = 308 nm). Analysis of the emission traces gave first‐order constants for reaction and relaxation, and their dependence on [H2O] and [HCN] yielded:
The kinetics and the mechanism of the thermal gas‐phase reaction between NO2 and 1,1‐dichlorodifluoroethylene, CF2CCl2
Authors: Czarnowski J. , Schumacher H. J.
Published: January 2005

The kinetics of the gas phase reaction between NO2 and CF2CCl2 has been investigated in the temperature range from 50 to 80°C. The reaction is homogeneous. Three products are formed: O2NCF2CCl2NO2 and equimolecular amounts of CINO and of O2NCF2C(O)Cl. The rate of consumption of the reactants is independent of the total pressure, the reaction products, and added inert gases and can be represented by a second‐order reaction:

However, the distribution of the products is influenced by the pressure of the present gases, which favor the formation of the dinitro‐compound in a specific way. The effect of CF2CCl2 is the greatest. In the absence of added gases, the ratio of O2NCF2CCl2NO2 to that of O2NCF2C(O)Cl is proportional to (CF2CCl2 + γP products).

The experimental results can be explaned by the following mechanism:
equation image
P and X represent the products and the added gases:
Temperature‐Induced Unfolding of Ribonuclease A Embedded in Spherical Polyelectrolyte Brushes
Authors: Wittemann Alexander , Ballauff Matthias
Published: January 2005

Summary: We use Fourier Transform infrared spectroscopy (FT‐IR) spectroscopy to study the thermal unfolding and refolding behavior of ribonuclease (RNase A) adsorbed to spherical polyelectrolyte brushes (SPB). The SPB consist of a solid poly(styrene) core of ca. 100 nm diameter onto which long chains of poly(styrene sulfonic acid), PSS have been densely attached. The particles bearing the adsorbed protein are dispersed in aqueous buffer solution at a pH close to the isoelectric point (9.6) of the protein. The secondary structure of the protein was analyzed by FT‐IR spectroscopy and compared to the structure of the native protein before adsorption. The unfolding of the free RNase A in solution was found to be fully reversible with an unfolding temperature of 65 °C, in accordance to previous studies. However, after adsorption to the SPB, the unfolding temperature of the protein molecule is lowered by 10 °C and the Van't Hoff enthalpy of the unfolding process is significantly reduced. Moreover the unfolding of the adsorbed protein is irreversible. The phenomenon may be explained by an increase in binding sites due to unfolding of the globular structure.

Protein adsorption to a spherical polyelectrolyte brush.

image

Protein adsorption to a spherical polyelectrolyte brush.
Studies on the Synthesis of 2,3‐O‐Hydroxyalkyl Ethers of Cellulose
Authors: Schaller Jens , Heinze Thomas
Published: January 2005

Summary: Novel 2,3‐O‐hydroxyethyl‐ and 2,3‐O‐hydroxypropyl cellulose products were synthesized by heterogeneous etherification of 6‐O‐(4‐monomethoxytrityl) cellulose (MMTC). Due to the very hydrophobic character of MMTC, the reaction was successful in the presence of anionic and non‐ionic detergent in the reaction mixture yielding the 2,3‐O‐cellulose ethers with a molar degree of substitution (MS) varying between 0.25 and 2.00 after detritylation. The products were characterized by means of 1H and 13C NMR spectroscopy including two‐dimensional methods. The 2,3‐O‐hydroxypropyl cellulose samples are soluble in water at a MS as low as 0.8. The spectroscopic studies showed that the unusual solubility results from a preferred substitution of hydroxy groups of the anhydroglucose unit while the newly formed hydroxy moieties are included in the reaction to a minor extent only. In contrast, conventionally synthesized hydroxypropyl cellulose is soluble in water starting at a MS of about 4.0 because of the formation of oxyethylene side chains.

13C DEPT 135 NMR spectrum of 2,3‐O‐hydroxypropyl cellulose.

image

13C DEPT 135 NMR spectrum of 2,3‐O‐hydroxypropyl cellulose.
Evolving anticancer drug valproic acid: Insights into the mechanism and clinical studies
Authors: Blaheta Roman A. , Michaelis Martin , Driever Pablo Hernáiz , Cinatl Jindrich
Published: January 2005

The short chain fatty acid valproic acid (VPA) and VPA‐analogs modulate the biology of diverse tumor cell entities by inducing differentiation, inhibiting proliferation, increasing apoptosis, and immunogenicity and by decreasing metastatic and angiogenetic potential. This review updates an earlier one in 2002, reflecting the interest in VPA as a potent anticancer drug. A number of in vitro studies show that the types of known tumor cells susceptible to VPA is steadily increasing. Of special note is the strong antineoplastic activity of VPA in chemoresistant cancer cells. A novel and promising approach is combining VPA with other drugs to achieve a broad therapeutic index. Clinical studies are underway and the preliminary results indicate that VPA alone or in combination offers a promising avenue of treatment, both in solid and hematopoetic malignancies. © 2005 Wiley Periodicals, Inc.
Bronchiolitis obliterans in children
Authors: Kurland Geoffrey , Michelson Peter
Published: January 2005

Bronchiolitis obliterans (BO) in children is a relatively rare diagnosis. The increase in lung and bone marrow transplantation in children, however, has led to a heightened interest in BO, as this is one of the important complications of those procedures. This article will discuss BO as an entity that can follow any of several illnesses or toxic exposures, in addition to following allogeneic lung or bone marrow transplantation. The complex and incompletely understood pathology, pathogenesis, and molecular pathology involved in BO remain the subject of ongoing investigations. As the prognosis for BO is uncertain and treatment is often unsuccessful, the continued need for the recognition of surrogate markers for BO in patients at risk and the development of better forms of therapy are paramount. This review will describe our current understanding of BO, and will call attention to those research areas that require continuing efforts in order to prevent or treat this entity. Pediatr Pulmonol. 2005; 39:193–208. © 2005 Wiley‐Liss, Inc.
Therapeutic efficacy of milrinone in the management of enterovirus 71‐induced pulmonary edema
Authors: Wang Shih‐Min , Lei Huan‐Yao , Huang Mei‐Chih , Wu Jing‐Min , Chen Chun‐Ta , Wang Jieh‐Neng , Wang Jen‐Ren , Liu Ching‐Chuan
Published: January 2005

Hand, foot, and mouth disease and herpangina are the major clinical manifestations of enterovirus 71 (EV71) infections. Brain‐stem encephalitis and pulmonary edema are severe complications that can lead to death. This study was designed to evaluate the potential therapeutic effect of milrinone, a phosphodiesterase (PDE) inhibitor, in the treatment of patients with EV71‐induced pulmonary edema. We conducted a historically controlled trial of 24 children with severe EV71‐induced pulmonary edema from April 1998–June 2003 in southern Taiwan. Patients were divided into groups treated before and after the introduction of milrinone therapy. Etiological diagnosis was established by viral cultures and confirmed by specific immunofluorescence and neutralization tests. All 24 patients were below 5 years of age. The mortality was lower in the milrinone‐treated vs. nontreated group (36.4% vs. 92.3%, P = 0.005). Sympathetic tachycardia was decreased in patients treated with milrinone compared to controls (144 ± 17/min vs. 206 ± 26/min, P = 0.004). A marked decrease in IL‐13 (77 ± 9 pg/ml vs. 162 ± 88 pg/ml, P = 0.001) was observed in milrinone‐treated patients compared to controls. There was a significant reduction in white blood cell (10,838 ± 4,537/mm3 vs. 19,475 ± 7,798/mm3, P = 0.009) and platelet (257 ± 45 × 103/mm3 vs. 400 ± 87 × 103/mm3, P = 0.001) counts in milrinone‐treated patients compared to controls. These results were associated with improvement in sympathetic regulation and decrease in IL‐13 production. Milrinone therapy may provide a useful therapeutic approach for this highly lethal disorder. Pediatr Pulmonol. 2005; 39:219–223. © 2005 Wiley‐Liss, Inc.
Die Ursachen der Bildsamkeit der Tone
Authors: Salmang Hermann
Published: January 2005

Zur Erzeugung einer bildsamen Masse aus einem festen und einem flüssigen Körper (z. B. aus Ton und Wasser) bedarf es

geeigneter morphologischer Eigenschaften des festen Körpers (geringe Korngröße, Blättchenform, Rauhheit, Spaltbarkeit und geringer Härte).

der Erzeugung einer viscosen Schicht zwischen den Teilchen, was durch eine chemische Oberflächenreaktion zwischen dem festen und dem flüssigen Körper bewirkt wird. Kolloide können die Bildsamkeit etwas erhöhen. Alle diese Anforderungen an bildsame Massen sind beim System Ton–Wasser am besten erfüllt

.
Die Oberflächenspannung geschmolzener Metalle und Legierungen. II. Die Oberflächenspannung von Zinn, Blei, Antimon, Kupfer, Zinn‐Wismut, Blei‐Wismut, Kupfer‐Antimon, Kupfer‐Zinnlegierungen und Gußeisen
Authors: Drath G. , Sauerwald F.
Published: January 2005

Die Methode der Messung des Maximalen Blasendruckes zur Bestimmung der Oberflächenspannung der Metalle wurde weiterhin bis zur Verwendbarkeit bei 1200° ausgebildet. Es wurden gemessen die Oberflächenspannungen von Sn, Pb, Sb, Cu und von BiSn‐, BiPb‐, VuSb‐, CuSn‐Legierungen und es wurden einige vorläufige Werte für Roheisen bestimmt.
Zähigkeit und Gallertbildung von Cerihydroxyd‐Sol
Authors: Chakravarti D. N. , Ghosh S. , Dhar N. R.
Published: January 2005

1. Man erhält feste, durchsichtige Gallerten, wenn man zu einem Sol von Cerihydroxyd — hergestellt durch Dialyse einer Lösung von Ceriammoniumnitrat in der Kälte — Elektrolyte zusetzt. Die Gallertbildung findet nicht statt bei dem Sol desselben Stoffes, das in der Hitze hergestellt ist.