bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics and mechanism of ninhydrin reaction with copper(II) complexes of glycine and α‐alanine. Elucidation of the template mechanism
Authors: Gupta Dileep , Khan Zaheer , Khan A. Aziz
Published: January 2005

Ninhydrin has been found to react with Cu(glycine)+ and Cu(alanine)+ in the ratio of 1:1. The kinetic studies of the reaction were carried out at different concentrations of the reactants at 80°C (pH = 5.0). The reaction proceeds through the formation of a ternary labile complex of ninhydrin with Cu(II) complexes of glycine and alanine. The kinetics were found to follow pseudo‐first‐order reaction path with respect to Cu(II)‐complex in presence of excess [Ninhydrin]. Formation of a ternary labile complex indicates a template reaction mechanism based on the reactions with coordinated ligands. The variation of pseudo‐first‐order rate constants with [ninhydrin] was found to be in good agreement with equation

where B1 and B2 are the unknown empirical parameters. The [acetate ion] has no significant effect on the rate constants. On the basis of observed data a probable mechanism has been proposed. © 1993 John Wiley & Sons, Inc.
Reactions of [NiIII(cyclam)] with aqueous sulfur dioxide: Exhibition of a deuterium isotope effect and catalysis by chloride and bromide
Authors: Linn Donald E. , Rumage Scott D. , Grutsch John L.
Published: January 2005

One unit of S(IV) (SO2 or SHO3−) is oxidized per 2 units of [NiIII(cyclam)] species to obtain sulfate. Kinetic analyses have been done by varying the acidities (0.013 ⩽ [H+] ⩽ 1.0 M) and halide concentrations (0.000 ⩽ [X−] ⩽ 0.012 M; X=Cl and Br) at constant ionic strength (μ = 1.0 M). The rate law that incorporates the [X−] and [H+] dependence is −d[NiIII]T/dt=2k[NiIII]T[S(IV)]T where 2k={ka[H+] + kbK + kK′X[H+] [X−] + kK′XK[X−]} {[H+] + K}−1 {1 + K′X[X−]}−1, here ka=87 ± 7 M−1 s−1, kb=(2.5 ± 0.5)×103 M−1 s−1 and pK = 1.8 ± 0.2. Rate constants ka and kb are attributed to the reactions of [NiIII(cyclam) (H2O)2]3+ with SO2 and SHO3−, respectively. Monohalo species apparent equilibrium constants K′Cl=(1600 ± 400) M−1 and K′Br=(190 ± 20) M−1 and rate constants k=80 ± 8 M−1 s−1 and k = 140 ± 15 M−1 s−1 are ascribed to the protonated pathway, involving the [NiIII(cyclam) (H2O)X]2+ and SO2(aq) reaction pairs. The other two rate constants of k=(5 ± 1)×103 M−1 s−1 and k=(3.1 ± 0.5)×104 M−1 s−1, refer to the deprotonated pathway and are assigned to the [NiIII(cyclam) (H2O)X]2+ /SHO3− redox couple. A deuterium H2O / D2O isotope effect of 2.1–2.8 can be attributed partially to an equilibrium isotope effect at low acidity though a small kinetic isotope (2.5 ± 0.5) effect is evident for the dihydrogen sulfito pathway, ka. The kinetic isotope effect and the absence of sulfite radical scavenging effects are explained by a mechanism entailing migration of a hydride from sulfur to the NiIII center to produce a NiIII—H species, which rapidly comproportionates, and S(VI). © 1993 John Wiley & Sons, Inc.
Kinetics of the BrO + NO2 association reaction. Temperature and pressure dependence in the falloff regime
Authors: Thorn R. P. , Daykin E. P. , Wine P. H.
Published: January 2005

A laser flash photolysis‐long path absorption technique has been employed to study the kinetics of the reaction products as a function of temperature (248–346 K), pressure (16–800 torr), and buffer gas identity (N2, CF4). The reaction is found to be in the falloff regime between third and second‐order over the entire range of conditions investigated. This is the first study where temperature‐dependent measurements of k1(P, T) have been reported at pressures greater than 12 torr; hence, our results help constrain choices of k1(P, T) for use in models of lower stratospheric BrOx chemistry. Approximate falloff parameters in a convenient form for atmospheric modeling are derived. © 1993 John Wiley & Sons, Inc.
High pressure fast‐flow technique for gas phase kinetics studies
Authors: Seeley John V. , Jayne John T. , Molina Mario J.
Published: January 2005

A fast‐flow technique suitable for measuring elementary rate constants over a wide range of pressures has been developed. The method operates under turbulent flow conditions, in contrast to laminar flow which characterizes the conventional low pressure technique. Flow visualization, velocity profile measurements, and tracer pulse studies have been carried out in a flow tube reactor to investigate the dynamics of both laminar and turbulent flow for chemical kinetics purposes. Furthermore, the wall collision frequency for the reactants has been determined: at the higher pressures it is greatly reduced in comparison with the frequency characteristic of the conventional low pressure laminar flow technique. Also, to test and validate the technique the bimolecular rate constants for the reactions H+Cl2 and H+O3 have been measured at total pressures in the 3–300 torr range; at pressures below 5 torr, as well as above 50 torr in the turbulent flow regime the agreement with the recommended literature values is excellent. © 1993 John Wiley & Sons, Inc.
UV absorption spectrum, and kinetics and mechanism of the self reaction of CF3CF2O2 radicals in the gas phase at 295 K
Authors: Sehested Jens , Ellermann Thomas , Nielsen Ole John , Wallington Timothy J. , Hurley Michael D.
Published: January 2005

The ultraviolet absorption spectrum, kinetics, and mechanism of the self reaction of CF3CF2O2 radicals have been studied in the gas phase at 295 K. Two techniques were used; pulse radiolysis UV absorption to measure the spectrum and kinetics, and long‐path length FTIR spectroscopy to identify and quantify the reaction products. Absorption cross sections were quantified over the wavelength range 220–270 nm. At 230 nm, σ = (2.74 ± 0.46) ×10−18 cm2 molecule−1. This absorption cross section was used to derive the observed self reaction rate constant for reaction (1), defined as, −d[CF3CF2O2]/dt = 2k1obs[CF3CF2O2]2:
equation image
k1obs = (2.10 ± 0.38) ×10−12 cm3 molecule−1 s−1 (2σ).

The observed products following the self reaction of CF3CF2O2 radicals were COF2, CF3O3CF3, CF3O3C2F5, and CF3OH. CF3O2CF3 was tentatively identified as a product. The carbon balance was 90–100%. The self reaction of CF3CF2O2 radicals was found to proceed via one channel to produce CF3CF2O radicals which then decompose to give CF3 radicals and COF2. In the presence of O2, CF3 radicals are converted into CF3O radicals. CF3O radicals have several fates; self reaction to give CF3O2CF3; reaction with CF3O2 radicals to give CF3O3CF3; reaction with C2F5O2 radicals to give CF3O3C2F5; or reaction with CF3CF2H to give CF3OH.
As part of this work a rate constant of (2.5 ± 0.6) ×10−16 cm3 molecule−s−1 was measured for the reaction of Cl atoms with CF3CHF2 using a relative rate technique.
Results are discussed with respect to the atmospheric chemistry of CF3CF2H (HFC‐125). © 1993 John Wiley & Sons, Inc.
The possible resurrection of the Chapman mechanism for atmospheric sodium chemiluminescence and ruminations on NaO reaction dynamics
Authors: Schofield Keith
Published: January 2005

A critical reappraisal and kinetic modeling is presented of a sodium/N2O system. The analysis provides a compelling argument that previously reported kinetic decay rates may refer not to the reaction of O with NaO but rather to that of O with Na2O. The system shows pronounced propensity for a significant portion of the NaO to be quantitatively converted to Na2O on a time scale commensurate with that of the Na/N2O titration reaction. The O atom in the system does appear to originate from the photolysis of a residual level of NaO. The observed Na(2P) chemiluminescence, used to track the O atom decay rates, can be consistent with the O + NaO reaction as previously surmised. It is unlikely that the alternate O + Na2 and O + Na2O chemiluminescent channels can generate the observed intensity levels. This reanalysis, which provides for the observed first order dependences on N2O(Na2O) and O atom concentrations has significant implications for the Chapman atmospheric mechanism of the sodium airglow. Its conclusions resurrect the viability of the original scheme which requires efficient branching of the O + NaO reaction to Na(2P). Recent suggestions invoking the participation of NaO(A2Σ+) require the latter to have a metastable nature with respect to its radiative and collisional quenching (N2, O2) channels, for which there is no current evidence.

An additional evaluation of the rate constant measurements for the fast reactions of NaO with NO or CO indicates that these most probably are kinetically complex and involve longlived transition states. Their rate constants are predicted to have small negative activation energies and pressure dependences. In the case of NaO with CO this may explain its low Na(2P) chemiluminescent efficiency. For the NaO + O reaction, a rate constant of about 4 ×10−11 cm3 molecule−1s−1 is predicted at room temperature. This is similar to that used in earlier atmospheric models. Its magnitude circumvents the consequences of the reaction's large entropy decrease which otherwise implies too large a cross‐section for the reverse reaction. A smaller value also is more likely to be consistent with a normal short‐lived collisional transition state, which will allow for a more significant Na(2P) quantum efficiency. © 1993 John Wiley & Sons, Inc.
Reduction of toluidine blue by stannous ion at low pH: Kinetics and simulations
Authors: Jonnalagadda S. B. , Dumba M.
Published: January 2005

A detailed kinetic study of the reaction between toluidine blue (tolonium chloride) (TB+Cl−) and stannous chloride is carried out in aqueous hydrochloric acid. The depletion kinetics of toluidine blue were spectrometrically monitored at 626 nm. The reaction had fractional order with respect to toluidine blue (one half), three halves with respect to Sn2+, and first‐order dependence on H+ ion. Stoichiometric ratio between reductant and oxidant is 1:1. During the reaction Sn2+ is oxidized to Sn4+ and toluidine blue is reduced to colorless base in two univalent steps. © 1993 John Wiley & Sons, Inc.
Kinetics of benzonitrile nitration with mixed acid under homogeneous conditions
Authors: Andreozzi R. , Insola A. , Aquila T. , Caprio V.
Published: January 2005

Chemical kinetics of benzonitrile nitration with mixed acid is investigated in the temperature range 283–299 K. Pseudo‐first‐order rate constants are evaluated by means of rate experiments on homogeneous reacting mixtures having large stoichiometric excesses of nitric acid.

The second‐order kinetic constants for nitronium ion attack to the aromatic substrate are derived on the basis of the assessed nitration mechanism. An activation energy of 604 ± 37 kJ mol−1 is calculated for this reaction step. © 1993 John Wiley & Sons, Inc.
The kinetics of the nitrate radical self‐reaction
Authors: Biggs P. , Canosa‐Mas C. E. , Monks P. S. , Wayne R. P. , Benter Th. , Schindler R. N.
Published: January 2005

This article describes the first direct determination of the rate coefficient for the self‐reaction between two NO3 radicals. A laser photolysis technique was used to generate NO3, and time‐resolved decays of NO3 were followed after stopping the photolysis. The products of the reaction are inferred to be NO2 and O2. The derived rate coefficient at room temperature for the self‐reaction of (2.3 ± 0.8) ×10−16 cm3 molecule−1s−1 is in excellent agreement with the only other data, which were obtained in an indirect study. Consideration is given to the magnitude and influence of secondary chemistry and to the participation of FO in the chemistry of the NO3 buildup phase. The studies were conducted over a pressure range of 8 to 100 torr in helium. No clear pressure dependence was observed, and some tentative inferences are drawn both from this result and from the absolute magnitude of the rate coefficient about the mechanism of the reaction. There is apparently no role for the reaction in the chemistry of the atmosphere. © 1993 John Wiley & Sons, Inc.
Kinetics of liquid phase synthesis of methyl tert‐butyl ether from tert‐butyl alcohol and methanol catalyzed by ion exchange resin
Authors: Matouq Mohammed H. , Goto Shigeo
Published: January 2005

Synthesis of methyl tert‐butyl ether (abbreviated as MTBE) from methanol (MeOH) and tert‐butyl alcohol (TBA) in the liquid phase was studied by using Amberlyst 15 in the H+ form as an acid catalyst. Experiments were carried out in a stirred batch reactor at different temperatures (313, 318, and 323 K) under atmospheric pressure.

It was found that catalyst sizes and rotation speeds had no significant effects on reaction rates. Mechanism studies showed that three reactions took place simultaneously. It was also found that dehydration of TBA could not be neglected. The experimental concentration profiles with time could be simulated well by simple kinetics. Finally, rate constants could be expressed by Arrhenius equations. © 1993 John Wiley & Sons, Inc.
Kinetics of coupling of diazotized sulfanilamid with 1‐naphthylamine
Authors: Demircioḡlu N. , Bayramoḡlu M. , Topcu N.
Published: January 2005

In this study, the coupling kinetics of sulfanilamid diazonium salt with 1‐naphthylamine has been studied by spectrophotometric method. In the experiments conducted at constant temperature, 25°C, pH has been varied between 2.2−3.4, reactant concentration between 1.25 × 10−5 − 5 × 10−5 M, and ionic strength between 0.1−1 M. The reaction has been confirmed to be of second‐order and rate constants and the dissociation constant of 1‐naphthylamine have been calculated. © 1993 John Wiley & Sons, Inc.
Decomposition kinetics of the N‐bromoaminoacids, N‐bromoalanine, N‐bromo‐2‐aminobutyric acid, and N‐bromonorvaline
Authors: Antelo Juan M. , Arce Florencio , Crugeiras Juan , Armesto José L.
Published: January 2005

A kinetic study of the decomposition reactions of N‐bromoalanine, N‐bromo‐2‐aminobutyric acid, and N‐bromonorvaline shows them to be first‐order with respect to N‐bromoaminoacid concentration and independent of both excess aminoacid and pH over the interval pH 9–11. In this pH range the mean rate constants at 298 K were 1.20 × 10−3 s−1, 1.37 × 10−3 s−1 and 1.28 × 10−3 s−1, respectively. © 1993 John Wiley & Sons, Inc.
Mono‐complex formation kinetics of iron(III) with nonsubstituted octane and nonane 2,4‐dicarbonyl ligands in aqueous solution
Authors: Blanco Carlos A. , Romero Jose M. , Verdu Jesus
Published: January 2005

The kinetics and mechanism of the reaction of complexation of iron(III) with 2,4‐octanedione and 2,4‐nonanedione have been investigated spectrophotometrically in aqueous solution at 10°C and ionic strength 0.5 mol dm−3 NaClO4. The equilibrium constants of the mono‐complexes have been determined. The mechanism proposed to account for the kinetic data involves a double reversible pathway where both Fe3+ and Fe(OH)2+ react with the enol tautomer of the ligand. 2,4‐Octanedione reacts with Fe3+ and Fe(OH)2+ with rate constants of 0.65 dm3 mol−1 s−1, and 14.07 dm3 mol−1 s−1, respectively. For 2,4‐nonanedione complexation the rate constants determined are 0.49 dm3 mol−1 s−1, and 11.39 dm3 mol−1 s−1, respectively. Some discussions are made on the basis of Eigen‐Wilkins theory considering the effect of solvent exchange on the complex formation. © 1993 John Wiley & Sons, Inc.
The kinetics of thermal dimerization of hexatriene
Authors: Bulatov V. , Oref I.
Published: January 2005

The thermal isomerization ofcis‐hexatriene (cHT) to cyclohexadiene (CHD) and the dimerization of CHD andtrans‐hexatriene (tHT) in the liquid phase in the temperature range 380 K‐473 K are reported.

The rate coefficients are: for thecHT to CHD isomerizationfortHT dimerizationlogand for CHD dimerization; endo formexo form© 1993 John Wiley & Sons, Inc.
Errors associated with nonuniform concentrations upon rate constants using absorption techniques
Authors: Fahr Askar , Laufer Allan H.
Published: January 2005

Kinetic absorption spectroscopy is a commonly used technique in the experimental determination of rate constants. Here we consider the effect of nonuniform reactant concentrations upon the measured results and the errors associated with the final determination of second‐order rate constants in particular. We conclude that the errors associated with nonuniformity of reactant, while significant, are comparable or less than other common systematic or random errors. © 1993 John Wiley & Sons, Inc.
High temperature pyrolysis of 1,5‐cyclooctadiene and 4‐vinylcyclohexene in shock waves
Authors: Hidaka Yoshiaki , Ninomiya Natsuhiko , Oshita Hidekazu , Kawano Hiroyuki , Koike Tohru
Published: January 2005

1,5‐cyclooctadiene or 4‐vinylcyclohexene mixture diluted with argon was heated to temperatures in the range 880–1230 K behind reflected shock waves. Profiles of IR‐laser absorption were measured at 3.39 μm. From these profiles, rate constants k1 and k2 for the decyclization reactions 1,5‐cyclooctadiene → biradical and 4‐vinylcyclohexene → biradical were evaluated as k1 = 5.2 × 1014 exp(−48.3 kcal/RT) s−1 and k2 = 3.5 × 1014 exp(−55.3 kcal/RT) s−1, respectively. © 1993 John Wiley & Sons, Inc.
Kinetics of CN radical reactions with formaldehyde and 1,3,5‐trioxane
Authors: Yu Tao , Yang David L. , Lin M. C.
Published: January 2005

Absolute rate constants were measured for the reaction CN + CH2O over the temperature range 297–673 K and CN + 1,3,5‐trioxane over the range of 297–600 K by the laser photolysis/laser induced fluorescence technique. The rate constants for these reactions can be effectively represented, in units of cm3/s, by: k(CH2O) = 2.82 × 10−19 T2.72 exp(718/T), and k(1,3,5‐trioxane) = 1.39 × 10−23 T4.26 exp(1333/T), respectively. Transition state theory calculations were able to fit the temperature dependence of the CN + CH2O rates relatively well. We attempted to correlate the CN reaction rate with CH2O and other molecules which occur through simple abstraction with the corresponding OH reaction rates, yielding only a qualitative linear correlation for a majority of the processes. The reactions which deviated significantly from linearity include those which contain strong dipoles, highlighting the significant role long‐range attractive forces play in CN and OH reactions. Using a simple electrostatic potential, cross‐sections were determined for reactions with CN. No linear correlation was found between the calculated and experimental cross sections for the majority of the reactions studied. © 1993 John Wiley & Sons, Inc.
Rate constants for the gas‐phase reactions of O3 with a series of cycloalkenes and α,β‐unsaturated ketones at 296 ± 2 K
Authors: Greene Chipper R. , Atkinson Roger
Published: January 2005

The kinetics of the gas‐phase reactions of O3 with a series of alkenes and two α,β‐unsaturated ketones have been investigated at atmospheric pressure (ca. 740 torr) of air and 296 ± 2 K, using a relative rate method in the presence of sufficient cyclohexane to scavenge OH radicals generated in these reactions. Combined with our previous relative rate measurements (Int. J. Chem. Kinet., 24, 803 (1992)), the rate constants obtained relative to k(O3 + propene) = 1.00 were: 3‐penten‐2‐one, 3.62 ± 0.16; 2‐cyclohexen‐1‐one, <0.19; bicyclo[2.2.2]‐2‐octene, 7.44 ± 0.48; 1,3‐cycloheptadiene, 16.1 ± 1.1; cycloheptene, 23.7 ± 1.6; 1,3‐cyclohexadiene, 134 ± 13; bicyclo[2.2.1]‐2‐heptene, 170 ± 16; and bicyclo[2.2.1]‐2,5‐heptadiene, 390 ± 36. The resulting rate constants then lead to a self‐consistent set of room temperature data for the reactions of O3 with these alkenes and α,β‐unsaturated ketones. These rate constants are compared with the literature data, and the effects of ring size discussed. © 1994 John Wiley & Sons, Inc.
Synthesis and pyrolysis of perfluoroazo‐2‐propane
Authors: Scherer K. V. , Batt L. , Stewart P. H.
Published: January 2005

An improved method has been used to synthesize perfluoroazo‐2‐propane. Pyrolysis over the temperature range 450–514 K in a static system has been shown to be a homogeneous, first‐order process. No pressure dependence was observed in the presence of excess inert gas (SF6). The only products were nitrogen and perfluoro‐2,3‐dimethylbutane. The rate constant (k) for the decomposition process is given by:

These results lead to a straightforward mechanism for the decomposition process
equation image
The results are compared with those for other azo compounds. © 1994 John Wiley & Sons, Inc.
Etching of GaAs (100) with gaseous H/CH3 mixtures
Authors: Meharg Paul F. A. , Ogryzlo Elmer A.
Published: January 2005

GaAs (100) wafers were etched in mixtures of hydrogen atoms and methyl radicals. The atoms were formed in a remote hydrogen plasma, and a fraction of these were converted into methyl radicals by introducing methane into the flow system upstream from the semiconductor surface. The flux of hydrogen atoms into the reaction chamber was determined by isothermal calorimetry. The methyl radical flux passing over the substrate was then calculated using previously determined rate parameters for the reaction between atomic hydrogen and methane, and a simple modeling program. The GaAs etch rates were about an order of magnitude faster when methyl radicals were present in the hydrogen atom stream, and were found to follow a first‐order dependence on the partial pressure of methyl radicals. Absolute rate constants were determined and an Arrhenius activation energy of 1.2 kcal mol−1 was calculated. The values of k and Ea are consistent with a diffusion‐controlled process. SEM photographs of the surface revealed small crystallographic features that made the surface appear very rough. XPS analysis indicated that these surfaces were arsenic deficient. A mechanism is proposed for the etching of GaAs by a combination of methyl radicals and hydrogen atoms. © 1994 John Wiley & Sons, Inc.
Two‐color multiphoton decomposition of 1‐bromo 2‐fluoroethane
Authors: McRae G. A. , Ivanco M. , Goodale J. W.
Published: January 2005

Multiphoton decomposition of 1‐bromo 2‐fluoroethane (CH2BrCH2F, BFE) with a two‐color CO2 infrared laser is reported as a function of number of laser pulses. For single color irradiation at a wavelength chosen to excite BFE, the decomposition product, vinyl fluoride, which accumulates during the many‐pulse MPD experiment, is found to deactivate BFE decomposition. When a second laser, tuned to a vinyl fluoride absorption is introduced, coincident with the first, the vinyl fluoride is found to activate further BFE decomposition. These results are accounted for in terms of a pressure‐dependent model. Changes in model parameters, upon addition of the second laser, are shown to be consistent with interpretations in terms of collision‐dependent reaction schemes. © 1994 John Wiley & Sons, Inc.
The rate of methyl radical decomposition at high temperatures and pressures
Authors: Su J. Z. , Teitelbaum H.
Published: January 2005

Rate constants are calculated for CH3 (+ Ar) ⇄ CH2 + H (+ Ar) at the limiting low‐pressure, the limiting high‐pressure, as well as the intermediate fall‐off ranges. The results show that published experimental rate constants for methyl dissociation correspond to the fall‐off region close to the low‐pressure limit. At the low‐pressure limit the activation energy is less than the bond dissociation energy, in agreement with experimental results. Forward and backward rate coefficients at the high‐pressure limit are compared with other theoretical calculations. More theoretical and experimental work is necessary to understand the reverse reaction and its competing reactions, as well as the decomposition channel leading to CH + H2. © 1994 John Wiley & Sons, Inc.
Thermal decomposition of di‐t‐butyl peroxide in the presence of (CH3)2CCH2: Reactions of CH3, (CH3)2ĊCH2CH3, and (CH3)2ĊCH2C(CH3)2CH2CH3 radicals
Authors: Seres Lászloó , Nacsa Ágnes , Arthur Neville L.
Published: January 2005

A study of the reaction initiated by the thermal decomposition of di‐t‐butyl peroxide (DTBP) in the presence of (CH3)2CCH2 (B) at 391–444 K has yielded kinetic data on a number of reactions involving CH3 (M·), (CH3)2CCH2CH3 (MB·) and (CH3)2ĊCH2C(CH3)2CH2CH3 (MBB·) radicals.

The cross‐combination ratio for M· and MB· radicals, rate constants for the addition to B of M· and MB· radicals relative to those for their recombination reactions, and rate constants for the decomposition of DTBP, have been determined. The values are, respectively,

where θ = RT ln 10 and the units are dm3/2 mol−1/2 s−1/2 for k2/k and k9/k, s−1 for k0, and kJ mol−1 for E.

Various disproportionation‐combination ratios involving M·, MB·, and MBB· radicals have been evaluated. The values obtained are: Δ1(M·, MB·) = 0.79 ± 0.35, Δ1(MB·, MB·) = 3.0 ± 1.0, Δ1(MBB·, MB·) = 0.7 ± 0.4, Δ1(M·, MBB·) = 4.1 ± 1.0, Δ1(MB·, MBB·) = 6.2 ± 1.4, and Δ1(MBB·, MBB·) = 3.9 ± 2.3, where Δ1 refers to H‐abstraction from the CH3 group adjacent to the center of the second radical, yielding a 1‐olefin. © 1994 John Wiley & Sons, Inc.
Infrared multiphoton decomposition of highly excited t‐butyl chloride‐d9
Authors: McAlpine Robertd , McRae Glenn A. , Goodale J. W.
Published: January 2005

The infrared multiphoton decomposition (IR MPD) of t‐butyl chloride‐d9 as a function of pressure and fluence is reported. The major decomposition route was molecular elimination of DCl in accord with earlier pyrolysis studies. The effect of added gases (2‐methyl propene‐d8, DCl and 2‐methyl propene‐h8) on the MPD is presented. This study is a further example of the utility of a new method of analysis of MPD experiments. © 1994 John Wiley & Sons, Inc.
Salt effects upon reactions of different charge type reactants: Peroxodisulphate Oxidations of Fe(CN)4(bpy)2−, cis‐Fe(CN)2(bpy)2 and Fe(bpy)32+ and Iron(II) Oxidation by Co(NH3)5Cl2+
Authors: Múñoz Ernestina , Graciani María Del Mar , Jiménez Rafael , Rodríguez Amalia , Moyá María Luisa , Sánchez Francisco
Published: January 2005

Salt effects on the oxidation of the iron(II) complexes Fe(CN)4(bpy)2−, cis‐(CN)2(bpy)2 and Fe(bpy)32+ by S2O82− as well as on the reaction Fe2+ + Co(NH3)5Cl2+ have been studied in concentrated electrolyte solutions at 298.2 K. We have gone from anion–anion to cation–cation reaction with the intermediate cases of anion–neutral and cation–anion reactions. Results show that the main cause of the kinetic salt effects observed is the interaction between supporting electrolytes and the solvent. © 1994 John Wiley & Sons, Inc.
Kinetics of solvolysis of 2‐chloroquinoxaline
Authors: Patel R. D.
Published: January 2005

Pseudo‐first‐order rate constants and activation parameters have been measured for the solvolysis of 2‐chloroquinoxaline in various aquo‐organic mixtures using methanol, ethanol, and isopropanol as the organic solvent. Excellent linear correlations are found between lnk and the mol fraction of cosolvent and ln[H2O]. The medium effect on the rates of solvolysis is assessed by Grunwald–Winstein's mY correlationship. The estimated values of m (0.55–0.72) and the entropy of activation (148–212 J deg−1 mol−1) for the reactions are well in the range for a bimolecular aromatic substitution reactions. © 1994 John Wiley & Sons, Inc.
On the role of transport in the combustion kinetics of a steady‐state premixed laminar CO + H2 + O2 flame
Authors: Mishra Manoj K. , Yetter Richard , Reuven Yakir , Rabitz Herschel , Smooke Mitchell D.
Published: January 2005

The role of mechanistic steps, diffusion, and their interrelation is explored in a steady‐state premixed laminar CO + H2 + O2 flame using a numerical model. Sensitivity coefficients and Green's functions calculated for this system offer systematic characterization of the role of diffusion and exothermicity in carbon monoxide oxidation kinetics. The results reveal that the uncertainties in transport parameters are as important to the model predictions as those in the kinetic steps. The rate controlling steps of the CO + H2 + O2 reaction are found to be different for adiabatic and nonadiabatic premixed flames, and also for systems with and without transport. In particular, the reactions of the hydroperoxyl radical with hydrogen, oxygen, and hydroxyl radicals are found to be important at all temperatures in the fuel lean (40 torr) adiabatic flame studied here. The diffusive mixing of chemical species from the low and the high temperature portions of the flame and the larger heats of reaction associated with the hydroperoxyl radicals are found to be responsible for the increased importance of these reactions. © 1994 John Wiley & Sons, Inc.
Kinetics of the acid and alkaline hydrolysis of Monofluorophosphite
Authors: Dishman Karla , Karnell Leigh Ann , Larson John W.
Published: January 2005

The kinetics of the acid and alkaline hydrolysis of monoflorophosphorous acid has been studied by P‐31 NMR and static pH titration over a wide temperature range. The acid catalyzed hydrolysis has a rate constant at 25°C equal to 0.35 dm3 mol−1 s−1 and an activation energy of 53 kJ while the alkaline hydrolysis has a rate constant of 4.6 dm3 mol−1 s−1 and an activation energy of 42 kJ. When the hydrogen in this compound is replaced by either fluorine or a hydroxyl group, the rates of reaction decrease by two orders of magnitude. © 1994 John Wiley & Sons, Inc.
Gas‐phase thermolysis of allyl propargyl amine, allyl cyanomethyl propargyl amine, allyl propargyl 2‐thiapropyl amine, and allyl methanesulfonyl propargyl amine
Authors: Martin Gonzalo , Ascanio Julian , Rodriguez Jesus
Published: January 2005

The title amines have been pyrolyzed in a stirred‐flow reactor, at temperatures of 360–500°C, pressures of 7–16 torr, and residence times of 0.5–2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7–1.6. The amines with CH2CN and SO2CH3 substituents also formed HCN and SO2. These appear to arise from complex free radical decomposition of the imine product. The first‐order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine:

Allyl cyanomethyl propargyl amine:

Allyl propargyl 2‐thiapropyl amine:

Allyl methanesulfonyl propargyl amine:

Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.
Kinetics and mechanism of the thermal decomposition reaction of acetone cyclic diperoxide in the gas phase
Authors: Cafferata Lázaro F. R. , Lombardo José D.
Published: January 2005

The kinetics of the thermal decomposition reaction of gaseous 3,3,6,6‐tetramethyl‐1,2,4,5‐tetroxane (ACDP) in the presence of n‐octane was studied in the 403.2–523.2 K temperature range. This reaction yields acetone as the organic product. Under optimum conditions, first‐order kinetics were observed, included when the S/V ratio of the Pyrex reaction vessel was increased by a nearly six‐fold factor. In the range 443.2–488.2 K the temperature dependence of the rate constants for the unimolecular reaction in conditioned vessels is given by In k1/(s−1) = (31.8 ± 2.5) − [(39.0 ± 2.5)/RT]. The value of the energy of activation in kcal/mol correspond to one OO bond homolysis of the ACDP molecule in a stepwise biradical initiated decomposition mechanism. At the lower reaction temperatures as well in preliminary experiments participation of a surface catalyzed ACDP decomposition process could be detected. © 1994 John Wiley & Sons, Inc.
Error analysis for complex kinetics systems methyl‐vinyl cross‐radical reactions
Authors: Fahr A. , Braun W.
Published: January 2005

Many rate constants, particularly for radical‐radical reactions, are determined in systems exhibiting complex kinetics. Parameters often comprise several species concentrations, absorption cross sections, and rate constants. They cannot be obtained from an exact analytic expression, and therefore, must be solved iteratively through an efficient numerical differential equation solver. We examine here the reaction kinetics of the CH3 and the C2H3 mixed‐radical system, generated by excimer laser photolysis of methyl vinyl ketone (MVK) at 193.3 nm. As a model, a detailed error analysis for determination of the cross‐radical reaction rate constant, the initial CH3 and C2H3 radical concentrations are performed using a least‐squares modeling program (Acufit). The least‐squares program, an assumed mechanism, a detailed set of signal‐averaged data, are viewed as the measuring “instrument.” The output of the “instrument” consists of a “signal” that is fit to the data using the least‐squares criterion. This gives estimated parameters that are examined with respect to random as well as systematic errors. The biases due to uncertainties of each known parameter and combined uncertainties on the measured parameters are assessed. © 1994 John Wiley & Sons, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Concerted mechanism of the aminolysis of 2,4,6‐trinitrophenyl o‐ethyl dithiocarbonate in aqueous ethanol
Authors: Castro Enrique A. , Cubillos María , Muñoz Gabriel , Santos José G.
Published: January 2005

The reactions of the title substrate with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, 25.0°C, and ionic strength 0.2 M (KCl). The Brönsted‐type plot (log kN vs. pKa of the amine, where kN is the second‐order rate coefficient) obtained is linear with slope β = 0.53, which indicates a concerted mechanism. The predicted Brönsted break for a hypothetical stepwise mechanism is pK = 8.7, which was not observed (pKa range of amines: 6–11). The same reaction in water is stepwise, which shows that the tetrahedral intermediate found in water is much destabilized by the change of solvent from water to aqueous ethanol. © 1994 John Wiley & Sons, Inc.
The heterogeneous propagation of the chains in the reaction of aliphatic aldehydes oxidation
Authors: Bakhchadjyan R. H. , Vardanyan I. A.
Published: January 2005

The low temperature gas‐phase oxidation of CH3CHO and C2H5CHO have been investigated as an example of heterogeneous‐homogeneous reaction. It has been shown that with the increase of S/V (surface/volume) ratio of the reaction vessel the maximum rate of the process increases and the heterogeneous consumption of aldehyde prevails over the homogeneous one. Peroxy radicals have been discovered by EPR method in vessels with different S/V ratios. The concentration of peroxy radicals and the accumulation rate of peracid in the gas phase did not change with the increase of S/V ratio in the same interval. Under the conditions of these experiments excluding the homogeneous propagation of chains the aldehydes oxidized heterogeneously. The peroxy radicals initiate this heterogeneous process which indicate the existence of short chains on the surface. The reaction between the peroxy radicals and aldehyde on the solid surface (SiO2, KCl/SiO2) has been shown by EPR, IR‐spectroscopy, and mass‐spectrometry methods. A conclusion has been drawn that the solid surface takes part in the chain propagation stage of aldehydes oxidation. © 1994 John Wiley & Sons, Inc.
Kinetics of the thermal decomposition of ferrocenyl azide: Character of ferrocenyl nitrene
Authors: Steel C. , Rosenblum M. , Geyh A. S.
Published: January 2005

The Arrhenius parameters for the thermal decomposition of ferrocenyl azide in isooctane are A = (5.1 ± 1.4) × 1012 s−1 and Eact = 113.1 ± 0.9 (kJ mol−1) and the rate is relatively insensitive to solvent (isooctane, benzene, acetonitrile: 1:1.7:2.4). The results indicate a relatively nonpolar transition state which is considerably “tighter” than for a normal bond fission reaction. The Arrhenius parameters are comparable to those for aromatic azides and do not offer any support for anchimeric assistance by the iron atom. A kinetic scheme is presented which accounts for the observed products: Nitrogen, ferrocene, aminoferrocene, azoferrocene, and insoluble material. Rates of hydrogen abstraction by the intermediate ferrocenyl nitrene from cyclohexane, benzene, and acetonitrile are used to show that the nitrene is nucleophilic. © 1994 John Wiley & Sons, Inc.
Liquid‐phase autoxidation of organic compounds at elevated temperatures. Absolute rate constant for intermolecular hydrogen abstraction in hexadecane autoxidation at 120–190°C
Authors: Jensen R. K. , Korcek S. , Zinbo M.
Published: January 2005

The absolute rate constants for the intermolecular hydrogen abstraction reactions of secondary hydrogens by secondary alkylperoxy radicals in hexadecane autoxidation, k3, have been determined in the temperature range of 120–190°C using the stirred flow reactor technique. Absolute rate constants determined in this study for hexadecane are in good agreement with those determined for other hydrocarbons in liquid phase, on a per hydrogen basis, at lower temperatures. Arrhenius parameters for k3/H derived from this study are A = 108.6 M−1 s−1 and Ea = 16.0 kcal/mol. The values of these parameters provide experimental confirmation for previous estimates made from both lower temperature reactions in the liquid phase and higher temperature reactions in the gas phase. © 1994 John Wiley & Sons, Inc.
Flowtube reactor study of the association reactions of CHCl2 and CCl3 with O2 at low pressure
Authors: Nottingham Winston C. , Rudolph R. Neil , Andrews Kevin P. , Moore John H. , Tossell John A.
Published: January 2005

The new flowtube reactor employing dissociative electron attachment to produce radicals and high‐pressure photoionization in the mass spectrometric detection of radicals is described. The system has been applied to a study of the association reactions of CHCl2 and CCl3 with O2 in a great excess of helium at total densities below 1017 cm−3 over the temperature range 286 to 332 K. Both reactions display a strong negative temperature coefficient. The results can be parameterized in the form k0(CHCl2 + O2) = (4.3 ± 0.2) × 10−31(T/300)−6.7±0.7 cm6 s−1, k0(CCl3 + O2) = (2.7 ± 0.2) × 10−31(T/300)−8.7±1.0 cm6 s−1. © 1994 John Wiley & Sons, Inc.
Branching ratio of the C2H2 + O reaction at 290 K from kinetic modelling of relative methylene concentration versus time profiles in C2H2/O/H systems
Authors: Peeters Jozef , Boullart Werner , Langhans Ivan
Published: January 2005

In earlier work on the room temperature oxidation of C2H2 by O atoms, two distinct sources of methylene radicals have been identified: (i) direct, primary production via channel 1b of the C2H2 + O reaction, and (ii) delayed formation via the secondary reaction 3 involving the products HCCO and H of the other primary channel 1a: magnified image Presently, it was confirmed by a detailed sensitivity analysis that the precise shapes of the resulting total methylene concentration‐versus‐time profiles in C2H2/O systems depend strongly on the k1a/k1b branching ratio. Along that line, the important parameter k1a/k1b was determined from relative CH2 concentration‐versus‐time profiles measured in a variety of C2H2/O/H systems using Discharge Flow‐Molecular Beam sampling Mass Spectrometry techniques (DF‐MBMS). The data analysis was carried out by deductive kinetic modelling; the method, as applied to profile shapes, is discussed at length. Via this novel, independent approach, the CH2(3B1) yield of the two‐channel C2H2 + O reaction was determined to be k1b/k1 = 0.17 ± 0.08. The indicated 2σ error includes possible systematic errors due to uncertainties in the rate constants of other reactions that influence the shapes of the CH2 profiles. The present result, which translates to an HCCO yield k1a/k1 = 0.83 ± 0.08, is in excellent agreement with other recent determinations. The above mechanism, with the subsequent reactions that it initiates, also reproduces the measured absolute [C2H2], [O], and [H] profiles with an average accuracy of 5%, thus validating the consistency of the C2H2/O/H reaction model put forward here. © 1994 John Wiley & Sons, Inc.
Micellar catalyzed redox reactions of bilirubin in CTAB medium. A pulse radiolysis study
Authors: Adhikari Soumya K. , Guha Shambhu N. , Gopinathan C.
Published: January 2005

The reaction of CO with bilirubin which is not detectable in homogeneous aqueous medium proceeds almost with diffusion controlled rate in CTAB micellar system. This could be explained on the basis of catalysis caused by the possible electrostatic surface potential of cationic CTAB Micelles. The rate constant for the oxidation of bilirubin by haloperoxyl radicals have been shown to increase with increasing solvent polarity. Although the polarity effect was small, it followed a trend in the expected direction. Micellar effect was not observed in the oxidation reactions when alcohol was present in high concentration. But a small increase in the rate constant was observed when alcohol concentration was lower. © 1994 John Wiley & Sons, Inc.
Iron(II)‐bis (salicyladimine) Schiff‐base complexes catalyzed decomposition of hydrogen peroxide
Authors: Salem I. A. , El‐Sheikh M. Y. , Zaki A. B. , Nickel Ulrich
Published: January 2005

The tetradentate Schiff‐base ligands, N,N′‐bis(salicylidene)‐ethylenediamine (Salen), N,N′‐bis(salicylidene) butylenediamine (Salbut), and N,N′‐bis(salicylidene)‐o–phenylenediamine, (sal‐o‐phen) are very strongly sorbed by cation exchange resin (Dowex‐50W) with Fe2+ ions as a counter ion, forming stable complexes. The kinetics of the catalytic decomposition of H2O2 using these complexes was studied in ethanolic medium. The reaction was first‐order with salen and sal‐o‐phen and second‐order with salbut with respect to [H2O2]. The rate of the H2O2 decomposition increased either from salen to salbut or from salen to sal‐o‐phen. Also, the k (per g dry resin) values decreased with increasing both the particle size and the degree of resin cross‐linkage. The active species formed at the beginning of the reaction, had an inhibiting effect on the reaction rate. The corresponding activation parameters were calculated from a least‐squares fit of the temperature dependence of the rate constant. A reaction mechanism is proposed. © 1994 John Wiley & Sons, Inc.
Kinetics and thermochemistry of the reaction of acetylene and nitric oxide
Authors: Benson Sidney W.
Published: January 2005

The shock tube data of Ogura [5] on the pyrolysis of C2H2/NO mixtures (1100–1500 K) is shown to be consistent with a simple mechanism whereby radicals are both initiated and terminated by NO (Scheme I). The scheme accounts for the rate of formation of the main product, vinylacetylene (VA), the lesser products CO and HCN and a very minor product, propionitrile. It is also shown to be consistent with other studies below 900 K and observation at 300 K on the reactions of vinyl radicals with NO. The substantial inhibition of vinyl acetylene formation by 5% NO makes untenable any substantial role of vinylidene in the C2H2 pyrolysis above 1000°K.

The reaction of NO with acetylene is an efficient source of HCN. It appears to be a general reaction of NO with substituted acetylenes and below 900 K a mechanism is presented to account for the production of acrylonitrile (AN) from the reaction of NO with VA.

Thermochemical data are estimated on ΔfH°298 and S°298 for some alkyl‐NO, vinyl NO, and acetylene NO compounds and radicals and some new and some revised group values are estimated for estimating ΔfH°298 of derivatives of hydroxyl amines, imines, and isoxazolines. © 1994 John Wiley & Sons, Inc.
Base catalyzed hydrolysis of Aerosol OT in Aqueous and Aquo‐Dioxane media
Authors: Mukherjee K. , Moulik S. P. , Mukherjee D. C.
Published: January 2005

The OH− ion catalyzed hydrolysis of AOT and sodium mono‐methyl succinate in aqueous and aquo‐dioxane media has been studied. The second‐order rate constant for the former has been found to be nearly ten times slower than that of the latter. At AOT concentrations above CMC, the rate constants become insensitive to the concentration in the studied range of temperature, 25°C–40°C. The activation parameters for the kinetic process have been found to be reasonable, negative entropy of activation has supported a stable transition state complex. A good enthalpy‐entropy compensation of the kinetic process has been found both for AOT and sodium monomethyl succinate in aqueous and aquo‐dioxane media supporting similar nature of the transition state complexes in the hydrolytic reactions. The enthalpies of hydrolysis of AOT and the half ester of succinic acid in aqueous and aquo‐dioxane media have been also reported. © 1994 John Wiley & Sons, Inc.
Catalytic activity of Manganese(II)‐Gluconate complex in reactions of Hydrogen Peroxide
Authors: Rocha Cleonice , Da Costa Ferreira Ana Maria
Published: January 2005

Kinetic studies of the hydrogen peroxide decomposition catalyzed by the dimeric Mn(II)‐gluconate complex, in alkaline medium, showed evidence for the oxidative cleavage of the ligand, leading to the formation of formaldehyde as one of the products. In the presence of a large excess of other hydroxylated substrates, such as methanol or ethylene glycol, a significant increase in the yield of formaldehyde was observed, corroborating the observed peroxidase activity in this system, in addition to the catalase activity. Oxygen free radicals were detected as intermediates of reaction, by ESR spectroscopy using the spintrapping method, only under aerobic conditions. Therefore, a nonradical mechanism was proposed for the reaction, based on the formation of a peroxo‐Mn(II) complex, and its further reduction to the previous Mn(II) species. © 1994 John Wiley & Sons, Inc.
The nitrosation of Amino Acids
Authors: Gil Rafael , Casado Julio , Izquierdo Carmen
Published: January 2005

With a view to clarifying analogies and differences between the mechanisms involved in the nitrosation of amino acids and secondary amines, we studied the kinetics of the nitrosation of five imino acids (azetidine‐2‐carboxylic acid, pyrrolidine‐2‐carboxylic acid, piperidine‐2‐carboxylic acid, piperidine‐3‐carboxylic acid, and piperidine‐4‐carboxylic acid) and of the ethyl esters of three of them. Reaction kinetics were determined by the initial rate method, by spectrophotometric monitoring of the concentration of nitroso amino acid formed. The presence of the COO− group in the amino acids opens a new mechanistic route for the nitrosation of the secondary amino group: a nitrosyl carboxylate formed initially acts as an internal nitrosating agent, resulting in intramolecular migration of N  O from the carboxylate group to the secondary amino group. The observed order of the α−, β−, and γ‐amino acids as regards the ease of N‐nitrosation by this route is explained in terms of the relative energies of (a) the equatorial and axial orientations of the CringCcarboxyl bond, and (b) the chair and boat forms of the piperidine ring. © 1994 John Wiley & Sons, Inc.
Kinetics of the 1,5‐dipolar cyclization of 2‐Vinylpyridinium ylides to Indolizines. Determination of rate parameters by laser flash photolysis
Authors: Liu Michael T. H. , Romashin Yuri N. , Bonneau Roland
Published: January 2005

Nanosecond laser flash photolysis (λ = 355 nm) of an aqueous solution of 3‐chloro‐3‐p‐chlorophenyldiazirine in isooctane produces a transient absorption at 310 nm due to the formation of the carbene. In the presence of 2‐vinylpyridine, a second transient with a broad absorption band peaking at 520 nm grows in. This absorption is attributed to 2‐vinylpyridinium ylide. The ylide decays with a lifetime equal to 33 µs at 25°C independent of the concentration of 2‐vinylpyridine. As the ylide decays, there is a concomitant growth of an absorption at 330 nm, attributed to the formation of inodolizine. The activation parameters for the 1,5‐dipolar cyclization of the ylide to indolizine were determined; Ea = 12.1 kcal mol−1 and log A = 13.4. © 1994 John Wiley & Sons, Inc.
Kinetics and mechanism of electron transfer reactions in aqueous solutions: Silver(I) catalyzed oxidation of aspartic acid by cerium (IV) in acid perchlorate medium
Authors: Sharma Indu , Devra Vijai , Gupta Divya , Gangwal C. M. , Sharma P. D.
Published: January 2005

Silver(I) catalyzed oxidation of aspartic acid by cerium(IV) was studied in acid perchlorate medium. The stoichiometry of the reaction is represented by the eq. (i)equation image

Dimeric cerium(IV) species has been indicated and employed in calculations of monomeric cerium(IV) species concentrations. The reaction is second‐order and uncatalyzed reaction also simultaneously occurs along with the silver(I) catalyzed reaction conforming to the rate law (ii)equation imagewherekis an observed second‐order rate constant. A probable reaction mechanism is suggested. © 1995 John Wiley & Sons, Inc.