Dependence Of K1 Research Articles

Cross-Validation of the Remarkably High Surface Oxygen Exchange Kinetics of PrBa0.5Sr0.5Co1.5Fe0.5O5+δ: A Combined Thin-Film Mass Relaxation and Bulk Electrical Conductivity Relaxation Study.

In this work, we measure the oxygen kinetic properties of double perovskite PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), a material widely used as the air electrode in solid oxide electrochemical cells, by mass relaxation (MR) and electrical conductivity relaxation (ECR) experiments. MR studies are carried out using thin films deposited on a gallium phosphate piezocrystal microbalance, and ECR studies are performed using a bulk bar sample with 97% theoretical density. Measurements are performed at 600 °C over the temperature oxygen partial pressure range from 10-4 to 0.21 atm. Despite the differences in experimental formats and surface microstructural features, the ks values extracted from the two methods are found to be in good agreement with one another. The rate constant is found to increase with oxygen partial pressure with a power law dependence, rising from 1.0 × 10-6 cm/s at 3.2 × 10-4 atm to 1.2 × 10-4 cm/s at 0.24 atm, as averaged over the oxidation and reduction directions. The rates in the oxidation direction are observed to be slightly higher than those in the reduction direction for a given pair of pO2 values, suggesting that the final pO2 value controls the overall relaxation behavior. The power law exponent describing the dependence of ks on pO2 is found to be 0.74 ± 0.01. The ECR study of the bulk sample reveals that even with a diffusion length of 1.8 mm, the relaxation process is largely free of diffusion limitations, indicating that PBSCF has the high bulk transport properties required for a double-phase boundary oxidation/reduction pathway.

Kinetics and Activation Parameters for Dyeing of Cellulose-Polyethylene Terephthalate Blends with a Reactive Dye Using a Convenient, Robust Dye Flow‑System

Dyeing of cellulose with reactive dyes (RDs) is an important commercial process because the fibers/fabrics have vivid colors with excellent fastness, since the RD is covalently bonded to cellulose. The subject of the present study is dying of cotton-polyethylene terephthalate (PET) blends using a flow system where the RD absorbance is contentiously monitored by UV-Vis spectroscopy. This allows the collection of extensive data points (≥ 300) to calculate the rate constants, hence the corresponding activation parameters. At a fixed pH = 11.2, a pseudo second-order rate law fits the absorbance vs. time data satisfactorily. At a constant temperature, the order of the dyeing rate constant (k2) is higher for the blend containing 88.9% cotton. The dyeing activation energy, on the other hand, is higher for the blend containing 50% cotton. These results were attributed to the adverse effects of (hydrophobic) PET on the diffusion of RD into the blend. We calculated an equation that shows the dependence of k2 on the temperature and cotton wt.% of the blend.

Effects of water stress on evapotranspiration of soybean

Based on the results of observations, it was specified that when decreasing soil moisture there is a disproportionate decrease in the average daily evapotranspiration (ET). Thus, in the range of soil moisture of 94-80% minimum moisture-holding capacity (MMHC) ET was 9,76 mm a day, and in the range of 70-62% MMHC - its value decreased by 3 times. When the soil moisture reached 58,5% MMHC, the value of ET did not exceed 0,5 mm a day, which is 20 times less than the initial one. It was determined that the decrease in soil moisture by 10% in the range of 90 - 70% MMHC occurs during 3 days, and from 70 to 60% MMHC and from 60 to 58% MMHC - during 8 days. When soil moisture is 70% MMHC and below, the actual evapotranspiration is less than ETo that proves the effect of water stress on soybeans ET. When calculating water stress coefficient (Ks), a mathematical model based on the dependence of Ks on soil moisture as a percentage of MMHC was obtained. The average absolute percentage error (MAPE) is 8,6%, which corresponds to the high accuracy of the obtained dependence. In the range of soil moisture from 58 to 80% MMHC, the water stress coefficient is calculated by the formula Ks =-0.0011·FC²+0.1925·FC-7,4541. When having soil moisture as 80% MMHC and above, Ks = 1. A comprehensive comparative assessment of existing methods for calculating waster stress coefficient Ks was taken and it was found out that the actual values of Ks when having soil moisture as 80-70 and 60-65% MMHC by 8-14 % and 72-32 %, respectively, less than Ks FAO 56, and by 35-40 % larger than those determined by Saxton method. It was proved the need of taking into account the reduction in evapotranspiration when calculating water balance under water stress of plants. The calculation of evapotranspiration (ETs) by the Penman-Monteith method, without taking into account the water stress coefficient, showed that the value of the actual and calculated water balance coincides only when soil moisture does not exceed 62% MMHC. With a further decrease in soil moisture, the estimated soil moisture was 20% less than the actual, which led to the errors in determining soil moisture after irrigation, because its actual value was almost 100% MMHC, and the estimated one was only 60% MMHC. It was proved that the determination of water balance by calculation methods without taking into account the water stress coefficient leads to significant errors.

Electrochemical Behavior of Titanium Complexes in the KCl-KF Melt with Additions of Alkaline Earth Metal Cations

The goal of the present investigation was to study of Mg2+, Ca2+, Sr2+ and Ва2+ strongly polarizing cations influence on the standard rate constants of charge transfer (ks ) for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt.Electrochemical studies were carried out in the temperature range of 1073-1173 K by cyclic voltammetry. Voltammetric curves were recorded at a glassy carbon electrode vs. a glassy carbon quasi-reference electrode. The sweep rate (v) varied from 0.1 up to 2.0 V s-1. The electrochemical redox process Ti(IV)+e-↔Ti(III) was classified as quasi-reversible at a sweep rate 1.0 V s-1≤ν≤2.0 V s-1.The values of k s were calculated by using the Nicholson’s method [1]. It was shown that k s increase with increasing the temperature. It is due to the number of particles capable of overcoming the potential barrier increases [2].Addition of alkaline earth metal cations resulted in increasing of ks up to the certain ratio of Me2+/Ti(IV) for all alkaline earth metal cations. It was determined the linear dependence of ks on ionic potential of alkaline earth metal cations.The activation energies of the charge transfer in the case of strongly polarizing cations addition were calculated. It was shown that values of the activation energy for molten systems with strongly polarizing cations are considerably less than activation energy of the initial melt and decrease with increasing of ionic potential.It was determined that the k s for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt (for all systems) are less than k s in the NaCl-KCl based melt [3].

Electrochemical Behavior of Titanium Complexes in the KCl-KF Melt with Additions of Alkaline Earth Metal Cations

The charge transfer kinetics for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt was studied. The standard rate constants of charge transfer (ks ) for the redox couple Ti(IV)/Ti(III) in the KCl-KF(10 wt.%)-K2TiF6 melt and the activation energy of charge transfer were calculated. Influence of strongly polarizing cations (Mg2+, Ca2+, Sr2+, and Ва2+) on the charge transfer kinetics was studied. It was determined the linear dependence of ks on the ionic potential of alkaline earth metal cations. The activation energies of charge transfer in case of strongly polarizing cations addition were found.

Influence of the Alkaline Earth Metal Cations on the Standard Rate Constants of Charge Transfer for the Redox Couple Ti(IV)/Ti(III) in Chloride-Fluoride Melts

The aim of the present investigation was study of charge transfer kinetics for the redox couple Ti(IV)/Ti(III) in the (NaCl-KCl)equimol.-NaF(10 wt.%)-K2TiF6 melt and the estimation of the alkali earth metal cations influence on the standard rate constants of charge transfer (ks ) for this redox couple. Method of cyclic voltammetry was employed for the determination of the standard rate constants of charge transfer. The electrochemical redox process: Ti(IV) + e-↔ Ti(III) (1) was classified as quasi-reversible in the range of scan rate 0.75 V s-1≤ν≤2.0 V s-1. The standard rate constants of charge transfer for the reaction (1) were calculated based on the Nicholson’s equation. It was shown, that k s increase with increasing temperature and the temperature dependence of k swas described by the following empirical equation: log k s=(1.505±0,32)–(3364±675)/Т (2) The activation energy of charge transfer calculated from (2) was found equal to (64.41±13) kJ mol-1. Influence of strongly polarizing cations of Mg2+, Ca2+, Sr2+ and Ba2+on the standard rate constants of charge transfer for the redox couple Ti(IV)/Ti(III) was studied. It was determined that addition of alkali earth metal cations resulted in increasing of ks up to the certain mole ratio of Me2+/Ti(IV), which was inversely proportional to ionic potential of cations. Further addition brought some decreasing of the standard rate constants. Increase of ks is connected with substitution of Na+ and K+ cations by strongly polarizing cations in the second coordination sphere of titanium complexes that led to increasing of the bond distance between Ti and F- ligands and decreasing of titanium fluoride complexes strength. Decrease of ks at the definite ratio of components can be explained by increasing of the viscosity melts, which brings to decreasing of the diffusion coefficients. It was established the linear dependence of ks on ionic potential of alkali earth metal cations and the maximum value was obtained for complexes with outer sphere cations of magnesium. The temperature dependences for the maximum values of ks in the melts containing strongly polarizing cations were fitted by empirical equations and the activation energies of charge transfer were calculated. Values of activation energy for systems with strongly polarizing cations are considerably less than activation energy for initial system. Acknowledgments The work was financially supported by Russian Foundation for Basic Research (15-03-02290_a).

Influence of the Alkaline Earth Metal Cations on the Standard Rate Constants of Charge Transfer for the Redox Couple Ti(IV)/Ti(III) in Chloride-Fluoride Melts

The standard rate constants of charge transfer (ks ) for the redox couple Ti(IV)/Ti(III) in the (NaCl-KCl)equimol.-NaF(10 wt.%)-K2TiF6 melt were determined. It was shown, that k s increase with temperature increasing. Influence of strongly polarizing cations on the charge transfer kinetics was studied. It was determined the linear dependence of ks on ionic potential of alkaline earth metal cations and the activation energies of charge transfer were calculated.

Kinetics of cisplatin binding to short r(GG) containing miRNA mimics - influence of Na(+)versus K(+), temperature and hydrophobicity on reactivity.

Nucleic acids are well recognized targets for platinum-based anticancer drugs, with RNA and DNA being kinetically comparable. In the case of RNA, previous studies have shown that the reaction between small duplex RNAs (dsRNAs) and monoaquated cisplatin (cis-Pt(NH3)2Cl(OH2)(+), ) can be followed by the metal induced hyperchromicity occurring directly after addition of to e.g. microRNA mimics. In the present study, we have used this approach to compare thermal stability and reactivity between intracellularly- and extracellularly relevant salt concentration (CNa(+) and CK(+)ca. 0.1 M), and also as a function of increased hydrophobicity (10% v/v EtOH). In addition, reactivity was studied as a function of temperature in the interval ca. 5-20 °C below the respective dsRNA melting temperatures (Tms). Four different 13- to 20-mer dsRNAs with two different central sequence motifs were used as targets containing either a central r(GG)·r(CC)- or r(GG)·r(UAU)-sequence. The reactions exhibited half-lives in the minute- to hour range at 38 °C in the presence of excess in the μM range. Further, a linear dependence was found between C and the observed pseudo-first-order rate constants. The resulting apparent second-order rate constants were significantly larger for the lower melting r(GG)·r(UAU)-containing sequences compared with that of the fully complementary ones; the higher and lower reactivities represented by RNA-1-3 and RNA-1-1 with k2,appca. 30 and 8 M(-1) s(-1) respectively at CNa(+) = 122 mM. For all RNAs a common small, but significant, trend was observed with increased reactivity in the presence of K(+) compared with Na(+), and decreased reactivity in the presence of EtOH. Finally, the temperature dependence of k2,app was evaluated using the Eyring equation. The retrieved activation parameters reveal positive values for both ΔH(≠) and ΔS(≠) for all dsRNAs, in the range ca. 23-34 kcal mol(-1) and 22-57 cal K(-1) mol(-1) respectively. These values indicate solvational effects to be important for the rate determining step of the reaction, and thus in support of a structural change of the dsRNA to take place in parallel with the adduct formation step.

Electrochemical and quantum-chemical studies of chromium(III,II) fluoride complexes in alkali chloride melts

The standard rate constants (ks) of charge transfer on a glass carbon electrode were determined for the Cr(III)/Cr(II) redox pair in the NaCl-KCl-K3CrF6, KCl-K3CrF6, and CsCl-K3CrF6 systems at 973–1173 K by cyclic voltammetry. The ks constant was found to increase at elevated temperatures and the following nonmonotonic dependence of ks on the nature of the outer-spheric cation was found: ks (CsCl) > ks (NaCl-KCl) > ks (KCl). On the basis of quantum-chemical data for the M3CrF6 + 18MCl (M = Na, K) model systems, it was shown that the complex chromium particles with four or five outer-spheric sodium or potassium cations had maximum thermodynamic stability. Quantum-chemical calculations were performed to interpret the experimental data on the effect of the second coordination sphere of the complexes on the standard charge transfer rate constants.

Comparison between diffusional and first-order kinetic model, and modeling the adsorption kinetics of pyridine onto granular activated carbon

In this work, a surface diffusion model (SDM) obtained in a previous work was verified in a wide range of experimental conditions to predict the adsorption kinetics of pyridine on activated carbon. Moreover, the predictions of SDM model were compared with that obtained by using the first-order kinetic model. The results showed that the first-order model adjusted satisfactorily the experimental data. The effect of the stirring speed, mass of pyridine adsorbed, (qe), and temperature on the rate constant of the first-order model, (k1), was analyzed and equations were proposed to correlate k1 as functions of qe and temperature. Nevertheless, the dependence of k1 regarding the temperature, stirring speed, and qe cannot be accurately correlated, indicating that the overall adsorption rate of pyridine on activated carbon is controlled by the intraparticle diffusion. Moreover, it was shown that the rate of adsorption on active site is not controlling the overall adsorption rate. On the other hand, the SDM model provided a much better prediction than the first-order kinetic model. The surface diffusion coefficient can be readily estimated from a correlation recommended in this work, whereas the value of k1 could not be predicted for some of the experimental conditions studied in this work.

Concentration dependence of the macroscopic magnetic anisotropy and of the ferrimagnetic line width in the gallium substituted europium iron garnet

Available experimental results on the dependence on concentration of the ferrimagnetic resonance of gallium substituted europium iron garnet, have been used to study the dependence on concentration of the macroscopic anisotropy constant K1 and the ferrimagnetic line width ΔH. Instead of employing a strict molecular field theory, the probabilities of finding different numbers of Fe ions that are first and third nearest neighbors to each Eu have been used to derive ΔH and K1. This method is an extension of the statistical treatment introduced by Nowik and Ofer to study the Mossbauer spectra of the same substituted garnets. The statistical theory gives a better description of the dependence of K1 on concentration than does a strict molecular field theory. Although the results obtained seem to indicate that the spin-lattice relaxation of Eu in EuIG is independent of the exchange field HH that measures the Fe–Eu interaction, these results do not seem conclusive enough to reject a relaxation rate proportional to H2ex.

Effect of the nature of inert solvent on the decay kinetics of the carbocation generated in the photolysis of 1,2-dihydroquinolines in methanol

The dependence of the quantum yield and the decay rate constant for the carbocation generated in the photolysis of 6-ethoxy-1,2,2,4-tetramethyl-1,2-dihydroquinoline (6-EtO-DHQ) in methanol on the solvent composition was studied in the mixtures of methanol with isopropanol, acetonitrile, and pentane by pulse photolysis. The addition of these solvents decreases the yield of the carbocation and differently affects the kinetic parameters of its decay. The carbocation decay in the mixtures MeOH-i-PrOH and MeOH-C5H12 is described by the pseudo-first order equation (k 1), with the dependence of k 1 having a maximum at 50 vol % of MeOH in the MeOH-i-PrOH mixtures, and k 1 increasing with a decrease in the MeOH concentration in the MeOH-C5H12 mixtures. In the MeOH-MeCN mixtures, the value of k 1 decreases with a decrease in the MeOH concentration, and, at the concentration of MeOH lower than 50 vol %, the contribution of the second-order reaction (k 2) is observed. The activation energies and preexponential factors were determined in the MeOH-C5H12 mixtures of different compositions, and it was shown that E act practically did not depend on the solvent composition and were close to E act for other carbocations obtained in MeOH. The increase in k 1 with a decrease in the MeOH concentration is caused by an increase in the preexponential factor. The results were discussed on the basis of the reaction mechanism involving the competing reactions of the carbocation combination with two nucleophilic particles, the MeOH molecule and the MeO− anion. The composition of the mixture and the nature of the inert solvent affect strongly the course of these reactions.

Kinetic Study on the Free Radical-Scavenging and Vitamin E-Regenerating Actions of Caffeic Acid and Its Related Compounds

Abstract A kinetic study involving 4-hydroxycinnamic acid derivatives (HCAs) was performed in order to clarify the mechanism for free radical-scavenging and vitamin E-regenerating. The second-order rate constants of the radical-scavenging reaction (ks) observed for caffeic acid derivatives are larger than those for ferulic acid derivatives. The result may be explained by i) the lower oxidation potential coming from the existence of the more electron-donating hydroxy group comparing with methoxy group, and ii) the stabilization effect of the corresponding radicals produced in the radical-scavenging reaction through intramolecular hydrogen bonding. The radical-scavenging activity of HCAs in ethanol mainly occurs via the hydrogen atom transfer from the phenolic OH-protons. The pH dependence of ks for ferulic acid in the aqueous Triton X-100 micelle solutions suggests the importance of the phenolic OH proton on the radical-scavenging reaction. On the other hand, the pH dependence of ks for caffeic acid and chlorogenic acid suggests the occurence of intramolecular hydrogen bonding and an electron-transfer process in the radical-scavenging reaction.

Flows of inelastic non-Newtonian fluids through arrays of aligned cylinders. Part 2. Inertial effects for square arrays

Numerical simulations are presented for flows of inelastic non-Newtonian fluids through periodic arrays of aligned cylinders. The truncated power-law fluid model is used for the relationship between the viscous stress and the rate-of-strain tensor. Results for the drag coefficient for creeping flows of such fluids have been presented in a companion paper [1]. In this second part the effects of finite fluid inertia are investigated for flows through square arrays. It is shown that the Reynolds-number dependence of the drag coefficient of a cylinder in the array is of the form C d≡ F/(ηU) = k 0 + k 2 Re2+ .. for small values of the Reynolds number Re ≡ ρaU/η, where F is the drag force, U is the averaged velocity in the array, η = K (U/a)n-1 is a viscosity scale with K and n the power-law coefficient and index and a the cylinder radius, and k 0 is the drag coefficient for creeping flows. The proportionality constant k 2 depends on the way the drag coefficient and the Reynolds number are defined. It is shown that the observed strong dependence of k 2 on n can almost be eliminated by using length scales different from a in the viscosity scales η used in the definition of Re and in the definition of the drag coefficient. Numerical simulation results are also presented for the velocity variance components. Results for flows at moderate Reynolds number, of order 100, are also presented; these are qualitatively similar to those for Newtonian fluids. The value of the Reynolds number beyond which the flow becomes unsteady was related to the Newtonian fluid case by rescaling. These results for moderate-Reynolds-number flow are compared against previously published experimental data.

Influence of interfaces on the rates of crosslinking in poly(dimethyl siloxane) coatings

AbstractWe have determined with infrared spectroscopic ellipsometry how the nature of the interface between a thin poly(dimethyl siloxane) (PDMS) coating and its substrate affects the rate of PDMS crosslinking reactions. Reactions between vinyl (CHCH2) end groups on PDMS and silyl (SiH) groups in a crosslinker (hydrosilylation) and between SiH groups and silanol (SiOH) groups, during the so‐called postcure crosslinking stage, have been probed in situ. The overall consumption of SiH follows first‐order reaction kinetics. The first‐order reaction coefficient (k1) for the hydrosilylation crosslinking reaction is the same for coatings on three different substrates: native oxide on silicon (SiO2/Si), polystyrene (PS), and poly(ethylene terephthalate). For the slower postcure reactions, however, the rate of SiH consumption depends on the substrate. In 2.5‐μm PDMS coatings on PS, k1 is about seven times greater than k1 in the same coating on SiO2/Si. In PDMS coatings on a PDMS substrate, when the effect of the interface is thus minimal, k1 is 16 times higher than on SiO2/Si. The dependence of k1 on the type of interface is probably the result of the interfacial segregation and complexation of the Pt catalyst for the postcure reactions. We propose that polar surfaces more strongly attract Pt and form complexes that inhibit the postcure reactions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1421–1431, 2004

Magnetic anisotropy and magnetostriction in a Lu2Fe17 intermetallic single crystal

The magnetic anisotropy and magnetostriction of a Lu2Fe17 single crystal are investigated. The temperature dependence of the magnetic anisotropy constant K 1 is measured in the range 4.2–300 K. The results obtained are compared with the data calculated using the Callen theoretical formula. It is found that the temperature dependence of K 1 for the Lu2Fe17 single crystal deviates from the temperature curve predicted by the localized single-ion model. The inference is drawn that a certain contribution to the magnetic anisotropy of the Lu2Fe17 compound is made by the magnetic anisotropy of band electrons. The longitudinal, transverse, and volume magnetostrictions of the Lu2Fe17 single crystal are studied, and the magnetostriction constants are calculated. It is demonstrated that the exchange integral of Lu2Fe17, as for the Y2Fe17 compound, substantially depends on the atomic volume. This dependence is responsible for the considerable difference between the Curie temperatures of the Lu2Fe17 and Y2Fe17 compounds. It is revealed that the magnetostriction of the Lu2Fe17 single crystal in the temperature range of the magnetic phase transition is determined by the two-ion exchange and single-ion contributions.

Temperature Dependence of Rate Coefficients of Reactions of NO2 with CH3S and C2H5S

Rate coefficients of reactions (1) CH3S + NO2 and (2) C2H5S + NO2 were determined using laser photolysis and laser-induced fluorescence. CH3S and C2H5S radicals were generated on photolysis of CH3SSCH3 and C2H5SSC2H5, respectively, with a KrF excimer laser at 248 nm. Their concentrations were monitored via fluorescence excited by emission from a dye laser at 371.4 nm (for CH3S) or 410.3 nm (for C2H5S) pumped with a pulsed XeCl excimer laser at 308 nm. Our measurements show that k1 (297 K) = (1.01 ± 0.15) × 10-10 cm3 molecule-1 s-1 is similar to a value reported by Balla et al. and approximately 50% greater than other previously reported values; listed errors represent 95% confidence limits. Reaction 1 has a negative activation energy: k1 = (4.3 ± 1.3) × 10-11 exp[(240 ± 100)/T] cm3 molecule-1 s-1 for T = 222−420 K. Reaction 2 has a rate coefficient similar to reaction 1 at room temperature: k2 (296 K) = (1.05 ± 0.16) × 10-10 cm3 molecule-1 s-1 but has a small positive activation energy with k2 = (2.4 ± 0.7) × 10-10 exp[−(210 ± 80)/T] cm3 molecule-1 s-1 for T = 223−402 K. The temperature dependence of k2 is determined for the first time. Reactions of NO2 with HS, CH3S, and C2H5S are compared.

酸性染料によるナイロン染色布の摩擦堅牢度

Several acid dyes whose molecular sizes were far different were used in this work. They were dyed with nylon fabrics and the characteristics of their rubbing-fastness were investigated. The amount of removed dyes were different from dye to dye and it had nothing to do with molecular size of dye. From kinetic analysis, the removal process of acid dyes could be treated as a reversible reaction of first order. The rate constant of transfer of acid dyes from dyed nylon fabrics to white cloth (k1) and the rate constant of reverse process (k-1) mostly increased with molecular weight of dyes but the equilibrium constant (K) did not depend on it. So far with cotton fabrics, the constants k1 and K generally depended on load weight on white cloth but k-1 did little, while with nylon fabrics dyed with acid dyes all those constants did. The dependence of k1 on load weight was the biggest, k-1 was the second and K was the third.

Kinetic and Mechanistic Studies of the Reactions of CF3O Radicals with NO and NO2

AbstractThe reactions of CF3O radicals with (1) NO and (2) NO2 were studied using two different experimental techniques. A laser photolysis/LIF detection method was applied for measuring the rate constants as a function of temperature (T = 222–302 K) and total pressure (ptot = 7–107 mbar). Whereas the reaction with (1) NO was found to be independent of temperature and pressure with k1 = (4.5±1.2)×10−11 cm3 s−1, the reaction with (2) NO2 was found to be dependent on both of these variables. The temperature dependence of k2 in the high pressure limit can be given by the expression k2,∝ (T) = (8±5)×10−13 exp ((863±194) K/T) cm3 s−1. The product distributions of the two reactions were determined in separate experiments using steady‐state photolysis combined with FTIR spectroscopy. For reaction (1) only CF2O was found as a reaction product with a yield of 0.93±0.10, independent of temperature. For reaction (2) several products (CF3ONO2, CF2O, FNO2) were identified, the overall yield, however, is dominated (≥90%) by the recombination product CF3ONO2. A theoretical analysis of the detailed mechanisms of both reactions was made by performing ab initio energy and geometry predictions in combination with RRKM calculations. Both reactions were found to proceed via an initial addition mechanism involving the CF3ONOx (x = 1, 2) intermediate and a four‐center transition state. A direct abstraction of an F atom by NO or NO2 can be excluded.

Chemiluminescence in the reaction of the RuII trisbipyridyl complex with dimethyldioxirane

The reaction of dimethyldioxirane (1) with the RuII trisbipyridyl complex accompanied by chemiluminescence (CL) was studied. It is established that the intensity of CL and the rate of its decay increase proportionally with the concentration of RuII. The bimolecular rate constant (k2) of the reaction of1 with RuII was determined. The activation parameters (Ea and logA) for this reaction were calculated from the temperature dependence ofk2. The excitation yield of RuII* (ηRu*) was estimated. The quenching of RuII* by dioxirane was studied, and the bimolecular quenching constant and the coefficient of excitation regeneration were determined. It was suggested that the catalysis of the decomposition of1 and the excitation of RuII occurvia a mechanism of chemically initiated electron exchange.