Gregory Poskrebyshev - Academia.edu (original) (raw)

Papers by Gregory Poskrebyshev

Journal of molecular modeling, Mar 16, 2024

Authorea (Authorea), Dec 21, 2021

The empirical linear scaling dependencies between the literature (?rHo(Xn,TAB)) and the calculate... more The empirical linear scaling dependencies between the literature (?rHo(Xn,TAB)) and the calculated (?rHo((Xn)i,CALC)) values of atomization of 31 reference aromatic and related compounds (T=298.15K), as well as their standard errors ((SE4)i?(?4)i, Stand.Dev.), are determined for the different quantum mechanical (QMi) approaches. These dependencies are compared and used for the determination of the values of ?rHo((Xn)i,CORRE)±3(SE4)i of atomization reactions of considered not reference aromatic compounds, as well as for the determination of their values of ?fHo((Xn)i,CORRE)+-3(SE4)i. The values of ?fHo((Xn)i,CORRE)MEAN+-3SEYE ([?]99.4% confidence interval), determined using the intersections of the 3(SE4)i intervals, are consistent with all QMi approaches and their literature values. The M06-2X/6-311++G(d,p), M08HX/6-311++G(d,p) and wB97XD/6-311++G(d,p) approaches are recommended for the achievement of accuracy (SEYE)[?]3.8 kJ/mol of the calculated values of ?fHo((Xn)i,CORRE)MEAN. The effects of the number of O-H groups, size and multiplicity of compounds on values of error, also studied in this work, demonstrate the limitations of using of several scaled dependencies.

Journal of Physical Chemistry A, Oct 26, 2002

... Hydroxo, Amino, Methyl, Chloro, Bromo, and Fluoro Functionalities. Bojana Ginovska, Donald M.... more ... Hydroxo, Amino, Methyl, Chloro, Bromo, and Fluoro Functionalities. Bojana Ginovska, Donald M. Camaioni, Michel Dupuis, Christine A. Schwerdtfeger and Quinn Gil. The Journal of Physical Chemistry A 2008 112 (42), 10604-10613. ...

Inorganic Chemistry, May 4, 2005

The pulse radiolysis of aqueous NO has been reinvestigated, the variances with the prior studies ... more The pulse radiolysis of aqueous NO has been reinvestigated, the variances with the prior studies are discussed, and a mechanistic revision is suggested. Both the hydrated electron and the hydrogen atom reduce NO to yield the ground-state triplet 3 NOand singlet 1 HNO, respectively, which further react with NO to produce the N 2 O 2radical, albeit with the very different specific rates, k(3 NO-+ NO)) (3.0 ± 0.8) × 10 9 and k(1 HNO + NO)) (5.8 ± 0.2) × 10 6 M-1 s-1. These reactions occur much more rapidly than the spin-forbidden acid−base equilibration of 3 NOand 1 HNO under all experimentally accessible conditions. As a result, 3 NOand 1 HNO give rise to two reaction pathways that are well separated in time but lead to the same intermediates and products. The N 2 O 2radical extremely rapidly acquires another NO, k(N 2 O 2-+ NO)) (5.4 ± 1.4) × 10 9 M-1 s-1 , producing the closedshell N 3 O 3anion, which unimolecularly decays to the final N 2 O + NO 2products with a rate constant of ∼300 s-1. Contrary to the previous belief, N 2 O 2is stable with respect to NO elimination, and so is N 3 O 3-. The optical spectra of all intermediates have also been reevaluated. The only intermediate whose spectrum can be cleanly observed in the pulse radiolysis experiments is the N 3 O 3anion (λ max) 380 nm, max) 3.76 × 10 3 M-1 cm-1). The spectra previously assigned to the NOanion and to the N 2 O 2radical are due, in fact, to a mixture of species (mainly N 2 O 2and N 3 O 3-) and to the N 3 O 3anion, respectively. Spectral and kinetic evidence suggests that the same reactions occur when 3 NOand 1 HNO are generated by photolysis of the monoprotonated anion of Angeli's salt, HN 2 O 3-, in NO-containing solutions.

ChemPhysChem, Feb 20, 2011

The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing dif... more The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing different numbers of ÀCF 3 groups next to olefinic carbon, CF 2 dCF 2 , CF 2 dCFCF 3 , CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , were measured between 230 and 480 K using the flash photolysis resonance fluorescence technique to give the following expressions: k C 2 F4 (250À 480 K) = 1.32 Â 10 À12 Â (T/298 K) 0.9 Â exp(þ600 K/T) cm 3 molecule À1 s À1 , k C 3 F6 (230À 480 K) = 9.75 Â10 À14 Â (T/298 K) 1.94 Â exp(þ922 K/T) cm 3 molecule À1 s À1 , k trans-C4F8 (230À370 K) = 7.50 Â 10 À14 Â (T/298 K) 1.68 Â exp(þ612 K/T) cm 3 molecule À1 s À1 , k cis-C 4 F8 (230À370 K) = 2.99 Â 10 À14 Â (T/298 K) 2.61 Â exp(þ760 K/T) cm 3 molecule À1 s À1 , and k C 6 F12 (250À480 K) = 2.17 Â 10 À15 Â (T/298 K) 3.90 Â exp(þ1044 K/T) cm 3 molecule À1 s À1. The kinetics of the OH reaction in an industrial sample of octofluoro-2-propene (a mixture of the cisand trans-isomers of CF 3 CFdCFCF 3) was studied to determine the "effective" reaction rate constant for the typically industrial mixture: k AEC 4 F8ae (230À480 K) = 7.89 Â 10 À14 Â (T/298 K) 1.71 Â exp(þ557 K/T) cm 3 molecule À1 s À1. On the basis of these results, the atmospheric lifetimes were estimated to be 1.2, 5.3, 21, 34, and 182 days for CF 2 dCF 2 , CF 3 CFdCF 2 , trans-CF 3 CFdCFCF 3 , cis-CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , respectively. The general pattern of halolalkene reactivity toward OH is discussed.

Journal of Physical Chemistry A, Mar 1, 2003

ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous sol... more ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous solutions were measured by pulse radiolysis. The formation and decay of the nitrate radical, NO3•, and the dichloride radical anion, Cl2•-, in irradiated aqueous solutions containing nitric acid and chloride ions were followed under various conditions. Because of the complexity of the system, the forward rate constant and the equilibrium constant were derived from modeling the experimental results, including secondary formation and decay reactions. The modeling study results in an equilibrium constant of Keq = (3.5 ± 0.5) at an ionic strength between 0.1 and 1 mol L-1 and a forward rate constant k1 = (3.5 ± 0.5) × 108 L mol-1 s-1. In contrast with previous reports, no effect of ionic strength (up to 2 mol L-1) on the forward rate constant was observed.

The Journal of Physical Chemistry, Oct 1, 1993

The radiation-induced chain bisulfite oxidation is of short chain length and is independent of th... more The radiation-induced chain bisulfite oxidation is of short chain length and is independent of the dose rate (1020-5 X 1021 eV L-I s-l) and the initial concentration (5 X 10-4-2 X M) of bisulfite. The mechanism of oxidation, including the propagation reaction SO; + SO<-SOL + SOL + 0 2 (kla) and the termination reaction SO; + SO;-S20S2-+ 0 2 (k l b) , has been proposed. The branching ratio k l a / k l b = 7 f 1 has been derived at room temperature.

Journal of Physical Chemistry A, Mar 1, 2003

ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous sol... more ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous solutions were measured by pulse radiolysis. The formation and decay of the nitrate radical, NO3•, and the dichloride radical anion, Cl2•-, in irradiated aqueous solutions containing nitric acid and chloride ions were followed under various conditions. Because of the complexity of the system, the forward rate constant and the equilibrium constant were derived from modeling the experimental results, including secondary formation and decay reactions. The modeling study results in an equilibrium constant of Keq = (3.5 ± 0.5) at an ionic strength between 0.1 and 1 mol L-1 and a forward rate constant k1 = (3.5 ± 0.5) × 108 L mol-1 s-1. In contrast with previous reports, no effect of ionic strength (up to 2 mol L-1) on the forward rate constant was observed.

Radiation Physics and Chemistry, Jun 1, 1995

The gas-phase transport process of an admixture to the surface of spraying aerosol droplets has b... more The gas-phase transport process of an admixture to the surface of spraying aerosol droplets has been experimentally investigated with reference to E-beam gas cleaning processes. The rate of SO2 uptake by alkali aerosol droplets with average radius ≊ 30 μm has been measured in gas-aerosol jet using light absorption technique. It has been shown that the rate of gas-phase transport is described by the molecular flux of the admixture. Gas-liquid reactions are considered to explain the observed improvement of radiation-induced NO removal in the presence of spraying alkali aerosol.

The Journal of Physical Chemistry, Mar 1, 1995

A continuous radiolysis has been used for the kinetic study of the radical driven bisulfite oxida... more A continuous radiolysis has been used for the kinetic study of the radical driven bisulfite oxidation in oxygenated and N20-02 saturated solutions. The initiation rates and initial bisulfite concentrations were varied over the ranges (3 x 10-1°)-(3 x lo-,) M s-l and 10- ,-(3 x M, respectively. For oxygenated and N20-02 saturated solutions the long chain length bisulfite oxidation with the rate determining propagation reaction SO5-+ HSO3-(k) was observed at low initiation rates. The measurement of the peroxydisulfate formation rates has shown that the main t e d n a t i o n step in an N20-02 saturated solution is the reaction S05-+ SOS-S20s2-+ 0 2 (k7b) and in oxygenated solution is the reaction S05-+ H02 (klo). The rate constants ks = (3.6 f 0.5) x lo3 and k10 = (5 f 1) x lo7 M-' have been derived. The upper limit of the initiation reaction between of hydroperoxyl radical and bisulfite H02 + HS03-has been estimated as 20 M-' s-l,

Journal of Physical Chemistry A, May 26, 2011

The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing dif... more The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing different numbers of ÀCF 3 groups next to olefinic carbon, CF 2 dCF 2 , CF 2 dCFCF 3 , CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , were measured between 230 and 480 K using the flash photolysis resonance fluorescence technique to give the following expressions: k C 2 F4 (250À 480 K) = 1.32 Â 10 À12 Â (T/298 K) 0.9 Â exp(þ600 K/T) cm 3 molecule À1 s À1 , k C 3 F6 (230À 480 K) = 9.75 Â10 À14 Â (T/298 K) 1.94 Â exp(þ922 K/T) cm 3 molecule À1 s À1 , k trans-C4F8 (230À370 K) = 7.50 Â 10 À14 Â (T/298 K) 1.68 Â exp(þ612 K/T) cm 3 molecule À1 s À1 , k cis-C 4 F8 (230À370 K) = 2.99 Â 10 À14 Â (T/298 K) 2.61 Â exp(þ760 K/T) cm 3 molecule À1 s À1 , and k C 6 F12 (250À480 K) = 2.17 Â 10 À15 Â (T/298 K) 3.90 Â exp(þ1044 K/T) cm 3 molecule À1 s À1. The kinetics of the OH reaction in an industrial sample of octofluoro-2-propene (a mixture of the cisand trans-isomers of CF 3 CFdCFCF 3) was studied to determine the "effective" reaction rate constant for the typically industrial mixture: k AEC 4 F8ae (230À480 K) = 7.89 Â 10 À14 Â (T/298 K) 1.71 Â exp(þ557 K/T) cm 3 molecule À1 s À1. On the basis of these results, the atmospheric lifetimes were estimated to be 1.2, 5.3, 21, 34, and 182 days for CF 2 dCF 2 , CF 3 CFdCF 2 , trans-CF 3 CFdCFCF 3 , cis-CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , respectively. The general pattern of halolalkene reactivity toward OH is discussed.

Journal of Physical Chemistry A, Apr 22, 2006

The rate constant for the reaction of OH radicals with molecular hydrogen was measured using the ... more The rate constant for the reaction of OH radicals with molecular hydrogen was measured using the flash photolysis resonance-fluorescence technique over the temperature range of 200-479 K. The Arrhenius plot was found to exhibit a noticeable curvature. Careful examination of all possible systematic uncertainties indicates that this curvature is not due to experimental artifacts. The rate constant can be represented by the following expressions over the indicated temperature intervals: k H 2 (250-479 K)) 4.27 × 10-13 × (T/ 298) 2.406 × exp{-1240/T} cm 3 molecule-1 s-1 above T) 250 K and k H 2 (200-250 K)) 9.01 × 10-13 × exp{-(1526 (70)/T} cm 3 molecule-1 s-1 below T) 250 K. No single Arrhenius expression can adequately represent the rate constant over the entire temperature range within the experimental uncertainties of the measurements. The overall uncertainty factor was estimated to be f H 2 (T)) 1.04 × exp{50 × |(1/T)-(1/ 298)|}. These measurements indicate an underestimation of the rate constant at lower atmospheric temperatures by the present recommendations. The global atmospheric lifetime of H 2 due to its reaction with OH was estimated to be 10 years.

Journal of Geophysical Research, Mar 1, 2001

The equilibrium reaction ·OH + HNO3 ⇆ H2O + NO3. was investigated by pulse radiolysis in aqueous ... more The equilibrium reaction ·OH + HNO3 ⇆ H2O + NO3. was investigated by pulse radiolysis in aqueous solutions. An estimate of the equilibrium constant was derived from the dependence of the optical absorbance due to NO3. radicals upon the concentration of HNO3. In addition, estimates of the forward and reverse rate constants were obtained from the dependence of the formation rate constant on the ratio of the activities of nitric acid and water. Studies were carried out at different values of the dose per pulse and at pH values of 1 and 0. The observations were modeled, taking into account all relevant reactions for the formation and decay of the nitrate radical. From these modeling studies the estimated rate and equilibrium constants were refined. The rate constant of the forward reaction is found to be (8.6 ± 1.3) × 107 L mol−1 s−1, the rate constant of the reverse reaction is found to be (3 ± 1) × 102 L mol−1 s−1, and the equilibrium constant Keq = (2.8 ± 0.4) × 105, all at zero ionic strength. From the latter value of Keq and taking E0(H+, .OH/H2O) = 2.72 V versus NHE, we calculate the reduction potentials E0(H+, NO3./HNO3) = (2.40 ± 0.01) V and E0(NO3./NO3−) = (2.48 ± 0.01) V. This value of the reduction potential for this couple leads to a Henry's law coefficient of KH = 0.018 mol L−1 bar−1 at 298 K for NO3.. This value suggests that the impact of NO3. on atmospheric droplets will be due solely to reactive uptake.

Talanta, Mar 15, 2007

A modified molybdenum blue method for fast and accurate measurement of arsenate and phosphate in ... more A modified molybdenum blue method for fast and accurate measurement of arsenate and phosphate in aqueous solution at concentrations below 10 mol l −1 is reported. The modification consists of optimizing the composition of the molybdenum-containing solution (potassium antimony tartrate, ammonium molybdate, sulfuric acid). Selective reduction of arsenate by sodium dithionite is used to determine phosphate concentrations, and for the speciation of arsenate and arsenite, in an aqueous mixture according to the scheme developed by Johnston and Pilson. Sodium dithionite is used for the first time to achieve complete, fast (<10 min), and selective reduction of arsenate in neutral solution. These two significant improvements afforded a colorimetric limit for As detection near 1 ppb, which easily meets the requirements imposed by the revised EPA threshold levels for As in drinking water.

Chemical Physics, Feb 1, 2016

Abstract Mechanism of thermal decomposition of 2-furyl radical is studied using UB3LYP, UBHandHLY... more Abstract Mechanism of thermal decomposition of 2-furyl radical is studied using UB3LYP, UBHandHLYP and UMP2/6-311++G(d, p) approaches. Thermodynamic properties of considered intermediates and products of 2-furyl radical decomposition are calculated. Two the most kinetically favorable channels of 2-furyl decomposition are found: cis–cis-5- C(H) C(H)C(H)CO (P1) → C2H2 + CHCO (1) and cis–trans-5- C(H) C(H)(H)C CO (P2) → CO + C3H3 (2), where P1 and P2 are the intermediate products of 2-furyl radical decomposition C4H3O → P1 ↔ P2 ↔ trans–trans-5- C(H) (H)CC(H)CO (P3). The values of equilibrium (Kp) and high pressure limits rate (k∞) constants of the reactions considered in the present work are calculated. The important values of k∞ = 2.85 × 10 13 T 298.15 1.05 e - 138.7 RT and = 2.7 × 10 12 T 298.15 1.05 e - 175.7 RT s - 1 are estimated, respectively, for reactions P1 → C2H2 + CHCO and P2 → H2C = CC(H)CO (P4) → CO + C3H3 . The values of Kp = 3.7 × 10 5 T 298.15 4.14 e - 11.9 RT and 3.35 T 298.15 - 0.201 e - 1.34 RT , respectively, for reactions C4H3O ↔ P1 and P1 ↔ P2 are determined. In addition, the importance of formation of most thermodynamically favorable intermediate P3 is reported and the value of Kp = 3.45 × 10 - 2 T 298.15 0.317 e 4.5 RT for reaction P2 ↔ P3 is calculated.

Atmospheric Environment, Feb 1, 1997

Manganese (II) is shown to be an efficient catalyst for radiation-induced HSO3− chain oxidation b... more Manganese (II) is shown to be an efficient catalyst for radiation-induced HSO3− chain oxidation by molecular oxygen in aqueous solutions. The catalytic activity of Mn(II) is explained in terms of a free radical chain mechanism. The rate-determining step with a rate constant of k9 ⩾ 1×106 M−1 s−1 is a reaction between SO5− radical and a manganese (II) bisulfite complex.

Gorenie i vzryv (Moskva) - Combustion and Explosion, 2019

Chemistry, Energy and the Environment, 1998

Journal of molecular modeling, Mar 16, 2024

Authorea (Authorea), Dec 21, 2021

The empirical linear scaling dependencies between the literature (?rHo(Xn,TAB)) and the calculate... more The empirical linear scaling dependencies between the literature (?rHo(Xn,TAB)) and the calculated (?rHo((Xn)i,CALC)) values of atomization of 31 reference aromatic and related compounds (T=298.15K), as well as their standard errors ((SE4)i?(?4)i, Stand.Dev.), are determined for the different quantum mechanical (QMi) approaches. These dependencies are compared and used for the determination of the values of ?rHo((Xn)i,CORRE)±3(SE4)i of atomization reactions of considered not reference aromatic compounds, as well as for the determination of their values of ?fHo((Xn)i,CORRE)+-3(SE4)i. The values of ?fHo((Xn)i,CORRE)MEAN+-3SEYE ([?]99.4% confidence interval), determined using the intersections of the 3(SE4)i intervals, are consistent with all QMi approaches and their literature values. The M06-2X/6-311++G(d,p), M08HX/6-311++G(d,p) and wB97XD/6-311++G(d,p) approaches are recommended for the achievement of accuracy (SEYE)[?]3.8 kJ/mol of the calculated values of ?fHo((Xn)i,CORRE)MEAN. The effects of the number of O-H groups, size and multiplicity of compounds on values of error, also studied in this work, demonstrate the limitations of using of several scaled dependencies.

Journal of Physical Chemistry A, Oct 26, 2002

... Hydroxo, Amino, Methyl, Chloro, Bromo, and Fluoro Functionalities. Bojana Ginovska, Donald M.... more ... Hydroxo, Amino, Methyl, Chloro, Bromo, and Fluoro Functionalities. Bojana Ginovska, Donald M. Camaioni, Michel Dupuis, Christine A. Schwerdtfeger and Quinn Gil. The Journal of Physical Chemistry A 2008 112 (42), 10604-10613. ...

Inorganic Chemistry, May 4, 2005

The pulse radiolysis of aqueous NO has been reinvestigated, the variances with the prior studies ... more The pulse radiolysis of aqueous NO has been reinvestigated, the variances with the prior studies are discussed, and a mechanistic revision is suggested. Both the hydrated electron and the hydrogen atom reduce NO to yield the ground-state triplet 3 NOand singlet 1 HNO, respectively, which further react with NO to produce the N 2 O 2radical, albeit with the very different specific rates, k(3 NO-+ NO)) (3.0 ± 0.8) × 10 9 and k(1 HNO + NO)) (5.8 ± 0.2) × 10 6 M-1 s-1. These reactions occur much more rapidly than the spin-forbidden acid−base equilibration of 3 NOand 1 HNO under all experimentally accessible conditions. As a result, 3 NOand 1 HNO give rise to two reaction pathways that are well separated in time but lead to the same intermediates and products. The N 2 O 2radical extremely rapidly acquires another NO, k(N 2 O 2-+ NO)) (5.4 ± 1.4) × 10 9 M-1 s-1 , producing the closedshell N 3 O 3anion, which unimolecularly decays to the final N 2 O + NO 2products with a rate constant of ∼300 s-1. Contrary to the previous belief, N 2 O 2is stable with respect to NO elimination, and so is N 3 O 3-. The optical spectra of all intermediates have also been reevaluated. The only intermediate whose spectrum can be cleanly observed in the pulse radiolysis experiments is the N 3 O 3anion (λ max) 380 nm, max) 3.76 × 10 3 M-1 cm-1). The spectra previously assigned to the NOanion and to the N 2 O 2radical are due, in fact, to a mixture of species (mainly N 2 O 2and N 3 O 3-) and to the N 3 O 3anion, respectively. Spectral and kinetic evidence suggests that the same reactions occur when 3 NOand 1 HNO are generated by photolysis of the monoprotonated anion of Angeli's salt, HN 2 O 3-, in NO-containing solutions.

ChemPhysChem, Feb 20, 2011

The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing dif... more The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing different numbers of ÀCF 3 groups next to olefinic carbon, CF 2 dCF 2 , CF 2 dCFCF 3 , CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , were measured between 230 and 480 K using the flash photolysis resonance fluorescence technique to give the following expressions: k C 2 F4 (250À 480 K) = 1.32 Â 10 À12 Â (T/298 K) 0.9 Â exp(þ600 K/T) cm 3 molecule À1 s À1 , k C 3 F6 (230À 480 K) = 9.75 Â10 À14 Â (T/298 K) 1.94 Â exp(þ922 K/T) cm 3 molecule À1 s À1 , k trans-C4F8 (230À370 K) = 7.50 Â 10 À14 Â (T/298 K) 1.68 Â exp(þ612 K/T) cm 3 molecule À1 s À1 , k cis-C 4 F8 (230À370 K) = 2.99 Â 10 À14 Â (T/298 K) 2.61 Â exp(þ760 K/T) cm 3 molecule À1 s À1 , and k C 6 F12 (250À480 K) = 2.17 Â 10 À15 Â (T/298 K) 3.90 Â exp(þ1044 K/T) cm 3 molecule À1 s À1. The kinetics of the OH reaction in an industrial sample of octofluoro-2-propene (a mixture of the cisand trans-isomers of CF 3 CFdCFCF 3) was studied to determine the "effective" reaction rate constant for the typically industrial mixture: k AEC 4 F8ae (230À480 K) = 7.89 Â 10 À14 Â (T/298 K) 1.71 Â exp(þ557 K/T) cm 3 molecule À1 s À1. On the basis of these results, the atmospheric lifetimes were estimated to be 1.2, 5.3, 21, 34, and 182 days for CF 2 dCF 2 , CF 3 CFdCF 2 , trans-CF 3 CFdCFCF 3 , cis-CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , respectively. The general pattern of halolalkene reactivity toward OH is discussed.

Journal of Physical Chemistry A, Mar 1, 2003

ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous sol... more ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous solutions were measured by pulse radiolysis. The formation and decay of the nitrate radical, NO3•, and the dichloride radical anion, Cl2•-, in irradiated aqueous solutions containing nitric acid and chloride ions were followed under various conditions. Because of the complexity of the system, the forward rate constant and the equilibrium constant were derived from modeling the experimental results, including secondary formation and decay reactions. The modeling study results in an equilibrium constant of Keq = (3.5 ± 0.5) at an ionic strength between 0.1 and 1 mol L-1 and a forward rate constant k1 = (3.5 ± 0.5) × 108 L mol-1 s-1. In contrast with previous reports, no effect of ionic strength (up to 2 mol L-1) on the forward rate constant was observed.

The Journal of Physical Chemistry, Oct 1, 1993

The radiation-induced chain bisulfite oxidation is of short chain length and is independent of th... more The radiation-induced chain bisulfite oxidation is of short chain length and is independent of the dose rate (1020-5 X 1021 eV L-I s-l) and the initial concentration (5 X 10-4-2 X M) of bisulfite. The mechanism of oxidation, including the propagation reaction SO; + SO<-SOL + SOL + 0 2 (kla) and the termination reaction SO; + SO;-S20S2-+ 0 2 (k l b) , has been proposed. The branching ratio k l a / k l b = 7 f 1 has been derived at room temperature.

Journal of Physical Chemistry A, Mar 1, 2003

ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous sol... more ABSTRACT The rate and equilibrium constants for the reaction NO3• + Cl- NO3- + Cl• in aqueous solutions were measured by pulse radiolysis. The formation and decay of the nitrate radical, NO3•, and the dichloride radical anion, Cl2•-, in irradiated aqueous solutions containing nitric acid and chloride ions were followed under various conditions. Because of the complexity of the system, the forward rate constant and the equilibrium constant were derived from modeling the experimental results, including secondary formation and decay reactions. The modeling study results in an equilibrium constant of Keq = (3.5 ± 0.5) at an ionic strength between 0.1 and 1 mol L-1 and a forward rate constant k1 = (3.5 ± 0.5) × 108 L mol-1 s-1. In contrast with previous reports, no effect of ionic strength (up to 2 mol L-1) on the forward rate constant was observed.

Radiation Physics and Chemistry, Jun 1, 1995

The gas-phase transport process of an admixture to the surface of spraying aerosol droplets has b... more The gas-phase transport process of an admixture to the surface of spraying aerosol droplets has been experimentally investigated with reference to E-beam gas cleaning processes. The rate of SO2 uptake by alkali aerosol droplets with average radius ≊ 30 μm has been measured in gas-aerosol jet using light absorption technique. It has been shown that the rate of gas-phase transport is described by the molecular flux of the admixture. Gas-liquid reactions are considered to explain the observed improvement of radiation-induced NO removal in the presence of spraying alkali aerosol.

The Journal of Physical Chemistry, Mar 1, 1995

A continuous radiolysis has been used for the kinetic study of the radical driven bisulfite oxida... more A continuous radiolysis has been used for the kinetic study of the radical driven bisulfite oxidation in oxygenated and N20-02 saturated solutions. The initiation rates and initial bisulfite concentrations were varied over the ranges (3 x 10-1°)-(3 x lo-,) M s-l and 10- ,-(3 x M, respectively. For oxygenated and N20-02 saturated solutions the long chain length bisulfite oxidation with the rate determining propagation reaction SO5-+ HSO3-(k) was observed at low initiation rates. The measurement of the peroxydisulfate formation rates has shown that the main t e d n a t i o n step in an N20-02 saturated solution is the reaction S05-+ SOS-S20s2-+ 0 2 (k7b) and in oxygenated solution is the reaction S05-+ H02 (klo). The rate constants ks = (3.6 f 0.5) x lo3 and k10 = (5 f 1) x lo7 M-' have been derived. The upper limit of the initiation reaction between of hydroperoxyl radical and bisulfite H02 + HS03-has been estimated as 20 M-' s-l,

Journal of Physical Chemistry A, May 26, 2011

The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing dif... more The rate constants for the reactions of OH radicals with fully fluorinated alkenes containing different numbers of ÀCF 3 groups next to olefinic carbon, CF 2 dCF 2 , CF 2 dCFCF 3 , CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , were measured between 230 and 480 K using the flash photolysis resonance fluorescence technique to give the following expressions: k C 2 F4 (250À 480 K) = 1.32 Â 10 À12 Â (T/298 K) 0.9 Â exp(þ600 K/T) cm 3 molecule À1 s À1 , k C 3 F6 (230À 480 K) = 9.75 Â10 À14 Â (T/298 K) 1.94 Â exp(þ922 K/T) cm 3 molecule À1 s À1 , k trans-C4F8 (230À370 K) = 7.50 Â 10 À14 Â (T/298 K) 1.68 Â exp(þ612 K/T) cm 3 molecule À1 s À1 , k cis-C 4 F8 (230À370 K) = 2.99 Â 10 À14 Â (T/298 K) 2.61 Â exp(þ760 K/T) cm 3 molecule À1 s À1 , and k C 6 F12 (250À480 K) = 2.17 Â 10 À15 Â (T/298 K) 3.90 Â exp(þ1044 K/T) cm 3 molecule À1 s À1. The kinetics of the OH reaction in an industrial sample of octofluoro-2-propene (a mixture of the cisand trans-isomers of CF 3 CFdCFCF 3) was studied to determine the "effective" reaction rate constant for the typically industrial mixture: k AEC 4 F8ae (230À480 K) = 7.89 Â 10 À14 Â (T/298 K) 1.71 Â exp(þ557 K/T) cm 3 molecule À1 s À1. On the basis of these results, the atmospheric lifetimes were estimated to be 1.2, 5.3, 21, 34, and 182 days for CF 2 dCF 2 , CF 3 CFdCF 2 , trans-CF 3 CFdCFCF 3 , cis-CF 3 CFdCFCF 3 , and (CF 3) 2 CdCFC 2 F 5 , respectively. The general pattern of halolalkene reactivity toward OH is discussed.

Journal of Physical Chemistry A, Apr 22, 2006

The rate constant for the reaction of OH radicals with molecular hydrogen was measured using the ... more The rate constant for the reaction of OH radicals with molecular hydrogen was measured using the flash photolysis resonance-fluorescence technique over the temperature range of 200-479 K. The Arrhenius plot was found to exhibit a noticeable curvature. Careful examination of all possible systematic uncertainties indicates that this curvature is not due to experimental artifacts. The rate constant can be represented by the following expressions over the indicated temperature intervals: k H 2 (250-479 K)) 4.27 × 10-13 × (T/ 298) 2.406 × exp{-1240/T} cm 3 molecule-1 s-1 above T) 250 K and k H 2 (200-250 K)) 9.01 × 10-13 × exp{-(1526 (70)/T} cm 3 molecule-1 s-1 below T) 250 K. No single Arrhenius expression can adequately represent the rate constant over the entire temperature range within the experimental uncertainties of the measurements. The overall uncertainty factor was estimated to be f H 2 (T)) 1.04 × exp{50 × |(1/T)-(1/ 298)|}. These measurements indicate an underestimation of the rate constant at lower atmospheric temperatures by the present recommendations. The global atmospheric lifetime of H 2 due to its reaction with OH was estimated to be 10 years.

Journal of Geophysical Research, Mar 1, 2001

The equilibrium reaction ·OH + HNO3 ⇆ H2O + NO3. was investigated by pulse radiolysis in aqueous ... more The equilibrium reaction ·OH + HNO3 ⇆ H2O + NO3. was investigated by pulse radiolysis in aqueous solutions. An estimate of the equilibrium constant was derived from the dependence of the optical absorbance due to NO3. radicals upon the concentration of HNO3. In addition, estimates of the forward and reverse rate constants were obtained from the dependence of the formation rate constant on the ratio of the activities of nitric acid and water. Studies were carried out at different values of the dose per pulse and at pH values of 1 and 0. The observations were modeled, taking into account all relevant reactions for the formation and decay of the nitrate radical. From these modeling studies the estimated rate and equilibrium constants were refined. The rate constant of the forward reaction is found to be (8.6 ± 1.3) × 107 L mol−1 s−1, the rate constant of the reverse reaction is found to be (3 ± 1) × 102 L mol−1 s−1, and the equilibrium constant Keq = (2.8 ± 0.4) × 105, all at zero ionic strength. From the latter value of Keq and taking E0(H+, .OH/H2O) = 2.72 V versus NHE, we calculate the reduction potentials E0(H+, NO3./HNO3) = (2.40 ± 0.01) V and E0(NO3./NO3−) = (2.48 ± 0.01) V. This value of the reduction potential for this couple leads to a Henry's law coefficient of KH = 0.018 mol L−1 bar−1 at 298 K for NO3.. This value suggests that the impact of NO3. on atmospheric droplets will be due solely to reactive uptake.

Talanta, Mar 15, 2007

A modified molybdenum blue method for fast and accurate measurement of arsenate and phosphate in ... more A modified molybdenum blue method for fast and accurate measurement of arsenate and phosphate in aqueous solution at concentrations below 10 mol l −1 is reported. The modification consists of optimizing the composition of the molybdenum-containing solution (potassium antimony tartrate, ammonium molybdate, sulfuric acid). Selective reduction of arsenate by sodium dithionite is used to determine phosphate concentrations, and for the speciation of arsenate and arsenite, in an aqueous mixture according to the scheme developed by Johnston and Pilson. Sodium dithionite is used for the first time to achieve complete, fast (<10 min), and selective reduction of arsenate in neutral solution. These two significant improvements afforded a colorimetric limit for As detection near 1 ppb, which easily meets the requirements imposed by the revised EPA threshold levels for As in drinking water.

Chemical Physics, Feb 1, 2016

Abstract Mechanism of thermal decomposition of 2-furyl radical is studied using UB3LYP, UBHandHLY... more Abstract Mechanism of thermal decomposition of 2-furyl radical is studied using UB3LYP, UBHandHLYP and UMP2/6-311++G(d, p) approaches. Thermodynamic properties of considered intermediates and products of 2-furyl radical decomposition are calculated. Two the most kinetically favorable channels of 2-furyl decomposition are found: cis–cis-5- C(H) C(H)C(H)CO (P1) → C2H2 + CHCO (1) and cis–trans-5- C(H) C(H)(H)C CO (P2) → CO + C3H3 (2), where P1 and P2 are the intermediate products of 2-furyl radical decomposition C4H3O → P1 ↔ P2 ↔ trans–trans-5- C(H) (H)CC(H)CO (P3). The values of equilibrium (Kp) and high pressure limits rate (k∞) constants of the reactions considered in the present work are calculated. The important values of k∞ = 2.85 × 10 13 T 298.15 1.05 e - 138.7 RT and = 2.7 × 10 12 T 298.15 1.05 e - 175.7 RT s - 1 are estimated, respectively, for reactions P1 → C2H2 + CHCO and P2 → H2C = CC(H)CO (P4) → CO + C3H3 . The values of Kp = 3.7 × 10 5 T 298.15 4.14 e - 11.9 RT and 3.35 T 298.15 - 0.201 e - 1.34 RT , respectively, for reactions C4H3O ↔ P1 and P1 ↔ P2 are determined. In addition, the importance of formation of most thermodynamically favorable intermediate P3 is reported and the value of Kp = 3.45 × 10 - 2 T 298.15 0.317 e 4.5 RT for reaction P2 ↔ P3 is calculated.

Atmospheric Environment, Feb 1, 1997

Manganese (II) is shown to be an efficient catalyst for radiation-induced HSO3− chain oxidation b... more Manganese (II) is shown to be an efficient catalyst for radiation-induced HSO3− chain oxidation by molecular oxygen in aqueous solutions. The catalytic activity of Mn(II) is explained in terms of a free radical chain mechanism. The rate-determining step with a rate constant of k9 ⩾ 1×106 M−1 s−1 is a reaction between SO5− radical and a manganese (II) bisulfite complex.

Gorenie i vzryv (Moskva) - Combustion and Explosion, 2019

Chemistry, Energy and the Environment, 1998