Ag(I)‐Catalyzed Chlorination of Linezolid during Water Treatment: Kinetics and Mechanism

The kinetic and mechanistic study of Ag(I)‐catalyzed chlorination of linezolid (LNZ) by free available chlorine (FAC) was investigated at environmentally relevant pH 4.0–9.0. Apparent second‐order rate constants decreased with an increase in pH of the reaction mixture. The apparent second‐order rate constant for uncatalyzed reaction, e.g., k″_app = 8.15 dm³ mol⁻¹ s⁻¹ at pH 4.0 and k″_app. = 0.076 dm³ mol⁻¹ s⁻¹ at pH 9.0 and 25 ± 0.2°C and for Ag(I) catalyzed reaction total apparent second‐order rate constant, e.g., k″_app = 51.50 dm³ mol⁻¹ s⁻¹ at pH 4.0 and k″_app. = 1.03 dm³ mol⁻¹ s⁻¹ at pH 9.0 and 25 ± 0.2°C. The Ag(I) catalyst accelerates the reaction of LNZ with FAC by 10‐fold. A mechanism involving electrophilic halogenation has been proposed based on the kinetic data and LC/ESI/MS spectra. The influence of temperature on the rate of reaction was studied; the rate constants were found to increase with an increase in temperature. The thermodynamic activation parameters E_a, ΔH^#, ΔS^#, and ΔG^# were evaluated for the reaction and discussed. The influence of catalyst, initially added product, dielectric constant, and ionic strength on the rate of reaction was also investigated. The monochlorinated substituted product along with degraded one was formed by the reaction of LNZ with FAC.     

Rate constants for the gas‐phase reaction of hexamethylbenzene with OH radicals and H atoms and of 1,3,5‐trimethylbenzene with H atoms

Rate constants for the gas‐phase reaction of hexamethylbenzene (HMB) with OH radicals and H atoms and of 1,3,5‐trimethylbenzene (TMB) with H atoms have been obtained in a flow system at 295 ± 2 K and a pressure of 25 mbar He using MS measurements. Obtained rate constants from a relative rate technique are k_(OH+HMB) = (1.13 ± 0.11) 10⁻¹⁰, k_(H+HMB) = (5.9 ± 3.4) 10⁻¹³ and k_(H+TMB) = (4.6 ± 2.7) 10⁻¹³ cm³ molecule⁻¹ s⁻¹, respectively. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 124–129, 2001     

Kinetics of the reversible photoaquation of the octacyanomolybdate(IV) ion

The kinetics of the photoaquation of the octacyanomolybdate(IV) ion in aqueous solution were studied by potentiometric and spectrophotometric methods. In an alkaline medium a simple scheme analogous to the photoaquation of the hexacyanoferrate(II) ion describes the process. The values of the constants of the kinetic equation are: (Φ = 1.0, k₈ = (6.55 ± 0.8) x 10⁻⁹ s⁻¹, and k₋₈ = (7.88 ± 0.5) x 10⁻² mol⁻¹ dm³ s⁻¹ (pH = 10.5). The reversibility of the photoaquation is also explained by the scheme. A simultaneous measurement of free cyanide ion concentration and the absorbance at 512nm shows that the red coloured transition product is a heptacyano complex.     

Kinetics of the complexation of Al3+ with aminoacids,IDA and NTA

The kinetics of the complexation of Al³⁺ with aminoacids, IDA and NTA are investigated by the stopped flow method with conductivity detection in the range of pH < 4. Reaction amplitudes and pseudo-first-order rate constants are evaluated yielding equilibrium and rate constants. It is shown that Al³⁺ forms only complexes with the negatively charged species and that the kinetics of all investigated ligands can be explained with the same reaction scheme. For aspartic acid, IDA and NTA a stepwise complexation is observed where monodentate complexes are formed by a fast reaction (2s ⁻¹ < k < 20s¹) which is base catalyzed. The rate determining step is the solvent exchange at Al³⁺ according to the Eigen-Wilkins mechanism. However, the ligand influences this exchange rate and a linear free energy relation is found between log k and pK_a, which also describes the kinetics of other ligands. This fast reaction is followed by the much slower formation of chelates (for NTA:k = 0.27 s ⁻¹) which is controlled by the deprotonation of the nitrogen atom. The overall association constant of the Al-NTA complex is determined as log (K_ass/dm³mol⁻¹) = 13.0 ± 0.3. © 1996 John Wiley & Sons, Inc.     

Cavity ring‐down spectroscopic study of the kinetics of the reactions of FCO radicals with O2 and NO at 295 K

Cavity ring‐down UV absorption spectroscopy was used to study the kinetics of the recombination reaction of FCO radicals and the reactions with O₂ and NO in 4.0–15.5 Torr total pressure of N₂ diluent at 295 K. k(FCO + FCO) is (1.8 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The pressure dependence of the reactions with O₂ and NO in air at 295 K is described using a broadening factor of Fc = 0.6 and the following low (k₀) and high (k_∞) pressure limit rate constants: k₀(FCO + O₂) = (8.6 ± 0.4) × 10⁻³¹ cm⁶ molecule⁻¹ s⁻¹, k_∞(FCO + O₂) = (1.2 ± 0.2) × 10⁻¹² cm³ molecule⁻¹ s⁻¹, k₀(FCO + NO) = (2.4 ± 0.2) × 10⁻³⁰ cm⁶ molecule⁻¹ s⁻¹, and k_∞ (FCO + NO) = (1.0 ± 0.2) × 10⁻¹² cm³ molecule⁻¹ s⁻¹. The uncertainties are two standard deviations. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 130–135, 2001     

Atmospheric chemistry of di-tert-butyl ether: Rates and products of the reactions with chlorine atoms,hydroxyl radicals,and nitrate radicals

The rate constants for the gas-phase reactions of di-tert-butyl ether (DTBE) with chlorine atoms, hydroxyl radicals, and nitrate radicals have been determined in relative rate experiments using FTIR spectroscopy. Values of k_(DTBE+CI) = (1.4 ± 0.2) × 10⁻¹⁰,k_(DTBE+OH) = (3.7 ± 0.7) × 10⁻¹², and k_(DTBE+N03) = (2.8 ± 0.9) × 10⁻¹⁶ cm³ molecule⁻¹ s⁻¹ were obtained. Tert-butyl acetate was identified as the major product of both Cl atom and OH radical initiated oxidation of DTBE in air in the presence of NO_x. The molar tert-butyl acetate yield was 0.85 ± 0.11 in the Cl atom experiments and 0.84 ± 0.11 in OH radical experiments. As part of this work the rate constant for reaction of Cl atoms with tert-butyl acetate at 295 K was determined to be (1.6 ± 0.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹. The stated errors are two standard deviations (2σ). © 1996 John Wiley & Sons, Inc.     

Determination of propagation and termination rate constants by using an extension to the rotating-sector method: Application to PLPC and DLPC bilayers

An extension to the rotating-sector method, which is usually applied to determine propagation and termination rate constants, is presented. The analytical treatment developed accounts for the simultaneous presence of a thermal initiation and of a first-order termination process. The applicability of the rotating-sector method is thus extended to situations where the rate in dark is higher than 5% of the rate in the presence of light, and more accurate estimates of the rate constants are obtained than before for any values of the “dark” rate. A previously published experiment on the application of the rotating-sector method to the autoxidation of styrene was reanalyzed. The estimates obtained for the propagation and the termination rate constants were 11% and 19% higher than the previous estimates, respectively. Finally, the improved rotating-sector method was also applied to the experimental determination of propagation (k_p) and termination rate constants (2×k_t) for both 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC) and 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (DLPC) liposomes. The following results were obtained at 37°C: for PLPC k_p =16.6 M⁻¹s⁻¹, and 2×k_t=1.27×10⁵ M⁻¹s⁻¹; for DLPC k_p(intermolecular)=(13.3–13.9) M⁻¹s⁻¹, k_p(intramolecular)=(4.7–5.4) s⁻¹, and 2×k_t=(0.99–1.05)×10⁵ M⁻¹s⁻¹. The separation of the intermolecular and intramolecular propagation rate constants for DLPC was made possible both by a special adaptation of the rotating-sector equations to substrates with two oxidizable moieties, and by the experimental determination of the ratio between partially oxidized DLPC molecules (only one acyl is oxidized) and fully oxidized DLPC molecules (both acyls are oxidized). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 753–767, 1998     

Kinetics of the gas‐phase reactions of Cl atom with selected C2–C5 unsaturated hydrocarbons at 283 < T < 323 K

The reaction of Cl atoms with a series of C₂–C₅ unsaturated hydrocarbons has been investigated at atmospheric pressure of 760 Torr over the temperature range 283–323 K in air and N₂ diluents. The decay of the hydrocarbons was followed using a gas chromatograph with a flame ionization detector (GC‐FID), and the kinetic constants were determined using a relative rate technique with n‐hexane as a reference compound. The Cl atoms were generated by UV photolysis (λ ≥ 300 nm) of Cl₂ molecules. The following absolute rate constants (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, with errors representing ±2σ) for the reaction at 295 ± 2 K have been derived from the relative rate constants combined to the value 34.5 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ for the Cl + n‐hexane reaction: ethene (9.3 ± 0.6), propyne (22.1 ± 0.3), propene (27.6 ± 0.6), 1‐butene (35.2 ± 0.7), and 1‐pentene (48.3 ± 0.8). The temperature dependence of the reactions can be expressed as simple Arrhenius expressions (in units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹): k_ethene = (0.39 ± 0.22) × 10⁻¹¹ exp{(226 ± 42)/T}, k_propyne = (4.1 ± 2.5) × 10⁻¹¹ exp{(118 ± 45)/T}, k_propene = (1.6 ± 1.8) × 10⁻¹¹ exp{(203 ± 79)/T}, k_1‐butene = (1.1 ± 1.3) × 10⁻¹¹ exp{(245 ± 90)/T}, and k_1‐pentene = (4.0 ± 2.2) × 10⁻¹¹ exp{(423 ± 68)/T}. The applicability of our results to tropospheric chemistry is discussed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 478–484, 2000     

Experimental study of the kinetics of reaction of chlorine atoms with tetrahydrofuran and fully deuterated tetrahydrofuran

The overall rate constants for H-abstraction (k_H) from tetrahydrofuran and D-abstraction (k_D) from fully deuterated tetrahydrofuran by chlorine atoms in the temperature range of 298-547 K were determined. In both cases, very weak negative temperature dependences of the overall rate constants were observed, described by the expressions: k_H = (1.55 ± 0.13) × 10⁻¹⁰ exp(52 ± 28/T) cm³ molecule⁻¹ s⁻¹ and k_D = (1.27 ± 0.25) × 10⁻¹⁰exp(55 ± 62/T) cm³ molecule⁻¹ s⁻¹. The experimental results show that the value of the kinetic isotope effect (k_H/k_D), amounting to 1.21 ± 0.10, is temperature independent at 298-547 K.     

A kinetic study of the reaction of chlorine and fluorine atoms with HC(O)F at 295±2 K

Using relative rate techniques the reactions of chlorine and fluorine atoms with HC(O)F have been determined to proceed with rate constants of k₁ = (1.9 ± 0.2) × 10⁻¹⁵ and k₂ = (8.3 ± 1.7) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹, respectively. Stated errors reflect statistical uncertainty; possible systematic uncertainties could add additional 10% and 20% ranges to the values of k₁ and k₂, respectively. Experiments were performed at 295 ± 2 K and 700 torr total pressure of air. The results are discussed with respect to the design and interpretation of laboratory studies of the atmospheric chemistry of CFC replacements. © 1997 John Wiley & Sons, Inc.     

A laser flash photolysis kinetic study of reactions of the Cl2− radical anion with oxygenated hydrocarbons in aqueous solution

A laser photolysis–long path laser absorption (LP‐LPLA) experiment has been used to determine the rate constants for H‐atom abstraction reactions of the dichloride radical anion (Cl₂⁻) in aqueous solution. From direct measurements of the decay of Cl₂⁻ in the presence of different reactants at pH = 4 and I = 0.1 M the following rate constants at T = 298 K were derived: methanol, (5.1 ± 0.3)·10⁴ M⁻¹ s⁻¹; ethanol, (1.2 ± 0.2)·10⁵ M⁻¹ s⁻¹; 1‐propanol, (1.01 ± 0.07)·10⁵ M⁻¹ s⁻¹; 2‐propanol, (1.9 ± 0.3)·10⁵ M⁻¹ s⁻¹; tert.‐butanol, (2.6 ± 0.5)·10⁴ M⁻¹ s⁻¹; formaldehyde, (3.6 ± 0.5)·10⁴ M⁻¹ s⁻¹; diethylether, (4.0 ± 0.2)·10⁵ M⁻¹ s⁻¹; methyl‐tert.‐butylether, (7 ± 1)·10⁴ M⁻¹ s⁻¹; tetrahydrofuran, (4.8 ± 0.6)·10⁵ M⁻¹ s⁻¹; acetone, (1.41 ± 0.09)·10³ M⁻¹ s⁻¹. For the reactions of Cl₂⁻ with formic acid and acetic acid rate constants of (8.0 ± 1.4)·10⁴ M⁻¹ s⁻¹ (pH = 0, I = 1.1 M and T = 298 K) and (1.5 ± 0.8) · 10³ M⁻¹ s⁻¹ (pH = 0.42, I = 0.48 M and T = 298 K), respectively, were derived. A correlation between the rate constants at T = 298 K for all oxygenated hydrocarbons and the bond dissociation energy (BDE) of the weakest C‐H‐bond of log k_2nd = (32.9 ± 8.9) − (0.073 ± 0.022)·BDE/kJ mol⁻¹ is derived. From temperature‐dependent measurements the following Arrhenius expressions were derived: k (Cl₂⁻ + HCOOH) = (2.00 ± 0.05)·10¹⁰·exp(−(4500 ± 200) K/T) M⁻¹ s⁻¹, E_a = (37 ± 2) kJ mol⁻¹ k (Cl₂⁻ + CH₃COOH) = (2.7 ± 0.5)·10¹⁰·exp(−(4900 ± 1300) K/T) M⁻¹ s⁻¹, E_a = (41 ± 11) kJ mol⁻¹ k (Cl₂⁻ + CH₃OH) = (5.1 ± 0.9)·10¹²·exp(−(5500 ± 1500) K/T) M⁻¹ s⁻¹, E_a = (46 ± 13) kJ mol⁻¹ k (Cl₂⁻ + CH₂(OH)₂) = (7.9 ± 0.7)·10¹⁰·exp(−(4400 ± 700) K/T) M⁻¹ s⁻¹, E_a = (36 ± 5) kJ mol⁻¹ Finally, in measurements at different ionic strengths (I) a decrease of the rate constant with increasing I has been observed in the reactions of Cl₂⁻ with methanol and hydrated formaldehyde. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 169–181, 1999     

Rate constants for reactions of OH radicals with a series of asymmetrical ethers and tert-Butyl alcohol

Absolute rate constants for the reactions of OH radicals with butyl ethyl ether (k₁), methyl tert-butyl ether (k₂), ethyl tert-butyl ether (k₃) tert-amyl methyl ether (k₄) and tert-butyl alcohol (k₅) have been measured over the temperature range 230–372 K using a pulsed laser photolysis-laser induced fluorescence (PLP-LIF) technique. The temperature dependence of k₁ − k₅ when expressed in Arrhenius form gave: k₁ = (6.59 ± 0.66) × 10 ⁻¹² exp|(362 ± 60)/T|, k₂ = (5.03 ± 0.27) × 10⁻¹² exp|&minus(133 ± 30)/T|, k₃ = (4.40 ± 0.24) × 10⁻¹² exp|(210 ± 37)/T|,k⁴ = (4.7 ± 0.7) × 10⁻¹² exp|(82 ± 85)/T|, and k₅ = (2.66 ± 0.48) × 10⁻¹² exp| −(270 ± 130)/T|. However, the Arrhenius plots for k₁–k₅, were slightly curved and are best fitted by the three parameter fits which are given in the article. The room temperature values of k₁, k₂, k₃, k₄, and k₅ are (2.08 ± 0.23) × 10⁻¹¹, (3.13 ± 0.36) × 10⁻¹², (8.80 ± 0.50) × 10⁻¹², (6.28 ± 0.45) × 10⁻¹², and (1.08 ± 0.10) × 10⁻¹², respectively, in cm³ molecule⁻¹ s⁻¹. © 1996 John Wiley & Sons, Inc.     

Theoretical and experimental studies of the diketene system: Product branching decomposition rate constants and energetics of isomers

The kinetics and mechanism for the thermal decomposition of diketene have been studied in the temperature range 510–603 K using highly diluted mixtures with Ar as a diluent. The concentrations of diketene, ketene, and CO₂ were measured by FTIR spectrometry using calibrated standard mixtures. Two reaction channels were identified. The rate constants for the formation of ketene (k₁) and CO₂ (k₂) have been determined and compared with the values predicted by the Rice–Ramsperger–Kassel–Marcus (RRKM) theory for the branching reaction. The first-order rate constants, k₁ (s⁻¹) = 10^{15.74 ± 0.72} exp(−49.29 (kcal mol⁻¹) (±1.84)/RT) and k₂ (s⁻¹) = 10^{14.65 ± 0.87} exp(−49.01 (kcal mol⁻¹) (±2.22)/RT); the bulk of experimental data agree well with predicted results. The heats of formation of ketene, diketene, cyclobuta-1,3-dione, and cyclobuta-1,2-dione at 298 K computed from the G2M scheme are −11.1, −45.3, −43.6, and −40.3 kcal mol⁻¹, respectively. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 580–590, 2007     

Kinetics and mechanisms of the reactions of chlorine atoms with ethane,propane, and n-butane

Absolute (flash photolysis) and relative (FTIR-smog chamber and GC) rate techniques were used to study the gas-phase reactions of Cl atoms with C₂H₆ (k₁), C₃H₈ (k₃), and n-C₄H₁₀ (k₂). At 297 ± 1 K the results from the two relative rate techniques can be combined to give k₂/k₁ = (3.76 ± 0.20) and k₃/k₁ = (2.42 ± 0.10). Experiments performed at 298–540 K give k₂/k₁ = (2.0 ± 0.1)exp((183 ± 20)/T). At 296 K the reaction of Cl atoms with C₃H₈ produces yields of 43 ± 3% 1-propyl and 57 ± 3% 2-propyl radicals, while the reaction of Cl atoms with n-C₄H₁₀ produces 29 ± 2% 1-butyl and 71 ± 2% 2-butyl radicals. At 298 K and 10–700 torr of N₂ diluent, 1- and 2-butyl radicals were found to react with Cl₂ with rate coefficients which are 3.1 ± 0.2 and 2.8 ± 0.1 times greater than the corresponding reactions with O₂. A flash-photolysis technique was used to measure k₁ = (5.75 ± 0.45) × 10⁻¹¹ and k₂ = (2.15 ± 0.15) × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ at 298 K, giving a rate coefficient ratio k₂/k₁ = 3.74 ± 0.40, in excellent agreement with the relative rate studies. The present results are used to put other, relative rate measurements of the reactions of chlorine atoms with alkanes on an absolute basis. It is found that the rate of hydrogen abstraction from a methyl group is not influenced by neighboring groups. The results are used to refine empirical approaches to predicting the reactivity of Cl atoms towards hydrocarbons. Finally, relative rate methods were used to measure rate coefficients at 298 K for the reaction of Cl atoms with 1- and 2-chloropropane and 1- and 2-chlorobutane of (4.8 ± 0.3) × 10⁻¹¹, (2.0 ± 0.1) × 10⁻¹⁰, (1.1 ± 0.2) × 10⁻¹⁰, and (7.0 ± 0.8) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 43–55, 1997.     

Rate coefficients for the reactions of chlorine atoms with methanol and acetaldehyde

Rate coefficients have been measured for the reactions of Cl atoms with methanol (k₁) and acetaldehyde (k₂) using both absolute (laser photolysis with resonance fluorescence) and relative rate methods at 295 ± 2 K. The measured rate coefficients were (units of 10⁻¹¹ cm³ molecule⁻¹ s⁻¹): absolute method, k₁ = (5.1 ± 0.4), k₂ = (7.3 ± 0.7); relative method k₁ = (5.6 ± 0.6), k₂ = (8.4 ± 1.0). Based on a critical evaluation of the literature data, the following rate coefficients are recommended: k₁ = (5.4 ± 0.9) × 10⁻¹¹ and k₂ = (7.8 ± 1.3) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹ (95% confidence limits). The results significantly improve the confidence in the database for reactions of Cl atoms with these oxygenated organics. Rate coefficients were also measured for the reactions of Cl₂ with CH₂OH, k₅ = (2.9 ± 0.6) × 10⁻¹¹ and CH₃CO, k₆ = (4.3 ± 1.5) × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, by observing the regeneration of Cl atoms in the absence of O₂. Based on these results and those from a previous relative rate study, the rate coefficient for CH₃CO + O₂ at the high pressure limit is estimated to be (5.7 ± 1.9) × 10⁻¹² cm³ molecule⁻¹ s⁻¹. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 776–784, 1999     

Rate constants and Arrhenius parameters for the reactions of Cl atoms with the halogenated ethers: CF3CH2OCHF2, CF3CHClOCHF2, and CF3CH2OCClF2

Rate constants have been determined for the reactions of Cl atoms with the halogenated ethers CF₃CH₂OCHF₂, CF₃CHClOCHF₂, and CF₃CH₂OCClF₂ using a relative‐rate technique. Chlorine atoms were generated by continuous photolysis of Cl₂ in a mixture containing the ether and CD₄. Changes in the concentrations of these two species were measured via changes in their infrared absorption spectra observed with a Fourier transform infrared (FTIR) spectrometer. Relative‐rate constants were converted to absolute values using the previously measured rate constants for the reaction, Cl + CD₄ → DCl + CD₃. Experiments were carried out at 295, 323, and 363 K, yielding the following Arrhenius expressions for the rate constants within this range of temperature:Cl + CF₃CH₂OCHF₂: k = (5.1₅ ± 0.7) × 10⁻¹² exp(−1830 ± 410 K/T) cm³ molecule⁻¹ s⁻¹ Cl + CF₃CHClOCHF₂: k = (1.6 ± 0.2) × 10⁻¹¹ exp(−2450 ± 250 K/T) cm³ molecule⁻¹ s⁻¹ Cl + CF₃CH₂OCClF₂: k = (9.6 ± 0.4) × 10⁻¹² exp(−2390 ± 190 K/T) cm³ molecule⁻¹ s⁻¹ The results are compared with those obtained previously for the reactions of Cl atoms with other halogenated methyl ethyl ethers. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 165–172, 2001     

Kinetics of the gas-phase reactions of the oh radical with selected glycol ethers,glycols, and alcohols

Using a relative rate method, rate constants have been measured for the gas-phase reactions of the OH radical with 1-hexanol, 1-methoxy-2-propanol, 2-butoxyethanol, 1,2-ethanediol, and 1,2-propanediol at 296±2 K, of (in units of 10⁻¹² cm³ molecule⁻¹ s⁻¹): 15.8±3.5; 20.9±3.1; 29.4±4.3; 14.7±2.6; and 21.5±4.0, respectively, where the error limits include the estimated overall uncertainties in the rate constants for the reference compounds. These OH radical reaction rate constants are higher than certain of the literature values, by up to a factor of 2. Rate constants were also measured for the reactions of 1-methoxy-2-propanol and 2-butoxyethanol with NO₃ radicals and O₃, with respective NO₃ radical and O₃ reaction rate constants (in cm³ molecule⁻¹ s⁻¹ units) of: 1-methoxy-2-propanol, (1.7±0.7)×10⁻¹⁵, and <1.1×10⁻¹⁹; and 2-butoxyethanol, (3.0±1.2)×10⁻¹⁵, and <1.1×10⁻¹⁹. The dominant tropospheric loss process for the alcohols, glycols, and glycol ethers studied here is calculated to be by reaction with the OH radical, with lifetimes of 0.4–0.8 day for a 24 h average OH radical concentration of 1.0×10⁶ molecule cm⁻³. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 533–540, 1998     

Temperature dependence of the rate constants of the reactions of oxygen atoms with 1-pentene, 1-hexene,cis-2-pentene,and trans-2-pentene

The kinetics of the reactions of ground state oxygen atoms with 1-pentene, 1-hexene, cis-2-pentene, and trans-2-pentene was investigated in the temperature range 200 to 370 K. In this range the temperature dependences of the rate constants can be represented by k = A′ Tⁿ exp(− E′_a/RT) with A′ = (1.0 ± 0.6) · 10⁻¹⁴ cm³ s⁻¹, n = 1.13 ± 0.02, E′_a = 0.54 ± 0.05 kJ mol⁻¹ for 1-pentene: A′ = (1.3 ± 1.2) · 10⁻¹⁴ cm³ s⁻¹, n = 1.04 ± 0.08, E′_a = 0.2 ± 0.4 kJ mol⁻¹ for 1-hexene; A′ = (0.6 ± 0.6) · 10⁻¹⁴ cm³ s⁻¹, n = 1.12 ± 0.05, E′_a = − 3.8 ± 0.8 kJ mol⁻¹ for cis-2-pentene; and A′ = (0.6 ± 0.8) · 10⁻¹⁴ cm³ s⁻¹, n = 1.14 ± 0.06, E′_a = − 4.3 ± 0.5 kJ mol⁻¹ for trans-2-pentene. The atoms were generated by the H₂-laser photolysis of NO and detected by time resolved chemiluminescence in the presence of NO. The concentrations of the O(³P) atoms were kept so low that secondary reactions with products are unimportant. © 1997 John Wiley & Sons, Inc.     

Kinetic study of the ligand substitution on the trimethylplatinum(iv) complexes with unidentate ligands

Ligand substitution kinetics for the reaction [Pt^IVMe₃(X)(NN)]+NaY=[Pt^IVMe₃(Y)(NN)]+NaX, where NN=bipy or phen, X=MeO⁻, CH₃COO⁻, or HCOO⁻, and Y=SCN⁻ or N₃⁻, has been studied in methanol at various temperatures. The kinetic parameters for the reaction are as follows. The reaction of [PtMe₃(OMe)(phen)] with NaSCN: k₁=36.1±10.0 s⁻¹; ΔH₁^≠=65.9±14.2 kJ mol⁻¹; ΔS₁^≠=6±47 J mol⁻¹ K⁻¹; k₋₂=0.0355±0.0034 s⁻¹; ΔH₋₂^≠=63.8±1.1 kJ mol⁻¹; ΔS₋₂^≠=−58.8±3.6 J mol⁻¹ K⁻¹; and k₋₁/k₂=148±19. The reaction of [PtMe₃(OAc)(bipy)] with NaN₃: k₁=26.2±0.1 s⁻¹; ΔH₁^≠=60.5±6.6 kJ mol⁻¹; ΔS₁^≠=−14±22 J mol⁻¹K⁻¹; k₋₂=0.134±0.081 s⁻¹; ΔH₋₂^≠=74.1±24.3 kJ mol⁻¹; ΔS₋₂^≠=−10±82 J mol⁻¹K⁻¹; and k₋₁/k₂=0.479±0.012. The reaction of [PtMe₃(OAc)(bipy)] with NaSCN: k₁=26.4±0.3 s⁻¹; ΔH₁^≠=59.6±6.7 kJ mol⁻¹; ΔS₁^≠=−17±23 J mol⁻¹K⁻¹; k₋₂=0.174±0.200 s⁻¹; ΔH₋₂^≠=62.7±10.3 kJ mol⁻¹; ΔS₋₂^≠=−48±35 J mol⁻¹K⁻¹; and k₋₁/k₂=1.01±0.08. The reaction of [PtMe₃(OOCH)(bipy)] with NaN₃: k₁=36.8±0.3 s⁻¹; ΔH₁^≠=66.4±4.7 kJ mol⁻¹; ΔS₁^≠=7±16 J mol⁻¹K⁻¹; k₋₂=0.164±0.076 s⁻¹; ΔH₋₂^≠=47.0±18.1 kJ mol⁻¹; ΔS₋₂^≠=−101±61 J mol⁻¹ K⁻¹; and k₋₁/k₂=5.90±0.18. The reaction of [PtMe₃(OOCH)(bipy)] with NaSCN: k₁ =33.5±0.2 s⁻¹; ΔH₁^≠=58.0±0.4 kJ mol⁻¹; ΔS₁^≠=−20.5±1.6 J mol⁻¹ K⁻¹; k₋₂=0.222±0.083 s⁻¹; ΔH₋₂^≠=54.9±6.3 kJ mol⁻¹; ΔS₋₂^≠=−73.0±21.3 J mol⁻¹ K⁻¹; and k₋₁/k₂=12.0±0.3. Conditional pseudo-first-order rate constant k₀ increased linearly with the concentration of NaY, while it decreased drastically with the concentration of NaX. Some plausible mechanisms were examined, and the following mechanism was proposed. [Note to reader: Please see article pdf to view this scheme.] © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 523–532, 1998     

Kinetics and mechanism of the Cl + CO reaction in air

Long-path FTIR spectroscopy was used to study the kinetics and mechanism of the reaction of Cl atoms with CO in air. The relative rate constants at 298 K and 760 torr for the forward direction of the reaction of Cl with ¹³CO and the reaction of Cl¹³CO with O₂ were k₁ = (3.4 ± 0.8) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹ and k₂ = (4.3 ± 3.2) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹, respectively (all uncertainty limits are 2σ). The rate constant for the net loss of ¹³CO due to reaction with Cl in 1 atm of air at 298 K was k_Cl+COobs = (3.0 ± 0.6) × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹. The only observed carbon-containing product of the Cl + ¹²CO reaction was ¹²CO₂, with a yield of 109 ± 18%. Our results are in good agreement with extrapolations from previous studies. The reaction mechanism and the implications for laboratory studies and tropospheric chemistry are discussed. © 1996 John Wiley & Sons, Inc.