Rate constants for hydrogen abstraction reactions of the sulfate radical,SO4−. Alcohols

Rate constants have been determined for the reactions of SO₄^? with a series of alcohols, including hydrated formaldehyde. The SO₄^? radical was produced by the laser-flash photolysis of persulfate, S₂O₈^2?. Rate constants for the reactions of SO₄^? with alcohols range from 1.0 × 10⁷ for methanol to 3.4 × 10⁸ M^?1 s^?1 for 1-octanol. Rate constants for the reactions of SO₄^? with deuterated methanol and ethanol are lower by about a factor of 2.5. For methanol, ethanol, and 2-propanol, the temperature dependence of the rate constant was determined over the range 10–45°C.     

Reactivity of selected volatile organic compounds (VOCs) toward the sulfate radical (SO4−)

Rate constants for a series of alcohols, ethers, and esters toward the sulfate radical (SO₄^?) have been directly determined using a laser photolysis set‐up in which the radical was produced by the photodissociation of peroxodisulfate anions. The sulfate radical concentration was monitored by following its optical absorption by means of time resolved spectroscopy techniques. At room temperature the following rate constants were derived: methanol ((1.6 ± 0.2) × 10⁷ M^?1 s^?1); ethanol ((7.8 ± 1.2) × 10⁷ M^?1 s^?1); tert‐butanol ((8.9 ± 0.3) × 10⁵ M^?1 s^?1); diethyl ether ((1.8 ± 0.1) × 10⁸ M^?1 s^?1); MTBE ((3.13 ± 0.02) × 10⁷ M^?1 s^?1); tetrahydrofuran (THF) ((2.3 ± 0.2) × 10⁸ M^?1 s^?1); hydrated formaldehyde ((1.4 ± 0.2) × 10⁷ M^?1 s^?1); hydrated glyoxal ((2.4 ± 0.2) × 10⁷ M^?1 s^?1); dimethyl malonate (CH₃OC(O)CH₂C(O)OCH₃) ((1.28 ± 0.02) × 10⁶ M^?1 s^?1); and dimethyl succinate (CH₃OC(O)CH₂CH₂C(O)OCH₃) ((1.37 ± 0.08) × 10⁶ M^?1 s^?1) where the errors represent 2σ. For the two latter species, we also measured the temperature dependence of the corresponding rate constants. A correlation of these kinetics with the bond dissociation energy is also presented and discussed. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 539–547, 2001     

Flash photolysis study for reactions of NO3· with sulfur compounds in acetonitrile solution

The rate constants for the reaction of NO₃· with sulfur compounds in acetonitrile have been determined by the flash photolysis method. The rate constant for dimethyl sulfone (2.7 × 10⁴ M^?1s^?1 at ?10°C) is larger than that of the deuterium derivative, indicating that NO₃· abstracts the hydrogen atom from dimethyl sulfone. In the case of dimethyl sulfide, the rate constant was evaluated to be 1.5 × 10⁹ M^?1 s^?1 at ?10°C; the transient absorption band attributable to the cation radical was observed after the decay of NO₃·, suggesting the electron transfer reaction from the sulfide to NO₃·. For diphenyl sulfide and dimethyl disulfide, the electron transfer reactions were also confirmed. For dimethyl sulfoxide, the reaction rate constant of 1.2 × 10⁹ M^?1 s^?1 (at ?10°C) was not practically affected by the deuterium substitution, suggesting that NO₃· adds to sulfur atom forming (CH₃)₂?(O)-ONO₂. On the other hand, for diphenyl sulfoxide, the electron transfer reaction occurs. By the comparison of these rate constants in acetonitrile solution with the reported rate constants in the gas phase, the change of the reaction paths was revealed.     

Rate constants for hydrogen abstraction reactions of the sulfate radical,SO4−. Alkanes and ethers

Rate constants have been determined for the reactions of SO₄^? with a series of alkanes and ethers. The SO₄^? radical was produced by the laser-flash photolysis of persulfate, S₂O₈^2?. For methane, only an upper limit of 1 × 10⁶ M^?1 s^?1 could be determined. For ethane, propane, and 2-methylpropane, rate constants of 0.44, 4.0, and 10.5 × 10⁷ M^?1 s^?1 were found. For ethyl and n-propyl ether, rate constants of 1.3 × 10⁸ and 2.2 × 10⁸ M^?1 s^?1 were found and for 1,4-dioxane and tetrahydrofuran, rate constants of 7.2 × 10⁷ and 2.8 × 10⁸ were obtained. The reaction of SO₄^? with allyl alcohol was also studied and found to have a rate constant of 1.4 × 10⁹ M^?1 s^?1.     

Kinetics of the gas-phase reactions of NO3 radicals with a series of alkynes,haloalkenes, and α,β-unsaturated aldehydes

Rate constants for the gas-phase reactions of NO₃ radicals with a series of alkynes, haloalkenes, and α,β-unsaturated aldehydes have been determined at 298 ± 2 K using a relative rate technique. Using rate constants for the reactions of NO₃ radicals with ethene and propene of (1.1 ± 0.5) × 10^?16 cm³ molecule^?1 s^?1 and (7.5 ± 1.6) × 10^?15 cm³ molecule^?1 s^?1, respectively, the following rate constants (in units of 10^?16 cm³ molecule^?1 s^?1) were obtained: acetylene, ≤0.23; propyne, 0.94 ± 0.44; vinyl chloride, 2.3 ± 1.1; 1,1-dichloroethene, 6.6 ± 3.1; cis-1,2-dichloroethene, 0.75 ± 0.35; trans-1,2-dichloroethene, 0.57 ± 0.27; trichloroethene, 1.5 ± 0.7; tetrachloroethene, <0.4; allyl chloride, 2.9 ± 1.3; acrolein, 5.9 ± 2.8; and crotonaldehyde, 41 ± 9. The atmospheric implications of these data are discussed.     

Kinetics of the gas-phase reactions of β-phellandrene with OH and NO3 radicals and O3 at 297 ± 2 K

Rate constants for the gas-phase reactions of the biogenically emitted monoterpene β-phellandrene with OH and NO₃ radicals and O₃ have been measured at 297 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm³ molecule^?1 s^?1 units): for reaction with the OH radical, (1.68 ± 0.41) × 10^?10; for reaction with the NO₃ radical, (7.96 ± 2.82) × 10^?12; and for reaction with O₃, (4.77 ± 1.23) × 10^?17, where the error limits include the estimated uncertainties in the reference reaction rate constants. Using these rate constants, the lifetime of β-phellandrene in the lower troposphere due to reaction with these species is calculated to be in the range of ca. 1–8 h, with the OH radical reaction being expected to dominate over the O₃ reaction as a loss process for β-phellandrene during daylight hours.     

Rate constants for some hydrogen abstraction reactions of the carbonate radical

Rate constants have been measured in aqueous solutions for the reactions of the carbonate radical, CO₃^˙?, with several saturated alcohols and one cyclic ether as a function of temperature. Arrhenius pre-exponential factors ranged from 2×10⁸ to 1×10⁹ ?? mol^?1 s^?1 and activation energies ranged from 16 to 29 kJ mol^?1. The results suggest that the reactions are not pure hydrogen abstraction, but involve an additional interaction of the radical with the ? OH or ? O? linkage. © 1993 John Wiley & Sons, Inc.     

Effects of ring strain on gas-phase rate constants. 3. NO3 radical reactions with cycloalkenes

Rate constants for the gas-phase reactions of NO₃ radicals with a series of cycloalkenes have been determined at 298 ± 2 K, using a relative rate technique. Using an equilibrium constant for the NO₂ + NO₃ ? N₂O₅ reactions of 3.4 × 10^?11 cm³ molecule^?1, the following rate constants (in units of 10^?13 cm³ molecule^?1 s^?1) were obtained: cyclopentene, 4.52 ± 0.52; cycloheptene, 4.71 ± 0.56; bicyclo[2.2.1]-2-heptene, 2.41 ± 0.28; bicyclo[2.2.2]-2-octene, 1.41 ± 0.17; bicyclo[2.2.1]-2,5-heptadiene, 9.92 ± 1.13; and 1,3,5-cycloheptatriene, 12.6 ± 2.9. When combined with previous literature rate constants for cyclohexene and 1,4-cyclohexadiene, these data show that the rate constants for the nonconjugated cycloalkenes studied depend to a first approximation on the number of double bonds and the degree and configuration of substitution per double bond. No obvious effects of ring strain energy on these NO₃ radical addition rate constants were observed. Our previous a priori predictive techniques for the alkenes and cycloalkenes can now be extended to strained cycloalkenes.     

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     

Hydroxyl radical reactions with halogenated ethanols in aqueous solution: Kinetics and thermochemistry

Laser flash photolysis combined with competition kinetics with SCN^? as the reference substance has been used to determine the rate constants of OH radicals with three fluorinated and three chlorinated ethanols in water as a function of temperature. The following Arrhenius expressions have been obtained for the reactions of OH radicals with (1) 2‐fluoroethanol, k₁(T) = (5.7 ± 0.8) × 10¹¹ exp((?2047 ± 1202)/T) M^?1 s^?1, (2) 2,2‐difluoroethanol, k₂(T) = (4.5 ± 0.5) × 10⁹ exp((?855 ± 796)/T) M^?1 s^?1, (3) 2,2,2‐trifluoroethanol, k₃(T) = (2.0 ± 0.1) × 10¹¹ exp((?2400 ± 790)/T) M^?1 s^?1, (4) 2‐chloroethanol, k₄(T) = (3.0 ± 0.2) × 10¹⁰ exp((?1067 ± 440)/T) M^?1 s^?1, (5) 2, 2‐dichloroethanol, k₅(T) = (2.1 ± 0.2) × 10¹⁰ exp((?1179 ± 517)/T) M^?1 s^?1, and (6) 2,2,2‐trichloroethanol, k₆(T) = (1.6 ± 0.1) × 10¹⁰ exp((?1237 ± 550)/T) M^?1 s^?1. All experiments were carried out at temperatures between 288 and 328 K and at pH = 5.5–6.5. This set of compounds has been chosen for a detailed study because of their possible environmental impact as alternatives to chlorofluorocarbon and hydrogen‐containing chlorofluorocarbon compounds in the case of the fluorinated alcohols and due to the demonstrated toxicity when chlorinated alcohols are considered. The observed rate constants and derived activation energies of the reactions are correlated with the corresponding bond dissociation energy (BDE) and ionization potential (IP), where the BDEs and IPs of the chlorinated ethanols have been calculated using quantum mechanical calculations. The errors stated in this study are statistical errors for a confidence interval of 95%. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 174–188, 2008     

Fast formation of aromatic cations in cyclohexane observed by pulse radiolysis

The fast formation of cations of benzophenone, biphenyl, naphthalene, anthracene and phenanthrene in liquid cyclohexane was studied by nanosecond pulse radiolysis. Rate constants between 2.3 × 10¹⁰ M^?1 s^?1 (for naphthalene) and not below 2.5 × 10¹² M^?1 s^?1 (for benzophenone) were derived and compared with the corresponding rate constants for anion formation.     

Rate constants for the gas-phase reactions of O3 with a series of carbonyls at 296 K

Rate constants for the gas-phase reactions of O₃ with the carbonyls acrolein, crotonaldehyde, methacrolein, methylvinylketone, 3-penten-2-one, 2-cyclohexen-1-one, acetaldehyde, and methylglyoxal have been determined at 296 ± 2 K. The rate constants ranged from <6 × 10^?21 cm³ molecule^?1 s^?1 for acetaldehyde to 2.13 × 10^?17 cm³ molecule^?1 s^?1 for 3-penten-2-one. The substituent effects of ? CHO and CH₃CO? groups on the rate constants are assessed and discussed, as are implications for the atmospheric chemistry of the natural hydrocarbon isoprene.     

Rate constants for the gas-phase reactions of cis-3-Hexen-1-ol,cis-3-Hexenylacetate,trans-2-Hexenal,and Linalool with OH and NO3 radicals and O3 at 296 ± 2 K,and OH radical formation yields from the O3 reactions

Rate constants for the gas-phase reactions of the four oxygenated biogenic organic compounds cis-3-hexen-1-ol, cis-3-hexenylacetate, trans-2-hexenal, and linalool with OH radicals, NO₃ radicals, and O₃ have been determined at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm³ molecule^?1 s^?1 units): cis-3-hexen-1-ol: (1.08 ± 0.22) × 10^?10 for reaction with the OH radical; (2.72 ± 0.83) × 10^?13 for reaction with the NO₃ radical; and (6.4 ± 1.7) × 10^?17 for reaction with O₃; cis-3-hexenylacetate: (7.84 ± 1.64) × 10^?11 for reaction with the OH radical; (2.46 ± 0.75) × 10^?13 for reaction with the NO₃ radical; and (5.4 ± 1.4) × 10^?17 for reaction with O₃; trans-2-hexenal: (4.41 ± 0.94) × 10^?11 for reaction with the OH radical; (1.21 ± 0.44) × 10^?14 for reaction with the NO₃ radical; and (2.0 ± 1.0) × 10^?18 for reaction with O₃; and linalool: (1.59 ± 0.40) × 10^?10 for reaction with the OH radical; (1.12 ± 0.40) × 10^?11 for reaction with the NO₃ radical; and (4.3 ± 1.6) × 10^?16 for reaction with O₃. Combining these rate constants with estimated ambient tropospheric concentrations of OH radicals, NO₃ radicals, and O₃ results in calculated tropospheric lifetimes of these oxygenated organic compounds of a few hours. © 1995 John Wiley & Sons, Inc.     

Gas phase reaction of NO2 with alkenes and dialkenes

The kinetics of the gas phase reactions of NO₂ with a series of organics have been studied at 295 ± 2 K. It was observed that only 2,3-dimethyl-2-butene and the conjugated dialkenes studied reacted at observable rates, with rate constants which ranged from 1.5 × 10^?20 cm³ molecule^?1 s^?1 for 2,3-dimethyl-2-butene to 1.3 × 10^?17 cm³ molecule^?1 s^?1 for α-phellandrene. These rate constants are compared with the available literature data and the mechanisms of these reactions are discussed.     

Rate constants for reactions of SO4˙− radicals in acetonitrile

Rate constants have been measured for the reactions of the sulfate radical, SO₄^˙?, with alkanes, alkenes, alcohols, ethers, and amines in 95% acetonitrile solution. The rate constants were in the range of 10⁶ L mol^?1 s^?1 for the abstraction reactions and 10⁷?10⁹ L mol^?1 s^?1 for the addition and electron transfer reactions. These values are 20 to 80 times lower than those measured in aqueous solutions. Furthermore, the rate constants for the reactions of SO₄^˙? with the primary alcohols increase with the number of carbon atoms and then level off, in contrast to the behavior observed in aqueous solution, where the rate constant increases more sharply for the larger alcohols. © 1993 John Wiley & Sons, Inc.     

Kinetics of the reactions of acenaphthene and acenaphthylene and structurally-related aromatic compounds with OH and NO3 radicals,N2O5 and O3 at 296 ± 2 K

The kinetics of the atmospherically important gas-phase reactions of acenaphthene and acenaphthylene with OH and NO₃ radicals, O₃ and N₂O₅ have been investigated at 296 ± 2 K. In addition, rate constants have been determined for the reactions of OH and NO₃ radicals with tetralin and styrene, and for the reactions of NO₃ radicals and/or N₂O₅ with naphthalene, 1- and 2-methylnaphthalene, 2,3-dimethylnaphthalene, toluene, toluene-α,α,α-d₃ and toluene-d₈. The rate constants obtained (in cm³ molecule^?1 s^?1 units) at 296 ± 2 K were: for the reactions of O₃; acenaphthene, <5 × 10^?19 and acenaphthylene, ca. 5.5 × 10^?16; for the OH radical reactions (determined using a relative rate method); acenaphthene, (1.03 ± 0.13) × 10^?10; acenaphthylene, (1.10 ± 0.11) × 10^?10; tetralin, (3.43 ± 0.06) × 10^?11 and styrene, (5.87 ± 0.15) × 10^?11; for the reactions of NO₃ (also determined using a relative rate method); acenaphthene, (4.6 ± 2.6) × 10^?13; acenaphthylene, (5.4 ± 0.8) × 10^?12; tetralin, (8.6 ± 1.3) × 10^?15; styrene, (1.51 ± 0.20) × 10^?13; toluene, (7.8 ± 1.5) × 10^?17; toluene-α,α,α-d₃, (3.8 ± 0.9) × 10^?17 and toluene-d₈, (3.4 ± 1.9) × 10^?17. The aromatic compounds which were observed to react with N₂O₅ and the rate constants derived were (in cm³ molecule^?1 s^?1 units): acenaphthene, 5.5 × 10^?17; naphthalene, 1.1 × 10^?17; 1-methylnaphthalene, 2.3 × 10^?17; 2-methylnaphthalene, 3.6 × 10^?17 and 2,3-dimethylnaphthalene, 5.3 × 10^?17. These data for naphthylene and the alkylnaphthalenes are in good agreement with our previous absolute and relative N₂O₅ reaction rate constants, and show that the NO₃ radical reactions with aromatic compounds proceed by overall H-atom abstraction from substituent-XH bonds (where X = C or O), or by NO₃ radical addition to unsaturated substituent groups while the N₂O₅ reactions only occur for aromatic compounds containing two or more fused six-membered aromatic rings.     

Kinetics of the reactions Br + NO2 + M and I + NO2+ M

The reactions Br + NO₂ + M → BrNO₂ + M (1) and I + NO₂ + M → INO₂ + M (2) have been studied at low pressure (0.6-2.2 torr) at room temperature and with helium as the third body by the discharge-flow technique with EPR and mass spectrometric analysis of the species. The following third order rate constants were found k₁₍₀₎ = (3.7 ± 0.7) × 10^?31 and k₂₍₀₎ = (0.95 ± 0.35) × 10^?31 (units are cm⁶ molecule^?2 s^?1). The secondary reactions X + XNO₂ → X₂ + NO₂ (X = Br, I) have been studied by mass spectrometry and their rate constants have been estimated from product analysis and computer modeling.     

Gas-phase reactions of azulene with OH and NO3 radicals and O3 at 298 ± 2 K

Azulene, which is isomeric with naphthalene, was studied to determine whether it behaves like a polycyclic aromatic hydrocarbon or an alkene in its gas-phase reactions with OH and NO₃ radicals and O₃. Using relative rate methods, rate constants for the reactions of azulene with OH and NO₃ radicals and O₃ of (2.73 ± 0.56) × 10^?10 cm³ molecule^?1 s^?1, (3.9) × 10^?10 cm³ molecule^?1 s^?1, and <7 × 10^?17 cm³ molecule^?1 s^?1, respectively, were obtained at 298 ± 2 K. The observation that the NO₃ radical reaction did not involve NO₂ in the rate determining step indicates that azulene behaves more like an alkene than a polycyclic aromatic hydrocarbon in this reaction. No conclusive evidence for the formation of nitroazulene(s) from either the OH or NO₃ radical-initiated reaction of azulene (in the presence of NO_x) was obtained.     

Rate constants for the reactions of conjugated olefins with NO2 in the gas phase

Gas-phase rate constants for the reaction of NO₂ with 16 conjugated olefins were determined at room temperature by either conventional methods for bimolecular processes or by competitive reactions. It was found that the rate constants for conjugated olefins were larger than those for simple mono-olefins by factors of 10³–10⁴. Temperature dependence studies reveal that the difference in the rate constants for the two types of reactions can primarily be attributed to differences in their activation energies: k_{1,3-cyclohexadiene} = 5.8 × 10^?14 exp[?(6.1 ± 1.6)/RT] cm³ molecule^?1 s^?1; k_cis-2-butene = 4.68 × 10^?14 exp(?11.2/RT) cm³ molecule^?1 s^?1 [2]. A linear free energy relationship between the reactions of OH and NO₂ with conjugated diolefins was observed.     

Kinetics of the gas-phase reactions of NO3 radicals with a series of aromatics at 296 ± 2 K

Rate constants have been determined at 296 ± 2 K for the gas phase reaction of NO₃ radicals with a series of aromatics using a relative rate technique. The rate constants obtained (in cm³ molecule^?1 s^?1 units) were: benzene, <2.3 × 10^?17; toluene, (1.8 ± 1.0) × 10^?17; o? xylene, (1.1 ± 0.5) × 10^?16; m? xylene, (7.1 ± 3.4) × 10^?17; p? xylene, (1.4 ± 0.6) × 10^?16; 1,2,3-trimethylbenzene, (5,6 ± 2.6) × 10^?16; 1,2,4-trimethylbenzene (5.4 - 2.5) × 10^?16; 1,3,5-trimethylbenzene, (2.4 ± 1.1) × 10^?16; phenol, (2.1 ± 0.5) × 10^?12; methoxybenzene, (5.0 ± 2.8) × 10^?17; o-cresol, (1.20 ± 0.34) × 10^?11; m-cresol, (9.2 ± 2.4) × 10^?12; p-cresol, (1.27 ± 0.36) × 10^?11; and benzaldehyde, (1.13 ± 0.25) × 10^?15. These kinetic data, together with, in the case of phenol, product data, suggest that these reactions proceed via H-atom abstraction from the substituent groups. The magnitude of the rate constants for the hydroxy-substituted aromatics indicates that the nighttime reaction of NO₃ radicals with these aromatics can be an important loss process for both NO₃ radicals and these organics, as well as being a possible source of nitric acid, a key component of acid deposition.