Gas-phase Reactions Of NO3 Radicals Research Articles

Kinetic and Mechanistic Study of the Reactions of NO3 Radicals with Unsaturated Aldehydes: 2-Butenal, 2-Methyl-2-butenal, and 3-Methyl-2-butenal.

The kinetics and mechanisms of the gas-phase reactions of NO3 radical with two branched unsaturated aldehydes, 2-methyl-2-butenal (also called 2-methyl-crotonaldehyde) and 3-methyl-2-butenal (or 3-methyl-crotonaldehyde), have been investigated by experimental and theoretical approaches. Kinetic data were also provided, for comparison, for 2-butenal (or crotonaldehyde). Experiments were performed in a simulation chamber at 295 ± 3 K and atmospheric pressure. Rate constants were determined using both absolute and relative rate methods. Experimental results were found to be in good agreement leading to the following rate constants (in cm3 molecule-1 s-1): k(2-butenal + NO3) = (4.6 ± 1.3) × 10-15; k(2-methyl-2-butenal + NO3) = (14.0 ± 2.8) × 10-15; and k(3-methyl-2-butenal + NO3) = (19.1 ± 4.1) × 10-15. Theoretical calculations were also performed using the DFT-BH&HLYP/6-311++G(d,p) method and lead to rate constants in agreement with experiments and allow us to explore mechanisms for abstraction and addition pathways. Impact on atmospheric chemistry is discussed.

Experimental and theoretical studies on gas-phase reactions of NO3 radicals with three methoxyphenols: Guaiacol, creosol, and syringol

Methoxyphenols, lignin pyrolysis products, are major biomass combustion components and are considered potential tracers for wood smoke emissions. Their atmospheric reactivity, however, has not been well characterized. Guaiacol, creosol, and syringol are three typical methoxyphenols generated in relatively high concentrations in fresh wood smoke. In this study, the gas-phase reactions of NO3 radicals with these methoxyphenols were investigated using a laboratory-built vacuum ultraviolet photoionization gas time-of-flight mass spectrometer (VUV-GTOFMS) and off-line GC-MS. By combining experimental and theoretical methods, 4-nitroguaiacol, 6-nitroguaiacol, and 4,6-dinitroguaiacol were determined as the primary degradation products for guaiacol; similarly, 6-nitrocreosol and 3-nitrosyringol were identified for creosol and syringol, respectively. Using the relative rate method, rate constants at 298 K and 1 atm for the gas-phase reactions of guaiacol, creosol, and syringol with NO3 radicals were measured to be 3.2 × 10−12, 2.4 × 10−13, and 4.0 × 10−13 cm3 molecule−1 s−1, respectively. At a typical tropospheric concentration of NO3 radicals (5 × 108 molecule cm−3), atmospheric lifetimes for guaiacol, creosol, and syringol toward NO3 radicals were 0.2, 2.3, and 1.4 h, respectively. These results indicate that the reaction with NO3 radicals can be a major sink for methoxyphenols at night.

Theoretical study of the gas-phase reactions of NO3 radical with a series of trans-2-unsaturated aldehydes: from acrolein to trans-2-octenal.

The density functional theory with the BH&HLYP functional has been used in this work to clarify discrepancies found in the literature about the effect of the increasing carbon chain on the reactivity of trans-2-alkenals from acrolein (C3) to trans-2-octenal (C8) with nitrate radical. In this work, it was found that (i) the alkyl chain length of the unsaturated aldehydes has little or no influence on the NO3 reaction rate coefficients (ii) the abstraction of the aldehydic hydrogen from the alkenal is always dominant (83% for trans-2-butanal to trans-2-octenal). The addition channel, which mainly concerns the β addition, has a small influence (17% of the total reaction for the whole series). These results are in good agreement with the experimental studies performed by Zhao et al. in 2011 and by Kerdouci et al. in 2012. All these findings will be useful to complete or improve structure-activity relationships developed to predict the reactivity of NO3 radicals with organic compounds.

Structure–activity relationship for the gas-phase reactions of NO3 radical with organic compounds: Update and extension to aldehydes

In this work is presented an extension and an update of a recently published structure–activity relationship (SAR) for the prediction of rate constants for gas-phase reactions of VOCs with NO3 radicals (See previous version in Kerdouci et al., 2011). Such predictive tools are very useful to describe the reactivity of organic compounds in atmospheric models. This SAR is constructed on the group-additivity method and is based on a wide kinetic database for 185 organic compounds. In addition to alkanes, alkenes and saturated and unsaturated oxygenated species already included in the first version of this SAR, this extended version comprises now aldehydes and unsaturated aldehydes. Indeed, since then, new kinetic studies have been performed for alkenals which allow the parameterization of this class of compounds. In addition, since new rate constants have been measured for unsaturated ethers, the parameterization of this family of compounds has been completed. Finally, this new version of the SAR shows very good predictive capabilities with more than 90% of the experimental rate coefficients being reproduced within a factor of two.

Effect of Structure on the Rate Constants for Reaction of NO3Radicals with a Series of Linear and Branched C5−C71-Alkenes at 296 ± 2 K

Rate constants for the gas-phase reactions of NO3 radicals with 13 linear and branched C5-C7 1-alkenes, CH2═CHR, where R = alkyl, have been measured at 296 ± 2 K and atmospheric pressure of air by a relative rate method. 1-Butene was used as the reference compound, and the rate constants obtained (in units of 10(-14) cm(3) molecule(-1) s(-1)) were as follows: 1-pentene, 1.50 ± 0.07; 1-hexene, 1.80 ± 0.08; 1-heptene, 2.06 ± 0.14; 3-methyl-1-butene, 1.39 ± 0.04; 3-methyl-1-pentene, 1.39 ± 0.03; 4-methyl-1-pentene, 1.52 ± 0.04; 3,3-dimethyl-1-butene, 1.54 ± 0.03; 3-methyl-1-hexene, 1.65 ± 0.08; 4-methyl-1-hexene, 1.86 ± 0.08; 5-methyl-1-hexene, 2.14 ± 0.08; 3,3-dimethyl-1-pentene, 1.44 ± 0.07; 3,4-dimethyl-1-pentene, 1.49 ± 0.10; and 4,4-dimethyl-1-pentene, 1.37 ± 0.06; where the indicated errors are two least-squares standard deviations and do not include uncertainties in the rate constant for the reference compound 1-butene. These rate constants increase along the series 1-butene < 1-pentene < 1-hexene < 1-heptene, and this is attributed to inductive effects. For a given carbon number, the rate constants depend on the position and degree of branching, and the observed trend of measured rate constants with position and degree of branching in the alkyl substituent group R correlates well with steric hindrance as calculated by McGillen et al. ( Phys. Chem. Chem. Phys. 2008 , 10 , 1757 ).

Kinetics of the gas-phase reactions of NO3 radicals with ethyl acrylate, n-butyl acrylate, methyl methacrylate and ethyl methacrylate

Abstract The relative rate method has been used to determine the rate constants for the gas-phase reactions of NO3 radicals with a series of acrylate esters: ethyl acrylate (k1), n-butyl acrylate (k2), methyl methacrylate (k3) and ethyl methacrylate (k4) at 298 ± 1 K and 760 Torr. The obtained rate constants are k1 = (1.8 ± 0.25) × 10−16 cm3 molecule−1 s−1, k2 = (2.1 ± 0.33) × 10−16 cm3 molecule−1 s−1, k3 = (3.6 ± 1.2) × 10−15 cm3 molecule−1 s−1, k4 = (4.9 ± 1.7) × 10−15 cm3 molecule−1 s−1. The experimental rate constants are in good agreement with theoretical rate constants calculated by an algorithm of the correlation between the rate constants and the orbital energies for the reactions of unsaturated VOCs with NO3 radicals. In addition, the atmospheric lifetimes of the compound against NO3 attack are estimated and the results show that NO3 reactions contribute little to the atmospheric losses of acrylate esters except in polluted regions.

Kinetics of the Gas-Phase Reactions of OH and NO3 Radicals and O3 with Allyl Alcohol and Allyl Isocyanate

Rate constants for the gas-phase reactions of OH radical, NO(3) radical, and ozone with allyl alcohol (AAL) and allyl isocyanate (AIC) have been measured using relative rate methods at atmospheric pressure in purified air. The experimental Arrhenius expression obtained for the reaction of the OH radical with AAL is (1.68 +/- 0.89) x 10(-12) x exp(1100/T) cm(3) molecule(-1) s(-1), for T = 282-315 K; the Arrhenius expression for the reaction of OH radical with AIC is (1.94 +/- 1.04) x 10(-14) x exp(2207/T) cm(3) molecule(-1) s(-1), for T = 282-317 K, where the indicated errors are one least-squares standard deviation. All OH radical reaction rate constants have been measured relative to k(OH + alpha-pinene) and k(OH + 1,3,5-trimethylbenzene). The rate constant for the gas-phase reaction of OH radical with allyl alcohol-d(6) isotopomer (AAL-d(6)) has been measured at T = 298 K, and the value is 5.10 x 10(-11) cm(3) molecule(-1) s(-1). The kinetic isotope effect is small, with k(AAL)/k(AAL-d(6)) = 1.32. Rate constants for the gas-phase reactions of NO(3) radical with AAL [relative to k(NO(3) +methacrolein)] and O(3) [relative to k(O(3) + beta-pinene)] have been measured, and the values are 7.7 x 10(-15) cm(3) molecule(-1) s(-1) at T = 298 K and 1.6 x 10(-17) cm(3) molecule(-1) s(-1) at T = 296 K, respectively. Rate constants for the gas-phase reactions of NO(3) radical and O(3) with AIC have been measured, and the values are 9.4 x 10(-16) cm(3) molecule(-1) s(-1) at T = 299 K and 5.54 x 10(-18) cm(3) molecule(-1) s(-1) at T = 299 K, respectively. Multireference ab initio calculations at the MRMP2/6-311G(d,p) level have been carried out for reactions of OH radical with AAL and AIC. Results indicate that prereactive hydrogen bonded complexes form in the entrance channels for these reactions.

Rate constants for the gas-phase reactions of a series of alkylnaphthalenes with the nitrate radical.

Naphthalene and its methyl-, ethyl-, and dimethyl-derivatives are semivolatile polycyclic aromatic hydrocarbons expected to be in the gas phase in ambient atmospheres and are subject to nighttime degradation by gas-phase reactions with the nitrate (NO3) radical. Using a relative rate method, rate constants for the gas-phase reactions of NO3 radicals with a series of alkylnaphthalenes have been measured at 298 +/- 2 K and atmospheric pressure of air. The compounds studied were 1- and 2-methylnaphthalene (1- and 2-MN), 1- and 2-ethylnaphthalene (1- and 2-EN), and the 10 dimethylnaphthalene isomers (1,2-, 1,3-, 1,4-,1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6-, and 2,7-DMN). Sampling in Riverside, CA showed that these alkylnaphthalenes were readily detected in ambient air, with the exception of 1,8-DMN. The reactions of naphthalene and the alkylnaphthalenes with NO3 radicals proceed by initial addition of the radical to form an aromatic-NO3 adduct (with rate constant k(a)) which either decomposes back to reactants (with rate constant kb) or reacts with NO2 to form products (with rate constant k(c). Using naphthalene as the reference compound, the values of (k(a)k(c)/k(b)) obtained for the NO3 radical reactions (in units of 10(-28) cm(6) molecule(-2) S(-1), indicated errors are two least-squares standard deviations) were as follows: 1-MN, 7.15 +/- 0.37; 2-MN, 10.2 +/- 1.0; 1-EN, 9.82 +/- 0.69; 2-EN, 7.99 +/- 0.99; 1,2-DMN, 64.0 +/- 2.3; 1,3-DMN, 21.3 +/- 1.2; 1,4-DMN, 13.0 +/- 0.5; 1,5-DMN, 14.1 +/- 1.3; 1,6-DMN, 16.5 +/- 1.8; 1,7-DMN, 13.5 +/- 0.7; 1,8-DMN, 212 +/- 59; 2,3-DMN, 15.2 +/- 0.5; 2,6-DMN, 21.2 +/- 1.6; 2,7-DMN, 21.0 +/- 1.5.

Gas-phase reaction of phenol with NO3.

The fast gas-phase reaction of NO3 radicals with phenol was found to yield 2-nitrophenol as the only relevant nitration product. The yield of this product was high and independent of the concentration of NO2 at the concentrations applied. In the presence of ozone, also significant amounts of 4-nitrophenol and p-benzoquinone were formed. The rate constant of the reaction between NO3 radicals and phenol was determined to be 5.8 x 10(-12) cm3 molecule-1 s-1. The selective formation of 2-nitrophenol (2) is suggested to derive from either the concerted keto-enol tautomerism in the reaction of a phenoxy radical with NO2 or the concerted elimination of nitric acid from a cyclohexa-3,5-diene intermediate.

An Experimental Study on the Temperature Dependence for the Gas-Phase Reactions of NO3 Radical with a Series of Aliphatic Aldehydes

The absolute rate constants for the gas-phasereactions of the NO3 radical with a series ofaldehydes such as acetaldehyde, propanal, butanal,pentanal, hexanal and, heptanal were measured overthe temperature range 298–433 K, using a dischargeflow system and monitoring the NO3 radical byLaser Induced Fluorescence (LIF).The measured rate constants at 298 K for thereaction of NO3, in units of 10−14 cm3molecule−1 s−1, were as follows:acetaldehyde 0.32 ± 0.04, propanal 0.60 ± 0.06, butanal 1.46± 0.16, pentanal 1.75 ±0.06, hexanal 1.83 ± 0.36, and heptanal 2.37 ±0.42. The proposed Arrhenius expressions arek1 = (6.2 ± 7.5) × 10−11 exp[−(2826 ± 866)/T] (cm3 molecule−1s−1),k2 = (1.7 ± 1.0) × 10−11 exp[−(2250 ± 192)/T] (cm3 molecule−1s1), k3 =(7.6 ± 9.8) × 1011 exp[−(2466 ± 505)/T] (cm3 molecule−1s−1),k4 = (2.8 ± 1.4) × 10−11 exp[−(2189 ± 156)/T] (cm3 molecule−1s−1), k5 = (7.0 ± 1.8) ×10−11 exp [−(2382 ± 998)/T](cm3 molecule−1 s−1), andk6 = (7.8 ± 1.0) × 10−11 exp[−(2406 ± 481)/T](cm3 molecule−1 s−1).Tropospheric lifetimes for these aldehydes werecalculated at night and during the day for typicalNO3 and OH average concentrations and showed thatboth radicals provide an effective tropospheric sinkfor these compounds and that the night-time reactionwith the NO3 radical can be an important, if notdominant, loss process for these emitted organics andfor NO3 radicals.

Absolute Rate Coefficients for the Gas-Phase Reactions of NO3 Radical with a Series of Monoterpenes at T = 298 to 433 K

The aim of this work is to study the reactivity of some naturally emitted terpenes, 2-carene, sabinene, myrcene, α-phellandrene, d-limonene, terpinolene and γ-terpinene, towards NO3 radical to evaluate the importance of these reactions in the atmosphere and their atmospheric impact. The experiments with these monoterpenes have been carried out under second-order kinetic conditions over the range of temperature 298–433 K, using a discharge flow system and monitoring the NO3 radical by Laser Induced Fluorescence (LIF). This work is the first temperature dependence study for the reactions of the nitrate radical with the above-mentioned monoterpenes. The measured rate constants at 298 K for the reaction of NO3 with such terpenes are as follows: 2-carene, 16.6 ± 1.8, sabinene 10.7 ± 1.6, myrcene 12.8 ± 1.1, α-phellandrene 42 ± 10, d-limonene 9.4 ± 0.9, terpinolene 52 ± 9 and γ-terpinene 24 ± 7, in units of 10-12 cm3 molecule-1 s-1. The proposed Arrhenius expressions, for the reactions of NO3 with 2-carene, sabinene, myrcene and α-phellandrene are, respectively k1 = (1.4 ± 0.7) × 10-12 exp[(741 ± 190/T)] (cm3 molecule-1 s-1), k2=(2.3 ± 1.3) × 10-10 exp[−(940 ± 200/T)] (cm3 molecule-1 s-1), k3 = (2.2 ± 0.2) × 10-12 exp[(523 ± 35/T)] (cm3 molecule1 s-1) and k4 = (1.9 ± 1.3) × 10-9 exp[−(1158 ± 270/T)] (cm3 molecule-1 s-1). A decrease in the rate constants when raising the temperature has also been found for the reaction of d-limonene with NO3 while an increase in the rate constant with temperature has been observed for the reactions of terpinolene and γ-terpinene with NO3. Tropospheric half-lives for these terpenes have been calculated at night and during the day for typical NO3 and OH concentrations showing that both radicals provide an effective tropospheric sink for these compounds and that the night-time reaction with NO3 radical can be an important, if not dominant, loss process for these naturally emitted organics and for NO3 radicals.

Kinetics of the gas-phase reactions of NO3 radicals with a series of alcohols, glycol ethers, ethers and chloroalkenes

Using a relative rate method, rate constants have been measured for the gas-phase reactions of the NO3 radical with methacrolein, a series of ethers, glycol ethers, alcohols and chloroalkenes at 298 ± 2 K and atmospheric pressure of air. The rate constants determined (in units of 10−16 cm3 molecule−1 s−1) were: methacrolein, 33 ± 10; diethyl ether, 31 ± 10; di-n-propyl ether, 49 ± 16; diisopropyl ether, 40 ± 13; ethyl tert-butyl ether, 45 ± 14; 1-methoxypropan-2-ol, ⩽15 ± 5; 2-butoxyethanol, ⩽31 ± 11; propan-1-ol, ⩽21 ± 8; propan-2-ol, ⩽17 ± 6; butan-1-ol, ⩽27 ± 10; butan-2-ol, ⩽25 ± 8; heptan-4-ol, ⩽60 ± 20; cis-1,2-dichloroethene, 1.3 ± 1.3; 1,1-dichloroethene, 18-6+9; trichloroethene, 3.6-1.5+2.0; tetrachloroethene, <1.8; and 3-chloropropene, 5.8-2.0+3.0. Carbonyl products of the alcohol reactions arising after H-atom abstraction at the carbon atom to which the –OH group is attached were observed, and rate constants for this reaction pathway obtained. Significant discrepancies with the literature concern propan-2-ol, ethyl tert-butyl ether and 3-chloropropene, with our relative rate constants for these compounds being factors of ca. 2, ca. 2, and ca. 8 lower, respectively, than previously reported absolute rate constant determinations.

Gas-phase reaction of NO3 radicals with isoprene: a kinetic and mechanistic study

The gas-phase reaction of NO3 radicals with isoprene was investigated under flow conditions at 298 K in the pressure range 6.8<P(mbar)<100 using GC-MS/FID, direct MS, and long-path FT–IR spectroscopy as detection techniques. By means of a relative rate method, the rate constant for the primary attack of NO3 radicals toward isoprene was determined to be (6.86±2.60)×10−13 cm3 molecule−1 s−1. The formation of the possible oxiranes, 2-methyl-2-vinyl-oxirane and 2-(1-methyl-vinyl)-oxirane, was observed in dependence on total pressure. In the presence of O2 in the carrier gas, the product distribution was found to be strongly dependent on the reaction pathways of formed peroxy radicals. If the peroxy radicals mainly reacted in a self-reaction, the formation of organic nitrates was detected and 4-nitroxy-3-methyl-but-2-enal was identified as a main product. On the other hand, when NO was added to the gas mixture and the peroxy radicals were converted via RO2+NO→RO+NO2, the formation of methyl vinyl ketone as the main product as well as 3-methylfuran and meth-acrolein was observed. From the ratio of the product yields if NO was added to the gas mixture it was concluded that the attack of NO3 radicals predominantly takes place in the 1-position. A reaction mechanism is proposed and the application of these results to the troposphere are discussed. © 1997 John Wiley & Sons, Inc.

Products and mechanism of the gas-phase reaction of NO3 radicals with α-pinene

T. Berndt and O. Böge, J. Chem. Soc., Faraday Trans., 1997, 93, 3021 DOI: 10.1039/A702364B

FTIR studies of the NO3 initiated degradation of but-2-yne: mechanism and rate constant determination

The products and mechanism of the gas-phase reaction of NO3 radicals with but-2-yne in purified air have been investigated by FTIR spectroscopy. The experiments were carried out at 298 ± 3 K and 760 ± 5 Torr in a 250 l stainless-steel reactor in which NO3 was generated by the thermal dissociation of N2O5. Experiments with 15NO3 were also performed. Products include butadione, peroxyacetyl nitrate, ketene and acetic acid. Ketene was observed to react further with NO3 and this reaction was also investigated. The rate constants for the NO3 reaction with but-2-yne and ketene were determined by the relative-rate method as 7.0 ± 0.8 and 10.6 ± 1.3 × 10–14 cm3 molecule–1 s–1, respectively, using (E)-but-2-ene as a reference. Reaction mechanisms for the but-2-yne and the ketene degradations are proposed.

Kinetics of the gas-phase reactions of NO3 radicals and O3 with 3-methylfuran and the OH radical yield from the O3 reaction

Using relative rate methods, rate constants have been measured for the gas-phase reactions of 3-methylfuran with NO3 radicals and O3 at 296 ± 2 K and atmospheric pressure of air. The rate constants determined were (1.31 ± 0.461) × 10−11 cm3 molecule−1 s−1 for the NO3 radical reaction and (2.05 ± 0.52) × 10−17 cm3 molecule−1 s−1 for the O3 reaction, where the indicated errors include the estimated overall uncertainties in the rate constants for the reference reactions. Based on the cyclohexanone plus cyclohexanol yield in the presence of sufficient cyclohexane to scavenge > 95% of OH radicals formed, it is estimated that the O3 reaction leads to the formation of OH radicals with a yield of 0.59, uncertain to a factor of ca. 1.5. In the troposphere, 3-methylfuran will react dominantly with the OH radical during daylight hours, and with the NO3 radical during nighttime hours for nighttime NO3 radical concentrations > 107 molecule cm −3. © 1996 John Wiley & Sons, Inc.

FTIR studies of reactions between the nitrate radical and haloethenes

Products and mechanisms for the gas-phase reactions of NO3 radicals with CH2=CHCl, CH2=CCl2, CHCl=CCl2,cis-CHCl=CHCl andtrans-CHCl=CHCl in air have been studied. The experiments were carried out at 295±2 K and 740±5 Torr in a 480-L Teflon-coated reaction chamber and at 295±2 K and 760±5 Torr in a 250-L stainless steel reactor. NO3 was generated by the thermal dissociation of N2O5. Experiments with15NO3 and CD2CDCl have also been performed. The initially formed nitrate peroxynitrates decay into carbonyl compounds, nitrates, HCl and ClNO2. In adidtion, there are indications of nitrooxy acid chlorides being produced. The reactions with CH2=CCl2 and CHCl=CCl2 are more complex due to release of chlorine atoms which eventually lead to formation of chloroacid chlorides.