Kinetics of the Reactions of NO₃ Radical with Methacrylate Esters

Abstract

Two different experimental methods (relative rate and absolute rate methods) were used to measure the rate coefficients for the reactions of NO radical with six methacrylate esters: methyl methacrylate (MMA, k), ethyl methacrylate (EMA, k), propyl methacrylate (PMA, k), isopropyl methacrylate (IPMA, k), butyl methacrylate (BMA, k), and isobutyl methacrylate (IBMA, k). In the relative rate method, the loss of the esters relative to that of a reference compound was followed in a 7300 L Teflon-walled chamber at 298 ± 2 K and 1000 ± 5 hpa. In the absolute method, the temporal profiles of NO and NO were followed by using a dual channel cavity ring-down spectrometer in the presence of an excess of ester in the 7300 L chamber. The rate coefficients from these two methods (weighted averages) in the units of 10 cm molecule s at 298 K are k = 2.98 ± 0.35, k = 4.67 ± 0.49, k = 5.23 ± 0.60, k = 7.9 ± 1.0, k = 5.91 ± 0.58, and k = 6.24 ± 0.66. The quoted uncertainties are at the 2σ level and include estimated systematic errors. Unweighted averages are also reported. In addition, the rate coefficient k for the reaction of NO radical with deuterated methyl methacrylate (MMA-d) was measured by using the relative rate method to be essentially the same as k. The trends in the measured rate coefficient with the length and nature of the alkyl group, along with the equivalence of k and k, strongly suggest that the reaction of NO with the methacrylate esters proceeds via addition to the double bond on the methacrylate group. The present results are compared with those from previous studies. Using the measured values of the rate coefficients, along with those for reactions of these esters with OH, O, and chlorine atoms, we calculated the atmospheric lifetimes of methacrylate esters. We suggest that NO radicals do contribute to the atmospheric loss of these unsaturated esters, but to a lesser extent than their reactions with OH and O.

Rate coefficients for the reactions of OH radical and ozone with a series of unsaturated esters

“…The room-temperature rate coefficients obtained in this work and from the literatures (unit in cm 3 molecule -1 s -1 ) were used to conduct the calculations: kOH_MMA = 4.24×10 -11 , kOH_EMA = 4.99×10 -11 , kOH_nPMA = 4.86×10 -11 , kOH_nBMA = 5.26×10 -11 , kOH_iPMA = 5.36×10 -11 , kOH_iBMA = 5.27×10 -11 , kO3_MMA = 6.63×10 -18 , kO3_EMA = 7.74×10 -18 , kO3_nPMA = 8.46×10 -18 , kO3_nBMA = 9.78×10 -18 , kO3_iPMA = 10.94×10 -18 , kO3_iBMA = 9.96×10 -18 , kCl_MMA = 2.82×10 -10 (Blanco et al, 2009b), kCl_EMA = 2.71×10 -10 (Martin Porrero et al, 2010), kCl_nBMA = 3.72×10 -10 (Blanco et al, 2009b;Martin Porrero et al, 2010). kNO3_MMA = 2.98×10 -15 , k NO3_EMA = 4.67×10 -15 , kNO3_nPMA = 5.23×10 -15 , kNO3_nBMA = 7.91×10 -15 , kNO3_iPMA = 5.91×10 -15 , kNO3_iBMA = 6.24×10 -15 extracted from study of Zhou et al (2017).…”

“…It is important to point out that O3 could have also an important contribution to the loss of the unsaturated ester during the nighttime. Zhou et al (2017) have reported the tropospheric lifetimes of the studied species with respect to NO3 reactions (occurring mainly at nighttime) using the rate coefficients they have measured and [NO3] = 5 × 10 8 molecule cm -3 (Shu and Atkinson, 1995). The calculated lifetimes ranges from 70 to 186 hrs.…”

“…Once released into the troposphere, the unsaturated esters will be subject to photodegradation mainly through reaction with OH radicals during the day-time (Blanco et al, 2009a;Blanco et al, 2006) and to a lesser extent with NO3 radicals during the nighttime (Zhou et al, 2017) and ozone during both day and night-time (Bernard et al, 2010;Gai et al, 2009;Gaona Colmán et al, 2013) and Cl atoms in certain environments such as marine area (Blanco et al, 2009b;Martin Porrero et al, 2010). Knowledge of the rate coefficients for the unsaturated esters reactions with tropospheric reactive species, as well as the degradation mechanisms are required to estimate their persistence and fate in the atmosphere.…”

Kinetics of the reactions of NO3 radical with alkanes

“…The experimental set up and the procedure used has been described in detail in a previous publication. 8 The rate coefficients for reactions (1-8) were measured by following the temporal profiles of NO3 and N2O5 in an excess of each alkane. The concentrations of NO3 and N2O5 were both measured via cavity ring down spectroscopy.…”

Catalyst‐free Azo‐arylation of Arenes/Heteroarenes at Room Temperature

“…[5] Azo dyes are widely used in textiles, leather articles, and food industries. [6] Recently, heteroaromatic scaffolds were considered to broaden their range of azo dye properties including azopyrimidine, [7] azopyridines, [8][9] azopyrroles, [10] azoimidazole, [11][12][13][14][15] azopyrazoles [16][17][18] and azoindazole scaffold. [19] They were used as photodissociable ligands in molecular switches and machines owing to their light driven cis/trans isomerisation.…”