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The kinetics of the F2 reaction with thiirane (C2H4S) was studied for the first time in a flow reactor combined with mass spectrometry at a total helium pressure of 2 Torr and in the temperature range of 220 to 800 K. The rate constant of the title reaction was determined under pseudo-first-order conditions, either monitoring the kinetics of F2 or C2H4S consumption in excess of thiirane or of F2, respectively: k1 = (5.79 ± 0.17) × 10−12 exp(−(16 ± 10)/T) cm3 molecule−1 s−1 (the uncertainties represent precision of the fit at the 2σ level, with the total 2σ relative uncertainty, including statistical and systematic errors on the rate constant being 15% at all temperatures). HF and CH2CHSF were identified as primary products of the title reaction. The yield of HF was measured to be 100% (with an accuracy of 10%) across the entire temperature range of the study. Quantum computations revealed reaction enthalpies ranging from −409.9 to −509.1 kJ mol−1 for all the isomers/conformers of the products, indicating a strong exothermicity. Boltzmann relative populations were then established for different temperatures. [ABSTRACT FROM AUTHOR]

Rate coefficients, k1, for the gas‐phase OH radical reaction with the heterocyclic ether C4H4O (1,4‐epoxybuta‐1,3‐diene, furan) were measured over the temperature range 273–353 K at 760 Torr (syn. air). Experiments were performed using: (i) the photochemical smog chamber THALAMOS (thermally regulated atmospheric simulation chamber, IMT NE, Douai‐France) equipped with Fourier Transform Infrared (FTIR) and Selected Ion Flow Tube Mass Spectrometry (SIFT‐MS) detection methods and (ii) a photochemical reactor coupled with FTIR spectroscopy (PCR, University of Crete, Greece). k1(273–353 K) was measured using a relative rate (RR) method, in which the loss of furan was measured relative to the loss of reference compounds with well‐established OH reaction rate coefficients. k1(273–353 K) was found to be well represented by the Arrhenius expression (1.30 ± 0.12) × 10−11 exp[(336 ± 20)/T] cm3 molecule−1 s−1, with k1(296 K) measured to be (4.07 ± 0.32) × 10−11 cm3 molecule−1 s−1. The k1(296 K) and pre‐exponential quoted error limits are 2σ and include estimated systematic errors in the reference rate coefficients. The observed negative temperature dependence is consistent with a reaction mechanism involving the OH radical association to a furan double bond. Quantum mechanical molecular calculations show that OH addition to the α‐carbon (ΔHr(296 K) = −121.5 kJ mol−1) is thermochemically favored over the β‐carbon (ΔHr(296 K) = −52.9 kJ mol−1) addition. The OH‐furan adduct was found to be stable over the temperature range of the present measurements. Maleic anhydride (C4H2O3) was identified as a minor reaction product, 3% lower‐limit yield, demonstrating a non‐ring‐opening active reaction channel. The present results are critically compared with results from previous studies of the OH + furan reaction rate coefficient. The infrared spectrum of furan was measured as part of this study and its estimated climate metrics are reported. [ABSTRACT FROM AUTHOR]

Molecular hydrogen (H2) is now considered among the most prominent substitute for fossil fuels. The environmental impacts of a hydrogen economy have received more attention in the last years, but still, the knowledge is relatively poor. In this work, the reaction of H2 with NO3 radical (the dominant night-time detergent of the atmosphere) is studied for the first time using high-level composite G3B3 and modification of high accuracy extrapolated ab initio thermochemistry (mHEAT) methods in combination with statistical kinetics analysis using non-separable semi-classical transition state theory (SCTST). The reaction mechanism is characterized, and it is found to proceed as a direct H-abstraction process to yield HNO3 plus H atom. The reaction enthalpy is calculated to be 12.8 kJ mol−1, in excellent agreement with a benchmark active thermochemical tables (ATcT) value of 12.2 ± 0.3 kJ mol−1. The energy barrier of the title reaction was calculated to be 74.6 and 76.7 kJ mol−1 with G3B3 and mHEAT methods, respectively. The kinetics calculations with the non-separable SCTST theory give a modified-Arrhenius expression of k(T) = 10−15 × T0.7 × exp(−6120/T) (cm3 s−1) for T = 200–400 K and provide an upper limit value of 10−22 cm3 s−1 at 298 K for the reaction rate coefficient. Therefore, as compared to the main consumption pathway of H2 by OH radicals, the title reaction plays an unimportant role in H2 loss in the Earth's atmosphere and is a negligible source of HNO3. [ABSTRACT FROM AUTHOR]

Formaldehyde (FM) and glyoxal (GL) are important atmospheric species of indoor and outdoor environments. They are either directly emitted in the atmosphere or they are formed through the oxidation of organic compounds by indoor and/or outdoor atmospheric oxidants. Despite their importance, the real-time monitoring of these compounds with soft ionization mass spectrometric techniques, e.g. proton transfer mass spectrometry (PTR-MS), remains problematic and is accompanied by low sensitivity. In this study, we evaluate the performance of a multi-ion selected ion flow tube mass spectrometer (SIFT-MS) to monitor in real-time atmospherically relevant concentrations of FM and GL under controlled experimental conditions. The SIFT-MS used is operated under standard conditions (SC), as proposed by the supplier, and customized conditions (CC), to achieve higher sensitivity. In the case of FM, SIFT-MS sensitivity is marginally impacted by RH, and the detection limits achieved are below 200 ppt. Contrariwise, in the case of GL, a sharp decrease of instrument sensitivity is observed with increasing RH when the H3O+ ion is used. Nevertheless, the detection of GL using NO+ precursor ion is moderately impacted by moisture with an actual positive sensitivity response. Therefore, we recommend the use of NO+ precursor for reliable detection and quantitation of GL. This work evidences that SIFT-MS can be considered as an efficient tool to monitor the concentration of FM and GL using SIFT-MS in laboratory experiments and potentially in indoor or outdoor environments. Furthermore, SIFT-MS technology still allows great possibilities for sensitivity improvement and high potential for monitoring low proton transfer affinity compounds. [ABSTRACT FROM AUTHOR]