Kinetic, Mechanistic, and Modeling Study of the OH-Radical-Initiated Oxidation of Di-n-butoxymethane (DNBM)

Abstract

FTIR product studies of the OH-radical-initiated oxidation of di-n-butoxymethane (DNBM) in the presence of NO x were performed in an indoor photoreactor and in the outdoor simulation chamber EUPHORE in Valencia, Spain. The reaction products observed in both reaction chambers were n-butoxymethyl formate (NBMF), propionaldeyhde, and di-n-butyl carbonate (DNBC). In the indoor reactor yields for NBMF and propionaldeyhde of 77 ± 15 and 78 ± 16 mol % were obtained in the system DNBM/MeONO/NO x /air/hν and 88 ± 18 and 69 ± 14 mol % in the system DNBM/H2O2/NO x /air/hν, respectively. In the outdoor chamber, yields of 80 ± 8 and 44 ± 11 mol % were obtained after sunlight irradiation of a DNBM/NO x /HONO/air mixture. For di-n-butyl carbonate (DNBC), an upper limit of ≤10 mol % was estimated for both reaction chambers. In the indoor photoreactor small amounts of n-butyl formate (NBF) and n-butoxymethyl butyrate (NBMB) were also detected with upper limits of 3 mol % for each compound. Bimolecular rate coefficients for the reactions of NBMF and DNBC with OH radicals were determined in the indoor photoreactor using the relative rate technique. Values of k OH+NBMF = (8.00 ± 0.91) × 10-12 cm3 s-1 and k OH+DNBC = (7.07 ± 1.64) × 10-12 cm3 s-1 were obtained. NBMF was synthesized and authentic samples were used for calibration. A photochemical mechanism was developed to describe the OH-initiated degradation of di-n-butoxymethane (DNBM) in the presence of NO x . The reaction scheme was tested by comparison of computer box model calculations and experimental data. Experimentally obtained and modeled concentration−time profiles for selected reactants are in excellent agreement.

Isomerization and Decomposition Reactions of Primary Alkoxy Radicals Derived from Oxygenated Solvents

“…12,24,25 Rates of decomposition reactions have been measured directly using laser-induced fluorescence to monitor the first-order rate of disappearance of alkoxy radicals produced by flash photolysis, but almost exclusively for the smaller members of the series of alkoxy radicals derived from alkanes. [26][27][28][29] Computations [30][31][32] and product yield studies [2][3][4][5][6][7][8][9][10][11]32 indicate that the activation barrier is significantly affected by the addition of functional groups.…”

“…Oxygenated organic compounds are present at high levels in the atmosphere; some of these are directly emitted from anthropogenic sources, some are biogenic, and others are atmospheric degradation products of directly emitted compounds. While there have been a number of studies of the degradation of oxygenated solvents in environmental chambers, − the absence of authentic standards for many potential products limits the knowledge that can be gained from these studies. A better understanding of the effects of oxygen-substituents on the fate of radical intermediates formed in the degradation of oxygenated compounds would help fill the gaps in our understanding of their atmospheric chemistry.…”