Room Temperature Rate Coefficients for the Reactions of OH Radicals with Some Monoethylene Glycol Monoalkyl Ethers

Abstract

Rate coefficients for the reactions of OH radicals with monoethylene glycol monoalkyl ethers have been determined by the competitive method at 297 ± 3 K. Relative to the value k OH+hexanol = 12.5 × 10-12 cm3 molecule-1 s-1, the rate coefficients are as follows (in units of 10-12 cm3 molecule-1 s-1): methoxyethanol, 10.8 ± 1.1; ethoxyethanol, 14.5 ± 0.4; propoxyethanol, 16.4 ± 0.7; butoxyethanol, 19.4 ± 2.0. In a second set of experiments relative rate coefficients were measured for the same series of glycol ethers (TST) against heptanol. In all cases the values of k TST/k heptanol divided by k TST/k hexanol yielded values of k heptanol/k hexanol consistent with our experimentally determined value of k heptanol/k hexanol = 1.24 ± 0.08. The results are discussed with respect to literature data and structure activity relationships, and the tropospheric lifetimes of the glycol ethers are estimated.

The hydroxyl radical reaction rate constant and atmospheric transformation products of 2-propoxyethanol

“…PF observation is consistent with previous studies of the hydroxyl reaction products of 2-ethoxyethyl acetate and ethyl 3-ethoxypropionate: the methylenes next to the ether oxygen are activated [4,5,10,11,21]. The PF product yield is larger than the trend expected using the data for 2-ethoxyethanol and 2-butoxyethanol that was reported by Stemmler et al [1,4]. A 43% ethyl formate yield was reported for 2-ethoxyethanol; a 35% butyl formate yield was reported for 2-butoxyethanol; while a 47% propyl formate yield was measured for 2-propoxyethanol [1,4].…”

“…Also, the similarity between the calculated versus the measured k 2PEOH supports these "reactive site" assignments. The k 2PEOH value reported in Stemmler et al [1] is somewhat smaller than the calculated value and the value reported here, but that discrepancy may be due to the OH rate constant of the reference used. The OH rate constant of 1-hexanol, the reference compound used in Stemmler et al, has been recently remeasured by Aschmann et al [25].…”

“…The PF product yield is larger than the trend expected using the data for 2-ethoxyethanol and 2-butoxyethanol that was reported by Stemmler et al [1,4]. A 43% ethyl formate yield was reported for 2-ethoxyethanol; a 35% butyl formate yield was reported for 2-butoxyethanol; while a 47% propyl formate yield was measured for 2-propoxyethanol [1,4]. The 2-ethyl-1,3-dioxolane (5.4 Ϯ 0.4%) product was observed using the GC/MS system and is formed from abstraction of methylene III.…”

“…2PEOH reacts with OH with a bimolecular rate constant of (21.4 Ϯ 6.0) ϫ 10 Ϫ12 cm 3 molecule Ϫ1 s Ϫ1 at 297 Ϯ 3 K and 1 atm total pressure, which is a little larger than previously reported [1]. Assuming an average OH concentration of 1 ϫ 10 6 molecules cm Ϫ3 , an atmospheric lifetime of 13 h is calculated for 2PEOH.…”

“…2-Propoxyethanol (2PEOH, CH 3 CH 2 CH 2 OCH 2 CH 2 (OH)) and similar compounds are present in coatings, coating removal, and cleaning formulations used by the military and by industry. While there is a single report of the hydroxyl radical rate constant for 2PEOH, there has been no previous investigation of this compound's atmospheric transformations [1]. In the work presented here, the rate constant, measured by the relative rate method [14], and the reaction products of OH/2PEOH are reported.…”