First Experimental Determination of the Absolute Gas-Phase Rate Coefficient for the Reaction of OH with 4-Hydroxy-2-Butanone (4H2B) at 294 K by Vapor Pressure Measurements of 4H2B

Abstract

The reaction of the OH radicals with 4-hydroxy-2-butanone was investigated in the gas phase using an absolute rate method at room temperature and over the pressure range 10-330 Torr in He and air as diluent gases. The rate coefficients were measured using pulsed laser photolysis (PLP) of H(2)O(2) to produce OH and laser induced fluorescence (LIF) to measure the OH temporal profile. An average value of (4.8 ± 1.2) × 10(-12) cm(3) molecule(-1) s(-1) was obtained. The OH quantum yield following the 266 nm pulsed laser photolysis of 4-hydroxy-2-butanone was measured for the first time and found to be about 0.3%. The investigated kinetic study required accurate measurements of the vapor pressure of 4-hydroxy-2-butanone, which was measured using a static apparatus. The vapor pressure was found to range from 0.056 to 7.11 Torr between 254 and 323 K. This work provides the first absolute rate coefficients for the reaction of 4-hydroxy-2-butanone with OH and the first experimental saturated vapor pressures of the studied compound below 311 K. The obtained results are compared to those of the literature and the effects of the experimental conditions on the reactivity are examined. The calculated tropospheric lifetime obtained in this work suggests that once emitted into the atmosphere, 4H2B may contribute to the photochemical pollution in a local or regional scale.

Investigation of the Gas-Phase Photolysis and Temperature-Dependent OH Reaction Kinetics of 4-Hydroxy-2-butanone

“…First, it should be stressed that the maximum 4H2B concentration used in the present work (57 ppm) is significantly lower than the saturated vapor pressure at 297 K (1900 ppm). 22 Preliminary experiments showed that no significant loss (<1% per hour) of 4H2B, acetone, formaldehyde, acetic acid, and methanol was observed for at least 8 h in the dark. Tests for possible loss of products through photolysis were carried out.…”

“…The experimental setups and the data analysis are similar to those used in previous studies 17,22 and are thus only briefly described in the following. More details can also be found in previous publications.…”

“…Vapors of 4H2B and H 2 O 2 were introduced into the cell by using a bubbler system. 22 Rate coefficients were determined under pseudo-first order conditions where the concentration of 4H2B was in large excess compared to that of OH. The concentrations of 4H2B were calculated by using the following equation: …”

“…The value obtained for 4H2B is close to those for hydroxyacetone (0.0075 h −1 ) and 3H3M2B (0.0095 h −1 ) 17 and consistent with the upper limit determined for 4-hydroxy-4-methyl-2-pentanone (<0.018 h −1 ). 19 Using the more realistic J acti atm values for the diurnal cycle 19 22 and a 24 h daytime average tropospheric OH concentration of 1 × 10 6 molecules cm −3 . 55 Thus, it is clear that reaction with OH is the dominant atmospheric loss process for 4H2B in the gas phase.…”

Reactivity of 3-hydroxy-3-methyl-2-butanone: Photolysis and OH reaction kinetics

“…For larger hydroxycarbonyls (!C 4 ), degradation pathways have not been well characterized. The few available studies indicate that saturated hydroxyketones are mainly removed by OH radicals (Aschmann et al, 2000;Magneron et al, 2003;Messaadia et al, 2012;El Dib et al, 2013;Messaadia et al, 2013;Sleiman et al, 2013). Reactivity with O 3 and NO 3 radicals is expected to be not important in the atmosphere (Calvert et al, 2011).…”