The Uptake of Methyl Vinyl Ketone, Methacrolein, and 2-Methyl-3-butene-2-ol onto Sulfuric Acid Solutions

Abstract

To investigate the link between molecular structure, reactivity, and partitioning of oxygenated organic compounds in acidic aerosols, the uptake of three compounds found in the atmosphere, methyl vinyl ketone (MVK), methacrolein (MACR), and 2-methyl-3-butene-2-ol (MBO), by sulfuric acid solutions has been measured using a rotated wetted-wall reactor (RWW) coupled to a chemical ionization mass spectrometer (CIMS). MVK was found to partition reversibly into 20-75 wt % H 2 SO 4 solutions, and we report Henry's law coefficients between 20 and 7000 M atm -1 over this range. A chemical reaction for MVK was likely responsible for the uptake observed for 80-96 wt % H 2 SO 4 solutions. We derive an upper limit to the aldol self-reaction rate coefficient for MVK in 80 wt % solution of ∼3 M -1 s -1 . MACR partitioned reversibly over most of the acidity range, and in contrast to that for MVK, the Henry's law coefficient was relatively independent of H 2 SO 4 content. These differences indicate that the increase of the coefficient with acidity is likely due to the ability of the carbonyl molecule to form an enol. These results indicate that aldol condensation can be facile in concentrated sulfuric acid solutions, but it should be negligibly slow in dilute acid solutions such as tropospheric aerosols. MBO uptake could be explained by a Henry's law coefficient that decreases slightly as acid content varies from 20 to 55 wt % H 2 SO 4 ; we also measured the value in water, 70 M atm -1 at 298 K. A steady-state uptake of MBO was observed onto 40-80 wt % H 2 SO 4 solutions, a reaction product was observed, and the reaction was tentatively identified as Pinacol rearrangement. Similar rearrangements could be at the origin of some substituted oxygenated species found in atmospheric aerosols.

Fundamental Heterogeneous Reaction Chemistry Related to Secondary Organic Aerosols (SOA) in the Atmosphere

“…(87) Oligomerization proceeds by the successive addition of a β-hydroxy ketone unit: (88) Yasmeen et al (2010) reported that an aldol condensation type reaction occurs at a higher pH value than acetal formation. Such an aldol condensation reaction has also been found for methyl vinyl ketone (Nozière et al, 2006;.…”

The formation, properties and impact of secondary organic aerosol: current and emerging issues

“…In order to evaluate the potential importance of carbonyl heterogeneous chemistry and understand the reaction mechanisms of carbonyls in the aerosol phase, a range of carbonyls have been exposed to acidic sulfate either as an acidic film or a pre-existing acidic inorganic seed using either flow reactors (Jang et al, 2003a;Nozière and Riemer, 2003;Zhao et al, 2005Zhao et al, , 2006Nozière et al, 2006) or a Teflon film chamber (Jang and Kamens, 2001;Kroll et al, 2005a). The majority of studies showed that, in general, aldehydes, such as hexanal and octanal, resulted in higher aerosol yields via heterogeneous acid-catalyzed reactions than ketones such as 2-octanone and 2,4-pentanedione .…”

Secondary organic aerosol formation in cloud droplets and aqueous particles (aqSOA): a review of laboratory, field and model studies

“…While aldol condensation products (e.g. from methylglyoxal) are thermodynamically favorable (Barsanti and Pankow, 2005), both experimental and theoretical studies have shown that rate constants of aldol condensation are too low to be important for significant aqSOA formation under typical atmospheric conditions (0.074 M −1 s −1 < k aldol < 15 M −1 s −1 (Casale et al, 2007;Minerath and Elrod, 2009) Noziere et al, 2006).…”