Rate Coefficients For The Oh + Hc(O)C(O)H (Glyoxal) Reaction Between 210 And 390 K
...Glyoxal, HC(O)C(O)H, the simplest R-dicarbonyl, is a stable
end-product formed in the atmospheric oxidation of a number
biogenic and anthropogenic volatile organic compounds (VOCs),
including isoprene1 and terpenoids.2-5 Satellite-based measurements
of glyoxal in the atmosphere suggest that the oxidation
of biogenic VOCs in tropical regions is an important source of
glyoxal globally.6 Glyoxal serves as a marker for “hot spots”
of atmospheric organic chemistry, in part because it is a
significant oxidation product of a variety of organic compounds.
6,7 The atmospheric processing of glyoxal also represents
a significant source of HOx (HOx ) OH + HO2),8 and it has
been suggested that glyoxal may play a role in secondary organic
aerosol (SOA) formation.9-11
The atmospheric lifetime of glyoxal is relatively short, on
the order of hours, and is primarily determined by its reaction
with the OH radical7,8,12
and by UV photolysis13
Deposition, uptake onto existing aerosol (SOA formation), and
gas-phase reaction with the NO3 radical are additional possible
loss processes for glyoxal. Despite the atmospheric importance
of glyoxal and its molecular simplicity, only one experimental
determination of the rate coefficient for reaction 1, k1, has been
reported in the literature to date; Plum et al.12 used a relative
rate method and reported k1(296 K) ) (1.06 ( 0.4) 10-11
cm3 molecule-1 s-1. This k1(296 K) value is in poor agreement
with the rate coefficient estimated using the structure-activity
relationships (SAR) developed by Kwok and Atkinson,14 2.5
10-11 cm3 molecule-1 s-1. The JPL15 and IUPAC16 kinetic
data evaluations currently recommend the rate coefficient
reported by Plum et al. but include large estimated uncertainties,
f(298 K) ) 1.5 and ¢log(k1) ) 0.4, respectively, due to the
lack of corroborative data. There are presently no...
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