Theoretical study on the water-catalyzed reaction of glyoxal with OH radical

Single water-molecule catalysis in the glyoxal + OH reaction under tropospheric conditions: Fact or fiction? A quantum chemistry and pseudo-second order computational kinetic study

“…[14]) by the fraction of glyoxal that is complexed: this fraction is simply K eq0 [water], which is equal to 0.0000171 for complex c-1, 0.0000327 for complex c-2 and 0.0001 for complex c-3 at 298 K. The latter approach allows us to make a direct comparison between the present result and similar calculations in which Step 0 was ignored. From Table 3, it can be seen that, if Step 0 is ignored, reaction of the glyoxal-water complex with OH is approximately 27 times (path 1) and 11 times (path 2) faster that the corresponding reaction for free glyoxal + OH.…”

“…The transition structures TS-1 and TS-2 were proposed in Ref. [14]. Starting from the new pre-reactive complex RC-3, we have identified two different off-plane H-abstraction transition structures, TS-3a and TS-3b.…”

“…The potential energy surface has been carefully searched, and a new stable complex (c-3) was found in addition to c-1 and c-2 proposed in Ref. [14]. These structures are shown in Figure 1.…”

“…The reaction of OH with glyoxal bound to a single water molecule has been studied by Long et al [14] using quantum chemistry methods. The authors found that the transition state energy for abstraction of a glyoxal hydrogen atom decreases in the presence of a single water molecule due to the formation of stabilizing hydrogen bonds, thus appearing to enhance the rate constant of the glyoxal + OH reaction.…”

Reactivity Trends in Radical-Molecule Tropospheric Reactions - A Quantum Chemistry and Computational Kinetics Approach

“…There has also been considerable speculation about the role of water complexes and other hydrogen-bonded molecular complexes on the kinetics and dynamics of gas-phase free radical reactions (Luo et al 2009;Long et al 2010). A field measurement in the near-infrared has revealed a relatively high concentration of 6 x 10 14 molecule cm -3 of water dimer in the atmosphere (Pfeilsticker et al 2003).…”