The
hydrolysis of CH2OO is not only a dominant sink
for the CH2OO intermediate in the atmosphere but also a
key process in the formation of aerosols. Herein, the reaction mechanism
and kinetics for the hydrolysis of CH2OO catalyzed by the
precursors of atmospheric aerosols, including H2SO4, H2SO4···H2O, and (H2SO4)2, have been studied
theoretically at the CCSD(T)-F12a/cc-pVDZ-F12//B3LYP/6-311+G(2df,2pd) level. The calculated results show
that the three catalysts decrease the energy barrier by over 10.3
kcal·mol–1; at the same time, the product formation
of HOCH2OOH is more strongly bonded to the three catalysts
than to the reactants CH2OO and H2O, revealing
that small clusters of sulfuric acid promote the hydrolysis of CH2OO both kinetically and thermodynamically. Kinetic simulations
show that the H2SO4-assisted reaction is more
favorable than the H2SO4···H2O- (the pseudo-first-order rate constant being 27.9–11.5
times larger) and (H2SO4)2- (between
2.8 × 104 and 3.4 × 105 times larger)
catalyzed reactions. Additionally, due to relatively lower concentration
of H2SO4, the hydrolysis of CH2OO
with H2SO4 cannot compete with the CH2OO + H2O or (H2O)2 reaction within
the temperature range of 280–320 K, since its pseudo-first-order
rate ratio is smaller by 4–7 or 6–8 orders of magnitude,
respectively. However, the present results provide a good example
of how small clusters of sulfuric acid catalyze the hydrolysis of
an important atmospheric species.
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