Catalytic influence of water and formic acid molecules on hydration of methylglyoxal in atmosphere

Abstract

The hydration of methylglyoxal [CH3C(O)CHO, MG] in the atmospheric condition has been explored at the CBS-QB3 level of theory. Special attention was paid to the influence of additional water and formic acid molecules. The calculated results show that the reaction of MG with water could take place through the water-mediated keto-enol isomerization mechanism, in contrast to the previously proposed addition mechanism producing germinal diol. The enol products of the former mechanism are vital for the oligomerization of MG which is the critical process of secondary organic aerosols (SOA) formation initiated by MG. On the other hand, the catalytic effects of additional water and formic acid molecules are significant, although the hydration mechanism is favored over the water-mediated keto-enol isomerization. Moreover, the catalytic effect of formic acid is much more effective than that of water molecules. The present study provides fundamental mechanism framework for the hydration of MG in atmosphere, which is of great of significance to understand the atmospheric chemistry of MG.