Influence of Nucleation Precursors on the Reaction Kinetics of Methanol with the OH Radical

The mechanism and kinetics of the reaction of methanol with the OH radical in the absence and presence of common atmospheric nucleation precursors (H2O, NH3, and H2SO4) have been investigated using different computational methods. The statistical Gibb's free energy of formation has been calculated using M06-2X/6-311++G(3df,3pd) in order to assess cluster stability. Methanol is found to have an unfavorable interaction with water and ammonia but form stable complexes with sulfuric acid. The reaction kinetics with the OH radical and methanol with or without the presence of nucleation precursors has been studied using a CCSD(T)-F12a/VDZ-F12//BH&HLYP/aug-cc-pVTZ vertical bar vertical bar Eckart methodology, and it is found that the presence of water is unlikely to change the overall reaction rate and mechanism of hydrogen abstraction from methanol. Ammonia is able to both enhance the reaction rate and change the reaction mechanism, but due to a very weak interaction with methanol, this process is unlikely to occur under atmospheric conditions. Sulfuric acid is, in contrast, found to be able to act as a stabilizing factor for methanol and is able to change the reaction mechanism. These findings show the first indications that nucleation precursors such as ammonia and sulfuric acid are able to alter the reaction mechanism of an atmospherically relevant organic compound.