Effect of a single water molecule on CH2OH + 3O2 reaction under atmospheric and combustion conditions

The hydroxymethyl (CH2OH) radical is an important intermediate species in both atmosphere and combustion reaction systems. The rate coefficients for CH2OH + O-3(2) and (CH2OH + O-3(2) (+H2O)) reactions were calculated using the Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation (ME) simulation and canonical variational transition state theory (CVT) between the temperature range of 200 to 1500 K based on the potential energy surface constructed using CCSD(T)//omega B97XD/6-311++G(3df,3pd). The results show that CH2OH + O-3(2) leads to the formation of CH2O and HO2 at temperatures below 800 K, and goes back to reactants at high temperature (>1000 K). When a water molecule is added to the reaction, the formation of CH2O and HO2 is favored at all temperatures. The calculated rate coefficient for the CH2OH + O-3(2) (2.8 x 10(-11) cm(3) molecule(-1) s(-1) at 298 K) is in good agreement with the previous experimental values (similar to 1 x 10(-11) cm(3) molecule(-1) s(-1) at 298 K). The rate coefficients for the water-assisted reaction (2.4 x 10(-16) cm(3) molecule(-1) s(-1) at 1000 K) is at least 3-4 orders of magnitude smaller than the water-free reaction (6.2 x 10(-12) cm(3) molecule(-1) s(-1) at 1000 K). This result is consistent with the similar types of reaction system. Our calculations also predict that the effect of a single water molecule favors the formation of CH2O in the combustion condition. However, the water-free reaction favors the formation of CH2O in the atmospheric condition. The current study helps to understand how a single water molecule changes the reaction mechanism and chemical kinetic behaviour under atmospheric and combustion conditions.

Automated summary

This study investigated the rate coefficients of CH2OH reacting with O3 and found that the presence of a water molecule affects the product distribution. The calculated rate coefficients were consistent with experimental values and revealed the impact of a water molecule on the reaction mechanism.