Trifluoroacetaldehyde aminolysis catalyzed by a single water molecule: An important sink pathway for trifluoroacetaldehyde and a potential pathway for secondary organic aerosol growth

High-level ab initio calculations and variational transition state theory with small curvature tunneling have been used to study the aminolysis of trifluoroacetaldehyde catalyzed by a single water molecule. The results of energetic studies indicate that the energy barrier of the trifluoroacetaldehyde aminolysis reaction decreases along ammonia, methylamine, and dimethylamine. A single water molecule can significantly reduce the reaction energy barrier of trifluomacetaldehyde aminolysis. In particular, the reaction involving dimethylamine has the lowest reaction energy barrier and the energy barrier is decreased to be -9.69 kcal/mol in the CF3CHO + (CH3)(2)NH + H2O reaction relative to CF3CHO, (CH3)(2)NH, and H2O separated reactants. Kinetic calculation shows that the rate coefficient of CF3CHO + (CH3)(2)NH center dot center dot center dot H2O ranges from 7.78 x 10(-13) to 4.45 x 10(-16) cm(3).molecules(-1).s(-1) at 190-350 K. Here, we find an important CF3CHO elimination pathway, which can compete with the reaction of CF3CHO + OH when the OH concentration is 10(4) molecules.cm(-3) and the dimethylamine concentration is higher than 10(9) molecules.cm(-3) in the temperature range between 240 and 330 K. In addition, once (CH3)(2)NCH(OH)CF3 is formed by the reaction of CF3CHO + (CH3)(2)NH + H2O, it will further promote the growth of secondary organic aerosols.

Automated summary

High-level ab initio calculations and variational transition state theory were used to study the aminolysis of trifluoroacetaldehyde catalyzed by a single water molecule, which significantly reduces the reaction energy barrier. Kinetic calculations showed a wide range of rate coefficients for the reaction. The study also identified a competitive elimination pathway for trifluoroacetaldehyde under certain conditions, which may lead to the growth of secondary organic aerosols.