Dimethylamine Addition to Formaldehyde Catalyzed by a Single Water Molecule: A Facile Route for Atmospheric Carbinolamine Formation and Potential Promoter of Aerosol Growth

Abstract

We use ab initio calculations to investigate the energetics and kinetics associated with carbinolamine formation resulting from the addition of dimethylamine to formaldehyde catalyzed by a single water molecule. Further, we compare the energetics for this reaction with that for the analogous reactions involving methylamine and ammonia separately. We find that the reaction barrier for the addition of these nitrogen-containing molecules onto formaldehyde decreases along the series ammonia, methylamine, and dimethylamine. Hence, starting with ammonia, the reaction barrier can be "tuned" by the substitution of an alkyl group in place of a hydrogen atom. The reaction involving dimethylamine has the lowest barrier with the transition state being 5.4 kcal/mol below the (CH3)2NH + H2CO + H2O separated reactants. This activation energy is significantly lower than that for the bare reaction occurring without water, H2CO + (CH3)2NH, which has a barrier of 20.1 kcal/mol. The negative barrier associated with the single-water molecule catalyzed reaction of dimethylamine with H2CO to form the carbinolamine (CH3)2NCH2OH suggests that this reaction should be energetically feasible under atmospheric conditions. This is confirmed by rate calculations which suggest that the reaction will be facile even in the gas phase. As amines and oxidized organics containing carbonyl functional groups are common components of secondary organic aerosols, the present finding has important implications for understanding how larger, less volatile organic compounds can be generated in the atmosphere by combining readily available smaller components as required for promoting aerosol growth.

Reactions of Criegee Intermediates are Enhanced by Hydrogen‐Atom Relay Through Molecular Design

“…DHAT reactions are important in the atmosphere, possibly participating in new particle formation . However, some atmospherically relevant DHAT reactions are too slow to be measured within laboratory time scales . Then, we have to rely on theoretical predictions.…”

Effect of Bisulfate, Ammonia, and Ammonium on the Clustering of Organic Acids and Sulfuric Acid

“…This is because bimolecular condensation reactions are very unlikely in the gas phase due to the high activation energy barriers. [65][66][67][68] This implies that the covalently-bound dimer or oligomer formation reactions could be occurring in the cluster, where other compounds, such as sulfuric acid, bases, or water, could act as the catalyst. Furthermore, if condensation reactions can take place in the cluster, the formed covalently-bound dimer very likely has a lower vapour pressure than the monomers because of a higher molecular mass and a larger number of functional groups.…”

Hydrogen bonding and orientation effects on the accommodation of methylamine at the air-water interface

“…This chemistry can explain the tendency of aged organic aerosols to form CCNs and nucleate clouds. 14 Moreover, these new carbonyl sites can accommodate additional methylamine molecules via the facile water-catalyzed addition reaction described in the recent work of Louie et al, 82 promoting aerosol growth. Given that just a single water molecule is sufficient to make this reaction cycle energetically feasible and facile, 82 this growth mechanism can occur under the conditions experienced by atmospheric aerosol.…”

“…14 Moreover, these new carbonyl sites can accommodate additional methylamine molecules via the facile water-catalyzed addition reaction described in the recent work of Louie et al, 82 promoting aerosol growth. Given that just a single water molecule is sufficient to make this reaction cycle energetically feasible and facile, 82 this growth mechanism can occur under the conditions experienced by atmospheric aerosol. Nevertheless, Figure 13 points also to the possibility of another channel with the formation of NH 2 radical and formaldehyde, which are also known to be preferentially located at the surface of liquid water.…”