US EPA

7715842 

Journal Article 

SN2 Reactions of N2O5 with Ions in Water: Microscopic Mechanisms, Intermediates, and Products 

Karimova, NV; Chen, J; Gord, JR; Staudt, S; Bertram, TH; Nathanson, GM; Gerber, RB 

2020 

No 

Journal of Physical Chemistry A
ISSN: 1089-5639
EISSN: 1520-5215 

Amer Chemical Soc 

United States 

124 

4 

711-720 

English 

31880456 

10.1021/acs.jpca.9b09095 

WOS:000510531200014 

Reactions of dinitrogen pentoxide (N2O5) greatly affect the concentrations of NO3, ozone, OH radicals, methane, and more. In this work, we employ ab initio molecular dynamics and other tools of computational chemistry to explore reactions of N2O5 with anions hydrated by 12 water molecules to shed light on this important class of reactions. The ions investigated are Cl-, SO42-, ClO4-, and RCOO- (R = H, CH3, C2H5). The following main results are obtained: (i) all the reactions take place by an SN2-type mechanism, with a transition state that involves a contact ion pair (NO2+NO3-) that interacts strongly with water molecules. (ii) Reactions of a solvent-separated nitronium ion (NO2+) are not observed in any of the cases. (iii) An explanation is provided for the suppression of ClNO2 formation from N2O5 reacting with salty water when sulfate or acetate ions are present, as found in recent experiments. (iv) Formation of novel intermediate species, such as (SO4NO2-) and RCOONO2, in these reactions is predicted. The results suggest atomistic-level mechanisms for the reactions studied and may be useful for the development of improved modeling of reaction kinetics in aerosol particles. 

The journal of physical chemistry. A