An unexpected feasible route for the formation of organosulfates by the gas phase reaction of sulfuric acid with acetaldehyde catalyzed by dimethylamine in the atmosphere

Abstract

An understanding of the formation of organosulfates is required for elucidating the formation of secondary organic aerosols in atmosphere. Herein, we report a new feasible reaction pathway for the formation of organosulfates in the reaction of sulfuric acid (H₂SO₄) with acetaldehyde (CH₃CHO) catalyzed by dimethylamine ((CH₃)₂NH) using quantum chemical methods and reaction rate theory. We found that dimethylamine has a strong catalytic effect in the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction because the energy barriers of the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction are reduced by 18.28–23.08 kcal mol⁻¹ as compared to the CH₃CHO + H₂SO₄ reaction. The calculated results show that the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction can compete well with the traditional sink for CH₃CHO by hydroxyl radicals (OH), when the OH, H₂SO₄, and (CH₃)₂NH concentrations are 10⁴ molecules per cm³ during the night and 1.0 × 10⁶ and 3.2 × 10⁹ molecules per cm³ at below 240 K, respectively. The calculated results also show that the CH₃CHO + H₂SO₄ + (CH₃)₂NH reaction makes a limited contribution to the sink for sulfuric acid in the atmosphere. The present findings provide a new insight into the generation of organosulfates, which could be extended to other aldehydes with sulfuric acid catalyzed by amines in the atmosphere.