Theoretical Study Of The Hydrolysis Of HOSO+NO₂ As A Source Of Atmospheric HONO:Effects Of H₂O Or NH₃

The reaction of HOSO+NO₂ is a source of t-HONO and SO₂, the role of water in the hydrolysis reaction of HOSO+NO₂ is concerned. This paper further studies the effects of water or ammonia molecules on the hydrolysis reaction of HOSO+NO₂. The main research contents are as follows:First, the water molecule in the hydrolysis reaction of HOSO+NO₂ not only acts as a catalyst giving the products of t-HONO+SO₂, but also as a reactant giving the products of t-HONO+H₂SO₃, c-HONO+H₂SO₃ and HNO₃+t-S?OH?2. The characteristics of the main paths were obtained. For the reaction of HOSO+NO₂+H₂O, the main reaction paths 2,7, and 9 are further investigated with an additional water or ammonia molecule.Second, the CBS-QB3 calculation result shows that the process of HOS?O?NO₂-H₂O? t-HONO-SO₂-H₂O is favorable with barrier 0.1 kcal mol-1. Though the following process of t-HONO-SO₂-H₂O?t-HONO-H₂SO₃ is unfavorable with barrier 33.6 kcal mol-1, the barrier is reduced by 17.3 or 26.3 kcal mol-1 with an additional water or ammonia molecule. To the path 7 and path 9, the energy barrier is reduced by 8.9 and 8.5 kcal mol-1 with an additional water molecule ?by 9.9 and 9.2 kcal mol-1 with an additional ammonia molecule?. For assist of HOSO+NO₂+H₂O reaction, the ammonia molecule shows more beneficial than water molecule.Third, three t-HONO-H₂SO₃ isomers which contain double intermolecular hydrogen bonds are studied by frequency and natural bond orbital calculations. Frequency calculation shows that all hydrogen bonds exhibit an obvious red shift. And the larger second-order stabilization energies are consistent with the shorter hydrogen bonds. H₂SO₃ can promote the process of t-HONO?c-HONO, and make the barrier reduced by 45.2 kcal mol-1. The product NH3-H₂SO₃ can further form larger cluster ?NH3-H₂SO₃?n ?n=2,4? including NH₄+HSO₃- ion pairs.