SO(2) hydrolysis: ab initio MD study of the formation of bisulfite ion

Stirling, András (2013) SO(2) hydrolysis: ab initio MD study of the formation of bisulfite ion. JOURNAL OF COMPUTER CHEMISTRY JAPAN, 12 (1). pp. 38-42. ISSN 1347-1767

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Abstract

Ab initio molecular dynamics simulations have been performed to study the dissolution of SO2 in water. It has been obtained that the hydrated SO2 is surrounded by the water molecules without any S-H hydrogen bond, restraining the sulfonate anion formation but allowing the bisulfite isomer formation. The metadynamics method has been employed to explore the free energy surface of the SO2 + H2O reaction. The simulations revealed that the hydrated SO2 forms bisulfite anion and hydronium cation after overcoming a ca. 17 kcal/mol free energy barrier. Direct, one-step H2SO3 formation could not been observed, in sharp contrast with earlier cluster calculations. These findings indicate a step-wise H2SO3 formation in water. The presence of the sulfur lone pair represents an important constraint on the mechanism: the nucleophilic H2O attack can occur only from certain angles as shown by the reactive trajectories.

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