Theoretical Study of Formic Acid−Sulfur Dioxide Dimers

Abstract

We report the first theoretical study of noncovalent and covalent interactions in formic acid (FA)-SO(2) complexes. Using ab initio and DFT model chemistries, five stable noncovalent complexes were identified, as well as a covalent adduct, formic sulfurous anhydride HOSO(2)CHO. syn-FA is predicted to form two nonplanar bidentate complexes with SO(2): the more stable one contains a normal hydrogen bond donated by OH, and the less stable one contains a blue-shifted hydrogen bond donated by CH. Both are stabilized by charge transfer from FA to SO(2). anti-FA forms three planar complexes of nearly equal energy containing OH-to-SO(2) hydrogen bonds. Formic sulfurous anhydride forms via an endothermic concerted cycloaddition. Natural bond orbital analysis showed that the bidentate SO(2)-FA complexes are stabilized by n → π* donation from FA to SO(2), and back-donation from SO(2) n and π* orbitals into FA σ(OH)* or σ(CH)* orbitals. The bidentate formic acid-SO(2) complex that contains an O-H···O hydrogen bond is more stable than the similar nitric acid-SO(2) complex. The latter contains a stronger hydrogen bond but shows no O→S charge transfer interaction.

Sulfur Dioxide–Pyridine Dimer. FTIR and Theoretical Evidence for a Low-Symmetry Structure

“…Perhaps pyridine C–H bond interactions are more likely in weak complexes where an ortho C–H bond can be oriented close to the acceptor molecule, and the interaction can contribute significant additional stabilization energy. SO 2 complexes with chloroform, methanol, , and formic acid all contain O···H–C hydrogen bonds like this. Therefore, assuming for the moment that SO 2 –pyridine complex has intermediate stability, that is, greater than SO 2 –chloroform, −methanol, and −formic acid, but less than SO 3 –pyridine, one may ask in this case whether or not the pyridine C–H participates as a hydrogen bond donor.…”

A Computational Re-examination of the Criegee Intermediate–Sulfur Dioxide Reaction

“…Finally, Vereecken et al 26 also predicted that diradical 13 can undergo an intramolecular 1,4-hydrogen shift (TS-18) to formyl sulfurous anhydride 19 (reaction 9): Species 19, whose existence had been predicted by Keller et al 27 only a few years before the Vereecken study, is formally derived from a cycloaddition of formic acid to SO 2 . RRKM/ME simulations indicated a substantial 15% yield of 19.…”

“…Species 19 , whose existence had been predicted by Keller et al only a few years before the Vereecken study, is formally derived from a cycloaddition of formic acid to SO 2 . RRKM/ME simulations indicated a substantial 15% yield of 19 .…”

Practical One Pot Synthesis of 2-Alkyl-substituted Benzothiazoles from Bis-(2-nitrophenyl)-disulfides.

“…The possibility of the acetic acidsulphur dioxide 1 : 1 adduct formation was experimentally proved in 1944 [ 27 ] by the structure of the complex still remain tentative. In 2010 the theoretical investigation of the formic acidsulphur dioxide system proposed the structure of covalent adducts as formic sulfurous anhydride (7, R3 = H) [ 28 ]. These types of adducts are more electrophilic in comparison with free acid.…”