title: Theoretical studies of proton-transfer reactions of 2-hydroxypyridine--(H2O)n (n = 0-2) in the ground and excited states.
abstract: The potential energy profiles for proton-transfer reactions of 2-hydroxypyridine and its complexes with water were determined by MP2, CASSCF and MR-CI calculations with the 6-31G** basis set. The tautomerization reaction between 2-hydroxypyridine (2HP) and 2-pyridone (2PY) does not take place at room temperature because of a barrier of approximately 35 kcal/mol for the ground-state pathway. The water-catalyzed enol-keto tautomerization reactions in the ground state proceed easily through the concerted proton transfer, especially for the two-water complex. The S1 tautomerization between the 2HP and 2PY monomers has a barrier of 18.4 kcal/mol, which is reduced to 5.6 kcal/mol for the one-water complex and 6.4 kcal/mol for the two-water complex. The results reported here predict that the photoinduced tautomerization reaction between the enol and keto forms involves a cyclic transition state having one or two water molecules as a bridge.
authors.affiliation: Department of Chemistry, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Quan-Song
authors.initials: QS
authors.lastname: Li
authors.forename: Wei-Hai
authors.initials: WH
authors.lastname: Fang
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: Yu
mesh_terms: D002627:Chemistry, Physical / Q000379:methods*; D004735:Energy Transfer; D008027:Light; D008956:Models, Chemical; D008968:Molecular Conformation; D015394:Molecular Structure; D010777:Photochemistry / Q000379:methods*; D011522:Protons; D011728:Pyridones / Q000737:chemistry*; D012984:Software; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D011522:Protons; D011728:Pyridones; D014867:Water; C017679:2-hydroxypyridine