title: Theoretical and spectroscopic study of 2-substituted indan-1,3-diones: a coherent picture of the tautomeric equilibrium.
abstract: The structures of some 2-substituted indan-1,3-diones are investigated in the gas phase and solution using quantum chemical calculations and spectral (NMR, IR, and UV) measurements. The influence of the substituent at the 2-position on the tautomeric equilibrium of 2-substituted indan-1,3-diones in solvents with different polarity is evaluated. It is shown that the equilibrium in 2-formyl-indan-1,3-dione and 2-acetyl-indan-1,3-dione is shifted to the 2-hydroxyalkylidene-indan-1,3-dione tautomer, while 2-carboxyamide-indan-1,3-dione exists as a mixture of two tautomers, 2-(hydroxyaminomethylidene)-indan-1,3-dione and 2-carboamide-1-hydroxy-3-oxo-indan, with extremely fast proton transfer between them. The situation for 2-carboxy-indan-1,3-dione is quite different - on the basis of the analysis of the obtained results, the possible existence of an anionic form of 2-carboxy-indan-1,3-dione in solution can be inferred.
authors.affiliation: Institute of Organic Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
authors.forename: Silvia
authors.initials: S
authors.lastname: Angelova
authors.forename: Venelin
authors.initials: V
authors.lastname: Enchev
authors.forename: Kalina
authors.initials: K
authors.lastname: Kostova
authors.forename: Marin
authors.initials: M
authors.lastname: Rogojerov
authors.forename: Galya
authors.initials: G
authors.lastname: Ivanova