title: Effect of ring size on the tautomerization and ionization reaction of cyclic 2-nitroalkanones: an experimental and theoretical study.
abstract: The keto-enol tautomerism of some cyclic 2-nitroalkanones was studied in cyclohexane. Keto-enol equilibrium constants, K(T), at 25 °C were obtained from (1)H NMR spectra. The relative enol content for the investigated ketones as a function of ring size decreases in the order 6 > 7 > 11 > 12 > 15. This trend apparently is different from that observed in water. Density functional theory (DFT) calculations have been performed to rationalize the effects of ring size and of the solvent on tautomerism. The acidity constants, K(a)(KH), for the different keto tautomers were measured spectrophotometrically at 25 °C in buffered aqueous solutions. No simple correlations between K(a)(KH) and ring size was observed, and this is in agreement with a DFT analysis performed on the same compounds.
authors.affiliation: Dipartimento di Scienze del Farmaco, Università G. d'Annunzio, Via dei Vestini 31, Chieti, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Angelini
authors.forename: Cecilia
authors.initials: C
authors.lastname: Coletti
authors.forename: Paolo
authors.initials: P
authors.lastname: De Maria
authors.forename: Roberto
authors.initials: R
authors.lastname: Ballini
authors.forename: Carla
authors.initials: C
authors.lastname: Gasbarri
authors.forename: Antonella
authors.initials: A
authors.lastname: Fontana
authors.forename: Marco
authors.initials: M
authors.lastname: Pierini
authors.forename: Gabriella
authors.initials: G
authors.lastname: Siani
mesh_terms: D003510:Cyclohexanes / Q000737:chemistry; D003512:Cyclohexanones / Q000737:chemistry; D006844:Hydrocarbons, Cyclic / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D012997:Solvents / Q000737:chemistry; D013329:Structure-Activity Relationship; D014867:Water / Q000737:chemistry
chemical_list: C533398:2-nitrocyclohexanone; D003510:Cyclohexanes; D003512:Cyclohexanones; D006844:Hydrocarbons, Cyclic; D007659:Ketones; D012997:Solvents; D014867:Water; C506365:Cyclohexane