25176-13-0Relevant academic research and scientific papers
Ionization and tautomerization of 2-nitrocyclohexanone in aqueous solution
Angelini, Guido,De Maria, Paolo,Fontana, Antonella,Pierini, Marco,Siani, Gabriella
, p. 4039 - 4047 (2007)
(Chemical Equation Presented) The keto-enol tautomerism of 2-nitrocyclohexanone (2-NCH) was studied in aqueous solution under different experimental conditions. Ketonization rate constants were measured spectrophotometrically at 25°C at an ionic strength of 0.4 mol dm -3 (NaCl) in diluted hydrochloric acid, in diluted sodium hydroxide, and in several buffers by using NaHSO3 as the scavenger of the keto form. A value of pKaEH = 4.78 for the enol form was obtained from the rate-pH profile of the reaction. A value of pK aKH = 5.97 for the keto form was directly obtained from the UV-vis spectra of 2-NCH recorded at different pHs. The equilibrium constant for the keto-enol tautomerism, pKT = -log([enol]/[ketone]) = 1.19, was obtained by combining the two pKa values (pKT = pKaKH - pKaEH). A comparison of these results with the corresponding values (Keefe, J. R.; Kresge, A. J. In The Chemistry of Enols; Rappoport, Z., Ed.; Wiley & Sons: New York, 1990; pp 399-480) for cyclohexanone shows the dramatic effects of an α-nitro substituent on the keto-enol acidities and the tautomerization constant of alicyclic ketones. Rates and equilibria were discussed in the light of the Bronsted equation, the principle of nonperfect synchronization, and the Marcus theory. It turns out that, on passing from nitroalkanes to nitroketones, the resonance contribution to pKa and deprotonation rate decreases, being overwhelmed by steric and inductive effects.
Solvent effects on the rate of the keto-enol interconversion of 2-nitrocyclohexanone
Siani, Gabriella,Angelini, Guido,De Maria, Paolo,Fontana, Antonella,Pierini, Marco
, p. 4236 - 4241 (2008)
The rates of tautomerization of 2-nitrocyclohexanone (2-NCH) have been measured spectrophotometrically at 25.0 ± 0.1 °C in several organic aprotic solvents and their binary mixtures. In cyclohexane the reaction is effectively catalyzed by bases and inhibi
