On the basis of extraction experiments and gamma-activity measurements, the extraction constant corresponding to the equilibrium H3O+(aq) + 1. Na+(nb) =1.H3O+(nb) + Na+(aq) occurring in the two-phase water-nitrobenzene system (1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K-ex, (H3O+, 1.Na+) = -0.4 +/- 0.1. Further, the stability constant of the 1.H3O+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 degrees C: log beta(nb) (1.H3O+) = 5.7 +/- 0.2. Finally, by using quantum mechanical OFT calculations, the most probable structure of the cationic complex species 1.H3O+ was derived. In the resulting complex, the "central" cation H3O+ is bound by two linear hydrogen bonds and one bifurcated hydrogen bond to the corresponding four oxygens of the parent ligand I. Besides, the whole 1.H3O+ complex structure is stabilized by two intramolecular H-bonds. The interaction energy of the considered 1.H3O+ complex was found to be -458.7 kJ/mol, confirming also the formation of this cationic species. (C) 2014 Elsevier B.V. All rights reserved.
Protonation of antamanide: Experimental and theoretical study
Ruzza Paolo
2014
Abstract
On the basis of extraction experiments and gamma-activity measurements, the extraction constant corresponding to the equilibrium H3O+(aq) + 1. Na+(nb) =1.H3O+(nb) + Na+(aq) occurring in the two-phase water-nitrobenzene system (1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K-ex, (H3O+, 1.Na+) = -0.4 +/- 0.1. Further, the stability constant of the 1.H3O+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 degrees C: log beta(nb) (1.H3O+) = 5.7 +/- 0.2. Finally, by using quantum mechanical OFT calculations, the most probable structure of the cationic complex species 1.H3O+ was derived. In the resulting complex, the "central" cation H3O+ is bound by two linear hydrogen bonds and one bifurcated hydrogen bond to the corresponding four oxygens of the parent ligand I. Besides, the whole 1.H3O+ complex structure is stabilized by two intramolecular H-bonds. The interaction energy of the considered 1.H3O+ complex was found to be -458.7 kJ/mol, confirming also the formation of this cationic species. (C) 2014 Elsevier B.V. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
