Potentiometric study of the protonation and distribution equilibria of d-gluconic-delta-lactone acid in sodium perchlorate solutions at 25 degrees C and construction of a thermodynamic model.
The protolytic behavior of d-gluconic-delta-lactone acid has been studied by means of automated potentiometric titrations at different ionic strengths in the range 0.1</=I</=3.0 mol dm(-3) in NaClO(4) at 25 degrees C. This study reveals a protolytic equilibrium of gluconic acid as well as a distribution equilibrium between gluconic acid (HG) and its lactone form (L). The values of the stoichiometric constants obtained have been correlated by means of the modified Bromley methodology. The thermodynamic constants obtained were logbeta(0)=3.92+/-0.10 for the protolytic equilibrium H(+)+G(-)right harpoon over left harpoonHG and logK(r)(0)=-0.81+/-0.09 for the distribution equilibrium HGright harpoon over left harpoonL.
Zubiaur
J
J
Kimika Analitikoaren Saila, Euskal Herriko Unibertsitatea, 644 PK, E-48080 Bilbao, Spain.
Castaño
R
R
Etxebarria
N
N
Fernández
L A
LA
Madariaga
J M
JM