Dissociation constants of parabens and limiting conductances of their ions in water.
Precise measurements of electrical conductivities of methylparaben, ethylparaben, propylparaben, and butylparaben sodium salts in dilute aqueous solutions were performed from 278.15 to 313.15 K in 5 K intervals. Experimental conductivity data were analyzed applying the Quint-Viallard conductivity equations by taking into account the salt hydrolysis in aqueous solutions. These evaluations yield the limiting conductances of paraben anions and the dissociation constants of the investigated parabens in water. From temperature dependence of dissociation constants, the thermodynamic functions associated with the dissociation process were estimated. It was discovered that the contributions of enthalpy and entropy to the Gibbs free energy are quite similar. The Walden products of paraben anions in water are independent of temperature, indicating that the hydrodynamic radii are not significantly affected by temperature.
Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 Ljubljana, Slovenia.
Ana
A
Kroflič
Alexander
A
Apelblat
Marija
M
Bešter-Rogač
D004553:Electric Conductivity; D007477:Ions / Q000737:chemistry; D010226:Parabens / Q000737:chemistry*; D012996:Solutions; D013696:Temperature; D014867:Water / Q000737:chemistry*
D007477:Ions; D010226:Parabens; D012996:Solutions; D014867:Water