Open AccessThermodynamics of ionization of 2,4- and 2,5-dinitrophenol in dimethylsulfoxide
Author(s) -
Kok Siong Siow,
K. P. Ang
Publication year - 1980
Publication title -
canadian journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.323
H-Index - 68
eISSN - 1480-3291
pISSN - 0008-4042
DOI - 10.1139/v80-153
Subject(s) - chemistry , ionization , enthalpy , dinitrophenol , 2,4 dinitrophenol , solvent , thermodynamics , organic chemistry , ion , biochemistry , physics
Ionization constants of 2,4- and 2,5-dinitrophenol in dimethylsulfoxide were measured by the conductance method at five temperatures ranging from 20 to 40 °C. The ionization constants of 2,4-dinitrophenol are much larger than those of 2,5-dinitrophenol, and in both cases they increase with temperature. The thermodynamic functions of ionization are discussed in terms of Hepler's theory for substituent and solvent effects. The ionization of phenols in dimethylsulfoxide is controlled by the enthalpy factor, both internal and environmental, which is in contrast to the entropy-controlled process in water.