Thermodynamics of proton ionization in aqueous solution.|nI.|pProton dissociation from several methyl- and ethyl-substituted aliphatic carboxylic acids at 10, 25, 40°.|nII.|pProton dissociation from several protonated primary, secondary and tertiary amines at 10, 25, and 40°.|nIII.|pLinear enthalpy-entropy relationships and their use in determining [delta]G° values

• Main Author: Slade, Marvin Dale
• Published: BYU ScholarsArchive 1971
• Subjects: Protons; Ionization; Chemistry
• Online Access: https://scholarsarchive.byu.edu/etd/8354

A calorimetric study has been made of proton ionization in dilute aqueous solution from aliphatic carboxylic acids at 10, 25, and 40° (13 acids) and at 25° (3 acids). Values of ΔS° are calculated by combining the resulting ΔH° values with ΔG° values obtained from the literature or determined from potentiometric or calorimetric measurements. The trends in ΔG°, ΔH°, and ΔS° are described by an electrostatic model, and deviations from this model are taken as a measure of nonelectrostatic substituent effects for carboxylic acids. A calorimetric study has also been made of proton ionization in dilute aqueous solution from several primary, secondary and tertiary amines at 10, 25 and 40°. ΔCp° values have been calculated and correlations made between ΔCp° values for proton ionization of several acids and amines and the dipole moments of the unprotonated acids or bases. Linear enthalpy-entropy relationships have been observed for proton ionization as a function of temperature. An equation has been derived to use this linear relationship between ΔH° and ΔS° to calculate ΔG° values at temperatures where only ΔH° values are available.