Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9633606 | The Journal of Chemical Thermodynamics | 2005 | 9 Pages |
Abstract
Saturation molalities m(sat) in H2O(l) have been measured for the substances 2â²-deoxyadenosine · H2O(cr), 2â²-deoxycytidine · H2O(cr), 2â²-deoxyguanosine · H2O(cr), 2â²-deoxyinosine(cr), and 2â²-deoxyuridine(cr) by using h.p.l.c. The states of hydration were established by performing Karl Fischer analyses on samples of these substances, which had been allowed to equilibrate with their respective aqueous saturated solutions for several days at T â 298 K and then dried with air at T â 296 K for â24 h. The crystalline forms of the substances were identified by comparison of the results of X-ray diffraction measurements with results from the literature. Also, calorimetric molar enthalpies of solution ÎsolHm(cal) for these substances were measured by using an isoperibol solution calorimeter. A self-association (stacking) model was used to estimate values of the activity coefficients γ and relative apparent molar enthalpies LÏ for these substances. These γ and LÏ values were used to adjust the measured values of m(sat) and ÎsolHm to the standard state and thus obtain values of the standard molar Gibbs free energy ÎsolGmâ and enthalpy changes ÎsolHmâ for the dissolution reactions of these substances. The values of the pKs and of the standard molar enthalpies of the ionization reactions were also used to account for speciation of the substances in the calculations of ÎsolGmâandÎsolHmâ.
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Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
Yadu B. Tewari, Patrick D. Gery, Mark D. Vaudin, Alan D. Mighell, Ralph Klein, Robert N. Goldberg,