Thermodynamics of nucleoside-solvent interactions. Uridine and cytidine in pure water and in 3m ethanol between 17 and 37 .degree.C

Saturation molalities and standard molar enthalpies of solution of cytidine(cr), hypoxanthine(cr), thymidine(cr), thymine(cr), uridine(cr), and xanthine(cr) in H2O(l)

“…In making the D vap H correction, we used values of the osmotic coefficient / calculated by using a stacking model (see Section 3.3.2). Values of the standard molar heat-capacity changes D sol C p;m have been determined (see Section 3.4 and footnotes to table 8) for the dissolution reactions for cytidine [22], thymine [23], and uridine [22]. These results were used to adjust the values of D sol H m (cal) for these substances from the experimental temperature T (see column 2 in Table 3) to T ¼ 298:15 K. For the remainder of the substances, the value D r C p;m ¼ 217 J AE K À1 AE mol À1 , based on the value of this quantity for the dissolution of adenosine(cr) [1], was used for this correction.…”

“…The values of K and D r H m for reaction (22) are given in table 6. The values of K and D r H m for cytidine(aq) and uridine(aq) are from Farquhar et al [28].…”

“…The value K ¼ 0:94 for thymidine(aq) was calculated by using the values of the osmotic coefficient / for thymidine(aq) given by Farquhar et al [28] who also reported the value D r H m ¼ À9:8 kJ AE mol À1 for reaction (16) involving thymidine(aq). In our calculations, we estimated the values K ¼ 0:8 and D r H m ¼ 11 kJ AE mol À1 for the stacking reaction (22) involving hypoxanthine(aq), thymine(aq), and xanthine(aq).…”

“…Additionally, values of the standard molar heat-capacity changes for the dissolution reactions have been reported for three substances. Thus, for cytidine(cr), Stern and Swanson [22] give D sol C p;m ¼ ð117 AE 33Þ J AE K À1 AE mol À1 . For thymine(cr), Alvarez and Biltonen [41] give D sol C p;m ¼ ð188 AE 17Þ J AE K À1 AE mol À1 , Kilday [23] gives D sol C p;m ¼ ð106 AE 26Þ J AE K À1 AE mol À1 , and Ahmed et al [43] give D sol C p;m ¼ ð170 AE 14Þ J AE K À1 AE mol À1 .…”

“…For thymine(cr), Alvarez and Biltonen [41] give D sol C p;m ¼ ð188 AE 17Þ J AE K À1 AE mol À1 , Kilday [23] gives D sol C p;m ¼ ð106 AE 26Þ J AE K À1 AE mol À1 , and Ahmed et al [43] give D sol C p;m ¼ ð170 AE 14Þ J AE K À1 AE mol À1 . For uridine(cr), Stern and Swanson [22] give D sol C p;m ¼ ð146 AE 33Þ J AE K À1 AE mol À1 . Also, Kishore et al [46] report values of the standard partial molar heat capacity C p;2;m for aqueous solutions of thymidine, thymine, and uridine.…”