Volumetric investigations of solute-solvent interactions of some alkylated derivatives of uracil in methanol, and N,N-dimethylformamide at 25 degrees C.

摘要

Densities of uracil, thymine, 1,3-dimethyluracil, 1,3,6-trimethyluracil, 1,3-dimethyl-6-ethyluracil, 1,3-dimethyl-6-propyluracil, 1,3-diethylthymine in methanol and N,N-dimethylformainide solutions at 25degreesC by means of Anton Paar DMA 60/602 digital densimeter were determined, then the partial molar volumes V-2(0) were evaluated. The contribution of CH2 groups present at the molecules studied in the V-2(0) value, using the simple additivity scheme, were calculated. The linear correlations V-2(0)=f(n(CH2)) were found. The model based on the assumption that the density of the solvation shell depends on the structure and polarity P of the solute molecule was applied. The structural parameters of the compounds investigated: molecular volumes V-2(M), volumes of solvation shell V-l,V-solv and molecular surface areas S-M, and their atomic partitions S-N, S-0, S-H(N) Were calculated. The determinations of P values were made assuming that both acceptors and donors of protons in aqueous solutions are involved into the specific solute-solvent interactions. Methanol more active as a donor than acceptor of protons interacts with the oxygen and nitrogen atoms, whereas DMF interacts solely with the hydrogen atom of the solute molecule. The transfer functions of DeltaV(2,tr)(0) water-methanol, water-N,N-dimethylformamide were also calculated. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 12]