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

Abstract

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-dimethylformamide solutions at 25°C 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 CH 2 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 CH 2 ) 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 1, 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 ΔV 2,tr 0 water-methanol, water-N,N-dimethylformamide were also calculated.