Thermodynamic investigations of cytosine and its methyl, methoxy and hydroxy derivatives. Enthalpies of solvation in methanol and N,N-dimethylformamide.

The enthalpies of solution Delta H-sol(m)infinity of cytosine, 1-methylcyto sine, 1,5-dimethylcytosine, 1-methyl-N-4-hydroxycytosine, 1,5-dimethyl-N-4- hydroxycytosine, 1-methyl-N-4-methoxycytosine, 1,5-dimethyl-N-4-methoxycyto sine in methanol and in N,N-dimethylformamide were determined and discussed with previously obtained data of the enthalpy of sublimation Delta H-g(s)m , partial molar volumes V-2(o) and structural parameters {e.g. molecular ac cessible surface areas S-M and their atomic partition S-N, S-O, S-H(N,S-O), molecular volumes V-2(M)} for compounds investigated. The enthalpies of so lvation Delta H-solv(m), the transfer enthalpies of solution Delta H-tr(m), water-methanol, water- N, N -dimethylformamide and enthalpies of interacti on Delta H-int(m) were calculated. Correlation between the enthalpy of solvation, volumetric and structural pa rameters was elaborated. It was demonstrated that the enthalpy of solvation and transfer enthalpy of solution correlate with surface accessible areas as well as with volumetric properties characterized by parameter beta, corr esponding to the difference between the partial molar and molecular volumes of compounds studied. (C) 2001 Elsevier Science BN. All rights reserved.