Hydrogen bonded interactions of methanol and water with purines and pyrimidines

Abstract

The solvation of benzimidazole, 4-azabenzimidazole, purine, adenine, uracil, thymine, and cytosine in water and methanol was determined by a combination of calorimetric and spectral analysis. Specific enthalpies have been assigned to each interaction site in the first solvation shell. Calculations, based on the enthalpies of hydrogen bond formation with water, and estimates for intermolecular hydrogen bond enthalpies, show that the self-association of purine and adenine in water through hydrogen bonded interactions is enthalpically possible.

Thermodynamics of organic mixtures containing amines. X. Phase equilibria for binary systems formed by imidazoles and hydrocarbons: Experimental data and modelling using DISQUAC

“…According to this theory, mean field models (c = 1) provide LLE curves which are too high at the UCST (upper critical solution temperature) and too low at the LCST [33] (lower critical solution temperature coefficients. The enthalpies of solution for the (methanol + 1H-imidazole) system [39,40] have been used TABLE 7 Interchange coefficients, DIS, and QUAC, C DIS ns;l and C QUAC ns;l , for (n, s) contacts in (imidazole + organic solvent) mixtures (type n, amine group in imidazoles, type s = a, aliphatic group in n-alkanes, toluene, 1-alkanols, or methyl-imidazoles; s = b, aromatic group in imidazoles, benzene, or toluene; s = c, cyclic group in cyclohexane; s = h, hydroxyl group in 1-alkanols).…”

Theoretical Study of the Interaction between Thymine and Water. Protonation and Deprotonation Enthalpies and Comparison with Uracil

“…It can be anticipated that the strength of the hydrogen bond between uracil and adenine will be governed not only by the proton acceptor ability of the O atom but also by the proton donor ability of the NH group. The basicity of uracil has been discussed in several works. − There are also experimental , and theoretical data on the proton affinity of thymine. , The computations have been carried out using rather low levels (HF/4-31G 13 or MINDO 14 ). The correlations between the proton affinity and hydrogen bond parameters are also well documented, − and it has been recently outlined that the nature of the proton transfer to O8 and the decarboxylation process in orotidine monophosphate is of general significance for understanding the activity of many enzymes …”

“…The basicity of uracil has been discussed in several works. [4][5][6][7][8][9][10] There are also experimental 11,12 and theoretical data on the proton affinity of thymine. 13,14 The computations have been carried out using rather low levels (HF/4-31G 13 or MINDO 14 ).…”