DFT Investig ation of t automerism in ۶-fl ourothymine: Com parison betw een gas p hase and solution

Quantum calculation s were carried out to determining structural parameters, energies an d thermod ynamic properties of various tautomers of ۶-flou rothymine ( FT). FT can be presente d by five t automeric fo rms. All tau tomers from ۱, ۳ hydrogen migrati on between N and O were optimized at the B۳L YP/۶-۳۱۱+ +g** level o f theory in gas phas and chloroform solvent. An d also by u sing frequency calculation at the s ame level thermodynamic properties such as Δ E,ΔH,ΔG and equili brium constant (Keq) fo r five taut omerism reactions wer e determined. Studies of tautome rism pheno mena have been valua ble in man y areas of chemistry a demonst rated by se veral review s of experimental and theoretical studies in c hemistry an d biochemistry. [۱]. Tautomeric equilibria of pyrimidine bases are o f continuing interest both from the theoretical [۲] and experimental [۳] points of view, partly due tosuggestions that t he presence of unusu al tautome rs may have important biolog ical properties,such as mutagenesis.One hypothesis suggests that the frequen cy of misp airing in D NA andthus, mutagenesis is correlated with equilibriu m constants for the keto-enol or amino±imin o tautomerisation [۴]. In the prese nt work, a c omplete tautomery sche me between tautomers for FT (Fig. ۱) were studied using B۳LYP/۶-۳۱۱++G(d,p) level of theo ry. In addition, From t he calculati ons, relativ e energies of different tautomers, and therm odynamic properties of tautomerism equilibrium in F T were obtained. Thence, the effects of solvent on t he equilibri um have bee n investigated using chloroform as solvent and gas phase

کلیدواژه ها:

Tautomerism ، ۶-flo urothymine ، SCRF ، Chl oroform ، B۳LYP