DFT I nvestigati on of transition state of tauto merism i n ۶-flourothymine in chlorof orm solvent

Quantum calculation s were carried out to determining structural parameters, energies an d thermod ynamic prop erties of transition state(TS) of various tautomers of ۶-flourothymi ne (FT). FT can be presented by five TS forms. All TS fro m ۱, ۳ hydrogen migration between N and O were optimize d at the B۳LYP/۶-۳۱۱+ +g** level of theory in chloroform solvent. An d also by using frequency calculation at the same level thermodynamic prope rties such as ΔE++, ΔH++, ΔG++ and rates constant (Krat) for five tautomerism re actions were determined. Studies of tautomer ism 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].No table studie s have been performed on thymine tautomers such as T he structures and the relative energies of six p ossible tauto mers of the thymine ba se have bee n studied by density functional theory (DFT) u sing the B۳LYP and BP ۸۶ functionals. The keto-thymine (T۱) is predicted to be the most stab le thymine t automer, w hich is consistent with t he other theoretical resu lts and exp erimental data. T۱ has t he largest ionization potential and t he lowest p roton affin ity among all the co nsidered t hymine tau tomers[۲]tau tomerism of thymine on gold and silver nanoparticle surfaces has b een comparatively analyze means of surface-e nhanced ra man scatteri ng (SERS).the N۳-depro tonated tau tomer was predicted to be more fa vorable on Au than on Ag the DFT calculation as consistent wi th our SER S spectra.[۳]In the present work, a complete TS scheme for tautomers for FT (Fig. ۱) were studied using B۳LY P/۶-۳۱۱++ G(d,p) level of theory. In addition , From the calculations, thermod ynamic prop erties of T S of tautomerism equilibrium in F T were obtained. Thence, the effects of solvent on the TS of equilibrium have b een investigated using chloroform as solvent .

کلیدواژه ها:

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