The DFT (B3LYP/6-31 + G) method was used to study the relative stabilities and probable proton transfer in isolated and monohydrated 2,4-dithiothymine molecules in gas phase. The effects of water on relative stabilities and the rate of the proton transfer were analysed. The results indicate that only one tautomer for 2,4-dithiothymine can exist in gas phase. Tlie interaction with one water molecule dose not change the order of relative stability and decreases tlie activation barriers of the proton transfer reactions for 2,4-dithiothymine.

Key words: THYMINE, ISOMER, ACTIVATION ENERGY, STABILITY