The computational study of the tautomerization of Carmustine drug in the biological system: DFT approach

Tautomers are isomers of a molecule that exist in solution or in a cell. They are interchangeable forms because chemical bonds are rearranged many times spontaneously. This is different from chirality, where molecules are mirror images (or enantiomers) of each other. DFT method was carried out to study the tautomerization of the mechanism of carmustine as an anti-cancer drug.  In the carmustine structure, two conformational tautomers were predicted and both two tautomer structures were demonstrated for considering the role of changing atoms in the conformation of carmustine.  Relative energies obtained at the B3LYP/6-311G++ (d,p) , Aug-cc-pVDZ and 6-311++g(2d,2p) basis sets. The highest occupied molecular orbital (HOMO),  The lowest unoccupied orbital (LUMO), and bandgap energy of structures were calculated. Electronics parameters were obtained. electrophilicity. Electronegativity, softness, and hardness for determining the reactivity of compounds in biological media. have been studied. According to the data, the structure of carmustine and two tautomer conformations are stable but T1 is more stable than the other one.