An FT-IR and DFT based new approach for the detection of tautomer proportions in solution

Tautomer proportions of acetylacetone (acac) in six different solvents are investigated with a new method by means of experimental absorptions (A) and theoretical absorption coefficients (ε). The specific absorption bands (key bands) for keto and enol tautomers were obtained from recorded FT-IR spectra in related solution at room temperature. The molar absorption coefficients for key bands of both keto and enol tautomers were calculated, which is impossible to obtain with experimental methods for individual isomers in equilibrium. The Lambert–Beer equation is used to detect tautomer proportions. The obtained results are in consistence with literature. The most stable enol tautomer is found to be (86%) in CCl4 and the keto tautomer is found to be most stable in DMSO (48%).