Solvent and substituent effect on the absorption spectra of some ethyl [[substituted benzylidene] dithio] diacetates

ABSTRACT

The UV and visible electronic spectral behavior of some ethyl [[substituted benzylidene] dithio] diacetates is measured using solvents of different polarities. The spectral bands due to pi-pi* transition and the intermolecular charge transfer are assigned. The contribution of the dielectric constant and the refractive index affecting the electronic spectral bands was studied using a multiple regression technique, where peak locations were visually determined and the coefficients K1, K2 describing the quantitative contribution of dielectric constant and the refractive index of the given solvent and the wave number of maximum absorption in the vapor phase gamma vap were calculated. The hydrogen bonding association constants Kass between the investigated compounds and acetic acid indioxane were calculated. A relationship between Kass and Hammett sigma-values was found