Electronic spectra and intramolecular proton transfer in mannich bases in liquid and solid vitreous solutions

Temperature Dependence of the Dipole Moment of Mannich Bases with An Intramolecular Hydrogen Bond

“…For compounds I1 and 111, which suffer a distinct decrease of ALI with increasing temperature (Tables 2, 31, an other interpretation has to be given: an attempt was made to describe the values obtained on the basis of the H-bond model with a proton transfer tautomeric equilibrium. Because the proton transfer equilibrium constant is relatively low in benzene for the compounds examined, and therefore difficult to determine accurately, the results of some measurements in more active solvents [6,10,11] were extrapolated from a plot versus the Reichardt polarity parameter ET [13] up to the appropriate value for benzene. In this way KpT was evaluated at 25OC (0.1005 and 0.085 for I1 and 111, respectively).…”

“…For the other two compounds (11; ApKa = +3.69 and 111; ApKa = +3.04) the UV [5,6,10] and IR spectra [ll] show that there exist proton transfer forms in benzene at room temperature and also that the proton transfer equilibrium is shifted with temperature. Consequently, an influence of temperature on the dipole moment of these compounds can be expected.…”