A Raman and infrared spectroscopic study of triethylenediamine (DABCO) and its protonated forms

The Raman and infrared spectra of DABCO have been measured as a function of the pH, and the vibrational bands of the two protonated forms of DABCO have been tabulated and assigned. The frequencies of several of the Raman bands were found to exhibit substantial shifts upon protonation, and the appearance of the Raman spectrum in the region between 900 and 1100 cm −1 in particular shows differences which can be used to differentiate between the three forms of DABCO. The values of the two pK a 's were determined from the intensity versus pH plots for the three species.