A vibrational study of the local anesthetic procaine hydrochloride in
the solid state and in aqueous solution was carried out. Assignment of
the amino groups was performed using deuterated and non-deuterated sa
mples. All the bands in the spectra were identified and assigned. The
structure of the procaine cation was determined using the AMI semi-emp
irical method. A comparison with crystallographic data was made. The f
requencies and intensities of the vibrations were also computed using
AM1. Vibrational scale factors were employed in the AM1 calculations.