Ft Ir Spectroscopy and Molecular Modelling of Benzocaine / Β-cyclodextrin Inclusion Complex

Benzocaine is a local anesthetic used for different pain treatments. Including it in various cyclodextrins one can increase the solubility of this drug. Several inclusion compounds of β-cyclodextrin (β-CD) with benzocaine, prepared by kneading and coprecipitation methods, were investigated. In order to understand the inclusion process mechanisms FT IR spectroscopic investigation and molecular mechanics calculations were used. The intensity changes and frequency shifts for several molecular vibrations indicate the molecular groups implied in the complexation process. The aromatic ring enters inside cyclodextrin cone, its motional freedom being restricted. The hydrogen bonds play an important role in the inclusion process. MM+ molecular mechanics calculations established the spatial geometry of this inclusion complex. The para-amino group is located near the primary O-H groups (the narrow rim) of the cyclodextrin whereas the ester group is situated near the secondary O-H groups (the larger rim) belonging to the CD truncated cone.