Amino Acid Chemistry in Solution:  Structural Study and Vibrational Dynamics of Glutamine in Solution. An ab Initio Reaction Field Model

The self-consistent reaction field (SCRF) theory was used to study structural and vibrational features of the amino acid <SCP>l</SCP>-glutamine in solution. Raman and infrared spectra of this molecule in solutions of H<INF>2</INF>O and D<INF>2</INF>O were recorded and measured. The bands were firstly assigned on the basis of the isotopic shifts. An ab initio quadratic force field at the 6-31+G* level was achieved. The calculation simulated a polar solvent by placing the molecule in an ellipsoidal cavity surrounded by a continuum dielectric. The theoretical results, in terms of structural parameters, vibrational frequencies and descriptions, and infrared intensities, were in satisfactory agreement with the experimental data.