4-hydroxy-l-proline is formed by hydroxylation of proline, an amino acid
found in protein, whose inhibition results in hair problems in humans, causing scurvy
disease. In this chapter, we discuss the DFT study on cis and trans conformers of 4-
hydroxy-l-proline, i.e., CHLP and THLP using the B3LYP/6-31+G(d,p)level. The
equilibrium structures of both conformers are obtained to analyze their vibrational
properties. We have also discussed the results of an in-depth study on
cis-4-hydroxy-d-proline (CHDP). The scan of potential energy surface provides the
global minimum structure of CHDP along with its possible conformers. HOMO,
LUMO, and MESP surfaces as well as charge distribution, are used to explain the
chemical reactivity. The equilibrium geometry of CHDP dimer has been obtained and
intermolecular interactions are explored by the NBO analyses. Vibrational analysis has
been carried out on CHLP, THLP, and CHDP (monomer and dimer). A complete
assignment to vibrational modes has been presented based on their potential energy
distribution. The calculated frequencies, after proper scaling, are compared with
experimental FT-IR frequencies recorded by KBr disc and Nujol mull techniques.
Several electronic as well as thermodynamic parameters have also been reported.
Keywords: B3LYP, Charge distribution, DFT, Dimer, Electronic parameter, FTIR,
H-bond, HOMO-LUMO, Hydroxyproline, Inter-molecular interaction, MESP,
NBO, Proline, Thermodynamic parameter, Vibrational spectra.
