These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Conformers of gaseous proline.
    Author: Czinki E, Császár AG.
    Journal: Chemistry; 2003 Feb 17; 9(4):1008-19. PubMed ID: 12584718.
    Abstract:
    Accurate geometries, relative energies, rotational and quartic centrifugal distortion constants, dipole moments, harmonic vibrational frequencies, and infrared intensities were determined from ab initio electronic structure calculations for eighteen conformers of the neutral form of the amino acid L-proline. Only four conformers have notable population at low and moderate temperature. The second most stable conformer is only 2+/-2 kJ mol(-1) above the global minimum, while the third and fourth conformers are nearly degenerate and have an excess energy of 7+/-2 kJ mol(-1) relative to the global minimum. All four conformers have one hydrogen bond: N.HO in the lower energy pair of conformers, and NH.O in the higher energy pair of conformers. The conformer pairs differ only in their ring puckering. The relative energies of the conformers include corrections for valence electron correlation, extrapolated to the complete basis set limit, as well as core correlation and relativistic effects. Structural features of the pyrrolidine ring of proline are discussed by using the concept of pseudorotation. The accurate rotational and quartic centrifugal distortion constants as well as the vibrational frequencies and infrared intensities should aid identification and characterization of the conformers of L-proline by rotational and vibrational spectroscopy, respectively. Bonding features of L-proline, especially intramolecular hydrogen bonds, were investigated by the atoms-in-molecules (AIM) technique.
    [Abstract] [Full Text] [Related] [New Search]