Topic
Conformational isomerism
About: Conformational isomerism is a research topic. Over the lifetime, 11563 publications have been published within this topic receiving 199312 citations.
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TL;DR: IR-absorption spectroscopy provides a clear identification of the reaction product and cis-AA converts back to trans-AA in a time scale of minutes at 8 K by tunneling.
Abstract: The high-energy conformer of acetic acid (cis-AA) is produced in an Ar matrix by vibrational excitation of the OH stretching overtone of the ground conformational state (trans-AA). IR-absorption spectroscopy provides a clear identification of the reaction product. cis-AA converts back to trans-AA in a time scale of minutes at 8 K by tunneling.
106 citations
TL;DR: Vicinal, equatorial OH groups in the (4)C(1) conformer of glucopyranose are, however, able to form strong bidentate hydrogen bonds with water molecules in a cooperative manner, each water molecule acting simultaneously as both hydrogen bond donor and acceptor.
Abstract: Topological analysis of the electron density profiles and the atomic basin integration data for the most energetically favorable 4C1 and 1C4 conformers of β-d-glucopyranose, calculated at the B3LYP/6-31+G(d), MPWlPW91/6-311+G(2d,p), and MP2/6-31+G(d) levels, demonstrates that intramolecular hydrogen bonding between adjacent ring OH groups does not occur in glucopyranose, given the need to demonstrate a bond critical point (BCP) of correct (3,−1) topology for such an interaction to be termed a hydrogen bond. On the other hand, pyranose ring OH groups separated by three, rather than just two, carbon atoms are able to form an intramolecular hydrogen bond similar in topological properties and geometry to that found for propane-1,3-diol. Vicinal, equatorial OH groups in the 4C1 conformer of glucopyranose are, however, able to form strong bidentate hydrogen bonds with water molecules in a cooperative manner, each water molecule acting simultaneously as both hydrogen bond donor and acceptor, and characterized by...
105 citations
TL;DR: In this paper, anharmonic vibrational ab initio calculations (CC-VSCF) for the trans and cis conformers of formic acid are reported and compared with the experimental spectra.
105 citations
TL;DR: In this article, a sub-Doppler resolution infrared spectra for both the linear and cyclic conformers of the hydrogen cyanide trimer was obtained, and the vibrational predissociation lifetime of the complex was found to be strongly mode specific.
Abstract: Sub‐Doppler resolution infrared spectra have been obtained for both the linear and cyclic conformers of the hydrogen cyanide trimer. In the case of the linear trimer, all three vibrational bands correlating with the C–H stretching fundamental of the hydrogen cyanide monomer (ν1) have been observed. The vibrational predissociation lifetime of the complex is found to be strongly mode specific. For the cyclic trimer, which has only one (doubly degenerate) infrared allowed band associated with the C–H stretch, the rotational structure is characteristic of an oblate planar symmetric top. Molecular constants are reported for both conformers. In addition, several other bands are observed in the spectrum which, although not rotationally resolved, are tentatively assigned to the tetramer.
104 citations
TL;DR: Findings provide strong support for the presence of four conformers of significantly different structure at the heme ligand-binding site and for rapid interconversions among these structures.
104 citations