R. Lavrich, A. Walker, D. Plusquellic
Sep 15, 2003
Citations
0
Influential Citations
28
Citations
Journal
Journal name not available for this finding
Abstract
Rotational spectra of two conformers of the peptide mimetic, ethyl-acetamidoacetate, were measured in a molecular beam using a Fourier-transform microwave spectrometer. In each conformer, internal rotation of the acetyl methyl group gives rise to observable splittings in the spectrum. From analysis of the torsion-rotation interactions, the methyl group’s orientation has been determined in the principal axis frame of each conformer and is shown to unambiguously identify its conformational form. One conformer exists in the all-trans configuration and belongs to CS point group and the second, higher-energy conformer has C1 symmetry. Two separate theoretical fitting procedures are applied to assess the reliability of the structural information and are shown to be essentially equivalent. For example, methyl torsional barriers are 63.7(1) cm−1 versus 67.1(1) cm−1 and 64.8(1) cm−1 versus 67.5(1) cm−1 for the CS and C1 conformers, respectively, and principal axis orientations of the methyl groups agree to ±0.1°. ...