Heavy-Atom Structure of Alaninamide from Rotational Spectroscopy

Abstract

The rotational transitions of seven isotopomers of alaninamide, the amide derivative of alanine, were measured using a Fourier transform microwave spectrometer. Least-squares fitting and Kraitchman's method of isotopic substitution were used to determine the heavy-atom structure and indicate that the spectra can be assigned to a conformation with an intramolecular hydrogen bond from the amide to the amine. This conformation corresponds to the lowest energy ab initio structure, optimized at the MP2/6-31+G†† level. The experimental structure of alaninamide is also compared to the structures of the amino acids glycine and alanine.