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Updated: Aug 23, 2025

Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
The many forms of alpha-methoxy phenylacetic acid in the gas phase: flexibility, internal dynamics, and their
Himanshi Singh1,2, Pablo Pinacho1, Daniel A Obenchain3
1Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg, Germany. pablo.pinacho@desy.de.
Abstract:
We present a rotational spectroscopy study of alpha-methoxy phenylacetic acid in the gas phase. This acid is a derivative of mandelic acid and is used in various organic reactions. The conformational landscape of alpha-methoxy phenylacetic acid was explored to gain insight into its intramolecular dynamics. A rich rotational spectrum was obtained using chirped-pulse Fourier transform microwave spectroscopy in the 2-8 GHz range. Five conformers out of six calculated low-energy forms were identified in the spectrum, and the assignment of the 13C singly substituted isotopologues for the lowest-energy conformer led to its accurate structure determination. Splitting patterns were analyzed and attributed to the internal rotation of a methyl top. The analysis of the non-covalent interactions within the molecule highlights the subtle balance in the stabilization of the different conformers. We thus provide high-level structural and intramolecular dynamics information that is also used to benchmark the performance of quantum-chemical calculations.
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