Issue 11, 2007

Rotational spectrum of a chiral α-hydroxyester: conformation stability and internal rotation barrier heights of methyl lactate

Abstract

High resolution spectrum of methyl lactate, a chiral α-hydroxyester, has been investigated using a molecular jet Fourier transform microwave spectrometer. High level ab initio calculations were employed to study the conformational isomerism of methyl lactate. The observed rotational spectrum confirms that the most stable conformer has an intramolecular hydrogen bond of OH⋯O[double bond, length as m-dash]C type, as predicted by the ab initio calculations. The internal rotation barrier heights of the ester methyl group and the α-carbon methyl group were calculated to be 5.4 and 14.5 kJ mol−1 at the MP2/aug-cc-pVDZ level of theory for the most stable conformer. The internal rotation splittings due to the ester methyl group were observed and analyzed and the ester methyl group tunneling barrier height was determined experimentally to be 4.762 (3) kJ mol−1.

Graphical abstract: Rotational spectrum of a chiral α-hydroxyester: conformation stability and internal rotation barrier heights of methyl lactate

Supplementary files

Article information

Article type
Paper
Submitted
16 Jun 2006
Accepted
05 Jan 2007
First published
02 Feb 2007

Phys. Chem. Chem. Phys., 2007,9, 1324-1328

Rotational spectrum of a chiral α-hydroxyester: conformation stability and internal rotation barrier heights of methyl lactate

N. Borho and Y. Xu, Phys. Chem. Chem. Phys., 2007, 9, 1324 DOI: 10.1039/B608561J

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