Jump to main content
Jump to site search
Access to RSC content Close the message box

Continue to access RSC content when you are not at your institution. Follow our step-by-step guide.


Issue 34, 2015
Previous Article Next Article

Rotational spectroscopy of methyl benzoylformate and methyl mandelate: structure and internal dynamics of a model reactant and product of enantioselective reduction

Author affiliations

Abstract

Pure rotational spectra of a prototypical prochiral ester, methyl benzoylformate (MBF), and the product of its enantioselective reduction, (R)-(−)-methyl mandelate (MM), were measured in the range of 5–16 GHz, using a cavity-based molecular beam Fourier-transform microwave spectrometer. Potential conformers were located using density functional theory calculations, and one conformer of each species was identified experimentally. The minimum energy conformer of MBF, in which the ester group is in a Z orientation, was observed for the first time. Based on an atoms-in-molecules analysis, MBF contains a weak CH⋯O[double bond, length as m-dash]C hydrogen bond between the carbonyl oxygen atom of the ester group and the nearest hydrogen atom of the aromatic ring. In the minimum energy conformer of MM, the ester group is oriented to accommodate a hydrogen bond between the hydrogen atom of the hydroxyl group and the carbonyl oxygen atom (OH⋯O[double bond, length as m-dash]C), rather than the sp3 oxygen atom (OH⋯O–C). For both species, splittings of the rotational transitions were observed, which are attributed to methyl internal rotation, and the orientations and barrier heights of the methyl tops were determined precisely. The barrier heights for MBF and MM are 4.60(2) and 4.54(3) kJ mol−1, respectively, which are consistent with values predicted by high-level wavefunction-based calculations. On the basis of an atoms-in-molecules analysis, we propose that destabilization of the sp3 oxygen atom of the ester group most directly dictates the barrier height.

Graphical abstract: Rotational spectroscopy of methyl benzoylformate and methyl mandelate: structure and internal dynamics of a model reactant and product of enantioselective reduction

Back to tab navigation

Supplementary files

Article information


Submitted
29 May 2015
Accepted
26 Jul 2015
First published
27 Jul 2015

Phys. Chem. Chem. Phys., 2015,17, 21942-21949
Article type
Paper
Author version available

Rotational spectroscopy of methyl benzoylformate and methyl mandelate: structure and internal dynamics of a model reactant and product of enantioselective reduction

E. G. Schnitzler, M. R. Poopari, Y. Xu and W. Jäger, Phys. Chem. Chem. Phys., 2015, 17, 21942
DOI: 10.1039/C5CP03114A

Social activity

Search articles by author

Spotlight

Advertisements