Home
Resources
Publications
Rotational Spectroscopy of Methyl Benzoylformate and Methyl Mandelate: Structure and Internal Dynamics of a Model Reactant and Product of Enantioselective Reduction

Rotational Spectroscopy of Methyl Benzoylformate and Methyl Mandelate: Structure and Internal Dynamics of a Model Reactant and Product of Enantioselective Reduction

Elijah G Schnitzler, Mohammad Reza Poopari, Yunjie Xu, Wolfgang Jäger

Phys Chem Chem Phys. 2015 Sep 14;17(34):21942-9.

PMID: 26234934

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=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=C), rather than the sp(3) 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 sp(3) oxygen atom of the ester group most directly dictates the barrier height.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP15206550	Methyl benzoylformate		15206-55-0	Price

As a specialist in analytical chemical Products, Alfa Chemistry offers consumers a wealth of raw materials and a full range of technologies and services.

QUICK LINKS

HEADQUARTERS

Tel:

Fax:

Email: