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Fourier Transform Microwave Spectrum and Ab Initio Study of Dimethyl Methylphosphonate

Published

Author(s)

R D. Suenram, Francis J. Lovas, David F. Plusquellic, A Lesarri, Y Kawashima, J O. Jensen, A C. Samuels

Abstract

The rotational spectrum of dimethyl methylphophonate (DMMP) has been studied using a pulsed molecular beam Fourier transform microwave spectrometer. The spectrum is complicated by the internal rotation motions of the three methyl tops in the molecule as well as an interconversion motion of the methoxy tops. In this paper, we present the experimental measurements, ab initio calculations, and the assignment of the rigid rotor A state of the molecule. The rotational constants for the A state are A = 2828.753(2) MHz, B = 1972.360(3) MHz and C = 1614.267(2) MHz. In the following paper, the group theoretical analysis is developed for DMMP. The observed conformation of the molecule has no symmetry and all three selection rules are active with c-type transitions being the most intense. Ab initio calculations were carried out at both the Hartree Fock and MP2 levels of theory. These calculations indicate that two low energy conformations are possible and the calculated lowest energy conformer is in agreement with the one observed experimentally. The relative energies of the two low energy conformers change a substantial amount between teh two levels of theory.
Citation
Journal of Molecular Spectroscopy
Volume
211
Issue
No. 1

Keywords

Ab initio calculations, dimethyl methyl phosphonate, fourier transform spectrum, internal rotation, inversion motion, rotational spectrum, structure

Citation

Suenram, R. , Lovas, F. , Plusquellic, D. , Lesarri, A. , Kawashima, Y. , Jensen, J. and Samuels, A. (2002), Fourier Transform Microwave Spectrum and Ab Initio Study of Dimethyl Methylphosphonate, Journal of Molecular Spectroscopy (Accessed April 12, 2024)
Created January 1, 2002, Updated February 17, 2017