CCSD(T) study of the far-infrared spectrum of ethyl methyl ether

Abstract

Band positions and intensities for the far-infrared bands of ethyl methyl ether are variationally determined from a three-dimensional ͑3D͒ potential energy surface calculated with CCSD͑T͒/ cc-pVTZ theory. For this purpose, the energies of 181 selected geometries computed optimizing 3n − 9 parameters are fitted to a 3D Fourier series depending on three torsional coordinates. The zero point vibrational energy correction and the search of a correct definition of the methyl torsional coordinate are taken into consideration for obtaining very accurate frequencies. In addition, second order perturbation theory is applied on the two molecular conformers, trans and cis-gauche, in order to test the validity of the 3D model. Consequently, a new assignment of previous experimental bands, congruent with the new ab initio results, is proposed. For the most stable trans-conformer, the 30 , 29 , and 28 fundamental transitions, computed at 115.3, 206.5, and 255.2 cm −1 , are correlated with the observed bands at 115.4, 202, and 248 cm −1 . For the cis-gauche the three band positions are computed at 91.0, 192.5, and 243.8 cm −1 . Calculations on the −d 3 isotopomer confirm our assignment. Intensities are determined at room temperature and at 10 K. Structural parameters, potential energy barriers, anharmonic frequencies for the 3n − 9 neglected modes, and rotational parameters ͑rotational and centrifugal distortion constants͒, are also provided.

Time evolution of the CO2 hydrogenation to fuels over Cu-Zr-SBA-15 catalysts

“…The band of adsorbed methane shows an increasing trend during the reaction. There are also other peaks in these regions which are indexed to other compounds and were detected in very small amounts in GC-MS (as mentioned above): methyl formate (MF) 39,50,51 , ethyl methyl ether (EME) 52 , ethanol [53][54][55] , propane [56][57][58] and butane 59 . This can be the result of random formation in the gas phase rather than the catalyst's activity.…”

Highly correlated ab initio study of the far infrared spectra of methyl acetate

“…Since methyl acetate has same symmetry properties than ethyl-methyl-ether, we have used various subroutines recently developed. 13,14 Our previous studies of molecules with methyl groups (acetic acid, 15 glicolaldehyde, 16 methyl formate, 17,18 methanol, 19 and dimethyl ether 20,21 ) are employed in the discussion of this paper.…”

Accurate Spectroscopic Characterization of Ethyl Mercaptan and Dimethyl Sulfide Isotopologues: A Route Toward Their Astrophysical Detection

“…State-of-the-art ab initio methods can be used to compute highly accurate spectroscopic constants, even for nonrigid molecules (Brites et al 2008;Halvick et al 2011;Puzzarini et al 2014a;Senent et al 2009Senent et al , 2014. Today, these constants are known to provide the required accuracy to guide experimental investigations of rotational and far-infrared spectra.…”