Ab InitioDetermination of the Roto-Torsional Energy Levels oftrans-1,3-Butadiene

Senent, María Luisa

doi:10.1006/jmsp.1998.7638

Cited by 52 publications

(75 citation statements)

References 25 publications

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“…High level ab initio and density functional calculations have generally supported the gauche geometry with a CCCC dihedral angle between 30°and 41°for the minor conformer in the gas phase. 44,45,[54][55][56][57][58][59][60] Michl and co-workers 10,[60][61][62] have championed a planar structure assignment on the basis of polarized IR spectra of matrix isolated s-cis-1,3-butadiene at low T. More recently, Michl et al have also reported Ar matrix isolated 1,3-butadiene conformer Raman spectra and calculations using density functional theory and the coupled-cluster method using double substitutions. 60 A gauche geometry of the 1,3-butadiene minor conformer was now considered possible, but as a structure that tunnels very rapidly between the two mirrorimage forms.…”

Section: Discussionmentioning

confidence: 99%

UV Spectrum of the High Energy Conformer of 1,3-Butadiene in the Gas Phase

2001

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Principal component analysis and singular value decomposition (PCA and SVD) with self-modeling (SM) based on the van't Hoff equation constraint, were applied to 1,3-butadiene UV spectra measured in the 5.0-93.0°C range. The shape of the resolved UV spectrum of the high-energy conformer of 1,3-butadiene is sensitive to broadening of the spectra of the individual conformers with increasing T. A simulated spectral set, in which temperature broadening was purposely included, was used to develop a procedure that allows precise recovery of the pure component spectra. A set of Gaussians is derived that, on convolution with the spectrum for each corresponding T, creates a uniformly broadened spectral set. Exact recovery of the "s-cis spectrum" from the simulated spectral set is accomplished. Treatments of the experimental spectra using this method yields a minor conformer 1,3-butadiene spectrum that is only slightly red-shifted relative to the s-trans-1,3-butadiene spectrum and is consistent with the s-gauche structure. Application of PCA-SM to the onsets of the simulated spectral set showed that temperature broadening does not significantly alter the conformer enthalpy difference derived from the best-fit van't Hoff plot (compare 3.00000 kcal/mol assumed with 2.99992 kcal/mol recovered). The experimental onset spectra give ∆H°) 2.926 kcal/mol, in excellent agreement with previously reported values.

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Section: Discussionmentioning

confidence: 99%

UV Spectrum of the High Energy Conformer of 1,3-Butadiene in the Gas Phase

2001

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“…For this purpose, the torsional energy levels were obtained by solving the following two-dimensional Hamiltonian, 67,68 …”

Section: Torsional Analysismentioning

confidence: 99%

Theoretical spectroscopic characterization at low temperatures of detectable sulfur-organic compounds: Ethyl mercaptan and dimethyl sulfide

Senent

Puzzarini

Domı́nguez-Gómez

et al. 2014

The Journal of Chemical Physics

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Microwave and ab initio studies of rare gas-methane van der Waals complexes J. Chem. Phys. 120, 9047 (2004); 10.1063/1.1691743 This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Highly correlated ab initio methods are used for the spectroscopic characterization of ethyl mercaptan (CH 3 CH 2 32 SH, ETSH) and dimethyl sulfide (CH 3 32 SCH 3 , DMS), considering them on the vibrational ground and excited torsional states. Since both molecules show non-rigid properties, torsional energy barriers and splittings are provided. Equilibrium geometries and the corresponding rotational constants are calculated by means of a composite scheme based on CCSD(T) calculations that accounts for the extrapolation to the complete basis set limit and core-correlation effects. The ground and excited states rotational constants are then determined using vibrational corrections obtained from CCSD/cc-pVTZ force-field calculations, which are also employed to determine anharmonic frequencies for all vibrational modes. CCSD(T) and CCSD force fields are employed to predict quartic and sextic centrifugal-distortion constants, respectively. Equilibrium rotational constants are also calculated using CCSD(T)-F12. The full-dimensional anharmonic analysis does not predict displacements of the lowest torsional excited states due to Fermi resonances with the remaining vibrational modes. Thus, very accurate torsional transitions are calculated by solving variationally two-dimensional Hamiltonians depending on the CH 3 and SH torsional coordinates of ethyl mercaptan or on the two methyl groups torsions of dimethyl-sulfide. For this purpose, vibrationally corrected potential energy surfaces are computed at the CCSD(T)/aug-cc-pVTZ level of theory. For ethyl mercaptan, calculations show large differences between the gauche (g) and trans (t) conformer spectral features. Interactions between rotating groups are responsible for the displacements of the g-bands with respect to the t-bands that cannot therefore be described with one-dimensional models. For DMS, the CCSD(T) potential energy surface has been semi-empirically adjusted to reproduce experimental data. New assignments are suggested for the methyl torsion bands of ETSH and a reassignment is proposed for the infrared bands of DMS (0 3 → 0 4 and 1 0 → 1 1). Our accurate spectroscopic data should be useful for the analysis of the microwave and far infrared spectra of ETSH and DMS recorded, at low temperatures, either in laboratory or in the interstellar medium.

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“…35 The pseudopotential V´as well as the B qiqj depend on the isotopic substitution. For each isotopologue and geometry, they can be calculated using the subroutine MATRIZG 27,28 implemented in the code ENEDIM 26 and fitted to equations formally identical to Eq. (2).…”

Section: M=0mentioning

confidence: 99%

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

Senent

Domı́nguez-Gómez

Carvajal

et al. 2013

The Journal of Chemical Physics

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Highly correlated ab initio calculations (CCSD(T)) are used to compute gas phase spectroscopic parameters of three isotopologues of the methyl acetate (CH 3 COOCH 3 , CD 3 COOCH 3 , and CH 3 COOCD 3 ), searching to help experimental assignments and astrophysical detections. The molecule shows two conformers cis and trans separated by a barrier of 4457 cm −1 . The potential energy surface presents 18 minima that intertransform through three internal rotation motions. To analyze the far infrared spectrum at low temperatures, a three-dimensional Hamiltonian is solved variationally. The two methyl torsion barriers are calculated to be 99.2 cm −1 (C-CH 3 ) and 413.1 cm

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Ab InitioDetermination of the Roto-Torsional Energy Levels oftrans-1,3-Butadiene

Cited by 52 publications

References 25 publications

UV Spectrum of the High Energy Conformer of 1,3-Butadiene in the Gas Phase

UV Spectrum of the High Energy Conformer of 1,3-Butadiene in the Gas Phase

Theoretical spectroscopic characterization at low temperatures of detectable sulfur-organic compounds: Ethyl mercaptan and dimethyl sulfide

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

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