| Autor: |
Toumi I; Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis, Tunisia., Dalbouha S; Laboratoire de Spectroscopie, Modélisation Moléculaire, Matériaux, Nanomatériaux, Eau et Environnement, LS3MN2E/CERNE2D, Faculté des Sciences Rabat, Université Mohammed V de Rabat, BP 1014 Rabat, Morocco.; Laboratoire de Chimie Organique et de Chimie Physique, Equipe de recherche: Modélisation Moléculaire, Matériaux et Environnement, Département de chimie, Faculté des Sciences d'Agadir, Université Ibn Zohr d'Agadir, BP 8106 Agadir, Morocco., Al-Mogren MM; Chemistry Department, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Kingdom of Saudi Arabia., Yazidi O; Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis, Tunisia.; Institut Préparatoire aux Etudes d'Ingénieurs el Manar, Université de Tunis El Manar, BP 244, 2092 Tunis, Tunisia., Jaïdane NE; Laboratoire de Spectroscopie Atomique Moléculaire et Applications, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis, Tunisia., Carvajal M; Departamento de Ciencias Integradas, Centro de Estudios Avanzados en Física, Matemática y Computación, Unidad Asociada GIFMAN, CSIC-UHU, Universidad de Huelva, 21071 Huelva, Spain.; Instituto Universitario Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071 Granada, Spain., Senent ML; Departamento de Química y Física Teóricas, Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006 Madrid, Spain.; Unidad Asociada GIFMAN, CSIC-UHU, Universidad de Huelva, 21071 Huelva, Spain. |
| Abstrakt: |
Two ketones of atmospheric interest, methyl glyoxal and methyl vinyl ketone, are studied using explicitly correlated coupled cluster theory and core-valence correlation-consistent basis sets. The work focuses on the far-infrared region. At the employed level of theory, the rotational constants can be determined to within a few megahertz of the experimental data. Both molecules present two conformers, trans/cis and antiperiplanar (A p )/synperiplanar (S p ), respectively. trans -Methyl glyoxal and A p -methyl vinyl ketone are the preferred structures. cis -Methyl glyoxal is a secondary minimum of very low stability, which justifies the unavailability of experimental data in this form. In methyl vinyl ketone, the two conformers are almost isoenergetic, but the interconversion implies a relatively high torsional barrier of 1798 cm -1 . A very low methyl torsional barrier was estimated for trans -methyl glyoxal ( V 3 = 273.6 cm -1 ). Barriers of 429.6 and 380.7 cm -1 were computed for A p - and S p -methyl vinyl ketone. Vibrational second-order perturbation theory was applied to determine the rovibrational parameters. The far-infrared region was explored using a variational procedure of reduced dimensionality. For trans -methyl glyoxal, the ground vibrational state was estimated to split by 0.067 cm -1 , and the two low excited energy levels (1 0) and (0 1) were found to lie at 89.588 cm -1 /88.683 cm -1 (A 2 /E) and 124.636 cm -1 /123.785 cm -1 (A 2 /E). For A p - and S p -methyl vinyl ketone, the ground vibrational state splittings were estimated to be 0.008 and 0.017 cm -1 , respectively. |
