Theoretical Spectrscopic Study of Two Ketones of Atmospheric Interest: Methyl Glyoxal (CH3COCHO) and Methyl Vinyl Ketone (CH3COCH=CH2)

Two ketones of atmospheric interest, methyl glyoxal and methyl vinyl ketone, are studied using explicitly correlated coupled cluster theory and core−valence correlationconsistent 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 (Ap)/ synperiplanar (Sp), respectively. trans-Methyl glyoxal and Ap-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 (V3 = 273.6 cm−1). Barriers of 429.6 and 380.7 cm−1 were computed for Ap- and Sp-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 (A2/E) and 124.636 cm−1/123.785 cm−1 (A2/E). For Ap- and Sp-methyl vinyl ketone, the ground vibrational state splittings were estimated to be 0.008 and 0.017 cm−1, respectively.European Commission 872081National Plan for Science, Technology and Innovation (MAARIFAH), King Abdulaziz City for Science and Technology, Kingdom of Saudi Arabia 0061-00101-17-2Spanish Government EIN2019-103072 PID2020112887GB-I00 PID2019-104002GB-C21ERDF A Way of Making Europe European Union Next Generation EU/PRTRCTI (CSIC)CESGARed Espanola de Computacion AECT-20202-0008 RES-AECT-2020-3-001

Theoretical Spectroscopic Study of Two Ketones of Atmospheric Interest: Methyl Glyoxal (CH3COCHO) and Methyl Vinyl Ketone (CH3COCH═CH2)

Two ketones of atmospheric interest, methyl glyoxal and methyl vinyl ketone, are studied using explicitly correlated coupled cluster theory and core-valence correlationconsistent 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 (Ap)/ synperiplanar (Sp), respectively. trans-Methyl glyoxal and Ap-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 (V3 = 273.6 cm-1). Barriers of 429.6 and 380.7 cm-1 were computed for Ap- and Sp-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 (A2/E) and 124.636 cm-1/123.785 cm-1 (A2/E). For Ap- and Sp-methyl vinyl ketone, the ground vibrational state splittings were estimated to be 0.008 and 0.017 cm-1, respectively.This project received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Marie Skłodowska-Curie Grant Agreement 872081. The authors acknowledge the National Plan for Science, Technology and Innovation (MAARIFAH), King Abdulaziz City for Science and Technology, Kingdom of Saudi Arabia (Award 0061-001- 01-17-2) and the Ministerio de Ciencia, Innovación y Universidades of Spain (Grants EIN2019-103072, PID2020- 112887GB-I00, PID2019-104002GB-C21, and ERDF A Way of Making Europe, by the European Union Next Generation EU/ PRTR). The authors acknowledge CTI (CSIC) and CESGA and the Red Española de Computación for Grants AECT-2020- 2-0008 and RES-AECT-2020-3-0011 for computing facilities

Theoretical Spectroscopic Study of Two Ketones of Atmospheric Interest: Methyl Glyoxal (CH3COCHO) and Methyl Vinyl Ketone (CH3COCH═CH2)

12 pags., 6 figs., 7 tabs. -- Published as part of The Journal of Physical Chemistry virtual special issue “Vincenzo Barone Festschrift”.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 (Ap)/synperiplanar (Sp), respectively. trans-Methyl glyoxal and Ap-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 (V3 = 273.6 cm-1). Barriers of 429.6 and 380.7 cm-1 were computed for Ap- and Sp-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 (A2/E) and 124.636 cm-1/123.785 cm-1 (A2/E). For Ap- and Sp-methyl vinyl ketone, the ground vibrational state splittings were estimated to be 0.008 and 0.017 cm-1, respectively.This project received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Marie Skłodowska-Curie Grant Agreement 872081. The authors acknowledge the National Plan for Science, Technology and Innovation (MAARIFAH), King Abdulaziz City for Science and Technology, Kingdom of Saudi Arabia (Award 0061-001- 01-17-2) and the Ministerio de Ciencia, Innovación y Universidades of Spain (Grants EIN2019-103072, PID2020- 112887GB-I00, PID2019-104002GB-C21, and ERDF A Way of Making Europe, by the European Union Next Generation EU/ PRTR). The authors acknowledge CTI (CSIC) and CESGA and the Red Española de Computación for Grants AECT-2020- 2-0008 and RES-AECT-2020-3-0011 for computing facilitie