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Dang NN, Pham HN, Kleiner I, Schwell M, Grabow JU, Nguyen HVL. Methyl Internal Rotation in Fruit Esters: Chain-Length Effect Observed in the Microwave Spectrum of Methyl Hexanoate. Molecules 2022; 27:molecules27092639. [PMID: 35565991 PMCID: PMC9105109 DOI: 10.3390/molecules27092639] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/13/2022] [Accepted: 04/18/2022] [Indexed: 12/02/2022] Open
Abstract
The gas-phase structures of the fruit ester methyl hexanoate, CH3-O-(C=O)-C5H11, have been determined using a combination of molecular jet Fourier-transform microwave spectroscopy and quantum chemistry. The microwave spectrum was measured in the frequency range of 3 to 23 GHz. Two conformers were assigned, one with Cs symmetry and the other with C1 symmetry where the γ-carbon atom of the hexyl chain is in a gauche orientation in relation to the carbonyl bond. Splittings of all rotational lines into doublets were observed due to internal rotation of the methoxy methyl group CH3-O, from which torsional barriers of 417 cm−1 and 415 cm−1, respectively, could be deduced. Rotational constants obtained from geometry optimizations at various levels of theory were compared to the experimental values, confirming the soft degree of freedom of the (C=O)-C bond observed for the C1 conformer of shorter methyl alkynoates like methyl butyrate and methyl valerate. Comparison of the barriers to methyl internal rotation of methyl hexanoate to those of other CH3-O-(C=O)-R molecules leads to the conclusion that though the barrier height is relatively constant at about 420 cm−1, it decreases in molecules with longer R.
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Affiliation(s)
- Nhu-Ngoc Dang
- Department of Life Sciences, University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam; (N.-N.D.); (H.-N.P.)
| | - Hoang-Nam Pham
- Department of Life Sciences, University of Science and Technology of Hanoi, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam; (N.-N.D.); (H.-N.P.)
| | - Isabelle Kleiner
- Université Paris Cité and Univ Paris Est Creteil, CNRS, LISA, 75013 Paris, France;
| | - Martin Schwell
- Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, 94010 Créteil, France;
| | - Jens-Uwe Grabow
- Institut für Physikalische Chemie und Elektrochemie, Gottfried-Wilhelm-Leibniz-Universität Hannover, Callinstraße 3A, 30167 Hannover, Germany
- Correspondence: (J.-U.G.); (H.V.L.N.)
| | - Ha Vinh Lam Nguyen
- Univ Paris Est Creteil and Université Paris Cité, CNRS, LISA, 94010 Créteil, France;
- Institut Universitaire de France (IUF), 75231 Paris, France
- Correspondence: (J.-U.G.); (H.V.L.N.)
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Buschmann P, Lengsfeld KG, Djahandideh J, Grabow JU. From rotational resolved spectra to an extended increment system of planar moments allowing ad-hoc conformational identification – Exemplification by the broadband microwave spectrum of α-hydroxyisobutyric acid. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2021.131805] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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3
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Dindić C, Nguyen HVL. Microwave Spectrum of Two-Top Molecule: 2-Acetyl-3-Methylthiophene. Chemphyschem 2021; 22:2420-2428. [PMID: 34546633 DOI: 10.1002/cphc.202100514] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 08/19/2021] [Indexed: 11/06/2022]
Abstract
The microwave spectrum of 2-acetyl-3-methylthiophene (2A3MT) was recorded in the frequency range from 2 to 26.5 GHz using a molecular jet Fourier transform microwave spectrometer and could be fully assigned to the anti-conformer of the molecule, while the syn-conformer was not observable. Torsional splittings of all rotational transitions in quintets due to internal rotations of the acetyl methyl and the ring methyl groups were resolved and analyzed, yielding barriers to internal rotation of 306.184(46) cm-1 and 321.813(64) cm-1 , respectively. The rotational and centrifugal distortion constants were determined with high accuracy, and the experimental values are compared to those derived from quantum chemical calculations. The experimentally determined inertial defect supports the conclusion that anti-2A3MT is planar, even though a number of MP2 calculations predicted the contrary.
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Affiliation(s)
- Christina Dindić
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany
| | - Ha Vinh Lam Nguyen
- Univ Paris Est Creteil and Université de Paris, CNRS, LISA, 94010, Créteil, France.,Institut Universitaire de France (IUF), 75231, Paris cedex 05, France
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Dindić C, Lüchow A, Vogt N, Demaison J, Nguyen HVL. Equilibrium Structure in the Presence of Methyl Internal Rotation: Microwave Spectroscopy and Quantum Chemistry Study of the Two Conformers of 2-Acetylfuran. J Phys Chem A 2021; 125:4986-4997. [PMID: 34080419 DOI: 10.1021/acs.jpca.1c01733] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
For 2-acetylfuran, quantum chemistry predicted and proton magnetic resonance study reported two conformers, anti and syn, differing in the position of the carbonyl group with respect to the O1-C2 bond of the furan ring. The microwave spectrum of the title molecule was recorded in the frequency range from 2 to 26.5 GHz using a molecular jet Fourier transform microwave spectrometer, confirming the presence of both conformers. Spectroscopic parameters such as the rotational and centrifugal distortion constants could be determined with high precision. The spectra of all 13C- and 18O-isotopologues of the energetically more favorable anti-conformer could be assigned, allowing the experimental determination of bond lengths and bond angles from the heavy atom substitution rs and the semi-experimental equilibrium reSE structures. Splittings arising from the internal rotation of the acetyl methyl group could be resolved for both conformers as well as for all assigned isotopologues, from which the barrier to methyl internal rotation was determined. The torsional barrier is largely invariant at around 319 cm-1 in the parent species of anti-2-acetylfuran and its isotopologues, showing that though isotopic substitution greatly influences the rotational properties of the molecule and causes a different microwave spectrum, its effect on the methyl torsion is negligible. On the other hand, conformational effects play a decisive role, as the torsional barrier of 239.780(13) cm-1 found for syn-2-acetylfuran differs significantly from the value for anti-2-acetylfuran. The results are compared and discussed with other methyl-substituted furan derivatives and acetyl group containing ketones for a better understanding of different effects influencing molecular geometry parameters and methyl internal rotations.
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Affiliation(s)
- Christina Dindić
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany
| | - Arne Lüchow
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany
| | - Natalja Vogt
- Section of Chemical Information Systems, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany.,Department of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russian Federation
| | - Jean Demaison
- Section of Chemical Information Systems, University of Ulm, Albert-Einstein-Allee 47, 89069 Ulm, Germany
| | - Ha Vinh Lam Nguyen
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université de Paris, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France.,Institut Universitaire de France (IUF), 1 rue Descartes, 75231 Paris Cedex 05, France
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Koziol KJ, Stahl W, Nguyen HVL. The effects of proton tunneling, 14N quadrupole coupling, and methyl internal rotations in the microwave spectrum of ethyl methyl amine. J Chem Phys 2020; 153:184308. [DOI: 10.1063/5.0025650] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Affiliation(s)
- Kenneth J. Koziol
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany
| | - Wolfgang Stahl
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany
| | - Ha Vinh Lam Nguyen
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université de Paris, Institut Pierre Simon Laplace, 61 Avenue du Général de Gaulle, 94010 Créteil, France
- Institut Universitaire de France (IUF), 1 Rue Descartes, 75231 Paris Cedex 05, France
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Andresen M, Schöngen D, Kleiner I, Schwell M, Stahl W, Nguyen HVL. Internal Rotation of the Acetyl Methyl Group in Methyl Alkyl Ketones: The Microwave Spectrum of Octan‐2‐one. Chemphyschem 2020; 21:2206-2216. [DOI: 10.1002/cphc.202000522] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 07/13/2020] [Indexed: 11/06/2022]
Affiliation(s)
- Maike Andresen
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS UMR Université Paris-Est Créteil Université de Paris Institute Pierre Simon Laplace 61 avenue du Général de Gaulle 94010 Créteil France
| | - Damian Schöngen
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany
| | - Isabelle Kleiner
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS UMR Université Paris-Est Créteil Université de Paris Institute Pierre Simon Laplace 61 avenue du Général de Gaulle 94010 Créteil France
| | - Martin Schwell
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS UMR Université Paris-Est Créteil Université de Paris Institute Pierre Simon Laplace 61 avenue du Général de Gaulle 94010 Créteil France
| | - Wolfgang Stahl
- Institute of Physical Chemistry RWTH Aachen University Landoltweg 2 52074 Aachen Germany
| | - Ha Vinh Lam Nguyen
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS UMR Université Paris-Est Créteil Université de Paris Institute Pierre Simon Laplace 61 avenue du Général de Gaulle 94010 Créteil France
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Khemissi S, Nguyen HVL. Two Equivalent Internal Rotations in the Microwave Spectrum of 2,6‐Dimethylfluorobenzene. Chemphyschem 2020; 21:1682-1687. [DOI: 10.1002/cphc.202000419] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2020] [Revised: 06/03/2020] [Indexed: 11/10/2022]
Affiliation(s)
- Safa Khemissi
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS UMR 7583 Université Paris-Est Créteil Université de Paris, Institut Pierre Simon Laplace 61 avenue du Général de Gaulle 94010 Créteil, France
| | - Ha Vinh Lam Nguyen
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA) CNRS UMR 7583 Université Paris-Est Créteil Université de Paris, Institut Pierre Simon Laplace 61 avenue du Général de Gaulle 94010 Créteil, France
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Herbers S, Fritz SM, Mishra P, Nguyen HVL, Zwier TS. Local and global approaches to treat the torsional barriers of 4-methylacetophenone using microwave spectroscopy. J Chem Phys 2020; 152:074301. [PMID: 32087663 DOI: 10.1063/1.5142401] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sven Herbers
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA
| | - Sean M. Fritz
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA
| | - Piyush Mishra
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA
| | - Ha Vinh Lam Nguyen
- Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), CNRS UMR 7583, Université Paris-Est Créteil, Université de Paris, Institute Pierre Simon Laplace, 61 avenue du Général de Gaulle, Créteil, France
| | - Timothy S. Zwier
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA
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Andresen M, Kleiner I, Schwell M, Stahl W, Nguyen HVL. Microwave Spectrum and Internal Rotations of Heptan-2-one: A Pheromone in the Gas Phase. J Phys Chem A 2020; 124:1353-1361. [DOI: 10.1021/acs.jpca.9b11577] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Maike Andresen
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52074 Aachen, Germany
- Institute Pierre Simon Laplace, CNRS UMR 7583, Université Paris-Est Créteil (UPEC), Université de Paris, Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), 61 avenue du Général de Gaulle, F-94010 Créteil, France
| | - Isabelle Kleiner
- Institute Pierre Simon Laplace, CNRS UMR 7583, Université Paris-Est Créteil (UPEC), Université de Paris, Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), 61 avenue du Général de Gaulle, F-94010 Créteil, France
| | - Martin Schwell
- Institute Pierre Simon Laplace, CNRS UMR 7583, Université Paris-Est Créteil (UPEC), Université de Paris, Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), 61 avenue du Général de Gaulle, F-94010 Créteil, France
| | - Wolfgang Stahl
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52074 Aachen, Germany
| | - Ha Vinh Lam Nguyen
- Institute Pierre Simon Laplace, CNRS UMR 7583, Université Paris-Est Créteil (UPEC), Université de Paris, Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), 61 avenue du Général de Gaulle, F-94010 Créteil, France
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Silva WGDP, Evangelisti L, van Wijngaarden J. Internal Motions and Sulfur Hydrogen Bonding in Methyl 3-Mercaptopropionate. J Phys Chem A 2019; 123:9840-9849. [PMID: 31674188 DOI: 10.1021/acs.jpca.9b08681] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effect of sulfur hydrogen bonding on the conformational equilibrium of methyl 3-mercaptopropionate was investigated using microwave spectroscopy in a supersonic jet expansion. The two most stable conformers (I and II) were assigned in the rotational spectra, and complex splitting patterns owing to the methyl internal rotation and SH tunneling motion were resolved and analyzed in detail. For both conformers, the experimental torsional barriers for the methyl top are similar and about 5.1 kJ mol-1, revealing that their geometrical differences do not affect the methyl internal rotation. The experimentally derived rotational and centrifugal distortion constants, along with the methyl internal rotation barriers, are discussed and compared with results from density functional theory and ab initio calculations. Quantum theory of atoms in molecules, noncovalent interactions, and natural bond orbital analyses show that the global minimum geometry (I), which has the thiol hydrogen oriented toward the carbonyl of the ester, is stabilized by an SH···O=C hydrogen bond. The presence of a hydrogen bond is confirmed by the derivation of an accurate experimental geometry that reveals a hydrogen bond distance and S-H-O angle of 2.515(4) Å and 117.4(1)°, respectively. These results are key benchmarks to expand the current knowledge of sulfur hydrogen bonds and the relationship between internal motions and conformational preferences in esters.
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Affiliation(s)
- Weslley G D P Silva
- Department of Chemistry , University of Manitoba , Winnipeg , Manitoba R3T 2N2 , Canada
| | - Luca Evangelisti
- Department of Chemistry "G. Ciamician" , University of Bologna , Via Selmi 2 , I-40126 Bologna , Italy
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