Dorsaf Missaoui, Sinda Brahem, Faouzi Najar, Ounaies Yazidi and María Luisa Senent*,
{"title":"甲氧基甲醇(CH3-O-CH2OH)的远红外光谱:理论研究","authors":"Dorsaf Missaoui, Sinda Brahem, Faouzi Najar, Ounaies Yazidi and María Luisa Senent*, ","doi":"10.1021/acsearthspacechem.4c00053","DOIUrl":null,"url":null,"abstract":"<p >Methoxymethanol (CH<sub>3</sub>OCH<sub>2</sub>OH), an oxygenated volatile organic compound of low stability detected in the interstellar medium, represents an example of nonrigid organic molecules showing various interacting and inseparable large-amplitude motions. The species discloses a relevant coupling among torsional modes, strong enough to prevent complete assignments using effective Hamiltonians of reduced dimensionality. Theoretical models for rotational spectroscopy can improve if they treat three vibrational coordinates together. In this paper, the nonrigid properties and the far-infrared region are analyzed using highly correlated ab initio methods and a three-dimensional vibrational model. The molecule displays two <i>gauche</i>–<i>gauche</i> (CGcg and CGcg′) and one <i>trans</i>–<i>gauche</i> (Tcg) conformers, whose relative energies are very small (CGcg/CGcg′/Tcg = 0.0:641.5:792.7 cm<sup>–1</sup>). The minima are separated by relatively low barriers (1200–1500 cm<sup>–1</sup>), and the corresponding methyl torsional barriers <i>V</i><sub>3</sub> are estimated to be 595.7, 829.0, and 683.7 cm<sup>–1</sup>, respectively. The ground vibrational state rotational constants of the most stable geometry have been computed to be <i>A</i><sub>0</sub> = 17233.99 MHz, <i>B</i><sub>0</sub> = 5572.58 MHz, and <i>C</i><sub>0</sub> = 4815.55 MHz, at Δ<i>A</i><sub>0</sub> = −3.96 MHz, Δ<i>B</i><sub>0</sub> = 4.76 MHz, and Δ<i>C</i><sub>0</sub> = 2.51 MHz from previous experimental data. Low-energy levels and their tunneling splittings are determined variationally up to 700 cm<sup>–1</sup>. The <i>A</i>/<i>E</i> splitting of the ground vibrational state was computed to be 0.003 cm<sup>–1</sup>, as was expected given the methyl torsional barrier (∼600 cm<sup>–1</sup>). The fundamental levels (100), (010), and (001) are predicted at 132.133 and 132.086 cm<sup>–1</sup> (methyl torsion), 186.507 and 186.467 cm<sup>–1</sup> (O–CH<sub>3</sub> torsion), and 371.925 and 371.950 cm<sup>–1</sup> (OH torsion), respectively.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":null,"pages":null},"PeriodicalIF":2.9000,"publicationDate":"2024-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsearthspacechem.4c00053","citationCount":"0","resultStr":"{\"title\":\"The Far-Infrared Spectrum of Methoxymethanol (CH3–O–CH2OH): A Theoretical Study\",\"authors\":\"Dorsaf Missaoui, Sinda Brahem, Faouzi Najar, Ounaies Yazidi and María Luisa Senent*, \",\"doi\":\"10.1021/acsearthspacechem.4c00053\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >Methoxymethanol (CH<sub>3</sub>OCH<sub>2</sub>OH), an oxygenated volatile organic compound of low stability detected in the interstellar medium, represents an example of nonrigid organic molecules showing various interacting and inseparable large-amplitude motions. The species discloses a relevant coupling among torsional modes, strong enough to prevent complete assignments using effective Hamiltonians of reduced dimensionality. Theoretical models for rotational spectroscopy can improve if they treat three vibrational coordinates together. In this paper, the nonrigid properties and the far-infrared region are analyzed using highly correlated ab initio methods and a three-dimensional vibrational model. The molecule displays two <i>gauche</i>–<i>gauche</i> (CGcg and CGcg′) and one <i>trans</i>–<i>gauche</i> (Tcg) conformers, whose relative energies are very small (CGcg/CGcg′/Tcg = 0.0:641.5:792.7 cm<sup>–1</sup>). The minima are separated by relatively low barriers (1200–1500 cm<sup>–1</sup>), and the corresponding methyl torsional barriers <i>V</i><sub>3</sub> are estimated to be 595.7, 829.0, and 683.7 cm<sup>–1</sup>, respectively. The ground vibrational state rotational constants of the most stable geometry have been computed to be <i>A</i><sub>0</sub> = 17233.99 MHz, <i>B</i><sub>0</sub> = 5572.58 MHz, and <i>C</i><sub>0</sub> = 4815.55 MHz, at Δ<i>A</i><sub>0</sub> = −3.96 MHz, Δ<i>B</i><sub>0</sub> = 4.76 MHz, and Δ<i>C</i><sub>0</sub> = 2.51 MHz from previous experimental data. Low-energy levels and their tunneling splittings are determined variationally up to 700 cm<sup>–1</sup>. The <i>A</i>/<i>E</i> splitting of the ground vibrational state was computed to be 0.003 cm<sup>–1</sup>, as was expected given the methyl torsional barrier (∼600 cm<sup>–1</sup>). The fundamental levels (100), (010), and (001) are predicted at 132.133 and 132.086 cm<sup>–1</sup> (methyl torsion), 186.507 and 186.467 cm<sup>–1</sup> (O–CH<sub>3</sub> torsion), and 371.925 and 371.950 cm<sup>–1</sup> (OH torsion), respectively.</p>\",\"PeriodicalId\":15,\"journal\":{\"name\":\"ACS Earth and Space Chemistry\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":2.9000,\"publicationDate\":\"2024-05-29\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://pubs.acs.org/doi/epdf/10.1021/acsearthspacechem.4c00053\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"ACS Earth and Space Chemistry\",\"FirstCategoryId\":\"92\",\"ListUrlMain\":\"https://pubs.acs.org/doi/10.1021/acsearthspacechem.4c00053\",\"RegionNum\":3,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"ACS Earth and Space Chemistry","FirstCategoryId":"92","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acsearthspacechem.4c00053","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
The Far-Infrared Spectrum of Methoxymethanol (CH3–O–CH2OH): A Theoretical Study
Methoxymethanol (CH3OCH2OH), an oxygenated volatile organic compound of low stability detected in the interstellar medium, represents an example of nonrigid organic molecules showing various interacting and inseparable large-amplitude motions. The species discloses a relevant coupling among torsional modes, strong enough to prevent complete assignments using effective Hamiltonians of reduced dimensionality. Theoretical models for rotational spectroscopy can improve if they treat three vibrational coordinates together. In this paper, the nonrigid properties and the far-infrared region are analyzed using highly correlated ab initio methods and a three-dimensional vibrational model. The molecule displays two gauche–gauche (CGcg and CGcg′) and one trans–gauche (Tcg) conformers, whose relative energies are very small (CGcg/CGcg′/Tcg = 0.0:641.5:792.7 cm–1). The minima are separated by relatively low barriers (1200–1500 cm–1), and the corresponding methyl torsional barriers V3 are estimated to be 595.7, 829.0, and 683.7 cm–1, respectively. The ground vibrational state rotational constants of the most stable geometry have been computed to be A0 = 17233.99 MHz, B0 = 5572.58 MHz, and C0 = 4815.55 MHz, at ΔA0 = −3.96 MHz, ΔB0 = 4.76 MHz, and ΔC0 = 2.51 MHz from previous experimental data. Low-energy levels and their tunneling splittings are determined variationally up to 700 cm–1. The A/E splitting of the ground vibrational state was computed to be 0.003 cm–1, as was expected given the methyl torsional barrier (∼600 cm–1). The fundamental levels (100), (010), and (001) are predicted at 132.133 and 132.086 cm–1 (methyl torsion), 186.507 and 186.467 cm–1 (O–CH3 torsion), and 371.925 and 371.950 cm–1 (OH torsion), respectively.
期刊介绍:
The scope of ACS Earth and Space Chemistry includes the application of analytical, experimental and theoretical chemistry to investigate research questions relevant to the Earth and Space. The journal encompasses the highly interdisciplinary nature of research in this area, while emphasizing chemistry and chemical research tools as the unifying theme. The journal publishes broadly in the domains of high- and low-temperature geochemistry, atmospheric chemistry, marine chemistry, planetary chemistry, astrochemistry, and analytical geochemistry. ACS Earth and Space Chemistry publishes Articles, Letters, Reviews, and Features to provide flexible formats to readily communicate all aspects of research in these fields.