Microwave spectrum, structure, and dipole moment of the trans-trans isomer of methylpropylether

Hayashi, Michiro; Inada, N.

doi:10.1016/0022-2852(80)90139-3

Cited by 21 publications

(5 citation statements)

References 8 publications

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“…For example, the two equivalent methyl groups in dimethyl sulfide undergo internal rotations with a torsional barrier of 736 cm −1 [117], significantly lower than the value of 944 cm −1 found for dimethyl ether [118]. Further examples are trans-ethyl methyl sulfide (693 cm −1 ) [119] vs. trans-ethyl methyl ether (893 cm −1 ) [120], or conformer III of n-propyl sulfide (699 cm −1 ) [121] vs. trans-trans-methyl-n-propyl ether (1154 cm −1 ) [122].…”

Section: Sole Methyl Substitution On the Ringmentioning

confidence: 90%

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

2022

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Large amplitude motions (LAMs) form a fundamental phenomenon that demands the development of specific theoretical and Hamiltonian models. In recent years, along with the strong progress in instrumental techniques on high-resolution microwave spectroscopy and computational capacity in quantum chemistry, studies on LAMs have become very diverse. Larger and more complex molecular systems have been taken under investigation, ranging from series of heteroaromatic molecules from five- and six-membered rings to polycyclic-aromatic-hydrocarbon derivatives. Such systems are ideally suited to create families of molecules in which the positions and the number of LAMs can be varied, while the heteroatoms often provide a sufficient dipole moment to the systems to warrant the observation of their rotational spectra. This review will summarize three types of LAMs: internal rotation, inversion tunneling, and ring puckering, which are frequently observed in aromatic five-membered rings such as furan, thiophene, pyrrole, thiazole, and oxazole derivatives, in aromatic six-membered rings such as benzene, pyridine, and pyrimidine derivatives, and larger combined rings such as naphthalene, indole, and indan derivatives. For each molecular class, we will present the representatives and summarize the recent insights on the molecular structure and internal dynamics and how they help to advance the field of quantum mechanics.

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Section: Sole Methyl Substitution On the Ringmentioning

confidence: 90%

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

2022

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“…The MP2/TZ//DZ method predicts, in agreement with previous theoretical results, that the ga conformer (CCCO 60°, CCOC –178°) is the global minimum followed by the aa conformer. It should be noted that the experimental structure determination of methyl propyl ether rests on the assumption that the aa conformer is the dominant species 115. If the ga conformer is indeed the global energy minimum, reanalysis of structural data for this compound may be needed.…”

Section: Discussionmentioning

confidence: 99%

Parameterization of OPLS–AA force field for the conformational analysis of macrocyclic polyketides

2002

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The parameters for the OPLS-AA potential energy function have been extended to include some functional groups that are present in macrocyclic polyketides. Existing OPLS-AA torsional parameters for alkanes, alcohols, ethers, hemiacetals, esters, and ketoamides were improved based on MP2/aug-cc-pVTZ and MP2/aug-cc-pVDZ calculations. Nonbonded parameters for the sp(3) carbon and oxygen atoms were refined using Monte Carlo simulations of bulk liquids. The resulting force field predicts conformer energies and torsional barriers of alkanes, alcohols, ethers, and hemiacetals with an overall RMS deviation of 0.40 kcal/mol as compared to reference data. Densities of 19 bulk liquids are predicted with an average error of 1.1%, and heats of vaporization are reproduced within 2.4% of experimental values. The force field was used to perform conformational analysis of smaller analogs of the macrocyclic polyketide drug FK506. Structures that adopted low-energy conformations similar to that of bound FK506 were identified. The results show that a linker of four ketide units constitutes the shortest effector domain that allows binding of the ketide drugs to FKBP proteins. It is proposed that the exact chemical makeup of the effector domain has little influence on the conformational preference of tetraketides.

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“…Similar observation was found while comparing the barrier heights of the thiomethyl group in trans methyl ethyl sulfide (692 cm 1 ) [21] and trans methyl ethyl ether (893 cm −1 ) [56]. For conformer III of methyl n-propyl sulfide, the value of 699.4(37) cm −1 of the thiomethyl group contributes a further data point to support this trend, as the ether methyl group in trans-trans methyl n-propyl ether also has a higher torsional barrier of 1154 cm 1 [35]. We expect the same observation in methyl n-alkyl sulfides and ethers with longer alkyl chain.…”

Section: Thioethers Vs Ethersmentioning

confidence: 97%

“…Comparison between torsional barriers of oxygen and sulfur analogues has shown that the barrier height is always larger in the oxygen analogue, for example 2-methylfuran (413 cm 1 ) [31] vs. 2-methylthiophene (194 cm 1 ) [32] and dimethylfuran (439 cm 1 ) [33] vs. dimethylthiophene (248 cm 1 ) [34]. In a previous study on methyl propyl ether, only one conformer with Cs symmetry was observed where the barrier to internal rotation of the methoxy methyl group was determined to be 1154(21) cm 1 [35]. We will also compare the conformations and methyl torsional barriers of methyl propyl sulfide with those of methyl propyl ether.…”

Section: Introductionmentioning

confidence: 99%

Laboratory rotational spectroscopy of methyl n-propyl sulfide: Conformational analysis and methyl internal rotation

Tulimat

Mouhib

Nguyen

et al. 2020

Journal of Molecular Spectroscopy

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The microwave spectra of methyl n-propyl sulfide, CH3-S-CH2-CH2-CH3, were recorded in the frequency region from 2.0 to 26.5 GHz, revealing three conformers. Quantum chemical calculations were carried out to support experimental work. Fine splittings arising from the internal rotation of the methyl group attached to the sulfur atom were resolved and analyzed. Torsional barriers of about 600 cm 1 for the two conformers with C1 symmetry and about 700 cm 1 for the Cs conformer could be deduced, showing that conformations affect the methyl internal rotation.Torsional splittings of the methyl group at the end of the propyl moiety were observed for some transitions, leading to the determination of barrier heights close to 1000 cm 1 . The spectrum of the 34 S isotopologue of the most stable conformer could be measured in natural abundance. The present laboratory work provides highly accurate spectroscopic parameters, which serve as reliable starting values for extrapolation in higher frequency ranges and for the search of this sulfur-containing molecule in the interstellar medium.

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Microwave spectrum, structure, and dipole moment of the trans-trans isomer of methylpropylether

Cited by 21 publications

References 8 publications

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

Parameterization of OPLS–AA force field for the conformational analysis of macrocyclic polyketides

Laboratory rotational spectroscopy of methyl n-propyl sulfide: Conformational analysis and methyl internal rotation

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