2014
DOI: 10.1002/cphc.201402727
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Conformational Transformations of Sulfur‐Containing Rings: 2‐Methyltetrahydrothiophene Gas‐Phase Structures

Abstract: Stable conformations of five-member rings with the prototype cyclopentane are well-known to exist as twist or envelope structures and are of general interest in chemistry. Here, we report on the conformational analysis of the sulfur-containing ring 2-methyltetrahydrothiophene studied by a combination of molecular beam Fourier transform microwave (MB-FTMW) spectroscopy and quantum chemistry. Two twist conformers were observed, whereby highly accurate molecular parameters could be determined. In addition, the (3… Show more

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Cited by 10 publications
(17 citation statements)
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“…As mentioned, conformer II is 4.34 kJ•mol −1 higher in energy than conformer I. In our investigations on two other five-membered rings, 2-methyltetrahydrothiophene 13 and dihydro-2-methyl-3-thiophenone, 14 which possess two similar twist structures with smaller energy difference, the assignment of the less stable conformer was straightforward. Therefore, we believe that conformer II of coffee furanone is not present under our molecular jet conditions with a very low rotational temperature of less than 2 K. given as an index (for atom numbering see Figure 1).…”
Section: Microwave Spectroscopysupporting
confidence: 59%
See 1 more Smart Citation
“…As mentioned, conformer II is 4.34 kJ•mol −1 higher in energy than conformer I. In our investigations on two other five-membered rings, 2-methyltetrahydrothiophene 13 and dihydro-2-methyl-3-thiophenone, 14 which possess two similar twist structures with smaller energy difference, the assignment of the less stable conformer was straightforward. Therefore, we believe that conformer II of coffee furanone is not present under our molecular jet conditions with a very low rotational temperature of less than 2 K. given as an index (for atom numbering see Figure 1).…”
Section: Microwave Spectroscopysupporting
confidence: 59%
“…Conformer II also has a twist structure 4 T3 with a little more envelope contribution of the envelope structure 4 E and the methyl substituent in axial orientation with q2 = 0.35 and ϕ2 = 277.6°. The optimized conformers of coffee furanone and some other related five-membered rings studied in the literature [13][14][15][16] are illustrated in Figure 2…”
Section: Quantum Chemical Calculationsmentioning
confidence: 99%
“…In previous studies using the same instruments, e.g. tetrahydrothiophen-3-one [8] and 2methyltetrahydrothiophene [29], the spectrum of the 34 S isotopologue in natural abundance of about 4% could be observed. Since many intense lines remained unassigned in the scan, we were able to assign them to the 34 S species of syn-2TPC.…”
Section: Spectral Assignment and Fitsmentioning
confidence: 84%
“…This angle was kept at a fixed value while the remaining degrees of freedom were allowed to relax during optimizations at the MP2/6-311++G(d,p) level of theory [28]. We chose this level of theory since previous microwave spectroscopic studies on related sulfur-containing rings such as 2methyltetrahydrothiophene [29], 2-methyl-1,3-dithiolane [30], and tetrahydrothiophen-3-one [8] have shown that it provides reliable rotational constants that can be used directly for the assignment of the experimental spectra. All calculations were carried out using the Gaussian 16 program package [31].…”
Section: Geometry Optimizationsmentioning
confidence: 99%
“…From many previousi nvestigations we know that splittings arising from such barriers are very small and cannot be resolved with our spectrometers. [15] …”
mentioning
confidence: 97%