The microwave spectrum of 2-methylthiazole: methyl internal rotation and 14N nuclear quadrupole coupling

Grabow, Jens‐Uwe; Hartwig, H.; Heineking, N.; Jäger, Wolfgang; Mäder, H.; Nicolaisen, H.‐W.; Stahl, Wolfgang

doi:10.1016/s0022-2860(02)00144-8

Cited by 14 publications

(15 citation statements)

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“…Some results obtained for 2MP are compared with those of other five-membered heterocycles in Figure 3. The V3 potential varies in a wide range from 34 cm 1 for 2-methylthiazole ( 6) [1], 106 cm 1 for 4-methylisothiazole ( 8) [2], 252 cm 1 for 2-methyloxazole ( 7) [21] to 280 cm 1 for 2MP (5).…”

Section: Discussionmentioning

confidence: 99%

“…Many investigations have been carried out on such aromatic systems, especially heterocyclic five-membered rings, to determine the methyl barrier heights, i.a. 2-methylthiazole (34.9 cm 1 ) [1], 4-methylisothiazole (105.8 cm 1 ) [2], 2,5dimethylthiophene (248.0 cm 1 ) [3], 2-acetyl-5-methylfuran (369.8 cm 1 for the trans conformer and 356.5 cm 1 for the cis conformer) [4], and 2,5-dimethylfuran (439.2 cm 1 ) [5]. From those studies it is obvious that the torsional potentials of methyl groups attached to planar aromatic rings vary in a wide range in both, shape and height.…”

Section: Introductionmentioning

confidence: 99%

“…In the case of the non-methylated systems inertial defects of 0.017, 0.074, 0.056, and 0.076 uÅ 2 are found for pyrrole(1) [26], thiazole (2)[27], oxazole (3)[28], and isothiazole (4) [29], respectively. The deviation from zero can be explained by the zero point vibrations of the rings.…”

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confidence: 99%

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¹⁴N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

et al. 2019

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Using two molecular jet Fourier transform microwave spectrometers, the rotational spectrum of 2methylpyrrole was recorded in the frequency range from 2 to 40 GHz. From the torsional splittings due to the internal rotation of the methyl group a barrier height of 279.7183(26) cm 1 was deduced.Because of the 14 N nucleus, all lines show a quadrupole hyperfine structure. The microwave spectra were analyzed using the XIAM and BELGI-Cs-hyperfine codes. The XIAM code enabled us to reproduce the whole data set with a root-mean-square deviation of 5.6 kHz while the BELGI-Cshyperfine code could provide a better root-mean-square almost by a factor of 2 compared to that of XIAM. The experimental results were complemented by quantum chemical calculations. The values of the methyl torsional barrier and the 14 N nuclear quadrupole coupling constants are discussed and compared with other methyl substituted pyrroles as well as other aromatic five-membered rings.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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¹⁴N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

et al. 2019

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“…18 The first molecule mentioned above, 2-methylthiazole (2MTA), has been studied by Grabow et al in the frequency range from 7 GHz to 13 GHz. 14 The V 3 potential of 34.938(20) cm −1 is the lowest of all examples. Two independent fits were performed in this previous investigation using the program XIAM.…”

Section: Introductionmentioning

confidence: 93%

“…The combination of a single 14 N quadrupole coupling nucleus and methyl internal rotation can be handled with the program RAM36, which implies the molecular symmetry to be Cs. 10 With the program XIAM, the symmetry is not restricted to Cs.…”

Section: Introductionmentioning

confidence: 99%

The microwave spectrum of 2-methylthiazole: 14N nuclear quadrupole coupling and methyl internal rotation

Nguyen

Van

Gutlé

et al. 2020

The Journal of Chemical Physics

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The rotational spectrum of 2-methylthiazole was recorded using two pulsed molecular jet Fourier transform microwave spectrometers operating in the frequency range of 2-40 GHz. Due to the internal rotation of the methyl group, all rotational transitions were split into A and E symmetry species lines, which were analyzed using the programs XIAM and BELGI-Cs-hyperfine, yielding a methyl torsional barrier of 34.796 75(18) cm −1 . This value was compared with that found in other monomethyl substituted aromatic five-membered rings. The 14 N quadrupole coupling constants were accurately determined to be χaa = 0.5166(20) MHz, χ bb − χcc = −5.2968(50) MHz, and χ ab = −2.297(10) MHz by fitting 531 hyperfine components. The experimental results were supplemented by quantum chemical calculations.

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Hydrogen Bonding and Molecular Geometry in Isolated Hydrates of 2‐Ethylthiazole Characterised by Microwave Spectroscopy

Cummings,

Walker

2024

ChemPhysChem

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Broadband microwave spectra of the isolated 2‐ethylthiazole molecule, and complexes of 2‐ethylthiazole···H2O and 2‐ethylthiazole···(H2O)2 have been recorded by probing a gaseous sample containing low concentrations of 2‐ethylthiazole and water within a carrier gas undergoing supersonic expansion. The identified conformer of the isolated 2‐ethylthiazole molecule and the 2‐ethylthiazole sub‐unit within each of 2‐ethylthiazole···H2O and 2‐ethylthiazole···(H2O)2 have C1 symmetry. The angle that defines rotation of the ethyl group relative to the plane of the thiazole ring, (S‐C2‐C6‐C7), is ‐98.6(10)° within the isolated 2‐ethylthiazole molecule. Analysis of molecular geometries and non‐covalent interactions reveals each hydrate complex contains a non‐linear primary hydrogen bond between an O‐H of H2O and the nitrogen atom while the O atom of the water molecule(s) interacts weakly with the ethyl group. The (Hb···N‐C2) parameter, which defines the position of the H2O molecule relative to the thiazole ring, is found to be significantly greater for 2‐ethylthiazole···H2O than for thiazole···H2O. The distance between the O atoms is determined to be 2.894(21) Å within the dihydrate complex which is shorter than observed within the isolated water dimer. The primary hydrogen bond within 2‐ethylthiazole···(H2O)2 is shorter and stronger than that in 2‐ethylthiazole···H2O as a result of cooperative hydrogen bonding effects.

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The microwave spectrum of 2-methylthiazole: methyl internal rotation and 14N nuclear quadrupole coupling

Cited by 14 publications

References 26 publications

¹⁴N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

¹⁴N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

The microwave spectrum of 2-methylthiazole: 14N nuclear quadrupole coupling and methyl internal rotation

Hydrogen Bonding and Molecular Geometry in Isolated Hydrates of 2‐Ethylthiazole Characterised by Microwave Spectroscopy

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The microwave spectrum of 2-methylthiazole: methyl internal rotation and 14N nuclear quadrupole coupling

Cited by 14 publications

References 26 publications

14N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

14N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

The microwave spectrum of 2-methylthiazole: 14N nuclear quadrupole coupling and methyl internal rotation

Hydrogen Bonding and Molecular Geometry in Isolated Hydrates of 2‐Ethylthiazole Characterised by Microwave Spectroscopy

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¹⁴N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole

¹⁴N Nuclear quadrupole coupling and methyl internal rotation in the microwave spectrum of 2-methylpyrrole