The rotational spectrum, structure and barrier V6 to internal rotation of p-fluorotoluene

Rottstegge, J.; Hartwig, H.; Dreizler, H.

doi:10.1016/s0022-2860(98)00656-5

Cited by 34 publications

(28 citation statements)

References 11 publications

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“…In the literature standard deviations up to 150 kHz are not unusual for least-square XIAM fits of molecules with relatively large torsional splittings in the microwave spectrum. For p-fluorotoluene, for example, the m = 0 and m = 1 torsion-rotation transitions (108 lines) could be fitted to about σ = 27 kHz using XIAM [26], while the m = 3 torsion-rotation transitions (66 lines) have a standard deviation of σ = 162 kHz [26]. Nevertheless, the XIAM fits were very useful for the global analysis of the rotational spectrum of (CH 3 ) 3 SnCl, since they helped to initially assign the large number of torsion-rotation transitions.…”

Section: Rigid Rotor Symmetric Top Analysismentioning

confidence: 99%

Towards the complete analysis of the rotational spectrum of (CH3)3SnCl

Schnell

Hougen

Grabow

2008

Journal of Molecular Spectroscopy

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The rotational spectrum of the symmetric top trimethyl tin chloride (CH 3 ) 3 SnCl has been studied using a pulsed molecular beam Fourier transform microwave spectrometer in the frequency range from 3 to 24 GHz. The spectrum is exceedingly complicated by the internal rotation motions of the three equivalent methyl tops, the high number of Sn-and Cl-isotopes and the quadrupole hyperfine structure of the chlorine nucleus. In this paper, we present the microwave spectrum, ab initio calculations, permutation inversion (PI) group-theoretical considerations, Starkeffect measurements and finally the assignments and fits of the different torsionrotation species. Based on the Stark-effect measurements, the dipole moment is µ = 3.4980(30) D. Due to ∆K = ±1-mixing effects we observe linear Stark-effect behavior and additional quadrupole splitting for some K = 0 torsion-rotation transitions in (CH 3 ) 3 SnCl, which can be group-theoretically explained. The symmetric rotor fit of A 1 states leads to an effective B-constant of 1680.040124(50) MHz for the main isotopologue (CH 3 ) 3 120 Sn 35 Cl. A global fit of 182 K = 0 torsion-rotation transitions yields a V 3 torsional barrier of 148.299(54) cm −1 .

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Section: Rigid Rotor Symmetric Top Analysismentioning

confidence: 99%

Towards the complete analysis of the rotational spectrum of (CH3)3SnCl

Schnell

Hougen

Grabow

2008

Journal of Molecular Spectroscopy

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“…The determination of the internal rotation barriers offers insight into the changes in the electronic structure of toluene caused by the substituent effects. A vast number of fluoro substituted toluenes have been investigated, such as the three isomers of fluorotoluene [1][2][3][4], the six isomers of difluorotoluene [5][6][7][8][9], and 2,6-dimethylfluorobenzene [10], but studies on chloro-substituted toluenes are rather scarce. The reason is probably the quadrupole moment of the chlorine nucleus coupling the nuclear spin I = 3/2 to the end-over-end rotation of the molecule, thereby causing a hyperfine structure (hfs) in addition to the methyl torsional splittings.…”

Section: Introductionmentioning

confidence: 99%

Internal rotation and chlorine nuclear quadrupole coupling in 2-chloro-4-fluorotoluene explored by microwave spectroscopy and quantum chemistry

Nair

Herbers

Bailey

et al. 2021

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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2-Chloro-4-fluorotoluene was investigated using a combination of molecular jet Fourier transform microwave spectroscopy in the frequency range from 5 to 21 GHz and quantum chemistry. The molecule experiences an internal rotation of the methyl group, which causes a fine splitting of all rotational transitions into doublets with separation on the order of a few tens of kHz. In addition, hyperfine effects originating from the chlorine nuclear quadrupole moment coupling its spin to the end-over-end rotation of the molecule are observed. The torsional barrier was derived using both the rho and the combined-axis-method, giving a value of 462.5(41) cm -1 . Accurate rotational constants and quadrupole coupling constants were determined for two 35 Cl and 37 Cl isotopologues and compared with Bailey's semi-experimental quantum chemical predictions. The gas phase molecular structure was deduced from the experimental rotational constants supplemented with those calculated by quantum chemistry at various levels of theory. The values of the methyl torsional barrier and chlorine nuclear quadrupole coupling constants were compared with the theoretical predictions and with those of other chlorotoluene derivatives.

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“…Especially for spectroscopy, the rotational spectrum of toluene has always attracted attention since its microwave spectrum was recorded and analyzed for the first time by Rudolph et al [1] Not only the structure of toluene was determined to great accuracy, several theoretical models and program codes have been also developed to reproduce the V 6 potential arising from the internal rotation of the C 3v methyl group attached to a phenyl frame with C 2v symmetry. [2][3][4][5] To gain insights into the substitution effect on this large amplitude motion (LAM) of toluene, studies on many fluorinated derivatives have been performed, such as the investigations on three isomers of fluorotoluene, [6][7][8] a systematic microwave investigation on the six isomers of difluorotoluene, [9][10][11][12][13] and the work on two isomers of trifluorotoluene. [14] All these studies have shown a variety of the potentials of the methyl torsion in both shape and height, which depend on the substituted position(s) of the fluorine atom(s).…”

Section: Introductionmentioning

confidence: 99%

“…[6] Finally, m-fluorotoluene has remained over half a century a challenge due to the low V 3 and V 6 terms which are comparable in magnitude. [7] Investigations on toluene derivatives with two methyl groups attached on the phenyl ring are scarce, such as those on the three isomers of dimethylbenzaldehyde [15] and the three isomers of dimethylanisole. [16][17][18] The reason is probably the complexity of the microwave spectrum due to the coupled LAMs of the two methyl groups, which makes it hard to assign and to model.…”

Section: Introductionmentioning

confidence: 99%

Two Equivalent Internal Rotations in the Microwave Spectrum of 2,6‐Dimethylfluorobenzene

Khemissi

Nguyen

2020

ChemPhysChem

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Large amplitude motion of methyl groups in isolated molecules is a fundamental phenomenon in molecular physics. The methyl torsional barrier is sensitive to the steric and electronic environment in the surrounding of the methyl group, making the methyl group a detector of the molecular structure. To probe this eﬀect, the microwave spectrum of 2,6‐dimethylfluorobenzene, one of the six isomers of dimethylfluorobenzene, was measured using two pulsed molecular jet Fourier transform microwave spectrometers operating in the frequency range from 2 to 40 GHz. Due to internal rotations of two equivalent methyl groups with relatively low torsional barriers, all rotational transitions split into quartets with separations of up to several hundreds of MHz. The splittings were analyzed and modeled to deduce a torsional barrier of 236.7922 (21) cm−1. The results are compared to those obtained from quantum chemical calculations and with other fluorine substituted toluene derivatives of the current literature where the methyl group is adjacent to a fluorine atom.

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The rotational spectrum, structure and barrier V6 to internal rotation of p-fluorotoluene

Cited by 34 publications

References 11 publications

Towards the complete analysis of the rotational spectrum of (CH3)3SnCl

Towards the complete analysis of the rotational spectrum of (CH3)3SnCl

Internal rotation and chlorine nuclear quadrupole coupling in 2-chloro-4-fluorotoluene explored by microwave spectroscopy and quantum chemistry

Two Equivalent Internal Rotations in the Microwave Spectrum of 2,6‐Dimethylfluorobenzene

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