The Microwave Spectrum of trans-2,3-Dimethyloxirane in Torsional Excited States

Hartwig, H.; Dreizler, H.

doi:10.1515/zna-1996-0807

Cited by 390 publications

(343 citation statements)

References 18 publications

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“…The barrier heights obtained were of 900 cm −1 (10.8 kJ mol −1 ), 1000 cm −1 (12.0 kJ mol −1 ), and 1150 cm −1 (13.8 kJ mol −1 ), for the C 8 , C 9 , and C 10 methyl groups, respectively. The methyl group internal rotational splittings predicted with these barriers, using the program XIAM, 28 are smaller than 1 kHz and therefore not resolvable in our experiment. Related molecules such as camphor, methyl internal rotation barriers, do not show internal rotation splittings in their spectra.…”

Section: A Rotational Spectrumcontrasting

confidence: 54%

Structure of fenchone by broadband rotational spectroscopy

Loru

Bermúdez

Sanz

2016

The Journal of Chemical Physics

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The bicyclic terpenoid fenchone (C10H16O, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-one) has been investigated by chirped pulse Fourier transform microwave spectroscopy in the 2-8 GHz frequency region. The parent species and all heavy atom isotopologues have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and effective (r0) structures of fenchone. Calculations at the B3LYP, M06-2X, and MP2 levels of theory with different basis sets were carried out to check their performance against experimental results. The structure of fenchone has been compared with those of norbornane (bicyclo[2.2.1]heptane) and the norbornane derivatives camphor (1,7,7-trimethylbicyclo[2.2.1]heptan-2-one) and camphene (3,3-dimethyl-2-methylenebicyclo[2.2.1]heptane), both with substituents at C2. The structure of fenchone is remarkably similar to those of camphor and camphene. Comparison with camphor allows identification of changes in ∠CCC angles due to the different position of the methyl groups. All norbornane derivatives display similar structural changes with respect to norbornane. These changes mainly affect the bond lengths and angles of the six-membered rings, indicating that the substituent at C2 drives structural adjustments to minimise ring strain after its introduction.

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Section: A Rotational Spectrumcontrasting

confidence: 54%

Structure of fenchone by broadband rotational spectroscopy

Loru

Bermúdez

Sanz

2016

The Journal of Chemical Physics

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“…In the course of the spectral analysis we performed fits of the rotational spectra of the three most abundant isotopologues (CH 3 ) 3 74 Ge 81 Br, (CH 3 ) 3 74 Ge 79 Br, and (CH 3 ) 3 72 Ge 79 Br using the least-squares fitting program XIAM, which also allows us to determine the torsional barrier V 3 [21] from the rotational spectra in the presence of nuclear quadrupole coupling hyperfine structure. XIAM is based on a Hamiltonian discussed in Ref.…”

Section: Spectral Analyses and Discussionmentioning

confidence: 99%

“…XIAM is based on a Hamiltonian discussed in Ref. [21]. The global rotational constants A and B, i.e., including torsion-rotation transitions of all measurable symmetry species, the centrifugal distortion constant D J as well as the chlorine quadrupole coupling constant eqQ were determined.…”

Section: Spectral Analyses and Discussionmentioning

confidence: 99%

Three-dimensional intramolecular dynamics: Internal rotation of (CH3)3GeBr

Schnell

Grabow

2008

Chemical Physics

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The microwave spectra of (CH 3 ) 3 74 Ge 79 Br and its isotopologues (CH 3 ) 3 72 Ge 79 Br and (CH 3 ) 3 74 Ge 81 Br have been studied in the frequency range from 2.4-20 GHz revealing the complex internal dynamics of this organometallic molecule with three internal rotors. The assignment of the complex spectrum has been facilitated by permutation-inversion theory -the appropriate molecular symmetry group is G 162 . The V 3 barrier to internal rotation is determined to be 4.783(12) kJ/mol. An analysis of the bromine quadrupole coupling yields the description of the Ge-Br and the Ge-C bonding characters. From this analysis we find that the bromine atom has a positive partial charge resulting from π-backbonding of the bromine towards germanium. From isotopic substitution, the Ge-Br bond distance could be determined to 2.34589(21) Å.

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“…At the beginning, the XIAM code (Hartwig & Dreizler 1996) was applied, which uses the Combined Axis Method (CAM). This method sets up the rotation-torsion Hamiltonian in the rho axis system for each top, and then converts the rho axis wave functions into the principal axis system.…”

Section: Theoretical Modelsmentioning

confidence: 99%

Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

Jabri

Van

Nguyen

et al. 2016

A&A

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Context. Dimethyl sulfide, CH 3 SCH 3 (DMS), is a nonrigid, sulfur-containing molecule whose astronomical detection is considered to be possible in the interstellar medium. Very accurate spectroscopic constants were obtained by a laboratory analysis of rotational microwave and millimeter wave spectra, as well as rotation-torsional far-infrared (FIR) spectra, which can be used to predict transition frequencies for a detection in interstellar sources. Aims. This work aims at the experimental study and theoretical analysis of the ground torsional state and ground torsional band ν 15 of DMS in a large spectral range for astrophysical use. Methods. The microwave spectrum was measured in the frequency range 2−40 GHz using two Molecular Beam Fourier Transform MicroWave (MB-FTMW) spectrometers in Aachen, Germany. The millimeter spectrum was recorded in the 50−110 GHz range. The FIR spectrum was measured for the first time at high resolution using the FT spectrometer and the newly built cryogenic cell at the French synchrotron SOLEIL. Results. DMS has two equivalent methyl internal rotors with a barrier height of about 730 cm −1 . We performed a fit, using the XIAM and BELGI-C s -2Tops codes, that contained the new measurements and previous transitions reported in the literature for the ground torsional state ν t = 0 (including the four torsional species AA, AE, EA and EE) and for the ground torsional band ν 15 = 1 ← 0 (including only the AA species). In the microwave region, we analyzed 584 transitions with J ≤ 30 of the ground torsional state ν t = 0 and 18 transitions with J ≤ 5 of the first excited torsional state ν t = 1. In the FIR range, 578 transitions belonging to the torsional band ν 15 = 1 ← 0 with J ≤ 27 were assigned. Totally, 1180 transitions were included in a global fit with 21 accurately determined parameters. These parameters can be used to produce a reliable line-list for an astrophysical detection of DMS.

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The Microwave Spectrum of trans-2,3-Dimethyloxirane in Torsional Excited States

Cited by 390 publications

References 18 publications

Structure of fenchone by broadband rotational spectroscopy

Structure of fenchone by broadband rotational spectroscopy

Three-dimensional intramolecular dynamics: Internal rotation of (CH3)3GeBr

Laboratory microwave, millimeter wave and far-infrared spectra of dimethyl sulfide

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