The Microwave Spectra of m-Xylene and m-Xylene-d10. Determination of the Low Methyl Internal Rotation Barrier

2001 ◽  
Vol 56 (9-10) ◽  
pp. 635-640 ◽  
Author(s):  
C. Thomsen ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Internal Rotation ◽  
Microwave Spectroscopy ◽  
Methyl Groups ◽  
Rotation Barrier ◽  
Rotational Constants ◽  
Moments Of Inertia ◽  
Rotational Spectra ◽  
Internal Rotation Barrier

Abstract The rotational spectra of m-xylene, (CH3)2C6H4 and of m-xylene-d10, (CD3)2C6D4 have been recorded between 6 and 26.5 GHz using pulsed beam Fourier transform microwave spectroscopy. The clue for the assignment of the internal rotation multiplets was the inertial defect derived from the A1A1 species transitions. The rotational constants for m-xylene and m-xylene-d10 are A = 3572.1117(1) MHz / 2896.1195(17) MHz, B = 1761.8621(1) MHz / 1446.0236(15) MHz, C =1197.3943(2) MHz / 988.2357(7) MHz, the barrier to internal rotation of the two methyl groups are V3 = 53.7(16) J/mol / 39.8(5) J/mol, their moments of inertia were assumed to be I∞= 3.14 uÅ2 / 6.28 uÅ2.

The Microwave Spectrum of 2,6-Lutidine, Analysis of Internal Rotation and 14 N Hyperfine Structure

1993 ◽  
Vol 48 (11) ◽  
pp. 1093-1101 ◽  
Author(s):  
C. Thomsen ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Hyperfine Structure ◽  
Internal Rotation ◽  
Molecular Beam ◽  
Microwave Spectrum ◽  
Methyl Groups ◽  
Rotational Spectrum ◽  
Rotational Constants ◽  
Moments Of Inertia ◽  
Nuclear Quadrupole

Abstract The rotational spectrum of 2,6-lutidine, (CH3)2C5H3N, has been recorded between 6 and 26.5 GHz using pulsed molecular beam microwave Fourier transform spectroscopy. The rotational constants are A = 3509.7139(84) MHz, B = 1906.8639(101) MHz, and C = 1254.6215(14) MHz, the barrier to internal rotation of the two methyl groups is V3 = 1.1752 kJ/mol, their moments of inertia were found to be Iα = 3.0808(9) uÅ2 . The nitrogen nuclear quadrupole constants are χaa = +1.600(5) MHz, χbb = -4.572(3) MHz and χcc = +2.972(5) MHz.

Determination of a High Barrier Hindering Internal Rotation from the Ground State Spectrum. The Methylbarrier of Propane

1985 ◽  
Vol 40 (3) ◽  
pp. 271-273 ◽  
Author(s):  
G. Bestmann ◽  
W. Lalowski ◽  
H. Dreizler
Keyword(s):  
Fine Structure ◽  
Internal Rotation ◽  
Ground State ◽  
Methyl Groups ◽  
Rotational Spectrum ◽  
Rotation Barrier ◽  
Rotation Axes ◽  
Internal Rotation Barrier ◽  
The Moment

The internal rotation barrier V3, the moment of inertia Iα of the methyl tops and the angle between the two internal rotation axes were determined from the torsional fine structure of the rotational spectrum in the torsional ground state. A tilt angle of 1.4° of the methyl groups toward each other results.

High Resolution Microwave Spectroscopy of Ethyl Vinyl Ether: Accurate Determination of the Methyl Top Internal Rotation Barrier

2000 ◽  
Vol 55 (5) ◽  
pp. 481-485 ◽  
Author(s):  
H. Dreizler ◽  
N. Hansen
Keyword(s):  
Internal Rotation ◽  
Vinyl Ether ◽  
Accurate Determination ◽  
Ethyl Vinyl Ether ◽  
Ethyl Vinyl ◽  
Methyl Group ◽  
Rotational Spectra ◽  
Internal Rotation Barrier ◽  
In Trans

Abstract We have performed an investigation of the internal rotation of the methyl group in trans-cis ethyl vinyl ether by using molecular beam-Fourier transform Microwave (MB-FTMW) spectroscopy. Rotational spectra (up to J = 20) were recorded in the frequency region 4-19 GHz. Due to the internal rotation of the methyl group, some rotational transitions were split and the torsional barrier could be determined to V3 (CH3) = 1074.4(4) cm-1 .

Determination of a High Potential Barrier Hindering Internal Rotation in 2-Methylcyclopentanone and α-Methyl-γ-Butyrolactone by Microwave Fourier Transform Spectroscopy

1992 ◽  
Vol 47 (6) ◽  
pp. 761-764 ◽  
Author(s):  
J. L. Alonso ◽  
N. Heineking ◽  
H. Dreizler ◽  
N. Heineking ◽  
H. Dreizler
Keyword(s):  
Fourier Transform ◽  
Internal Rotation ◽  
Excited States ◽  
Fourier Transform Spectroscopy ◽  
Vibrationally Excited ◽  
Methyl Group ◽  
Internal Rotation Barrier ◽  
High Potential Barrier ◽  
Method Analysis

AbstractThe microwave spectra of α-methyl-γ-butyrolactone and 2-methylcyclopentanone have been reinvestigated using microwave Fourier transform spectroscopy. A-E splittings due to internal rotation of the methyl group have been observed in the ground and several vibrationally excited states for both molecules. From an internal-axis-method analysis of these splittings, values of the methyl group internal rotation barrier of 2.61 kcal mol-1 for α-methyl-γ-butyrolactone and 2.41 kcal mol-1 for 2-methylcyclopentanone have been obtained.

Mikrowellenspektrum, Hinderungspotential der internen Rotation und Dipolmoment des para-Fluortoluols

1965 ◽  
Vol 20 (12) ◽  
pp. 1682-1686 ◽  
Author(s):  
Heinz Dieter Rudolph ◽  
Helmut Seiler
Keyword(s):  
Dipole Moment ◽  
Internal Rotation ◽  
Absorption Lines ◽  
Type I ◽  
Rotational Spectrum ◽  
Rotation Barrier ◽  
Rotational Constants ◽  
Methyl Group ◽  
Microwave Rotational Spectrum ◽  
Internal Rotation Barrier

The microwave rotational spectrum of para-fluoro-toluene has been investigated in the region from 7 to 31 kmc/s. The three types of absorption lines to be expected in the case of a molecule of this type, i. e. with a very low sixfold barrier hindering the internal rotation of the methyl group, have been found: m=0, | m | ≠ 0, 3 n, | m | = 3 n. From the lines m=0 the rotational constants and the dipole moment, (1.96 ± 0.02) D, have been deduced; from the lines |m|=3 the internal rotation barrier could be calculated as V6=13.82 cal/mole. This V6 is compared with the values found for similar molecules.

Determination of the Internal Rotation Barrier of [15N]Formamide from Gas-Phase1H NMR Spectra

1998 ◽  
Vol 120 (8) ◽  
pp. 1934-1935 ◽  
Author(s):  
Angela N. Taha ◽  
Susan M. Neugebauer Crawford ◽  
Nancy S. True
Keyword(s):  
Internal Rotation ◽  
Nmr Spectra ◽  
Rotation Barrier ◽  
Internal Rotation Barrier

Analysis of Internal Rotation and Determination of the Heavy Atom Structure of anti-2,3-Dimethylthiirane by Fourier Transform Microwave Spectroscopy

1996 ◽  
Vol 51 (10-11) ◽  
pp. 1099-1106 ◽  
Author(s):  
Holger Hartwig ◽  
Helmut Dreizler
Keyword(s):  
Fourier Transform ◽  
Internal Rotation ◽  
Ground State ◽  
Heavy Atom ◽  
Microwave Spectroscopy ◽  
Rotational Spectrum ◽  
Advanced Technique ◽  
Fourier Transform Microwave Spectroscopy ◽  
Potential Parameters

Abstract We used the advanced technique of Fourier transform microwave spectroscopy to measure and assign the ground state rotational spectrum of anti-2,3-dimethylthiirane, and to analyse the internal rotation of the two methyl groups. The potential parameters obtained are V3 = 13.1678(21) and V12' = -1.6678(25) kJ/mol. The measurement and assignment of the 13C and 34S isotopomers in the ground state allowed to determine the molecular structure of the heavy atom frame using the Τs and Τ0 methods.

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