The structure and low-barrier methyl torsion of 3-fluorotoluene

The rotational spectrum of ethyl acetylene has been investigated between 70 and 320 GHz. A Coriolis interaction has been found between the first excited state of the methyl torsion and the C - C = C in plane deformation. Splittings of transitions in the first excited torsional state show that the barrier hindering internal rotation of the methyl group amounts to 3271 cal/mole.

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Acetyl Methyl Torsion inN-Ethylacetamide: A Challenge for Microwave Spectroscopy and Quantum Chemistry

ChemPhysChem ◽

10.1002/cphc.201500087 ◽

2015 ◽

Vol 16 (9) ◽

pp. 1906-1911 ◽

Cited By ~ 12

Author(s):

Raphaela Kannengießer ◽

Marcel J. Lach ◽

Wolfgang Stahl ◽

Ha Vinh Lam Nguyen

Keyword(s):

Quantum Chemistry ◽

Microwave Spectroscopy ◽

Methyl Torsion

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Three-Dimensional Vibrational Study of the Coupling between Methyl Torsion and the Molecular Frame in the S0 State of Acetaldehyde

The Journal of Physical Chemistry ◽

10.1021/j100021a010 ◽

1995 ◽

Vol 99 (21) ◽

pp. 8510-8515 ◽

Cited By ~ 11

Author(s):

Alfonso Nino ◽

Camelia Munoz-Caro ◽

David C. Moule

Keyword(s):

Three Dimensional ◽

Vibrational Study ◽

Methyl Torsion ◽

Molecular Frame

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Rotationally resolved spectra of transitions involving methyl torsion and C–C–O bend of acetaldehyde in the system of Ã1A″–X̃1A′

The Journal of Chemical Physics ◽

10.1063/1.1424312 ◽

2002 ◽

Vol 116 (3) ◽

pp. 1003-1011 ◽

Cited By ~ 4

Author(s):

Yung-Ching Chou ◽

Cheng-Liang Huang ◽

I-Chia Chen ◽

Chi-Kung Ni ◽

A. H. Kung

Keyword(s):

Methyl Torsion

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Computational (DFT and MP2) and spectral interpretations, normal coordinate analysis, force constants and barriers to internal rotations of Trimethylacetonitrile

Journal of Theoretical and Computational Chemistry ◽

10.1142/s0219633616500346 ◽

2016 ◽

Vol 15 (04) ◽

pp. 1650034 ◽

Cited By ~ 1

Author(s):

Tarek A. Mohamed ◽

Ibrahim A. Shaaban ◽

Usama A Soliman ◽

Lee D. Wilson

Keyword(s):

Chemical Shifts ◽

Structural Parameters ◽

Energy Difference ◽

High Energy ◽

Normal Coordinate Analysis ◽

Basis Set ◽

Normal Coordinate ◽

Methyl Torsion ◽

Surface Scan ◽

C Nmr

The Raman (3500[Formula: see text]cm[Formula: see text]100[Formula: see text]cm[Formula: see text] and IR spectra (4000[Formula: see text]cm[Formula: see text]400[Formula: see text]cm[Formula: see text] of liquid trimethylacetonitrile (C5H9N, TMA) have been obtained. In addition, the 1H and [Formula: see text]C NMR spectra of TMA were obtained in DMSO-[Formula: see text] and CDCl3. The staggered conformer (C[Formula: see text] was favored using MP2 and DFT(B3LYP/[Formula: see text]B97XD) quantum mechanical calculations utilizing a 6-311[Formula: see text]G(d,p) basis set. High energy difference estimates of 4534[Formula: see text]cm[Formula: see text]5338[Formula: see text]cm[Formula: see text] (12.96[Formula: see text]kcal/mol[Formula: see text]15.26[Formula: see text]kcal/mol) were predicted, along with three imaginary torsion frequencies for the eclipsed conformer, therefore considered a transition state. The 1H and [Formula: see text]C NMR chemical shifts were predicted with B3LYP and [Formula: see text]B97XD methods using the GIAO approximation and 6-311[Formula: see text]G(d,p) basis set. B3LYP frequencies calculation is favored herein owing to the relatively good compilation with the experimental measurements. The computed structural parameters are well correlated to those reported from electron diffraction and microwave studies. Moreover, the [Formula: see text]C[Formula: see text]H coupling constant was estimated and found consistent with that observed for the sample dissolved in DMSO-[Formula: see text]/CDCl3 solvents. Using the observed methyl torsion at 266[Formula: see text]cm[Formula: see text] in gas phase and the kinetic parameter F number, a potential function (V[Formula: see text] of [Formula: see text][Formula: see text]cm[Formula: see text]([Formula: see text][Formula: see text]kcal/mol) was obtained, this barrier to internal rotation is well correlated to 1527[Formula: see text]cm[Formula: see text] (4.37[Formula: see text]kcal/mol) predicted from MP2/6-311[Formula: see text]G(d,p) potential surface scan. Aided by the predicted wavenumbers and their IR intensity/Raman activity, the observed IR/Raman bands were intensively discussed and therefore assigned to their corresponding fundamentals, in agreement with novel normal coordinate analysis and potential energy distributions (PEDs).

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