Methyl Internal Rotation in the Microwave Spectrum of Vinyl Acetate

Nguyen, Ha Vinh Lam; Jabri, Atef; Van, Vinh; Stahl, Wolfgang

doi:10.1021/jp5075829

Cited by 33 publications

(55 citation statements)

References 30 publications

(66 reference statements)

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“…The assignments were more difficult because the barrier height is very low, causing large splittings in the microwave spectrum. This observation has been found previously in other low barrier internal rotation problems treated by XIAM, such as ethyl acetate (101.606(23) cm À1 , 85.3 kHz), [27] allyl acetate (98.093(12) cm À1 , 54.0 kHz), [28] vinyl acetate (151.492(34) cm À1 , 92.3 kHz), [29] and 3-pentyn-1-ol (9.4552(94) cm À1 , 20.7 kHz). The standard deviation of 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 90.4 kHz of this fit is much larger than the measurement accuracy.…”

Section: Gas Phase By Microwave Spectroscopysupporting

confidence: 85%

Interplay Between Microwave Spectroscopy and X‐ray Diffraction: The Molecular Structure and Large Amplitude Motions of 2,3‐Dimethylanisole

et al. 2018

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To determine the structural properties of 2,3-dimethylanisole, a multidisciplinary approach was carried out where gas phase rotational spectroscopy recording a spectrum from 2 to 26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer was combined with solid-state X-ray diffraction. Both methods revealed that only one conformer with a planar heavy-atom structure exists. In the solid state, the packing in the monoclinic space group is P2 /n with Z=4. In the gas phase spectrum, torsional splittings due to the internal rotations of two methyl groups attached to the phenyl ring were resolved and analyzed, providing an estimate of the barriers to methyl internal rotation of V =26.9047(5) and 518.7(12) cm for the methyl groups at the ortho- and meta-position, respectively. The coupling between the two internal rotations is modeled on a two-dimensional potential energy surface, which was obtained by quantum chemical calculations at the B3LYP/6-311++G(d,p) level of theory.

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Section: Gas Phase By Microwave Spectroscopysupporting

confidence: 85%

Interplay Between Microwave Spectroscopy and X‐ray Diffraction: The Molecular Structure and Large Amplitude Motions of 2,3‐Dimethylanisole

et al. 2018

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“…For the acetyl methyl torsion, it is known from as eries of saturated acetates that the barrieri sl argely invariant. [2][3][4] However, in unsaturated acetates such as vinyl acetate [5] and isopropenyl acetate, [6] p-electron conjugation becomes possible and the barrier increases significantly.T his leads us to ask what situation might be found in acetamides, where complex electronic conjugationb etween p electrons and the lone electron pairi sp resent?B yu sing methyl internal rotation as as ensitive probe,t his question can be answered by comparing the torsional barriers in N-methyland N-ethylacetamide.…”

Section: Introductionmentioning

confidence: 99%

“…[24] Only for tert-butyl acetate, the steric effect of the bulky tert-butyl group caused as lightly higherb arriero f 112cm À 1 . [25] In vinyl acetate [5] and isopropenyl acetate, [6] where the vinyl group is bound directly to the ester group and p-electron conjugation,e xtending from the vinyl double bond to the ester group, is possible, the barrier heights increase significantly to 151.492(34) cm À1 and 135.3498(38)cm…”

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confidence: 99%

Acetyl Methyl Torsion in N‐Ethylacetamide: A Challenge for Microwave Spectroscopy and Quantum Chemistry

et al. 2015

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The gas-phase structures and parameters describing acetyl methyl torsion of N-ethylacetamide are determined with high accuracy, using a combination of molecular beam Fourier-transform microwave spectroscopy and quantum chemical calculations. Conformational studies at the MP2 level of theory yield four minima on the energy surface. The most energetically favorable conformer, which possesses C1 symmetry, is assigned. Due to the torsional barrier of 73.4782(1) cm(-1) of the acetyl methyl group, fine splitting up to 4.9 GHz is found in the spectrum. The conformational structure is not only confirmed by the rotational constants, but also by the orientation of the internal rotor. The (14) N quadrupole hyperfine splittings are analyzed and the deduced coupling constants are compared with the calculated values.

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“…For consistency, apart from the 62 CP-FTMW and 2220 millimeter wave transitions measured in this work, 72 additional transitions from Velino et al (2009) and 154 transitions measured by Nguyen et al (2014) …”

Section: Spectroscopic Analysismentioning

confidence: 72%

“…1, is the most stable one. Recently, another work on vinyl acetate in the microwave range from 6 to 40 GHz was performed (Nguyen et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Laboratory millimeter wave spectrum and astronomical search for vinyl acetate

Kolesníková

Peña

Alonso

et al. 2015

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Context. The recent discovery of methyl acetate in Orion KL makes vinyl acetate, CH 3 C=OOCH=CH 2 , a potential molecule in the interstellar medium. We obtained very accurate spectroscopic constants in a comprehensive laboratory analysis of its rotational spectra which can be used to predict those transition frequencies towards interstellar sources. Aims. We present the experimental study and theoretical analysis of the ground torsional state of vinyl acetate in a large spectral range for astrophysical use. Methods. The room-temperature rotational spectrum of vinyl acetate has been measured from 125 to 305 GHz to provide direct frequencies to the astronomical community. Additional measurements have also been made using a broadband CP-FTMW spectrometer in the region of 6−18 GHz. Transition lines, corresponding to the most stable conformer, have been observed and assigned. All the rotational transitions revealed the A-E splitting due to the methyl internal rotation and had to be treated with a specific internal rotation code (BELGI-Cs). Results. We analyzed 2508 transitions up to J = 75 for v t = 0 for the most stable conformer of vinyl acetate. The new lines were globally fitted with previously published data and 24 parameters of the Hamiltonian were accurately determined. The spectral features of vinyl acetate were then searched for in Orion KL. Using the whole line survey of Orion KL (80−280 GHz) obtained with the IRAM 30 m radio telescope we can provide only an upper limit to the column density of vinyl acetate. However, using the ALMA science verification data we obtain a tentative detection of this species that will require further search at other frequencies to confirm its presence in this high mass star forming region.

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Methyl Internal Rotation in the Microwave Spectrum of Vinyl Acetate

Cited by 33 publications

References 30 publications

Interplay Between Microwave Spectroscopy and X‐ray Diffraction: The Molecular Structure and Large Amplitude Motions of 2,3‐Dimethylanisole

Interplay Between Microwave Spectroscopy and X‐ray Diffraction: The Molecular Structure and Large Amplitude Motions of 2,3‐Dimethylanisole

Acetyl Methyl Torsion in N‐Ethylacetamide: A Challenge for Microwave Spectroscopy and Quantum Chemistry

Laboratory millimeter wave spectrum and astronomical search for vinyl acetate

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