The microwave spectrum of n-butyl acetate

Attig, Thomas G.; Sutikdja, L.W.; Kannengießer, Raphaela; Kleiner, Isabelle; Stahl, Wolfgang

doi:10.1016/j.jms.2013.02.003

Cited by 31 publications

(43 citation statements)

References 23 publications

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“…Rotation about the C1−O7 bond results in trans and cis ester configurations. In agreement with our previous investigations and results from quantum‐chemical calculations, cis esters are stable conformations; on the other hand, they possess much higher relative energies than trans esters and cannot be observed under our molecular‐jet conditions. Therefore, we only focus on trans esters in the present study.…”

Section: Quantum‐chemical Calculationssupporting

confidence: 93%

“…So far,w ehave found that all acetates can be divided into three classes. Class Ic ontains a,bsaturated acetates,f or which the torsional barrieri sa lways close to 100 cm À1 .E xamples are methyl acetate, [1] ethyl acetate, [2] n-propyl acetate, [3] three conformers of n-butyl acetate, [4] two conformers of n-pentyl acetate, [5] n-hexyla cetate, [6] and allyl acetate. [7] Even if the alkyl chain is branched, as in the case of isopropyl acetate [8] and isoamyl acetate, [9] the barrier height seems to be almostu naffected.…”

Section: Introductionmentioning

confidence: 99%

“…To rsional barriers [cm À1 ]o ft he acetyl methyl groupsi nacetates. Class I: methyla cetate (1), [1] ethyl acetate (2), [2] n-propyl acetate (3), [3] n-butyl acetate (4), [4] n-pentyl acetate (5), [5] n-hexyl acetate (6), [6] isopropyl acetate (7), [8] isoamyl acetate (8), [9] and allyl acetate (9). [7] Class II:vinyl acetate (10), [10,11] (E)-butadienyl acetate (11)(this work), and (Z)-butadienyl acetate (12)( this work).…”

Section: Introductionmentioning

confidence: 99%

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Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy

et al. 2016

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The Fourier transform microwave spectra of the E and Z isomers of butadienyl acetate were measured in the frequency range from 2 to 26.5 GHz under molecular-jet conditions. The most stable conformer of each isomer, in which all heavy atoms are located in a symmetry plane, was identified after analyzing the spectrum by comparison with the results from quantum-chemical calculations. The barriers to internal rotation of the acetyl methyl group were found to be 149.1822(20) and 150.2128(48) cm(-1) for the E and Z isomers, respectively, which are similar to that of vinyl acetate. A comparison between two theoretical approaches treating internal rotation, the rho axis method and combined axis method, was also performed. The influence of the alkyl R chain on the methyl torsional barriers in CH3 -COOR acetates was explored.

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Section: Quantum‐chemical Calculationssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy

et al. 2016

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“…The two main factors determining the value of a rotational barrier are electrostatic and steric effects. While different conformations possess almost the same barrier height in e. g. nalkyl acetates, [5][6][7][8][9][10] the double bond in α,β-unsaturated acetates [11][12][13] augments the torsional barrier of the acetyl methyl group from around 100 cm À 1 found for n-alkyl acetates to 135 cm À 1 -150 cm À 1 . As another example, the steric hindrance of the bulky tert-butyl group has been reported to increase the torsional barrier of tert-butyl acetate from the value of approximately 100 cm À 1 for other acetates to 111 cm À 1 .…”

Section: Introductionmentioning

confidence: 92%

“…Here, the most abundant conformer shows a different C 1 structure, where the δ-carbon and not the γ-carbon is synclinal bent, and all other dihedral angles stay trans. [7][8][9][10] It seems that a hydrogen bond between the α-oxygen and a hydrogen atom attached at the δcarbon stabilizes this conformation of acetates. It is noteworthy that even weak intramolecular interactions, like van der Waals forces, might be strong enough to switch the preference from an all-trans to a bent structure, as has been shown for stretched and double layered hairpin conformers of n-alkanes with a chain length of at least 16-18 carbons.…”

Section: Conformational Stabilitymentioning

confidence: 99%

Internal Rotation of the Acetyl Methyl Group in Methyl Alkyl Ketones: The Microwave Spectrum of Octan‐2‐one

et al. 2020

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Methyl n-alkyl ketones form a class of molecules with interesting internal dynamics in the gas-phase. They contain two methyl groups undergoing internal rotations, the acetyl methyl group and the methyl group at the end of the alkyl chain. The torsional barrier of the acetyl methyl group is of special importance, since it allows for the discrimination of the conformational structures. As part of the series, the microwave spectrum of octan-2-one was recorded in the frequency range from 2 to 40 GHz, revealing two conformers, one with C 1 and one with C s symmetry. The barriers to internal rotation of the acetyl methyl group were determined to be 233.340(28) cm À 1 and 185.3490(81) cm À 1 , respectively, confirming the link between conformations and barrier heights already established for other methyl alkyl ketones. Extensive comparisons to molecules in the literature were carried out, and a small overview of general trends and rules concerning the acetyl methyl torsion is given. For the hexyl methyl group, the barrier height is 973.17(60) cm À 1 for the C 1 conformer and 979.62(69) cm À 1 for the C s conformer.

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Sensing the Molecular Structures of Hexan‐2‐one by Internal Rotation and Microwave Spectroscopy

et al. 2019

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Using two molecular jet Fourier transform spectrometers, the microwave spectrum of hexan‐2‐one, also called methyl n‐butyl ketone, was recorded in the frequency range from 2 to 40 GHz. Three conformers were assigned and fine splittings caused by the internal rotations of the two terminal methyl groups were analyzed. For the acetyl methyl group CH3COC3H6CH3, the torsional barrier is 186.9198(50) cm−1, 233.5913(97) cm−1, and 182.2481(25) cm−1 for the three observed conformers, respectively. The value of this parameter could be linked to the structure of the individual conformer, which enabled us to create a rule for predicting the barrier height of the acetyl methyl torsion in ketones. The very small splittings arising from the internal rotation of the butyl methyl group CH3COC3H6CH3 could be resolved as well, yielding the respective torsional barriers of 979.99(88) cm−1, 1016.30(77) cm−1, and 961.9(32) cm−1.

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The microwave spectrum of n-butyl acetate

Cited by 31 publications

References 23 publications

Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy

Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy

Internal Rotation of the Acetyl Methyl Group in Methyl Alkyl Ketones: The Microwave Spectrum of Octan‐2‐one

Sensing the Molecular Structures of Hexan‐2‐one by Internal Rotation and Microwave Spectroscopy

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