The microwave spectrum of methyl neopentyl ketone

Zhao, Yue-Yue; Jin, Jing; Stahl, Wolfgang; Kleiner, Isabelle

doi:10.1016/j.jms.2012.09.002

Cited by 13 publications

(33 citation statements)

References 22 publications

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“…Atypical spectrum of the 6 16 ! 5 15 transitiono fthe trans conformer of AMF with its (00), (10), (01), (11), and (12) torsionalspecies. The frequency is in megahertz;the line width is approximately 13-25 kHz (full width at half-height), corresponding to ameasurementa ccuracy of 2kHz.…”

Section: Resultsmentioning

confidence: 99%

“…We found av alue of 307.78(59) cm À1 fort he trans and 212.71(30) cm À1 for the cis conformer.F rom many previous investigations, it is known that the torsional barriero ft he acetyl methyl group in ketones depends strongly on the substitution at the other side of the carbonylg roup (Figure8). [15][16][17][18][19][20][21] This behavior in ketones,w hereby the substituent on the other side of the carbonyl group causes the acetyl-methyl barrier to vary over aw ider ange without any apparent trends, is in strong contrast to acetates, which can be divided into classes with predictable barrier heights. [22] For example in a,b-saturated alkyl acetates,t he barrier to internal rotationi sa pproximately 100 cm À1 and remains largely invariant.…”

Section: Resultsmentioning

confidence: 99%

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The Structure and Torsional Dynamics of Two Methyl Groups in 2‐Acetyl‐5‐methylfuran as Observed by Microwave Spectroscopy

2016

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The molecular-beam Fourier transform microwave spectrum of 2-acetyl-5-methylfuran is recorded in the frequency range 2-26.5 GHz. Quantum chemical calculations calculate two conformers with trans or cis configuration of the acetyl group, both of which are assigned in the experimental spectrum. All rotational transitions split into quintets due to the internal rotations of two nonequivalent methyl groups. By using the program XIAM, the experimental spectra can be simulated with standard deviations within the measurement accuracy, and yield well-determined rotational and internal rotation parameters, inter alia the V potentials. Whereas the V barrier height of the ring-methyl rotor does not change for the two conformers, that of the acetyl-methyl rotor differs by about 100 cm . The predicted values from quantum chemistry are only on the correct order of magnitude.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

The Structure and Torsional Dynamics of Two Methyl Groups in 2‐Acetyl‐5‐methylfuran as Observed by Microwave Spectroscopy

2016

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“…[36] Unfortunately, no 13 C isotopologues could be measured in the spectrum of any methyl alkyl ketone in the series. Other molecules exhibiting "pseudo-C s " geometries are e. g. methyl neopentyl ketone, [37] cat ketone, [38] and diethyl ketone. [39]…”

Section: The C S or "Pseudo-c S " Conformermentioning

confidence: 99%

“…As depicted in Figure 6, the barrier height is always about 180 cm À 1 and firmly linked to the presence of a "pseudo-C s " structure (see Section 5.1.1.). Other molecules belonging to this class are methyl neopentyl ketone (6), [37] cat ketone (7), [38] and the C 1 -δ conformer of hexan-2-one (3) [3] (for molecule numbering, see Figure 6). The second class encloses all C 1 conformers of the methyl alkyl ketone series, [2][3][4] therefore called the "C 1 class", as well as allyl acetone (8) [47] and methyl isobutyl ketone (9).…”

Section: Structure-barrier Dependencementioning

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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“…15 This method and basis set was chosen, since it yielded reasonable rotational constants for other ketones such as methyl isobutyl ketone 16 and methyl neopentyl ketone. 17 It is also widely used in the microwave spectroscopic community. [18][19][20] The potential curves obtained using the different methods MP2, B3LYP, HF, and the basis set 6-311++G(d,p) are shown in Fig.…”

Section: Quantum Chemical Calculationsmentioning

confidence: 99%

The effects of two internal rotations in the microwave spectrum of ethyl methyl ketone

Nguyen

Van

Stahl

et al. 2014

The Journal of Chemical Physics

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The rotational spectra of ethyl methyl ketone, CH3CH2COCH3, were measured in the microwave region from 2 to 40 GHz using two molecular beam Fourier transform microwave spectrometers. Splittings due to internal rotations of both, the acetyl methyl group -COCH3 and the ethyl methyl group CH3CH2CO-, could be completely resolved. All measured transitions were fitted using two different codes, XIAM and BELGI-Cs-2Tops. Molecular parameters like the rotational constants and the centrifugal distortion constants were determined with very high accuracy. The barrier to internal rotation of the acetyl methyl group was fitted to 181.502(98) cm(-1), much lower than the value of 763.87(65) cm(-1) found for the ethyl methyl group. The splittings in the spectrum due to internal rotation of the acetyl methyl group are accordingly much larger, up to 1.2 GHz, whereas for the ethyl methyl group only splittings from a few hundreds of kHz up to 4 MHz were observed.

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The microwave spectrum of methyl neopentyl ketone

Cited by 13 publications

References 22 publications

The Structure and Torsional Dynamics of Two Methyl Groups in 2‐Acetyl‐5‐methylfuran as Observed by Microwave Spectroscopy

The Structure and Torsional Dynamics of Two Methyl Groups in 2‐Acetyl‐5‐methylfuran as Observed by Microwave Spectroscopy

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

The effects of two internal rotations in the microwave spectrum of ethyl methyl ketone

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