Reinvestigation of the microwave spectrum of 2-methylmalonaldehyde

Ilyushin, V. V.; Alekseev, E. A.; Chou, Yung Ching; Hsu, Yuan-Hao; Hougen, Jon T.; Lovas, F. J.; Picraux, Laura B.

doi:10.1016/j.jms.2008.01.005

Cited by 22 publications

(84 citation statements)

References 10 publications

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“…This inverted torsional structure and its mechanism are similar to those found in 2-methylmalonaldehyde [25,26] and acetaldehyde(S 1 ) [31].…”

Section: Discussionsupporting

confidence: 76%

“…An inverted torsional structure (A > G > E) in the upper inversion sublevel, compared with the structure in the lower one (E > G > A), could thus be observed in enolic acetylacetone with the C s equilibrium structures if the intramolecular hydrogen transfer dominates over the two torsions. This behavior of the energy order and its mechanism are similar to those found in 2-methylmalonaldehyde [25,26] and acetaldehyde(S 1 ) [31] which both have an inversion-like motion accompanied by a ''corrective internal rotation". In these three molecules, the energy of the non-degenerate (A or B) sublevels change faster than those of the E (and G) sublevels with the increasing of the tunneling splitting of the inversion-like motion, and the non-degenerate sublevel becomes the highest one in the upper inversion sublevel when the inversion-like motion dominates.…”

Section: Discussionsupporting

confidence: 73%

“…Similar to the ''hydrogen-transfer-methyl-torsion" interaction in 2-methylmalonaldehyde [25,26], the act of hydrogen transfer in enolic acetylacetone induces a tautomeric rearrangement of CC, CO single and double bonds, and then triggers two additional 60°internal rotation, one in each of the two methyl groups attached to the hydrogen-bonded malonaldehyde ring.…”

Section: Introductionmentioning

confidence: 98%

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Group-theoretical investigation of the tunneling splitting patterns of enolic acetylacetone

Chou¹

2010

Journal of Molecular Spectroscopy

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“…This inverted torsional structure and its mechanism are similar to those found in 2-methylmalonaldehyde [25,26] and acetaldehyde(S 1 ) [31].…”

Section: Discussionsupporting

confidence: 76%

Section: Discussionsupporting

confidence: 73%

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Group-theoretical investigation of the tunneling splitting patterns of enolic acetylacetone

Chou¹

2010

Journal of Molecular Spectroscopy

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“…From a spectroscopic point of view, the current study of the 5MT microwave spectrum was motivated by recent progress 5,6 in our quantitative understanding of the analogous tunneling system, 2-methylmalonaldehyde, 1 and by the associated question of how the system will behave when the hydrogen to be transferred and the methyl top to be rotated are well separated from each other in the molecule. Microwave spectroscopy is well suited to quantitatively determine the energy splittings associated with the intramolecular motions under discussion.…”

Section: Introductionmentioning

confidence: 99%

A microwave study of hydrogen-transfer-triggered methyl-group rotation in 5-methyltropolone

Ilyushin

Cloessner²,

Chou³

et al. 2010

The Journal of Chemical Physics

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We present here the first experimental and theoretical study of the microwave spectrum of 5-methyltropolone, which can be visualized as a seven-membered "aromatic" carbon ring with a five-membered hydrogen-bonded cyclic structure at the top and a methyl group at the bottom. The molecule is known from earlier studies in the literature to exhibit two large-amplitude motions, an intramolecular hydrogen transfer and a methyl torsion. The former motion is particularly interesting because transfer of the hydrogen atom from the hydroxyl to the carbonyl group induces a tautomerization in the molecule, which then triggers a 60° internal rotation of the methyl group. Measurements were carried out by Fourier-transform microwave spectroscopy in the 8-24 GHz frequency range. Theoretical analysis was carried out using a tunneling-rotational Hamiltonian based on a G(12)(m) extended-group-theory formalism. Our global fit of 1015 transitions to 20 molecular parameters gave a root-mean-square deviation of 1.5 kHz. The tunneling splitting of the two J=0 levels arising from a hypothetical pure hydrogen-transfer motion is calculated to be 1310 MHz. The tunneling splitting of the two J=0 levels arising from a hypothetical pure methyl top internal-rotation motion is calculated to be 885 MHz. We have also carried out ab initio calculations, which support the structural parameters determined from our spectroscopic analysis and give estimates of the barriers to the two large-amplitude motions.

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“…From this, the complete nuclear permutation-inversion (CNPI) group has been developed, which has its origins in the work of LonguetHiggins [10] and Hougen. [11] In the recent past, PI group theory has been successfully applied to a broad variety of complex nonrigid molecules, such as the water dimer (H 2 O) 2 (see also Section 3), [12,13] the methanol dimer (CH 3 OH) 2 , [14] 2-methylmalonaldehyde, [15,16] the dimer CH 3 FÀCHF 3 , [4] acetaldehyde CH 3 COH, [17,18] and the benzene dimer (C 6 H 6 ) 2 , [19] to mention just some to give an impression of its broad applicability. In a recent article, Hougen summarized strategies for advanced applications of PI groups to the microwave spectra of molecules with large-amplitude motions.…”

Section: Introductionmentioning

confidence: 99%

Understanding High‐Resolution Spectra of Nonrigid Molecules Using Group Theory

Schnell

2010

ChemPhysChem

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Permutation-inversion group theory has developed to become an important tool in the high-resolution spectroscopy of nonrigid molecules. This large class of molecules is very intriguing to study. Small molecules such as ammonia or Na(3) are known to be nonrigid. With increasing size, however, several large-amplitude motions are possible in a molecule, and can even interact with each other. The high-resolution spectra of nonrigid molecules are known to be quite complicated and very rich in information. Details about the molecule and its internal dynamics can be extracted, such as the molecular structure, the character of the chemical bonds, and the barrier heights to internal rotation and their dependence on the chemical bonds. However, due to the nonrigidity of the molecule and the complexity of such spectra, their analysis is usually quite challenging. Theoretical methods are needed for their prediction and analysis. This Review concentrates on permutation-inversion group theory and its usefulness for the analysis of high-resolution spectra of nonrigid molecules, which is examined in more detail using different examples. In a separate section, a special aspect of molecular symmetry is discussed: the breakdown of symmetry principles. Special emphasis is placed on the breakdown of space inversion symmetry (parity violation) in chiral molecules and its possible implications in high-resolution spectroscopy.

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Reinvestigation of the microwave spectrum of 2-methylmalonaldehyde

Cited by 22 publications

References 10 publications

Group-theoretical investigation of the tunneling splitting patterns of enolic acetylacetone

Group-theoretical investigation of the tunneling splitting patterns of enolic acetylacetone

A microwave study of hydrogen-transfer-triggered methyl-group rotation in 5-methyltropolone

Understanding High‐Resolution Spectra of Nonrigid Molecules Using Group Theory

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