Proton inversion tunneling in the rotational spectrum of acetone cyanohydrin

Buschmann, Philipp; Lengsfeld, Kevin G.; Aydt, Kathryn; Jahn, Michaela K.; Herbers, Sven; Travers, Michael J.; Nguyen, Ha Vinh Lam; Grabow, Jens‐Uwe

doi:10.1016/j.jms.2020.111372

Cited by 7 publications

(4 citation statements)

References 133 publications

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“…The inversion of the two hydrogen atoms in primary amines is a typical example, which is always accompanied by the internal rotation of the entire amino -NH 2 group [30][31][32][33]. However, though not occurring as frequently as internal rotation, many molecules of great interest and importance feature this tunneling effect, such as hydrazine [34], ethylene diamine [35], gauche-1,3-butadiene [36], phenol [37], acetocyanhydrin [38], and especially dimers in particular [39,40] and complexes in general [41][42][43][44], making inversion tunneling an important LAM subject in rotational spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

2022

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Large amplitude motions (LAMs) form a fundamental phenomenon that demands the development of specific theoretical and Hamiltonian models. In recent years, along with the strong progress in instrumental techniques on high-resolution microwave spectroscopy and computational capacity in quantum chemistry, studies on LAMs have become very diverse. Larger and more complex molecular systems have been taken under investigation, ranging from series of heteroaromatic molecules from five- and six-membered rings to polycyclic-aromatic-hydrocarbon derivatives. Such systems are ideally suited to create families of molecules in which the positions and the number of LAMs can be varied, while the heteroatoms often provide a sufficient dipole moment to the systems to warrant the observation of their rotational spectra. This review will summarize three types of LAMs: internal rotation, inversion tunneling, and ring puckering, which are frequently observed in aromatic five-membered rings such as furan, thiophene, pyrrole, thiazole, and oxazole derivatives, in aromatic six-membered rings such as benzene, pyridine, and pyrimidine derivatives, and larger combined rings such as naphthalene, indole, and indan derivatives. For each molecular class, we will present the representatives and summarize the recent insights on the molecular structure and internal dynamics and how they help to advance the field of quantum mechanics.

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Section: Introductionmentioning

confidence: 99%

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

2022

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“…Specifically, the breadth of experimental work on systems with similar −OH torsional motion has led to the development of empirical correlations between tunneling frequency and barrier height. For example, in the study of acetone cyanohydrin, the authors used an apparent logarithmic relationship between Δ E and the barrier to −OH torsion to predict a value of Δ E when it also could not be determined from the microwave spectra. Using the smaller of the two predicted barrier heights for MSA of 0.69 kcal mol –1 in the linear regression from ref gives a value of Δ E = 224 GHz.…”

Section: Discussionmentioning

confidence: 99%

“…For example, in the study of acetone cyanohydrin, the authors used an apparent logarithmic relationship between Δ E and the barrier to −OH torsion to predict a value of Δ E when it also could not be determined from the microwave spectra. Using the smaller of the two predicted barrier heights for MSA of 0.69 kcal mol –1 in the linear regression from ref gives a value of Δ E = 224 GHz. Additionally, Medel has described various models that include correlating the tunneling energies of the −OH and −OD isotopologues of a particular species .…”

Section: Discussionmentioning

confidence: 99%

Microwave and Computational Study of Methanesulfonic Acid and Its Complex with Water

2023

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Spectra of methanesulfonic acid (CH3SO3H, MSA) and its complex with water have been studied by microwave spectroscopy and density functional theory calculations. For the monomer, spectra were obtained for both the parent and −OD isotopologues and, in each case, revealed a pair of tunneling states that are attributed to large amplitude motion of the hydroxyl hydrogen about the S–O(H) bond. Transitions crossing between tunneling states were not found in the parent spectrum and are estimated to be outside the range of the spectrometer, thus precluding the direct determination of the tunneling energy. For the −OD form, however, the tunneling energy was determined to be ΔE = 6471.9274(18) MHz from direct measurement of the cross-state c-type transitions. In its complex with water, the acidic hydrogen of the MSA forms a hydrogen bond with the water oxygen. A secondary hydrogen bond involving the water hydrogen and an SO3 oxygen completes a six-membered ring, forming a cyclic structure typical of hydrated oxyacids. No evidence of internal motion was observed. Rotational spectra of the CH3SO3H···D2O and CH3SO3D···D2O isotopologues were also obtained and analyzed. Comparison with theoretical calculations confirms the cyclic structure, though the orientation of the unbound water hydrogen is ambiguous.

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“…Infrared (IR) spectroscopy can provide key information on the tunneling dynamics and influence of vibrational couplings in a hydrogen-bonded complex on this process. In the last years there appeared several theoretical studies of proton tunneling in different systems, − as well as experimental ones. − …”

Section: Introductionmentioning

confidence: 99%

Theoretical Study of Proton Tunneling in the Imidazole–Imidazolium Complex

et al. 2021

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Proton tunneling in the hydrogen-bonded imidazole–imidazolium complex ion has been studied theoretically. Ab initio CASSCF/6-311++G(d,p) calculations concerning geometry optimization and vibrational frequencies have been carried out for equilibrium and transition state structures of the system. Two-dimensional double-well model potentials were constructed on the basis of ab initio results and used to analyze the proton dynamics in the hydrogen bond and the influence of the excitation of low-frequency hydrogen-bond vibrations on the proton tunneling splittings. The energy of tunneling-split vibrational sublevels of the high-frequency tunneling mode have been calculated for its ground and first excited vibrational state for the series of excitations of the coupled low-frequency intramolecular hydrogen-bond modes. The promoting and suppressing effect of the low-frequency modes on the proton splittings was shown in the ground and first excited vibrational state of the tunneling mode. The vibrational sublevels form the two separate semicontinuous bands between which the absorption transitions may occur. This mechanism explains the experimentally observed splitting and doublet-component broadening of the high-frequency N–H stretching infrared (IR) absorption band.

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Proton inversion tunneling in the rotational spectrum of acetone cyanohydrin

Abstract: first reported high resolution microwave spectrum of acetone cyanohydrin• first characterization regarding Coriolis and hyperfine structure• revealing complexity due to large amplitude motions

Cited by 7 publications

References 133 publications

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

The LAM of the Rings: Large Amplitude Motions in Aromatic Molecules Studied by Microwave Spectroscopy

Microwave and Computational Study of Methanesulfonic Acid and Its Complex with Water

Theoretical Study of Proton Tunneling in the Imidazole–Imidazolium Complex

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