Chirped‐Pulse and Cavity‐Based Fourier Transform Microwave Spectra of the Methyl Lactate⋅⋅⋅Ammonia Adduct

Thomas, Javix; Sukhorukov, Oleksandr; Jäger, Wolfgang; Xu, Yunjie

doi:10.1002/anie.201300707

Cited by 20 publications

(15 citation statements)

References 34 publications

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“…The addition conformer is significantly less stable and is not expected to be observed. This is consistent with previous findings in studies of methyl lactate–ammonia, methyl lactate–water, and (lactic acid) 2 –(water) 2,4,6 , namely, that the insertion conformations tend to be considerably more stable than the addition ones 20. 26, 27 The two insertion conformers have very similar stability and rotational constants because they differ only in which electron lone pair of the water oxygen atom is utilized in the intermolecular H‐bond, corresponding to whether the nonbonded water H atom points up or down with respect to the carboxyl group.…”

Section: Resultssupporting

confidence: 93%

“…This is consistent with previous findings in studies of methyl lactate-ammonia, methyl lactatewater, and (lactic acid) 2 -(water) 2,4,6 , namely, that the insertion conformations tend to be considerably more stable than the addition ones. [20,26,27] The two insertion conformers have very similar stability and rotational constants because they differ only in which electron lone pair of the water oxygen atom is utilized in the intermolecular H-bond, corresponding to whether the nonbonded water H atom points up or down with respect to the carboxyl group. The two insertion conformers, however, have drastically different dipole moment components, depending sensitively on the pointing direction of the nonbonded water H atom.…”

Section: Pfba Monohydratementioning

confidence: 99%

“…The MW experiments were carried out in Alberta by using a chirped pulse FTMW spectrometer18 and a cavity based pulsed jet FTMW spectrometer 19. These instruments were recently applied to rotational spectroscopic studies of H‐bonded systems, such as the methyl lactate–ammonia adduct20 and the glycidol–propylene oxide complex 21. Our aim was to identify the most stable conformations of this longer‐chain PFCA and its monohydrate and obtain detailed structural and dynamical information about these systems.…”

Section: Introductionmentioning

confidence: 99%

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Perfluorobutyric Acid and Its Monohydrate: A Chirped Pulse and Cavity Based Fourier Transform Microwave Spectroscopic Study

Thomas

Serrato²,

Lin³

et al. 2014

Chemistry A European J

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Rotational spectra of perfluorobutyric acid (PFBA) and its monohydrate were studied with a broadband chirped pulse and a narrow-band cavity based Fourier transform microwave spectrometer, and high-level ab initio calculations. Extensive conformational searches were performed for both the acid and its monohydrate at the MP2/6-311++G(2d,p) level of theory. Two and three conformers were predicted to exist for PFBA and its monohydrate, respectively. One set of rotational transitions was observed and assigned for each, PFBA and its monohydrate. Based on the measured broadband spectra, we confidently conclude that only one dominant conformer exists in each case. The orientation of the hydroxyl group in PFBA was determined by using isotopic analysis. Comparison of the observed transition intensities and the calculated electric dipole moment components allowed us to identify the most stable monohydrate conformation, which takes on an insertion hydrogen-bonding topology. Comparisons to the shorter chain analogues, that is, trifluoroacetic acid, perfluoropropionic acid, and their monohydrates, are made to elucidate the general trend in their conformational preference and binding topologies.

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Section: Resultssupporting

confidence: 93%

Section: Pfba Monohydratementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Perfluorobutyric Acid and Its Monohydrate: A Chirped Pulse and Cavity Based Fourier Transform Microwave Spectroscopic Study

Thomas

Serrato²,

Lin³

et al. 2014

Chemistry A European J

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“…Two conformers of ML-NH 3 were identified as the carriers of the observed IR and VCD spectra. We further note that the most stable conformer identified in this VCD study is the same one identified in the subsequent FTMW spectroscopic study (Borho and Xu, 2007 ; Thomas et al, 2013a , b ).…”

Section: Water Solvationsupporting

confidence: 77%

The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy

et al. 2016

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Vibrational optical activity spectroscopies, namely vibrational circular dichroism (VCD) and Raman optical activity (ROA), have been emerged in the past decade as powerful spectroscopic tools for stereochemical information of a wide range of chiral compounds in solution directly. More recently, their applications in unveiling solvent effects, especially those associated with water solvent, have been explored. In this review article, we first select a few examples to demonstrate the unique sensitivity of VCD spectral signatures to both bulk solvent effects and explicit hydrogen-bonding interactions in solution. Second, we discuss the induced solvent chirality, or chiral transfer, VCD spectral features observed in the water bending band region in detail. From these chirality transfer spectral data, the related conformer specific gas phase spectroscopic studies of small chiral hydration clusters, and the associated matrix isolation VCD experiments of hydrogen-bonded complexes in cold rare gas matrices, a general picture of solvation in aqueous solution emerges. In such an aqueous solution, some small chiral hydration clusters, rather than the chiral solutes themselves, are the dominant species and are the ones that contribute mainly to the experimentally observed VCD features. We then review a series of VCD studies of amino acids and their derivatives in aqueous solution under different pHs to emphasize the importance of the inclusion of the bulk solvent effects. These experimental data and the associated theoretical analyses are the foundation for the proposed “clusters-in-a-liquid” approach to account for solvent effects effectively. We present several approaches to identify and build such representative chiral hydration clusters. Recent studies which applied molecular dynamics simulations and the subsequent snapshot averaging approach to generate the ROA, VCD, electronic CD, and optical rotatory dispersion spectra are also reviewed. Challenges associated with the molecular dynamics snapshot approach are discussed and the successes of the seemingly random “ad hoc explicit solvation” reported before are also explained. To further test and improve the “clusters-in-a-liquid” model in practice, future work in terms of conformer specific gas phase spectroscopy of sequential solvation of a chiral solute, matrix isolation VCD measurements of small chiral hydration clusters, and more sophisticated models for the bulk solvent effects would be highly valuable.

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“…The SsC conformer forms the same five-membered ring structure as MG Ss due to the intramolecular hydrogen bond and also has similar torsional flexibility. Thomas et al reported the rotational spectroscopic and ab initio theoretical studies on two kinds of the hydrogen bond clusters of ML, ML-NH 3 [9] and ML-(H 2 O) 1,2 [10].…”

Section: Introductionmentioning

confidence: 99%

Fourier transformation microwave spectroscopy of the methyl glycolate–H2O complex

Fujitake

Tanaka

Ohashi

2018

Journal of Molecular Spectroscopy

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The rotational spectrum of one conformer of the methyl glycolate-H 2 O complex has been measured by means of the pulsed jet Fourier transform microwave spectrometer. The observed aand b-type transitions exhibit doublet splittings due to the internal rotation of the methyl group. On the other hand, most of the c-type transitions exhibit quartet splittings arising from the methyl internal rotation and the inversion motion between two equivalent conformations. The spectrum was analyzed using parameterized expressions of the Hamiltonian matrix elements derived by applying the tunneling matrix formalism. Based on the results obtained from ab initio calculation, the observed complex of methyl glycolate-H 2 O was assigned to the most stable conformer of the insertion complex, in which a non-planer seven membered-ring structure is formed by the intermolecular hydrogen bonds between methyl glycolate and H 2 O subunits. The inversion motion observed in the c-type transitions is therefore a kind of ring-inversion motion between two equivalent conformations. Conformational flexibility, which corresponds to the ring-inversion between two equivalent conformations and to the isomerization between two possible conformers of the insertion complex, was investigated with the help of the ab initio calculation.

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Chirped‐Pulse and Cavity‐Based Fourier Transform Microwave Spectra of the Methyl Lactate⋅⋅⋅Ammonia Adduct

Cited by 20 publications

References 34 publications

Perfluorobutyric Acid and Its Monohydrate: A Chirped Pulse and Cavity Based Fourier Transform Microwave Spectroscopic Study

Perfluorobutyric Acid and Its Monohydrate: A Chirped Pulse and Cavity Based Fourier Transform Microwave Spectroscopic Study

The Clusters-in-a-Liquid Approach for Solvation: New Insights from the Conformer Specific Gas Phase Spectroscopy and Vibrational Optical Activity Spectroscopy

Fourier transformation microwave spectroscopy of the methyl glycolate–H2O complex

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