Browsing by Author "Matsuda, Yoshiyuki"

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An infrared spectroscopic study on proton transfer from CH bonds in ionized dimers of cyclic ethers
(2018-03-07)
Xie, Min
;
Matsuda, Yoshiyuki
;
Fujii, Asuka
;
應用化學系
;
應用化學系分子科學碩博班
Infrared (IR) spectroscopy of neutral and cationic dimers of tetrahydrofuran (THF) and tetrahydropyran (THP) is carried out to investigate isomerization reactions of these dimers following ionization. In the neutral state, both the THF and THP dimers tend to form the stacking structures bound essentially by dispersion. After ionization, both of these dimer cations form the proton transferred structures, in which the proton of the C alpha H bond is intermolecularly transferred and shared between the oxygen atoms. Along with the pseudorotation of the five-member ring, the barrierless proton transfer from CH occurs in the ionized THF dimer, and the dimer finally forms the proton transferred structure. In the case of the THP dimer cation, the barrierless intracluster proton transfer occurs with the conformational change of the proton donor site because the acidic CH site of the THP cation strongly depends on its conformation. These isomerization processes involving proton transfer from CH are discussed based on IR spectroscopy and theoretical reaction path searches. Published by AIP Publishing.
An integrated experimental and theoretical reaction path search: analyses of the multistage reaction of an ionized diethylether dimer involving isomerization, proton transfer, and dissociation
(2018-06-07)
Matsuda, Yoshiyuki
;
Xie, Min
;
Fujii, Asuka
;
應用化學系
;
應用化學系分子科學碩博班
An ionization-induced multistage reaction of an ionized diethylether (DEE) dimer involving isomerization, proton transfer, and dissociation is investigated by combining infrared (IR) spectroscopy, tandem mass spectrometry, and a theoretical reaction path search. The vertically-ionized DEE dimer isomerizes to a hydrogen-bonded cluster of protonated DEE and the [DEE-H] radical through barrierless intermolecular proton transfer from the CH bond of the ionized moiety. This isomerization process is confirmed by IR spectroscopy and the theoretical reaction path search. The multiple dissociation pathways following the isomerization are analyzed by tandem mass spectrometry. The isomerized cluster dissociates stepwise into a [protonated DEE-acetaldehyde (AA)] cluster, protonated DEE, and protonated AA. The structure of the fragment ion is also analyzed by IR spectroscopy. The reaction map of the multistage processes is revealed through a harmony of these experimental and theoretical methods.
Infrared Spectroscopic Investigation of the Acidic CH Bonds in Cationic n-Alkanes: Pentane, Hexane, and Heptane
(2016-08-18)
Xie, Min
;
Matsuda, Yoshiyuki
;
Fujii, Asuka
;
應用化學系
;
應用化學系分子科學碩博班
Radical cations of n-alkanes (pentane, hexane, and heptane) in the gas phase are investigated by infrared predissociation spectroscopy with the argon Or nitrogen tagging. All-trans and gauche-involving conformers are identified for these cations by comparisons of observed infrared spectra and vibrational simulations. Intense CH stretch bands are observed in the frequency region lower than the normal alkyl CH stretch frequency. These low frequencies and high intensities of the CH stretch bands are caused by the CH bond weakening and the enhanced positive charge of the hydrogen atoms through the delocalization of the sigma electron in the CH bonds. These effects of the delocalization of the a electron result in the enhanced acidity of the CH bonds. The conformation as well as alkyl chain length dependence of the acidity of the CH bonds is demonstrated by the CH stretch frequency shift trend.