Infrared spectroscopy of CH stretching vibrations of jet-cooled alkylbenzene cations by using the “messenger” technique

Fujii, Asuka; Fujimaki, Eiji; Ebata, Takayuki; Mikami, Naohiko

doi:10.1063/1.481272

Cited by 70 publications

(93 citation statements)

References 74 publications

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“…Remarkable intensity enhancement of the CH stretch band has been reported in the toluene and tert-butyl cations. 9,10 Moreover, conformation dependence of the CH stretch frequency has recently been investigated for the methanol and diethyl ether cations. 11,12 The large variation of the stretch frequency and band intensity of the C α H bond was found in the diethyl ether cation, and it was concluded that the acidity of the cationic CH bond highly depends on the internal rotational conformation of the ethyl group, which affects the hyperconjugation between the C α H bond and the neighboring oxygen atom.…”

Section: Introductionmentioning

confidence: 99%

Infrared Spectroscopic Investigation of Photoionization-Induced Acidic C–H Bonds in Cyclic Ethers

2015

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Infrared (IR) predissociation spectroscopy based on vacuum-ultraviolet photoionization detection is performed for the neutral and cationic tetrahydrofuran (THF) and tetrahydropyran (THP). The CH bonds in neutral THF and THP are regarded as aprotic, even though the CH bonds are weakened by the negative hyperconjugation. After 118 nm photoionization, however, the negative hyperconjugation changes to the positive hyperconjugation and their CH bond acidities remarkably increase. In the IR spectrum of the THF cation, an intense band is observed at ca. 2700 cm(-1). This band is assigned to the antisymmetric stretch vibration of the two CαH bonds next to the oxygen atom. The high intensity and low frequency of this band are due to the delocalization of the σ electrons of the two CαH bonds to the singly occupied molecular orbital (SOMO) through the hyperconjugation. In the IR spectrum of the THP cation, on the other hand, the stretch bands of the CαH bonds do not show obvious low-frequency shift and intensity enhancement, while the stretch band of the equatorial CγH bond, at the para-position to the oxygen atom, appears at 2855 cm(-1) with high intensity. This acidity enhancement of the equatorial CγH bond is attributed to the mutiple hyperconjugation among the CγH bond, two CαCβ bonds, and SOMO of the oxygen atom. These results suggest that the difference of the hyperconjugation mechanism between the THF and THP cations arises from their preferable conformations.

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Section: Introductionmentioning

confidence: 99%

Infrared Spectroscopic Investigation of Photoionization-Induced Acidic C–H Bonds in Cyclic Ethers

2015

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“…The spectrum of particles before exposure to TEM (Figure 7a) shows a strong adsorption peak at 3050 cm −1 , which is characteristic of the aromatic CH stretches, typically present in the 3050−3090 cm −1 range. 49 Absorption bands are observed at 2980 and 1660 cm −1 , corresponding to sp 3 C−H (alkyl) stretching and the alkene group, CC, respectively. After exposure to the beam (Figure 7b), the spectrum contains adsorption bands at 2860 and 2930 cm −1 that are assigned to alkyl CH stretches.…”

Section: ■ Resultsmentioning

confidence: 99%

Microbubble Formation from Plasma Polymers

2012

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We document the formation of liquid-like particles in a toluene glow discharge that subsequently solidify via a process that releases hydrogen to form a solid microbubble with micrometer-size diameter, nanometer-size shell thickness, and high volume fraction, in excess of 90%. Liquid-like particles are produced in a toluene plasma under conditions that promote low degree of cross-linking (low power, high pressure). When these are transferred for observation in TEM, they are seen to transform under irradiation by the electron beam into solid bubbles with diameter of about 3 μm. This transformation also takes place under laser irradiation of sufficient power and under heating. We present evidence that the formation of these microbubbles is due to solidification of the liquid-like precursor that is accompanied by release of hydrogen. This mechanism is supported by a geometric model that provides a quantitative description of the particle size before and after solidification. These unique stimuli-responsive particles exhibit the potential of using temperature, electron beam, or laser as a source to change their size and structure which may find application in thermal insulators, lightweight materials, and light scattering agents.

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“…12 The CH stretching vibrations of neutral benzene are well studied by IR spectroscopy. 19,20 The CH stretching vibrations of the aromatic rings of benzene and toluene are thought to exist in the 3000-3200 cm Ϫ1 region. 19 The methyl group of toluene has the CH stretching vibrations around 2900 cm Ϫ1 .…”

Section: A Electronic Spectramentioning

confidence: 99%

“…19,20 The CH stretching vibrations of the aromatic rings of benzene and toluene are thought to exist in the 3000-3200 cm Ϫ1 region. 19 The methyl group of toluene has the CH stretching vibrations around 2900 cm Ϫ1 . 19 Mikami and co-workers suggested that the infrared intensity of the CH stretching vibrations of the monomer ions of benzene and toluene is fairly lower than that of the corresponding neutral species.…”

Section: A Electronic Spectramentioning

confidence: 99%

“…19 The methyl group of toluene has the CH stretching vibrations around 2900 cm Ϫ1 . 19 Mikami and co-workers suggested that the infrared intensity of the CH stretching vibrations of the monomer ions of benzene and toluene is fairly lower than that of the corresponding neutral species. 17 On the other hand, the cluster ions accompanied by the CR interaction have the in-frared intensity stronger than that of the neutral species.…”

Section: A Electronic Spectramentioning

confidence: 99%

See 1 more Smart Citation

Positive charge distribution in (benzene)1(toleune)2+ and (benzene)2(toluene)1+ studied by photodissociation spectroscopy

Inokuchi

Ohashi²,

Sekiya

et al. 2002

The Journal of Chemical Physics

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Infrared spectroscopy of CH stretching vibrations of jet-cooled alkylbenzene cations by using the “messenger” technique

Cited by 70 publications

References 74 publications

Infrared Spectroscopic Investigation of Photoionization-Induced Acidic C–H Bonds in Cyclic Ethers

Infrared Spectroscopic Investigation of Photoionization-Induced Acidic C–H Bonds in Cyclic Ethers

Microbubble Formation from Plasma Polymers

Positive charge distribution in (benzene)1(toleune)2+ and (benzene)2(toluene)1+ studied by photodissociation spectroscopy

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