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Yoshihiro Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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Solvent effect on Raman spectra of conformational key bands of Chloroacetone and bromoacetone
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1999Co-Authors: Yosuke Shiratori, Minoru Kato, Yoshihiro TaniguchiAbstract:Abstract Raman spectra were measured for Chloroacetone and bromoacetone in various solvents at 20°C. The authors recorded the C–X (X:Cl and Br) stretching modes for both Chloroacetone and bromoacetone and the CO stretching mode for bromoacetone. In each spectrum for aqueous solutions, an additional band appeared on the lower frequency side of the band of the syn conformer. These bands are assigned to the syn conformer which forms a hydrogen bond between each halogen atom of haloacetones and water molecule. From solvent effects on peak frequencies, half band widths and band profiles, the authors discussed local hydration structures of haloacetones.
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Effect of water and deuterated water on Raman spectra of Chloroacetone: evidence for the conformational effect on hydration
Chemical Physics Letters, 1998Co-Authors: Minoru Kato, Yoshiaki Nanba, Yoshihiro TaniguchiAbstract:Abstract The gauche–syn isomerization of Chloroacetone in water has been studied using Raman spectroscopy as a model for the effects of hydration on molecular conformation. The spectra in water and deuterate water indicate the formation of a new type of hydrogen bonding between the chlorine atom and water only in the syn conformer. A close contact between the chlorine and oxygen atoms in the syn form facilitates the chlorine atom forming this hydrogen bond.
Minoru Kato - One of the best experts on this subject based on the ideXlab platform.
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Solvent effect on Raman spectra of conformational key bands of Chloroacetone and bromoacetone
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1999Co-Authors: Yosuke Shiratori, Minoru Kato, Yoshihiro TaniguchiAbstract:Abstract Raman spectra were measured for Chloroacetone and bromoacetone in various solvents at 20°C. The authors recorded the C–X (X:Cl and Br) stretching modes for both Chloroacetone and bromoacetone and the CO stretching mode for bromoacetone. In each spectrum for aqueous solutions, an additional band appeared on the lower frequency side of the band of the syn conformer. These bands are assigned to the syn conformer which forms a hydrogen bond between each halogen atom of haloacetones and water molecule. From solvent effects on peak frequencies, half band widths and band profiles, the authors discussed local hydration structures of haloacetones.
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Effect of water and deuterated water on Raman spectra of Chloroacetone: evidence for the conformational effect on hydration
Chemical Physics Letters, 1998Co-Authors: Minoru Kato, Yoshiaki Nanba, Yoshihiro TaniguchiAbstract:Abstract The gauche–syn isomerization of Chloroacetone in water has been studied using Raman spectroscopy as a model for the effects of hydration on molecular conformation. The spectra in water and deuterate water indicate the formation of a new type of hydrogen bonding between the chlorine atom and water only in the syn conformer. A close contact between the chlorine and oxygen atoms in the syn form facilitates the chlorine atom forming this hydrogen bond.
Laurie J. Butler - One of the best experts on this subject based on the ideXlab platform.
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Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C–Cl bond photofission in Chloroacetone at 193 nm
The Journal of chemical physics, 2011Co-Authors: Bridget W. Alligood, Daniel B. Straus, Laurie J. ButlerAbstract:We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of Chloroacetone at 193 nm: C–Cl bond photofission yielding CH3C(O)CH2 radicals, C–C bond photofission yielding CH3CO and CH2Cl products, and C–CH3 bond photofission resulting in CH3 and C(O)CH2Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C–Cl bond photofission is followed by the dissociation of the vibrationally excited CH3C(O)CH2 radicals to CH3 + COCH2. Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH3 + C(O)CH2Cl photofission channel. We find that about 89% of the Chloroacetone molecules undergo C–Cl bond ...
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analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon c cl bond photofission in Chloroacetone at 193 nm
Journal of Chemical Physics, 2011Co-Authors: Bridget W. Alligood, Daniel B. Straus, Laurie J. ButlerAbstract:We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of Chloroacetone at 193 nm: C–Cl bond photofission yielding CH3C(O)CH2 radicals, C–C bond photofission yielding CH3CO and CH2Cl products, and C–CH3 bond photofission resulting in CH3 and C(O)CH2Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C–Cl bond photofission is followed by the dissociation of the vibrationally excited CH3C(O)CH2 radicals to CH3 + COCH2. Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH3 + C(O)CH2Cl photofission channel. We find that about 89% of the Chloroacetone molecules undergo C–Cl bond ...
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What Woodward and Hoffmann didn't tell us: the failure of the Born–Oppenheimer approximation in competing reaction pathways
J. Chem. Soc. Faraday Trans., 1994Co-Authors: G. C. G. Waschewsky, Phillip W. Kash, Tanya L. Myers, D. C. Kitchen, Laurie J. ButlerAbstract:The experiments presented here identify a class of organic reactions, allowed by overall electronic symmetry but Woodward–Hoffmann forbidden, in which the failure of the Born–Oppenheimer approximation results in a marked change in the expected branching between energetically allowed chemical bond fission channels.We first review crossed laser-molecular beam experiments on the competition between photodissociation pathways in bromoacetyl and bromopropionyl chloride at 248 nm and bromoacetone at 308 nm. In the competition between C—Cl and C—Br fission in Br(CH2)nCOCl, the barrier to C—Br fission on the lowest 1A″ potential-energy surface is formed from a weakly avoided electronic configuration crossing, so that non-adiabatic recrossing of the barrier dramatically reduces the branching to C—Br fission. The experimental results and supporting ab initio calculations investigate the strong intramolecular distance dependence of the electronic configuration interaction matrix elements which split the adiabats at the barrier to C—Br fission. The second set of experiments reviewed investigates the competition between C—C and C—Br bond fission in bromoacetone excited in the 1[n(O), π*(CO)] absorption, elucidating the role of molecular conformation in influencing the probability of adiabatically traversing the conical intersection along the C—C fission reaction coordinate.The paper finishes by presenting new experiments on the photodissociation of Chloroacetone at 308 nm which test the conclusions of the earlier work. Photofragment velocity and angular distribution measurements show that C—C fission competes with C—Cl fission in this molecule, while only C—Cl fission occurs in acetyl chloride upon 1[n(O), π*(CO)] excitation. We investigate two contributing factors to understand the difference in branching. Ab initio calculations show that the splitting at the avoided crossing between the noπ*CO and the npClσ*C—Cl configurations which forms the barrier to C—Cl fission is smaller, on average, in trans-Chloroacetone than in acetyl chloride, so the rate constant for C—Cl fission is more suppressed by non-adiabtic recrossing of the reaction barrier. In addition, C—C fission can proceed more adiabatically from the gauche conformer of Chloroacetone than from near-planar geometries in acetyl chloride owing to a conformation dependence of non-adiabatic recrossing near the conical intersection. A final measurement of the conformation population dependence of the branching investigates the second contributing factor.
Hiromasa Nishikiori - One of the best experts on this subject based on the ideXlab platform.
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photoinduced reactions of Chloroacetone in solid ar identification of ch2 cocich3
Chemical Physics Letters, 2014Co-Authors: Nobuaki Tanaka, Yoshitaka Urashima, Hiromasa NishikioriAbstract:Abstract The UV light-induced reactions of Chloroacetone in a cryogenic Ar matrix were investigated using infrared spectroscopy. The photoinduced isomerisations of gauche -Chloroacetone to syn -Chloroacetone and hypochlorous acid 1-methylethenyl ester were confirmed by comparing the experimental and calculated spectra. In addition, the photolysis products were found to be CH 2 C O and a cyclopropanone⋯HCl complex. The cyclopropanone⋯HCl complex was further decomposed into CH 2 CH 2 , CO and HCl. The hypochlorous acid 1-methylethenyl ester was further isomerized to 2-chloro-2-methyloxirane.
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Photoinduced reactions of Chloroacetone in solid Ar: Identification of CH2=COCICH3
Chemical Physics Letters, 2014Co-Authors: Nobuaki Tanaka, Yoshitaka Urashima, Hiromasa NishikioriAbstract:Abstract The UV light-induced reactions of Chloroacetone in a cryogenic Ar matrix were investigated using infrared spectroscopy. The photoinduced isomerisations of gauche -Chloroacetone to syn -Chloroacetone and hypochlorous acid 1-methylethenyl ester were confirmed by comparing the experimental and calculated spectra. In addition, the photolysis products were found to be CH 2 C O and a cyclopropanone⋯HCl complex. The cyclopropanone⋯HCl complex was further decomposed into CH 2 CH 2 , CO and HCl. The hypochlorous acid 1-methylethenyl ester was further isomerized to 2-chloro-2-methyloxirane.
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Computational study of the reaction between Chloroacetone and OH radical
Computational and Theoretical Chemistry, 2013Co-Authors: Nobuaki Tanaka, S. Yamagishi, Hiromasa NishikioriAbstract:Abstract In this study, the reaction of the Chloroacetone with OH radical was studied theoretically using density functional theory (DFT) and transition state theory. The potential energy surface of the reaction was calculated at the CAM-B3LYP/6-311++G(2d,2p) and M06-2X/6-311++G(2d,2p) levels. We initially considered four possible reaction paths: (1) the hydrogen atom abstraction from Chloroacetone by OH radical; (2) the addition of the OH radical to the carbonyl carbon; (3) chlorine atom abstraction; and (4) S N 2 displacement. The conventional transition state theory was employed to calculate the rate constants. The hydrogen abstraction from the –CH 2 Cl group was found to be dominant. Since, the predicted total rate constant at the CAM-B3LYP/6-311++G(2d,2p) level was in good agreement with the experimental value at 298 K, the level of theory used in this study to describe this reaction is appropriate.
Bridget W. Alligood - One of the best experts on this subject based on the ideXlab platform.
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Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C–Cl bond photofission in Chloroacetone at 193 nm
The Journal of chemical physics, 2011Co-Authors: Bridget W. Alligood, Daniel B. Straus, Laurie J. ButlerAbstract:We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of Chloroacetone at 193 nm: C–Cl bond photofission yielding CH3C(O)CH2 radicals, C–C bond photofission yielding CH3CO and CH2Cl products, and C–CH3 bond photofission resulting in CH3 and C(O)CH2Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C–Cl bond photofission is followed by the dissociation of the vibrationally excited CH3C(O)CH2 radicals to CH3 + COCH2. Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH3 + C(O)CH2Cl photofission channel. We find that about 89% of the Chloroacetone molecules undergo C–Cl bond ...
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analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon c cl bond photofission in Chloroacetone at 193 nm
Journal of Chemical Physics, 2011Co-Authors: Bridget W. Alligood, Daniel B. Straus, Laurie J. ButlerAbstract:We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of Chloroacetone at 193 nm: C–Cl bond photofission yielding CH3C(O)CH2 radicals, C–C bond photofission yielding CH3CO and CH2Cl products, and C–CH3 bond photofission resulting in CH3 and C(O)CH2Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C–Cl bond photofission is followed by the dissociation of the vibrationally excited CH3C(O)CH2 radicals to CH3 + COCH2. Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH3 + C(O)CH2Cl photofission channel. We find that about 89% of the Chloroacetone molecules undergo C–Cl bond ...