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Jin S, Hu Y, Wang P, Zhan H, Lu Q, Liu F, Sheng L. Hydrogen bonding and dominant conformations of hydrated sugar analogue complexes using tetrahydrofurfuryl alcohol as the model sugar molecule. Phys Chem Chem Phys 2018; 20:7351-7360. [DOI: 10.1039/c7cp07935d] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Water molecules, which serve as both hydrogen bond donors and acceptors, have been found to influence the conformational landscape of gas-phase phenyl-β-d-glucopyranoside.
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Affiliation(s)
- Shan Jin
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Pengchao Wang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Huaqi Zhan
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Qiao Lu
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Fuyi Liu
- National Synchrotron Radiation Laboratory
- University of Science and Technology of China
- Hefei
- P. R. China
| | - Liusi Sheng
- National Synchrotron Radiation Laboratory
- University of Science and Technology of China
- Hefei
- P. R. China
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Wang P, Hu Y, Zhan H, Chen J, Jin S, Song W, Li Y. Vibrational spectroscopy of the mass-selected tetrahydrofurfuryl alcohol monomers and its dimers in gas phase using IR depletion and VUV single photon ionization. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2017; 185:63-68. [PMID: 28544895 DOI: 10.1016/j.saa.2017.04.089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 04/22/2017] [Accepted: 04/30/2017] [Indexed: 06/07/2023]
Abstract
Tetrahydrofurfuryl alcohol (THFA, C5H10O2) is a close chemical analog of the sugar rings present in the phosphate-deoxyribose backbone structure of the nucleic acids. In present report, the infrared (IR) spectra of the size-selected THFA monomer and its dimer have been investigated in a pulsed supersonic jet using infrared-vacuum ultraviolet (VUV) ionization. Herein, the laser light at 118nm wavelength served as the source of "soft" ionization in a time-of-flight mass spectrometer. The IR features for the monomers located at 3622cm-1 can be assigned to the intramolecular hydrogen bonding stretch vibrations mainly referring to A and C conformers. Compared with the monomer, however, characteristic peaks for the dimer centered at 3415 and 3453cm-1, red shifted 207 and 169cm-1, respectively, were associated with the intermolecular hydrogen bonding stretch vibrations. Combined with the quantum-chemical calculations, the dimer in the gas phase preferred cyclic AC conformer stabled by forming two strong intermolecular hydrogen bonds, which shown the high hydrogen bond selectivity in the cluster. The conclusions drawn from the role played in the conformational flexibility by the hydroxyl and ether groups may be extended to other biomolecules.
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Affiliation(s)
- Pengchao Wang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China
| | - Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China.
| | - Huaqi Zhan
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China
| | - Jiaxin Chen
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China
| | - Shan Jin
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China
| | - Wentao Song
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China
| | - Yujian Li
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, P. R. China
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Zhan H, Hu Y, Wang P, Chen J. Molecular structures of gas-phase neutral morpholine and its monohydrated complexes: experimental and theoretical approaches. RSC Adv 2017. [DOI: 10.1039/c6ra26582k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Morpholine (NH(CH2CH2)2O) is a typical six-membered aliphatic heterocyclic compound.
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Affiliation(s)
- Huaqi Zhan
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Pengchao Wang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Jiaxin Chen
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
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Wang P, Hu Y, Zhan H, Chen J. Gas-phase conformational preference of the smallest saccharide (glycolaldehyde) and its hydrated complexes with bridged hydrogen bonding. RSC Adv 2017. [DOI: 10.1039/c6ra26965f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Glycoaldehyde (GA, HOCH2CHO) is the simplest sugar unit of the carbohydrates and the only sugar to have been detected in interstellar space to date.
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Affiliation(s)
- Pengchao Wang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Huaqi Zhan
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
| | - Jiaxin Chen
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science
- College of Biophotonics
- South China Normal University
- Guangzhou 510631
- P. R. China
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Hu Y, Guan J, Bernstein ER. Mass-selected IR-VUV (118 nm) spectroscopic studies of radicals, aliphatic molecules, and their clusters. MASS SPECTROMETRY REVIEWS 2013; 32:484-501. [PMID: 24122973 DOI: 10.1002/mas.21387] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 04/25/2013] [Accepted: 04/25/2013] [Indexed: 06/02/2023]
Abstract
Mass-selected IR plus UV/VUV spectroscopy and mass spectrometry have been coupled into a powerful technique to investigate chemical, physical, structural, and electronic properties of radicals, molecules, and clusters. Advantages of the use of vacuum ultraviolet (VUV) radiation to create ions for mass spectrometry are its application to nearly all compounds with ionization potentials below the energy of a single VUV photon, its circumventing the requirement of UV chromophore group, its inability to ionize background gases, and its greatly reduced fragmenting capabilities. In this review, mass-selected IR plus VUV (118 nm) spectroscopy is introduced first in a general manner. Selected application examples of this spectroscopy are presented, which include the detections and structural analysis of radicals, molecules, and molecular clusters in a supersonic jet.
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Affiliation(s)
- Yongjun Hu
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou, 510631, China
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Chen SY, Lee YP. Transient infrared absorption of t-CH3C(O)OO, c-CH3C(O)OO, and alpha-lactone recorded in gaseous reactions of CH3CO and O2. J Chem Phys 2010; 132:114303. [PMID: 20331293 DOI: 10.1063/1.3352315] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient species produced in gaseous reactions of CH(3)CO and O(2); IR absorption spectra of CH(3)C(O)OO and alpha-lactone were observed. Absorption bands with origins at 1851+/-1, 1372+/-2, 1169+/-6, and 1102+/-3 cm(-1) are attributed to t-CH(3)C(O)OO, and those at 1862+/-3, 1142+/-4, and 1078+/-6 cm(-1) are assigned to c-CH(3)C(O)OO. A weak band near 1960 cm(-1) is assigned to alpha-lactone, cyc-CH(2)C(=O)O, a coproduct of OH. These observed rotational contours agree satisfactorily with simulated bands based on predicted rotational parameters and dipole derivatives, and observed vibrational wavenumbers agree with harmonic vibrational wavenumbers predicted with B3LYP/aug-cc-pVDZ density-functional theory. The observed relative intensities indicate that t-CH(3)C(O)OO is more stable than c-CH(3)C(O)OO by 3+/-2 kJ mol(-1). Based on these observations, the branching ratio for the OH+alpha-lactone channel of the CH(3)CO+O(2) reaction is estimated to be 0.04+/-0.01 under 100 Torr of O(2) at 298 K. A simple kinetic model is employed to account for the decay of CH(3)C(O)OO.
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Affiliation(s)
- Sun-Yang Chen
- Department of Applied Chemistry, National Chiao Tung University, Hsinchu 30010, Taiwan
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Villano SM, Eyet N, Wren SW, Ellison GB, Bierbaum VM, Lineberger WC. Photoelectron spectroscopy and thermochemistry of the peroxyacetate anion. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2010; 16:255-268. [PMID: 20530835 DOI: 10.1255/ejms.1055] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The 351.1 nm photoelectron spectrum of the peroxyacetate anion, (CH(3)C(O)OO(-)) was measured. Analysis of the spectrum shows that the observed spectral features arise almost exclusively from transitions between the trans-conformer of the anion and the X(2)A'' and A (2)A' states of the corresponding radical. The electron affinity of trans-CH(3)C(O)OO is 2.381+/- 0.007 eV and the term energy splitting of the A (2)A' state is 0.691 +/- 0.009 eV, in excellent agreement with two prior values [Zalyubovsky et al. J. Phys. Chem. A 107, 7704 (2003); Hu et al. J. Phys. Chem. 124, 114305/1 (2006); Hu et al. J. Phys. Chem. 110, 2629 (2006)]. The gas-phase acidity of trans-peroxyacetic acid was bracketed between the acidity of acetic acid and tert-butylthiol at Delta(a)G(298)(trans-CH(3)C(O)OOH)=1439 +/- 14 kJ mol(-1) and Delta(a)H(298)(trans-CH(3)C(O)OOH)=1467+/-14 kJ mol(-1). The acidity of cis-CH(3)C(O)OOH was found by adding a calculated energy correction to the acidity of the trans-conformer; Delta(a)G(298)[cis-CH(3)C(O)OOH] = 1461 +/- 14 kJ mol(-1) and Delta(a)H(298)[cis- CH(3)C(O)OOH]=1490+/-14 kJ mol(-1). The O-H bond dissociation energies for both conformers were determined using a negative ion thermodynamic cycle to be D(0)[trans- CH(3)C(O)OOH]=381+/-14 kJ mol(-1) and D(0)[cis- CH(3)C(O)OOH]=403+/-14 kJ mol(-1). The atmospheric implications of these results and relations to the thermochemistry of peroxyacetyl nitrate are discussed briefly.
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Affiliation(s)
- Stephanie M Villano
- JILA, University of Colorado and the National Institute of Standards and Technology and Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0440, USA
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Hu Y, Bernstein ER. Vibrational and Photoionization Spectroscopy of Neutral Valine Clusters. J Phys Chem A 2009; 113:8454-61. [DOI: 10.1021/jp901208f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yongjun Hu
- MOE Key Lab of Laser Life Science & Institute of Laser Life Science, South China Normal University, Guangzhou 510631, P. R. China, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872
| | - Elliot R. Bernstein
- MOE Key Lab of Laser Life Science & Institute of Laser Life Science, South China Normal University, Guangzhou 510631, P. R. China, and Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872
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Sharp EN, Rupper P, Miller TA. The structure and spectra of organic peroxy radicals. Phys Chem Chem Phys 2008; 10:3955-81. [DOI: 10.1039/b800954f] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Hu YJ, Fu HB, Bernstein ER. IR plus vacuum ultraviolet spectroscopy of neutral and ionic organic acid monomers and clusters: Propanoic acid. J Chem Phys 2006; 125:184309. [PMID: 17115754 DOI: 10.1063/1.2378628] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The vibrational spectrum of molecular propanoic acid, cooled in a supersonic expansion, in the region of 2500 to 7500 cm(-1) is obtained employing infrared plus vacuum ultraviolet nonresonant ionization detected spectroscopy. The fundamental and first overtone of the CH and OH stretch modes of cold propanoic acid molecules can be identified in the spectrum. Propanoic acid neutral and ionic clusters are also studied employing nonresonant ion dip and photodissociation spectroscopic techniques, respectively. For the neutral dimer, a sequence of features observed at ca. 2500-2700 cm(-1) can be assigned as combination bands of low frequency modes with the COH bending overtone; these features characterize the cyclic dimer ring structure. IR spectra of the larger neutral clusters n=3, 4, 5 indicate that they also have cyclic structures in which the OH groups are engaged in the cluster hydrogen bonding network. The CH groups are not involved in this hydrogen bonding structure. Free OH features are observed for the protonated ion clusters (C(2)H(5)COOH)(n)H(+), n=1,...,5, indicating that at least one OH group of these cluster ions is not involved in the cluster hydrogen bonding network. A comparison of the results for four hydrogen bonding neutral and ionic clusters (CH(3)OH, C(2)H(5)OH, CH(3)COOH, and C(2)H(5)COOH) is presented and discussed.
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Affiliation(s)
- Y J Hu
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
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Hu YJ, Fu HB, Bernstein ER. IR plus vacuum ultraviolet spectroscopy of neutral and ionic organic acid molecules and clusters: Acetic acid. J Chem Phys 2006; 125:184308. [PMID: 17115753 DOI: 10.1063/1.2378626] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Infrared (IR) vibrational spectroscopy of acetic acid (A) neutral and ionic monomers and clusters, employing vacuum ultraviolet (VUV), 10.5 eV single photon ionization of supersonically expanded and cooled acetic acid samples, is presented and discussed. Molecular and cluster species are identified by time of flight mass spectroscopy: the major mass features observed are A(n)H(+) (n=1-9), ACOOH(+) (VUV ionization) without IR radiation present, and A(+) with both IR and VUV radiation present. The intense feature ACOOH(+) arises from the cleavage of (A)(2) at the beta-CC bond to generate ACOOH(+)+CH(3) following ionization. The vibrational spectrum of monomeric acetic acid (2500-7500 cm(-1)) is measured by nonresonant ionization detected infrared (NRID-IR) spectroscopy. The fundamentals and overtones of the CH and OH stretches and some combination bands are identified in the spectrum. Mass selected IR spectra of neutral and cationic acetic acid clusters are measured in the 2500-3800 cm(-1) range employing nonresonant ionization dip-IR and IR photodissociation (IRPD) spectroscopies, respectively. Characteristic bands observed at approximately 2500-2900 cm(-1) for the cyclic ring dimer are identified and tentatively assigned. For large neutral acetic acid clusters A(n)(n>2), spectra display only hydrogen bonded OH stretch features, while the CH modes (2500-2900 cm(-1)) do not change with cluster size n. The IRPD spectra of protonated (cationic) acetic acid clusters A(n)H(+) (n=1-7) exhibit a blueshift of the free OH stretch with increasing n. These bands finally disappear for n> or =6, and one broad and weak band due to hydrogen bonded OH stretch vibrations at approximately 3350 cm(-1) is detected. These results indicate that at least one OH group is not involved in the hydrogen bonding network for the smaller (n< or =5) A(n)H(+) species. The disappearance of the free OH stretch feature at n> or =6 suggests that closed cyclic structures form for A(n)H(+) for the larger clusters (n> or =6).
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Affiliation(s)
- Y J Hu
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
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Hu YJ, Fu HB, Bernstein ER. Infrared plus vacuum ultraviolet spectroscopy of neutral and ionic methanol monomers and clusters: New experimental results. J Chem Phys 2006; 125:154306. [PMID: 17059254 DOI: 10.1063/1.2357953] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
We present new observations of the infrared (IR) spectrum of neutral methanol and neutral and protonated methanol clusters employing IR plus vacuum ultraviolet (vuv) spectroscopic techniques. The tunable IR light covers the energy ranges of 2500-4500 cm(-1) and 5000-7500 cm(-1). The CH and OH fundamental stretch modes, the OH overtone mode, and combination bands are identified in the vibrational spectrum of supersonic expansion cooled methanol (2500-7500 cm(-1)). Cluster size selected IR plus vuv nonresonant infrared ion-dip infrared spectra of neutral methanol clusters, (CH(3)OH)(n) (n=2,[ellipsis (horizontal)],8), demonstrate that the methanol dimer has free and bonded OH stretch features, while clusters larger than the dimer display only hydrogen bonded OH stretch features. CH stretch mode spectra do not change with cluster size. These results suggest that all clusters larger than the dimer have a cyclic structure with OH groups involved in hydrogen bonding. CH groups are apparently not part of this cyclic binding network. Studies of protonated methanol cluster ions (CH(3)OH)(n)H(+) n=1,[ellipsis (horizontal)],7 are performed by size selected vuv plus IR photodissociation spectroscopy in the OH and CH stretch regions. Energies of the free and hydrogen bonded OH stretches exhibit blueshifts with increasing n, and these two modes converge to approximately 3670 and 3400 cm(-1) at cluster size n=7, respectively.
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Affiliation(s)
- Y J Hu
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
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Hu YJ, Fu HB, Bernstein ER. Infrared plus vacuum ultraviolet spectroscopy of neutral and ionic ethanol monomers and clusters. J Chem Phys 2006; 125:154305. [PMID: 17059253 DOI: 10.1063/1.2357952] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
A high sensitivity spectroscopy is employed to detect vibrational antiitions of ethanol neutrals and ions in a supersonic expansion. The infrared (IR) features located at 3682 and 3667 cm(-1) can be assigned to the OH stretch for the two neutral C(2)H(5)OH conformers, anti and gauche, respectively. Their overtone energies located at 7179 (anti) and 7141 (gauche) cm(-1) are also identified. The OH fundamental stretch for ethanol ions is redshifted around 210 cm(-1), while the CH stretch modes are unchanged for neutral and ionic C(2)H(5)OH at around 2900-3000 cm(-1). The charge on the ethanol ion is apparently localized on the oxygen atom. IR induced photodissociation spectroscopy is applied to the study of neutral and protonated ethanol clusters. Neutral and protonated ethanol cluster vibrations are observed. The CH modes are not perturbed by the clustering process. Neutral clusters display only hydrogen bonded OH features, while the protonated ionic clusters display both hydrogen bonded and non-hydrogen-bonded features. These spectroscopic results are analyzed to obtain qualitative structural information on neutral and ionic ethanol clusters.
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Affiliation(s)
- Y J Hu
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
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Liu B, Leung J, Li L, Au C, Cheung AC. TOF-MS investigation on methane aromatization over 3%Mo/HZSM-5 catalyst under supersonic jet expansion condition. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.08.131] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Fu HB, Hu YJ, Bernstein ER. Generation and detection of alkyl peroxy radicals in a supersonic jet expansion. J Chem Phys 2006; 125:014310. [PMID: 16863301 DOI: 10.1063/1.2209680] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Alkyl peroxy radicals are synthesized in a supersonic jet expansion by the initial production of alkyl radicals and subsequent reaction with molecular oxygen. Parent ions CH3OO+/CD3OO+ are observed employing vacuum ultraviolet (VUV) single photon ionizationtime-of-flight mass spectroscopy (TOFMS). Employing infrared (IR) + VUV photofragmentation detected spectroscopy, rotationally resolved infrared spectra of jet-cooled CH3OO and CD3OO radicals are recorded for the A 2A' <-- X 2A" transition by scanning the IR laser frequency while monitoring the CH3 + and CD3 + ion signals generated by the VUV laser. The band origins of the A 2A'<--X 2A" transition for CH3OO and CD3OO are identified at 7381 and 7371 cm(-1), respectively. Rotational simulation for the CH3OO and CD3OO 0(0) 0 transitions of A<--X yields a rotational temperature for these radicals of approximately 30 K. With the aid of ab initio calculations, two and five vibrational modes for the A 2A' excited electronic state are assigned for CH3OO and CD3OO radicals, respectively. Both experimental and theoretical results suggest that the ground electronic state of the ions of ethyl and propyl peroxy radicals are not stable although their ionization energies (IE) are less than 10.5 eV. The C2H5OO+/C3H7OO+ cations can readily decompose to C2H5 +/C3H7 + and O2. This is partially responsible for the inability of IR+VUV photofragmentation spectroscopy to detect the near IR A<--X electronic transition for these radicals.
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Affiliation(s)
- H B Fu
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, USA
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