1
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Casavola AR, Cartoni A, Castrovilli MC, Borocci S, Bolognesi P, Chiarinelli J, Catone D, Avaldi L. VUV Photofragmentation of Chloroiodomethane: The Iso-CH 2I-Cl and Iso-CH 2Cl-I Radical Cation Formation. J Phys Chem A 2020; 124:7491-7499. [PMID: 32786965 PMCID: PMC8010789 DOI: 10.1021/acs.jpca.0c05754] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Dihalomethanes
XCH2Y (X and Y = F, Cl, Br, and I) are a class of compounds
involved in several processes leading to the release of halogen atoms,
ozone consumption, and aerosol particle formation. Neutral dihalomethanes
have been largely studied, but chemical physics properties and processes
involving their radical ions, like the pathways of their decomposition,
have not been completely investigated. In this work the photodissociation
dynamics of the ClCH2I molecule has been explored in the
photon energy range 9–21 eV using both VUV rare gas discharge
lamps and synchrotron radiation. The experiments show that, among
the different fragment ions, CH2I+ and CH2Cl+, which correspond to the Cl- and I-losses,
respectively, play a dominant role. The experimental ionization energy
of ClCH2I and the appearance energies of the CH2I+ and CH2Cl+ ions are in agreement
with the theoretical results obtained at the MP2/CCSD(T) level of
theory. Computational investigations have been also performed to study
the isomerization of geminal [ClCH2I]•+ into the iso-chloroiodomethane isomers: [CH2I–Cl]•+ and [CH2Cl–I]•+.
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Affiliation(s)
- Anna Rita Casavola
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo, Italy
| | - Antonella Cartoni
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo, Italy.,Department of Chemistry, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Mattea Carmen Castrovilli
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo, Italy
| | - Stefano Borocci
- Department for Innovation in Biological, Agrofood and Forest Systems, University of Tuscia, Viterbo 01100, Italy.,Institute for Biological Systems-CNR (ISB-CNR), Area della Ricerca di Roma 1, Via Salaria, Km 29.500,, 00015 Monterotondo, Italy
| | - Paola Bolognesi
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo, Italy
| | - Jacopo Chiarinelli
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo, Italy
| | - Daniele Catone
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Tor Vergata, Via del Fosso del Cavaliere, 00133 Rome, Italy
| | - Lorenzo Avaldi
- Institute of Structure of Matter-CNR (ISM-CNR), Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo, Italy
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2
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Park S, Choi J, Ki H, Kim KH, Oang KY, Roh H, Kim J, Nozawa S, Sato T, Adachi SI, Kim J, Ihee H. Fate of transient isomer of CH 2I 2: Mechanism and origin of ionic photoproducts formation unveiled by time-resolved x-ray liquidography. J Chem Phys 2019; 150:224201. [PMID: 31202228 DOI: 10.1063/1.5099002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Diiodomethane, CH2I2, in a polar solvent undergoes a unique photoinduced reaction whereby I2 - and I3 - are produced from its photodissociation, unlike for other iodine-containing haloalkanes. While previous studies proposed that homolysis, heterolysis, or solvolysis of iso-CH2I-I, which is a major intermediate of the photodissociation, can account for the formation of I2 - and I3 -, there has been no consensus on its mechanism and no clue for the reason why those negative ionic species are not observed in the photodissociation of other iodine-containing chemicals in the same polar solvent, for example, CHI3, C2H4I2, C2F4I2, I3 -, and I2. Here, using time-resolved X-ray liquidography, we revisit the photodissociation mechanism of CH2I2 in methanol and determine the structures of all transient species and photoproducts involved in its photodissociation and reveal that I2 - and I3 - are formed via heterolysis of iso-CH2I-I in the photodissociation of CH2I2 in methanol. In addition, we demonstrate that the high polarity of iso-CH2I-I is responsible for the unique photochemistry of CH2I2.
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Affiliation(s)
- Sungjun Park
- Department of Chemistry and KI for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Jungkweon Choi
- Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 34141, South Korea
| | - Hosung Ki
- Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 34141, South Korea
| | - Kyung Hwan Kim
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang 37673, South Korea
| | - Key Young Oang
- Radiation Center for Ultrafast Science, Quantum Optics Division, Korea Atomic Energy Research Institute (KAERI), Daejeon 34057, South Korea
| | - Heegwang Roh
- Department of Chemistry and KI for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
| | - Joonghan Kim
- Department of Chemistry, The Catholic University of Korea, Bucheon 14662, South Korea
| | - Shunsuke Nozawa
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Tokushi Sato
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Shin-Ichi Adachi
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Jeongho Kim
- Department of Chemistry, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, South Korea
| | - Hyotcherl Ihee
- Department of Chemistry and KI for the BioCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, South Korea
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3
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Paredes-Roibás D, Balaganesh M, Kasai T, Gavira-Vallejo JM, Lin KC. Cavity Ring-Down Absorption Spectroscopy: Optical Characterization of ICl Product in Photodissociation of CH 2ICl at 248 nm. J Phys Chem A 2018; 122:8344-8353. [PMID: 30278130 DOI: 10.1021/acs.jpca.8b07012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iodine monochloride (ICl) elimination from one-photon dissociation of CH2ICl at 248 nm is monitored by cavity ring-down absorption spectroscopy (CRDS). The spectrum of ICl is acquired in the transition of B3Π0 ← X1Σ+ and is confirmed to result from a primary photodissociation, that is, CH2ICl + hν → CH2 + ICl. The vibrational population ratio is determined with the aid of spectral simulation to be 1:(0.36 ± 0.10):(0.11 ± 0.05) for the vibrational levels ν = 0, 1, and 2 in the ground electronic state, corresponding to a Boltzmann-like vibrational temperature of 535 ± 69 K. The quantum yield of the ICl molecular channel for the reaction is obtained to be 0.052 ± 0.026 using a relative method in which the scheme CH2Br2 → CH2 + Br2 is adopted as the reference reaction. The ICl product contributed by the secondary collisions is minimized such that its quantum yield obtained is not overestimated. With the aid of the CCSD(T)//B3LYP/MIDI! level of theory, the ICl elimination from CH2ICl is evaluated to follow three pathways via either (1) a three-center transition state or (2) two isomerization transition states. However, the three-center concerted mechanism is verified to be unfavorable.
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Affiliation(s)
- Denís Paredes-Roibás
- Departamento de Ciencias y Técnicas Fisicoquímicas , Facultad de Ciencias, Universidad Nacional de Educación a Distancia (UNED) , Paseo de la Senda del Rey 9 , E-28040 Madrid , Spain
| | - Muthiah Balaganesh
- Department of Chemistry , National Taiwan Univeristy , Taipei 10617 , Taiwan.,Institute of Atomic and Molecular Sciences , Academia Sinica , Taipei 10617 , Taiwan
| | - Toshio Kasai
- Department of Chemistry , National Taiwan Univeristy , Taipei 10617 , Taiwan.,Institute of Scientific and Industrial Research , Osaka University , Ibaraki, Osaka 567-0047 , Japan
| | - José María Gavira-Vallejo
- Departamento de Ciencias y Técnicas Fisicoquímicas , Facultad de Ciencias, Universidad Nacional de Educación a Distancia (UNED) , Paseo de la Senda del Rey 9 , E-28040 Madrid , Spain
| | - King Chuen Lin
- Department of Chemistry , National Taiwan Univeristy , Taipei 10617 , Taiwan.,Institute of Atomic and Molecular Sciences , Academia Sinica , Taipei 10617 , Taiwan
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4
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Abstract
The dynamics of chemical reactions in liquid solutions are now amenable to direct study using ultrafast laser spectroscopy techniques and advances in computer simulation methods. The surrounding solvent affects the chemical reaction dynamics in numerous ways, which include: (i) formation of complexes between reactants and solvent molecules; (ii) modifications to transition state energies and structures relative to the reactants and products; (iii) coupling between the motions of the reacting molecules and the solvent modes, and exchange of energy; (iv) solvent caging of reactants and products; and (v) structural changes to the solvation shells in response to the changing chemical identity of the solutes, on timescales which may be slower than the reactive events. This article reviews progress in the study of bimolecular chemical reaction dynamics in solution, concentrating on reactions which occur on ground electronic states. It illustrates this progress with reference to recent experimental and computational studies, and considers how the various ways in which a solvent affects the chemical reaction dynamics can be unravelled. Implications are considered for research in fields such as mechanistic synthetic chemistry.
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Affiliation(s)
- Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, UK.
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5
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Kapnas KM, Toulson BW, Foreman ES, Block SA, Hill JG, Murray C. UV photodissociation dynamics of CHI 2Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate. Phys Chem Chem Phys 2017; 19:31039-31053. [PMID: 29160321 DOI: 10.1039/c7cp06532a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photolysis of geminal diiodoalkanes in the presence of molecular oxygen has become an established route to the laboratory production of several Criegee intermediates, and such compounds also have marine sources. Here, we explore the role that the trihaloalkane, chlorodiiodomethane (CHI2Cl), may play as a photolytic precursor for the chlorinated Criegee intermediate ClCHOO. CHI2Cl has been synthesized and its UV absorption spectrum measured; relative to that of CH2I2 the spectrum is shifted to longer wavelength and the photolysis lifetime is calculated to be less than two minutes. The photodissociation dynamics have been investigated using DC slice imaging, probing ground state I and spin-orbit excited I* atoms with 2 + 1 REMPI and single-photon VUV ionization. Total translational energy distributions are bimodal for I atoms and unimodal for I*, with around 72% of the available energy partitioned in to the internal degrees of freedom of the CHICl radical product, independent of photolysis wavelength. A bond dissociation energy of D0 = 1.73 ± 0.11 eV is inferred from the wavelength dependence of the translational energy release, which is slightly weaker than typical C-I bonds. Analysis of the photofragment angular distributions indicate dissociation is prompt and occurs primarily via transitions to states of A'' symmetry. Complementary high-level MRCI calculations, including spin-orbit coupling, have been performed to characterize the excited states and confirm that states of A'' symmetry with highly mixed singlet and triplet character are predominantly responsible for the absorption spectrum. Transient absorption spectroscopy has been used to measure the absorption spectrum of ClCHOO produced from the reaction of CHICl with O2 over the range 345-440 nm. The absorption spectrum, tentatively assigned to the syn conformer, is at shorter wavelengths relative to that of CH2OO and shows far weaker vibrational structure.
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Affiliation(s)
- Kara M Kapnas
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697, USA.
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6
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Orr-Ewing AJ. Perspective: Bimolecular chemical reaction dynamics in liquids. J Chem Phys 2014; 140:090901. [PMID: 24606343 DOI: 10.1063/1.4866761] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bimolecular reactions in the gas phase exhibit rich and varied dynamical behaviour, but whether a profound knowledge of the mechanisms of isolated reactive collisions can usefully inform our understanding of reactions in liquid solutions remains an open question. The fluctuating environment in a liquid may significantly alter the motions of the reacting particles and the flow of energy into the reaction products after a transition state has been crossed. Recent experimental and computational studies of exothermic reactions of CN radicals with organic molecules indicate that many features of the gas-phase dynamics are retained in solution. However, observed differences may also provide information on the ways in which a solvent modifies fundamental chemical mechanisms. This perspective examines progress in the use of time-resolved infra-red spectroscopy to study reaction dynamics in liquids, discusses how existing theories can guide the interpretation of experimental data, and suggests future challenges for this field of research.
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Affiliation(s)
- Andrew J Orr-Ewing
- School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom
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7
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Reid SA. When isomerisation is electron transfer: the intriguing story of the iso-halocarbons. INT REV PHYS CHEM 2014. [DOI: 10.1080/0144235x.2014.942548] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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8
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Anderson CP, Spears KG, Wilson KR, Sension RJ. Solvent dependent branching between C-I and C-Br bond cleavage following 266 nm excitation of CH2BrI. J Chem Phys 2014; 139:194307. [PMID: 24320326 DOI: 10.1063/1.4829899] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
It is well known that ultraviolet photoexcitation of halomethanes results in halogen-carbon bond cleavage. Each halogen-carbon bond has a dominant ultraviolet (UV) absorption that promotes an electron from a nonbonding halogen orbital (nX) to a carbon-halogen antibonding orbital (σ*C-X). UV absorption into specific transitions in the gas phase results primarily in selective cleavage of the corresponding carbon-halogen bond. In the present work, broadband ultrafast UV-visible transient absorption studies of CH2BrI reveal a more complex photochemistry in solution. Transient absorption spectra are reported spanning the range from 275 nm to 750 nm and 300 fs to 3 ns following excitation of CH2BrI at 266 nm in acetonitrile, 2-butanol, and cyclohexane. Channels involving formation of CH2Br + I radical pairs, iso-CH2Br-I, and iso-CH2I-Br are identified. The solvent environment has a significant influence on the branching ratios, and on the formation and stability of iso-CH2Br-I. Both iso-CH2Br-I and iso-CH2I-Br are observed in cyclohexane with a ratio of ~2.8:1. In acetonitrile this ratio is 7:1 or larger. The observation of formation of iso-CH2I-Br photoproduct as well as iso-CH2Br-I following 266 nm excitation is a novel result that suggests complexity in the dissociation mechanism. We also report a solvent and concentration dependent lifetime of iso-CH2Br-I. At low concentrations the lifetime is >4 ns in acetonitrile, 1.9 ns in 2-butanol and ~1.4 ns in cyclohexane. These lifetimes decrease with higher initial concentrations of CH2BrI. The concentration dependence highlights the role that intermolecular interactions can play in the quenching of unstable isomers of dihalomethanes.
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Affiliation(s)
- Christopher P Anderson
- Department of Chemistry and Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
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9
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Jain A, Sibert EL. Vibrational relaxation of chloroiodomethane in cold argon. J Chem Phys 2013; 139:144312. [PMID: 24116624 DOI: 10.1063/1.4823837] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Electronically exciting the C-I stretch in the molecule chloroiodomethane CH2ClI embedded in a matrix of argon at 12 K can lead to an isomer, iso-chloroiodomethane CH2Cl-I, that features a chlorine iodine bond. By temporally probing the isomer at two different frequencies of 435 nm and 485 nm, multiple timescales for isomerization and vibrational energy relaxation were inferred [T. J. Preston, et al., J. Chem. Phys. 135, 114503 (2011)]. This relaxation is studied theoretically using molecular dynamics by considering 2 and 3 dimensional models. Multiple decay rate constants of the same order of magnitude as the experiment are observed. These decay rate constants are interpreted within the context of the Landau-Teller theory. Sensitivity of the decay rate constants on the bath and system parameters shed more light into the mechanism of vibrational energy relaxation.
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Affiliation(s)
- Amber Jain
- Department of Chemistry and Theoretical Chemistry Institute, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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10
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Pal SK, Mereshchenko AS, Butaeva EV, El-Khoury PZ, Tarnovsky AN. Global sampling of the photochemical reaction paths of bromoform by ultrafast deep-UV through near-IR transient absorption and ab initio multiconfigurational calculations. J Chem Phys 2013; 138:124501. [DOI: 10.1063/1.4789268] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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11
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Preston TJ, Dutta M, Esselman BJ, Kalume A, George L, McMahon RJ, Reid SA, Fleming Crim F. Formation and relaxation dynamics of iso-CH2Cl–I in cryogenic matrices. J Chem Phys 2011; 135:114503. [DOI: 10.1063/1.3633697] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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12
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El-Khoury PZ, George L, Kalume A, Reid SA, Ault BS, Tarnovsky AN. Characterization of iso-CF2I2 in frequency and ultrafast time domains. J Chem Phys 2010; 132:124501. [DOI: 10.1063/1.3357728] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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Carrier SL, Preston TJ, Dutta M, Crowther AC, Crim FF. Ultrafast Observation of Isomerization and Complexation in the Photolysis of Bromoform in Solution. J Phys Chem A 2009; 114:1548-55. [DOI: 10.1021/jp908725t] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stacey L. Carrier
- Department of Chemistry University of Wisconsin—Madison, Madison, Wisconsin 53706
| | - Thomas J. Preston
- Department of Chemistry University of Wisconsin—Madison, Madison, Wisconsin 53706
| | - Maitreya Dutta
- Department of Chemistry University of Wisconsin—Madison, Madison, Wisconsin 53706
| | - Andrew C. Crowther
- Department of Chemistry University of Wisconsin—Madison, Madison, Wisconsin 53706
| | - F. Fleming Crim
- Department of Chemistry University of Wisconsin—Madison, Madison, Wisconsin 53706
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14
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Switching on molecular iodine elimination through isomerization: The F2C–I–I isomer of difluorodiiodomethane. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.07.028] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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15
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Zhao C, Lin X, Kwok WM, Guan X, Du Y, Wang D, Hung KF, Phillips DL. Water-Catalyzed Dehalogenation Reactions of the Isomer of CBr4 and Its Reaction Products and a Comparison to Analogous Reactions of the Isomers of Di- and Trihalomethanes. Chemistry 2005; 11:1093-108. [PMID: 15742469 DOI: 10.1002/chem.200400695] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A combined experimental and theoretical study of the UV photolysis of a typical tetrahalomethane, CBr4, in water and acetonitrile/water was performed. Ultraviolet photolysis of low concentrations of CBr4 in water mostly leads to the production of four HBr leaving groups and CO2. Picosecond time-resolved resonance Raman (Ps-TR3) experiments and ab initio calculations indicate that water-catalyzed O-H insertion/HBr elimination of the isomer of CBr4 and subsequent reactions of its products lead to the formation of these products. The UV photolyses of di-, tri-, and tetrahalomethanes at low concentrations in water-solvated environments are compared to one another. This comparison enables a general reaction scheme to be deduced that can account for the different products produced by UV photolysis of low concentrations of di-, tri-, and tetrahalomethanes in water. The fate of the (halo)formaldehyde intermediate in the chemical reaction mechanism is the key to determining how many strong acid leaving groups are produced and which carbon atom final product is likely formed by UV photolysis of a polyhalomethane at low concentrations in a water-solvated environment.
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Affiliation(s)
- Cunyuan Zhao
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China
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16
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Affiliation(s)
- Wolfgang Kirmse
- Fakultät für Chemie, Ruhr‐Universität Bochum, 44780 Bochum, Germany
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17
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Kwok WM, Zhao C, Guan X, Li YL, Du Y, Phillips DL. Efficient dehalogenation of polyhalomethanes and production of strong acids in aqueous environments: Water-catalyzed O–H-insertion and HI-elimination reactions of isodiiodomethane (CH2I–I) with water. J Chem Phys 2004; 120:9017-32. [PMID: 15267837 DOI: 10.1063/1.1701699] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A combined experimental and theoretical study of the ultraviolet photolysis of CH2I2 in water is reported. Ultraviolet photolysis of low concentrations of CH2I2 in water was experimentally observed to lead to almost complete conversion into CH2(OH)2 and 2HI products. Picosecond time-resolved resonance Raman spectroscopy experiments in mixed water/acetonitrile solvents (25%-75% water) showed that appreciable amounts of isodiiodomethane (CH2I-I) were formed within several picoseconds and the decay of the CH2I-I species became substantially shorter with increasing water concentration, suggesting that CH2I-I may be reacting with water. Ab initio calculations demonstrate the CH2I-I species is able to react readily with water via a water-catalyzed O--H-insertion and HI-elimination reaction followed by its CH2I(OH) product undergoing a further water-catalyzed HI-elimination reaction to make a H2C=O product. These HI-elimination reactions produce the two HI leaving groups observed experimentally and the H2C=O product further reacts with water to produce the other final CH2(OH)2 product observed in the photochemistry experiments. These results suggest that CH2I-I is the species that reacts with water to produce the CH2(OH)2 and 2HI products seen in the photochemistry experiments. The present study demonstrates that ultraviolet photolysis of CH2I2 at low concentration leads to efficient dehalogenation and release of multiple strong acid (HI) leaving groups. Some possible ramifications for the decomposition of polyhalomethanes and halomethanols in aqueous environments as well as the photochemistry of polyhalomethanes in the natural environment are briefly discussed.
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Affiliation(s)
- Wai Ming Kwok
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, China
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18
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Kwok WM, Zhao C, Li YL, Guan X, Phillips DL. Direct observation of an isopolyhalomethane O–H insertion reaction with water: Picosecond time-resolved resonance Raman (ps-TR3) study of the isobromoform reaction with water to produce a CHBr2OH product. J Chem Phys 2004; 120:3323-32. [PMID: 15268486 DOI: 10.1063/1.1640997] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Picosecond time-resolved resonance Raman (ps-TR3) spectroscopy was used to obtain the first definitive spectroscopic observation of an isopolyhalomethane O-H insertion reaction with water. The ps-TR3 spectra show that isobromoform is produced within several picoseconds after photolysis of CHBr3 and then reacts on the hundreds of picosecond time scale with water to produce a CHBr2OH reaction product. Photolysis of low concentrations of bromoform in aqueous solution resulted in noticeable formation of HBr strong acid. Ab initio calculations show that isobromoform can react with water to produce a CHBr2(OH) O-H insertion reaction product and a HBr leaving group. This is consistent with both the ps-TR3 experiments that observe the reaction of isobromoform with water to form a CHBr2(OH) product and photolysis experiments that show HBr acid formation. We briefly discuss the implications of these results for the phase dependent behavior of polyhalomethane photochemistry in the gas phase versus water solvated environments.
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Affiliation(s)
- Wai Ming Kwok
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China
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19
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Guan X, Du Y, Li YL, Kwok WM, Phillips DL. Comparison of the dehalogenation of polyhalomethanes and production of strong acids in aqueous and salt (NaCl) water environments: Ultraviolet photolysis of CH[sub 2]I[sub 2]. J Chem Phys 2004; 121:8399-409. [PMID: 15511161 DOI: 10.1063/1.1803508] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ultraviolet photolysis of CH(2)I(2) was studied in water and salt water solutions using photochemistry and picosecond time-resolved resonance Raman spectroscopy. Photolysis in both types of environments produces mainly CH(2)(OH)(2) and HI products. However, photolysis of CH(2)I(2) in salt water leads to the formation of different products/intermediates (CH(2)ICl and Cl(2) (-)) not observed in the absence of salt in aqueous solutions. The amount of CH(2)(OH)(2) and HI products appears to decrease after photolysis of CH(2)I(2) in salt water compared to pure water. We briefly discuss possible implications of these results for photolysis of CH(2)I(2) and other polyhalomethanes in sea water and other salt aqueous environments compared to nonsalt water solvated environments.
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Affiliation(s)
- Xiangguo Guan
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of China
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20
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Grimm C, Kling M, Schroeder J, Troe J, Zerbs J, Schroeder J, Troe J. Density-dependent photochemical branching ratio in supercritical CO2: Photodissociation and isomerization of diiodomethane. Isr J Chem 2003. [DOI: 10.1560/d8hj-jqtw-w43y-qf1g] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Li YL, Zhao C, Kwok WM, Guan X, Zuo P, Phillips DL. Observation of a HI leaving group following ultraviolet photolysis of CH2I2 in water and anab initioinvestigation of the O–H insertion/HI elimination reactions of the CH2I–I isopolyhalomethane species with H2O and 2H2O. J Chem Phys 2003. [DOI: 10.1063/1.1595636] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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22
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Towrie M, Grills DC, Dyer J, Weinstein JA, Matousek P, Barton R, Bailey PD, Subramaniam N, Kwok WM, Ma C, Phillips D, Parker AW, George MW. Development of a broadband picosecond infrared spectrometer and its incorporation into an existing ultrafast time-resolved resonance Raman, UV/visible, and fluorescence spectroscopic apparatus. APPLIED SPECTROSCOPY 2003; 57:367-380. [PMID: 14658632 DOI: 10.1366/00037020360625899] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We have constructed a broadband ultrafast time-resolved infrared (TRIR) spectrometer and incorporated it into our existing time-resolved spectroscopy apparatus, thus creating a single instrument capable of performing the complementary techniques of femto-/picosecond time-resolved resonance Raman (TR3), fluorescence, and UV/visible/infrared transient absorption spectroscopy. The TRIR spectrometer employs broadband (150 fs, approximately 150 cm(-1) FWHM) mid-infrared probe and reference pulses (generated by difference frequency mixing of near-infrared pulses in type I AgGaS2), which are dispersed over two 64-element linear infrared array detectors (HgCdTe). These are coupled via custom-built data acquisition electronics to a personal computer for data processing. This data acquisition system performs signal handling on a shot-by-shot basis at the 1 kHz repetition rate of the pulsed laser system. The combination of real-time signal processing and the ability to normalize each probe and reference pulse has enabled us to achieve a high sensitivity on the order of deltaOD approximately 10(-4) - 10(-5) with 1 min of acquisition time. We present preliminary picosecond TRIR studies using this spectrometer and also demonstrate how a combination of TRIR and TR3 spectroscopy can provide key information for the full elucidation of a photochemical process.
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Affiliation(s)
- Michael Towrie
- Central Laser Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom
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23
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Kwok WM, Ma C, Parker AW, Phillips D, Towrie M, Matousek P, Phillips DL. Picosecond Time-Resolved Resonance Raman Study of CH2I−I Produced after Ultraviolet Photolysis of CH2I2 in CH3OH, CH3CN/H2O and CH3OH/H2O Solutions. J Phys Chem A 2003. [DOI: 10.1021/jp021611b] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Wai Ming Kwok
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
| | - Chensheng Ma
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
| | - Anthony W. Parker
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
| | - David Phillips
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
| | - Michael Towrie
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
| | - Pavel Matousek
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
| | - David Lee Phillips
- Department of Chemistry, Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2AY, U.K., Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K., and Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S. A. R., P. R. China
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24
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Wang D, Phillips DL, Fang WH. Density Functional Theory Investigation of the Reaction of the Chlorine Atom−Carbon Disulfide Molecular Complex with Dimethylbutane: Implications for Tertiary Selectivity in Alkane Photochlorination Reactions. J Phys Chem A 2003. [DOI: 10.1021/jp021406w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Dongqi Wang
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P. R. China, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - David Lee Phillips
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P. R. China, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Wei-Hai Fang
- Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong S.A.R., P. R. China, and Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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25
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Li YL, Wang D, Phillips DL. Time-resolved resonance Raman spectroscopy and density functional theory investigation of the CH2I–I isomer and CH2I2⋯I molecular complex products produced from ultraviolet photolysis of CH2I2 in the solution phase: Comparison of the structure and chemical reactivity of polyhalomethane isomers and polyhalomethane–halogen atom molecular complexes. J Chem Phys 2002. [DOI: 10.1063/1.1511724] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Li YL, Chen DM, Wang D, Phillips DL. Time-resolved resonance Raman and density functional theory investigation of iodocyclopropanation and addition reactions with alkenes after ultraviolet photolysis of iodoform. J Org Chem 2002; 67:4228-35. [PMID: 12054958 DOI: 10.1021/jo011163o] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A time-resolved resonance Raman spectroscopic investigation is reported for the ultraviolet photolysis of CHI(3) in pure cyclohexane and mixed cyclohexane/cyclohexene solvents. The ICHI-I species is observed in pure cyclohexane solvent. Upon addition of cyclohexene, the ICHI-I species lifetime is reduced and new bands from an I(2):cyclohexene complex are observed. Density functional theory computations show that ICHI-I and CHI(2) species have similar barriers of reaction toward addition to the C=C of ethylene. The addition reaction of ICHI-I with ethylene results in formation of an iodocyclopropane and I(2) molecule while addition of.CHI(2) results in initial formation of a diiodopropyl radical intermediate. Ultraviolet photolysis of CHI(3) in the presence of cyclohexene is known to produce a reasonable yield of iodonorcarane product and some addition reaction products. We present a mechanism for the iodocyclopropanation reaction that is consistent with both experimental and theoretical characterization of reaction intermediates formed after ultraviolet photolysis of CHI(3). We briefly discuss the concentration dependence of the time-resolved resonance Raman spectra and photochemistry in relation to the competition between the reaction of the ICHI-I and CHI(2) species with the C=C bond of olefins.
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Affiliation(s)
- Yun-Liang Li
- Department of Chemistry, University of Hong Kong, Pokfulam Road, SAR, People's Republic of China
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27
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Tarnovsky AN, Wall M, Gustafsson M, Lascoux N, Sundström V, Åkesson E. Ultrafast Study of the Photodissociation of Bromoiodomethane in Acetonitrile upon 266 nm Excitation. J Phys Chem A 2002. [DOI: 10.1021/jp014306j] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Magnus Wall
- Department of Chemical Physics, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Magnus Gustafsson
- Department of Chemical Physics, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Noelle Lascoux
- Department of Chemical Physics, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Villy Sundström
- Department of Chemical Physics, Lund University, Box 124, SE-221 00 Lund, Sweden
| | - Eva Åkesson
- Department of Chemical Physics, Lund University, Box 124, SE-221 00 Lund, Sweden
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28
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Li YL, Wang D, Phillips DL. Transient Resonance Raman Spectroscopy and Density Functional Theory Investigation of Iso-Dibromoacetic Acid Photoproduct Produced From Ultraviolet Photolysis of Dibromoacetic Acid in the Solution Phase. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2002. [DOI: 10.1246/bcsj.75.943] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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29
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Wang D, Phillips DL, Fang WH. Density functional theory investigation of the reactions of CH2Br–I, CH2I–Br, CH2Cl–I, and CH2I–Cl isopolyhalomethanes with ethylene. Phys Chem Chem Phys 2002. [DOI: 10.1039/b204898c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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30
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Transient resonance Raman and density functional theory investigation of the ultraviolet photolysis of dibromoacetonitrile in the solution phase. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)01279-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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31
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Li YL, Lee Phillips D. Transient resonance Raman and density functional theory investigation of CH3I–I produced from ultraviolet photolysis of iodomethane in the solution phase. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)01197-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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32
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Ming Kwok W, Ma C, Phillips D, Parker AW, Towrie M, Matousek P, Lee Phillips D. Picosecond time-resolved resonance Raman observation of Iso-CH2Br–I following A-band photodissociation of CH2BrI in the solution phase. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)00491-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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