Download or read book Time Resolved Resonance Raman Investigation of Selected Para Substituted Phenylnitrenium Ions and the 2 Fluorenylnitrenium Ion Reaction with Guanosine written by Pik-Ying Chan and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Time-resolved Resonance Raman Investigation of Selected Para-substituted Phenylnitrenium Ions and the 2-fluorenylnitrenium Ion Reaction With Guanosine" by Pik-ying, Chan, 陳碧瑩, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled TIME-RESOLVED RESONANCE RAMAN INVESTIGATION OF SELECTED PARA-SUBSTITUTED PHENYLNITRENIUM IONS AND THE 2-FLUORENYLNITRENIUM ION REACTION WITH GUANOSINE Submitted by Pik Ying CHAN for the degree of Doctor of Philosophy at The University of Hong Kong in August 2005 Arylnitrenium ions (ArNR ) are believed to play an important role in the carcinogenic reactions of aromatic amines with DNA. Arylnitrenium ions are very short-lived species and difficult to study. However, photochemical methods have recently been developed to study them. There is currently only limited structural information available for arylnitrenium ions and their reaction intermediates. This thesis presents the use of time-resolved resonance Raman (TR ) and density functional theory (DFT) to study selected arylnitrenium ions and their reactions with a guanine derivative. This work provides new and valuable structural and chemical reactivity information about the selected arylnitrenium ions investigated in this thesis. The first time-resolved resonance Raman spectra for the 4-methoxyphenylnitrenium, 4-ethoxyphenylnitrenium and 4-acetamidophenylnitrenium ions are reported. The experimental Raman bands observed in conjunction with the DFT calculation results indicates these arylnitrenium ions are singlet state species. These para-substituted phenylnitrenium ions were found to have significant iminocyclohexadienyl character to a degree very similar to that previously found for the 2-fluorenylnitrenium ion. The 4-methoxyphenylnitrenium and 4-ethoxyphenylnitrenium ions also have significant oxocarbocation character while the 4-acetamidophenylnitrenium ion has noticeable charge on both the acetamido and nitrenium moieties. Their structure and properties are compared to those of other arylnitrenium ions. The chemical reactivity and selectivity of the 4-acetamidophenylnitrenium ions are compared to the two alkoxy-substituted phenylnitrenium ions and other para-substituted phenylnitrenium ions. A picosecond Kerr-gated time-resolved resonance Raman examination of the 2-fluorenylnitrene and 4-methoxyphenylnitrene reactions with water to form the singlet 2-fluorenylnitrenium and 4-methoxyphenylnitrenium ions, respectively, is given. Photolysis of 2-fluorenyl azide and 4-methoxyphenyl azide in mixed water/acetonitrile solvents both led to formation of transient species within a few picoseconds, and these were tentatively assigned to the 2-fluorenylnitrene and 4-methoxyphenylnitrene species, respectively. These arylnitrenes are observed to directly react with water to produce their respective singlet arylnitrenium ions. The decay of the 4-methoxyphenylnitrene species and its accompanying growth of the 4-methoxyphenylnitrenium ion were found to be much faster than the decay of the 2-fluorenylnitrene and its accompanying growth of its 2-fluorenylnitrenium ion, indicating these two different arylnitrenes have noticeably different chemical reactivity toward water. Time-resolved resonance Raman spectroscopy was also applied to directly observe the reaction of the 2-fluorenylnitrenium ion with guanosine to produce a "C8 intermediate" species. This is the first time-resolved vibrational spectroscopic characterization of an arylnitrenium ion reaction with a guanine derivative and of a "C8 intermediate"
Download or read book Time resolved Resonance Raman Investigation of Selected Para substituted Phenylnitrenium Ions and the 2 fluorenylnitrenium Ion Reaction with Guanosine written by Pik-ying Chan and published by . This book was released on 2005 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Time Resolved Resonance Raman and Density Functional Theory Studies of Selected Para Phenyl Substituted Arylnitrenium Ions and Arylnitrenes written by Peizhi Zhu and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Time-resolved Resonance Raman and Density Functional Theory Studies of Selected Para-phenyl Substituted Arylnitrenium Ions and Arylnitrenes" by Peizhi, Zhu, 朱沛志, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b3124637 Subjects: Ions Nitrenes - Spectra Raman spectroscopy Density functionals
Download or read book Time Resolved Resonance Raman and Density Functional Theory Studies of Selected Arylnitrenium Ions and Their Reactions with Guanosine Derivatives and Aryl Azides written by Jiadan Xue and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Time-resolved Resonance Raman and Density Functional Theory Studies of Selected Arylnitrenium Ions and Their Reactions With Guanosine Derivatives and Aryl Azides" by Jiadan, Xue, 薛佳丹, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b4129091 Subjects: Nitrenes - Spectra Ions Nucleotides Azides - Spectra Time-resolved spectroscopy Raman spectroscopy Raman effect, Resonance Density functionals
Download or read book Time resolved Resonance Raman and Density Functional Theory Studies of Selected Para phenyl Substituted Arylnitrenium Ions and Arylnitrenes written by Peizhi Zhu and published by . This book was released on 2003 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Time resolved Resonance Raman and Density Functional Theory Studies of Selected Arylnitrenium Ions and Their Reactions with Guanosine Derivatives and Aryl Azides written by Jiadan Xue and published by . This book was released on 2008 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Resonance Raman and Time Resolved Spectroscopic Studies of Selected Chlorobenzophenone and Fluoroquinolones written by Wen Li and published by . This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Resonance Raman and Time-resolved Spectroscopic Studies of Selected Chlorobenzophenone and Fluoroquinolones" by Wen, Li, 李闻, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Nanosecond time-resolved resonance Raman (ns-TR3) spectroscopy was used in this thesis to study the photoreduction reactions and the photochemistry of chloro-substituted benzophenone (ClBP) triplets. The 3-chlorobenzophenone (3-ClBP), 4-chlorobenzophenone (4-ClBP) and 4,4′-dichlorobenzophenone (4,4′-diClBP) triplets exhibit similar properties to the parent BP triplet. In isopropyl alcohol (IPA), the hydrogen abstraction reactions were observed for the 3-ClBP, 4-ClBP and 4,4′-diDlBP triplets. The diphenylketyl (DPK) radicals produced from the hydrogen abstraction reactions were observed and the recombination of the DPK and dimethylketyl radicals at the para-position was observed to form a light absorption transient (LAT) species. In MeCN: H2O/1:1 aqueous solutions, these DPK radicals were also observed but with a slower formation rate and the LAT species was produced by reaction with OH radicals. Density functional theory (DFT) calculations were employed to help identify the intermediates seen in the TR3 spectra and to help provide information about the vibrational motions of the molecules examined. The 2-Cl-DPK radical was also observed in the TR3 spectra obtained in an IPA solvent. However, the yield of the 2-Cl-DPK radical and the hydrogen abstraction rate was observed to be significantly lower than that of the other ClBP examined here under the same experimental conditions. The results DFT calculations show that the 2-chloro substituent changes the geometry and the electron density of the molecular orbitals of the BP triplet so that the 2-chloro substituent reduces the hydrogen abstraction ability the triplet state, which is different the hypothesis put forward by some previous studies that an electron-withdrawing group should increase the photoreduction ability of BP derivatives. Norfloxacin (NF) and Enoxacin (EN) are representative derivatives of Fluoroquinolones (FQ). There are four forms of NF and EN and these different forms can coexist in aqueous solutions. The UV-vis absorption and resonance Raman (RR) spectra of NF and EN have been obtained in neat acetonitrile (MeCN), MeCN: HClO4-H2O/1:1 (pH?1), MeCN: H2O/1:1 (pH?7.5) and MeCN: NaOH-H2O/1:1 (pH?13) solutions. The species observed in the spectra are assigned by comparison of the experimental spectra to the DFT calculated spectra and the vibrational modes are also described from the results of the DFT calculations. The absorption spectra of NF and EN obtained in MeCN: H2O/1:1 solutions show that some other species coexist with the tautomeric forms in the neutral aqueous solution. The RR spectra of the tautomeric forms of NF and EN were obtained by subtraction of the RR spectra of the neutral and anionic forms from the RR spectra of NF and EN in neutral aqueous solutions. The results suggest that NF and EN exists in neutral, anionic and tautomeric forms in neutral aqueous solutions. The time dependant DFT calculation results suggest that the fluorine atom has little contribution to the lowest unoccupied molecular orbitals of the different forms of NF and EN. DOI: 10.5353/th_b4807974 Subjects: Benzoates Organic compounds - Spectra Photochemistry Rama
Download or read book Time Resolved Resonance Raman Investigation of Selected Arylnitrenes and Their Reactions written by Shing-Yau Ong and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Time-resolved Resonance Raman Investigation of Selected Arylnitrenes and Their Reactions" by Shing-yau, Ong, 王承祐, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b3122774 Subjects: Azides - Spectra Nitrenes - Spectra Raman spectroscopy Raman effect, Resonance Photochemistry
Download or read book Resonance Raman Time Resolved Resonance Raman and Density Functional Theory Study of Benzoin Diethyl Phosphate Selected P Hydroxy and P Methoxy Substituted Phenacyl Ester Phototrigger and Model Compounds written by Wing-Sum Chan and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Resonance Raman, Time-resolved Resonance Raman and Density Functional Theory Study of Benzoin Diethyl Phosphate, Selected P-Hydroxy and P-methoxy Substituted Phenacyl Ester Phototrigger and Model Compounds" by Wing-sum, Chan, 陳穎心, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: RESONANCE RAMAN, TIME-RESOLVED RESONANCE RAMAN AND DENSITY FUNCTIONAL THEORY STUDY OF BENZOIN DIETHYL PHOSPHATE, SELECTED P-HYDROXY AND P-METHOXY SUBSTITUTED PHENACYL ESTER PHOTOTRIGGER AND MODEL COMPOUNDS Submitted by Wing Sum CHAN for the degree of Doctor of Philosophy at The University of Hong Kong in August 2005 Resonance Raman (RR) spectroscopy and density functional theory (DFT) calculations were done to characterize the structure and dynamics of selected phototrigger and model compounds. Nanosecond time-resolved resonance Raman (ns-TR ) spectra of p-hydroxyphenacyl diethyl phosphate (HPDP), 4-methxoyphenacyl diethyl phosphate (MPDP) and its model compound 4''-methoxyacetophenone (MPA) in acetonitrile and in the water/acetonitrile mixed solvents are reported. The results from the DFT calculations and the ns-TR spectra indicate hydrogen-bonding leads to substantial modification of both the electronic properties and structural conformation of the triplet state MAP molecule. The free triplet MAP molecule was found to have a slightly twisted geometry with a delocalized ππ* character whereas the H-bonded MAP complex has a planar geometry with a significant ring localized biradical ππ nature. A strong solvent effect on the triplet quenching dynamics was observed for the HPDP molecule. This in conjunction with the leaving group dependence of the triplet decay observed in HPDP and related molecules are consistent with a solvent assisted triplet heterolytic cleavage pathway for the HPDP photodeprotection reaction. Intermolecular hydrogen-bonding of the HPDP molecule with the solvent water molecules appears to be essential to drive its cleavage or deprotection reaction. A spiroketone intermediate was proposed to be an intermediate after the deprotection reaction of HPDP and before the rearrangement process that results in the formation of the p-hydroxyphenylacetic acid (HPAA) final product. The results reported here provide important kinetics and structural data for the photodeprotection reactions of p-hydroxy and p-methoxy phenacyl ester phototriggers. This new data provides an improved understanding of the reaction mechanism occurring after photolysis of HPDP and related phototrigger compounds in various solvents. The RR spectra of benzoin diethyl phosphate (BDP) were obtained in acetonitrile solvent with excitation to its nπ* and ππ* excited states. DFT calculations were done to determine the structure and vibrational frequencies for the ground state and the excitation energies and molecular orbitals for the lower excited states of the BDP molecule. The DFT results were used to assign the observed RR bands and for comparison and interpretation of the resonance enhancement of the experimental RR spectra. It was found that Raman modes exhibiting strong enhancement are mainly related to the benzoinyl moiety for both excited states. The results for BDP indicate there is only a relatively small displacement between the nπ* excited state and the ground state but a larger displacement between the ππ* state and the ground state. The absence of RR bands in the RR spectra related to the cleavage motion of the diethyl phosphate group rules out any direct photodissociation pathway for the BDP photodeprotection
Download or read book Time Resolved Resonance Raman and Density Functional Theory Investigation of the T1 Triplet States and Radical Cations of Substituted Biphenyl Compounds written by 李昌運 and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Time-resolved Resonance Raman and Density Functional Theory Investigation of the T1 Triplet States and Radical Cations of Substituted Biphenyl Compounds" by 李昌運, Cheong-wan, Lee, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b3122462 Subjects: Radicals (Chemistry) Triplet state Biphenyl compounds - Spectra Cations Raman spectroscopy Density functionals
Download or read book DNA Adducts written by International Agency for Research on Cancer and published by World Health Organization. This book was released on 1994 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first and only handbook to provide a comprehensive review of the critical intermediates in the first step of the process of carcinogenesis. This volume reviews current knowledge of DNA adducts formed by a wide range of classes of chemical compound, including the metabolism of chemicals, mechanisms of adduction, preparation and properties of standard compounds, adduct formation in vitro, measurements of adducts in humans, and biological significance. Additional chapters review our understanding of specific types of gene damage and mutagenecity and their reaction to cancer. This volume will provide invaluable, up-to-date facts for all researchers in mechanism of carcinogenesis, toxicology, and molecular epidemiology.
Download or read book Nitrenes and Nitrenium Ions written by Daniel E. Falvey and published by John Wiley & Sons. This book was released on 2013-04-10 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: Featuring contributions respected leaders in the field, Nitrene and Nitrenium Ions is the first comprehensive book to explore the role of reactive intermediate nitrene and nitrenium ions in chemistry and biochemistry. Covering a broad range of topics, including ultrafast studies, computational studies, behavior in aqueous solution, electronic structures, and reactions with aromatic compounds, this valuable resource will empower graduate students and researchers to better understand and expand their synthetic utility.
Download or read book Tables of Ionization Potentials written by Robert Wayne Kiser and published by . This book was released on 1960 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reviews of Reactive Intermediate Chemistry written by Matthew S. Platz and published by John Wiley & Sons. This book was released on 2007-04-20 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemistry of reactive intermediates is central to a modern mechanistic and quantitative understanding of organic chemistry. Moreover, it underlies a significant portion of modern synthetic chemistry and is integral to a molecular view of biological chemistry. Reviews in Reactive Intermediate Chemistry presents an up-to-date, authoritative guide to this fundamental topic. Although it follows Reactive Intermediate Chemistry by the same authors, it serves as a free-standing resource for the entire chemical and biochemical community. The book includes: Relevant, practical applications Coverage of such topics as mass spectrometry methods, reactive intermediates in interstellar medium, quantum mechanical tunnelling, solvent effects, reactive intermediates in biochemical processes, and excited state surfaces Discussions of emerging areas, particularly those involving dynamics and theories Concluding sections identifying key directions for future research are provided at the end of each chapter
Download or read book Carbocation Chemistry written by George A. Olah and published by Wiley-Interscience. This book was released on 2004-10-19 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed understanding of reactive intermediates is at the heart of chemical transformations, and thus of modern organic synthetic chemistry. Carbocations are electron deficient species that are the most important intermediates in organic chemistry. This comprehensive review gives practical information on the synthesis, mechanisms, and spectral studies related to carbocation chemistry * A detailed reference for all aspects of charbocation chemistry. * With numerous classical examples of studies of carbocations to serve as illustrative principles in organic and physical organic chemistry. * Provides insight into future developments in the field and practical applications.
Download or read book Electronic Properties of Conjugated Polymers written by Hans Kuzmany and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with electrical, electrochemical, structural, magnetic, optical and lattice dynamical properties of conjugated polymers such as polyaniline, polyacetylene, polydiacetylene, polypyrrole, polyparaphenylene and polythiophene. Several new conjugated systems and model polyenes are also considered. Since the previous winter school on this topic held in 1985, the focus of interest in the field has broadened and now covers not only conductivity and relaxation phenomena of polyacetylene but also nonlinear optical properties, highly oriented and single crystal polymers, and electrochemical and opto-electrochemical properties of special materials. Particular attention is paid in this volume to the possible applications of these systems, for example, in electrochemical cells as electrode materials and in nonlinear optics devices, which now appear to be much more realistic than previously. The detailed contributions are complemented by short reviews of thin film polymers (Langmuir-Blodgett layers), filled polymers, ferromagnetic polymers, superconducting low-dimensional systems (including organic superconductors and high-temperature superconductors) and the application of fractal models to polymers.
