Department of Chemistry
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Collection consists of research, scholarship and publications produced by graduate students and faculty members of the Department of Chemistry.
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Item Open Access 1,8-Naphthalene Linked Cofacial Binuclear Phthalocyanines(Wiley-Blackwell, 1987) Lever, A.B.P.; Janda, Pavel; Kobayashi, Nagao; Nevin, Andrew W.; Lam, Herman; Leznoff, Clifford C.Item Open Access 1999 Alfred Bader Lecture. From Early Developments in Multi-Step Organic Synthesis on Solid Phase to Multi-Nuclear Phthalocyanines.(Canadian Journal of Chemistry, NRC Research Press, 2000) Leznoff, Clifford C.Early developments in solid phase organic synthesis are traced. Particular emphasis is placed on the use of cross-linked polystyrene in the first general method of monoblocking symmetrical difunctional compounds. The monoprotected polymer-bound symmetrical starting materials were then used in multi-step syntheses of a variety of compounds, particularly insect pheromones. Asymmetric synthesis on polymer supports was demonstrated. Diels-Alder and 1,3-dipolar additions on polymer supports proceeded readily as did macrocyclic formation of porphyrins and phthalocyanines. All of these reactions clearly showed that most organic chemical reactions could be performed on solid phases and laid the basis for the development of combinatorial chemistry. The first unsymmetrical phthalocyanine was prepared using the solid phase method and this led eventually to solution phase methods of preparing bi-, tri-, tetra-, and even a dendritic-like pentanuclear phthalocyanine.Item Open Access 2,4-Di-O-methylgyrophoric Acid and 2,4,5-Tri-O-methylhiascic Acid. New Tridepsides from Parmelia damaziana(CSIRO Publishing, 1981) Leznoff, Clifford C.; Jayanthi, Vilas K.; Elix, John A.Item Open Access A Rapid Derivatization for Quantitation of Perfluorinated Car-boxylic Acids from Aqueous Matrices by Gas Chromatography-Mass Spectrometry(ACS Publications, 2023-05-03) Ye, RenXi; Di Lorenzo, Robert A.; Clouthier, Jessica; Young, Cora; VandenBoer, TrevorUltrashort chain perfluorocarboxylic acids (PFCAs) are receiving more attention due to their ever-increasing presence in the environment. Methods have been established for the analysis of short and long-chain PFCAs, while robust quantitation of ultrashort chain species are scarce. Here we develop a novel derivatization method using diphenyl diazomethane for quantitation of C2-C14 PFCAs in aqueous matrices. The method is highlighted by rapid completion of derivatization (<1 min), and retention and separation of ultrashort chain (C2/C3) PFCA derivatives using H2 carrier gas (R > 1.5). A weak anion solid phase extraction procedure for analyte recovery from representative aqueous samples was developed and validated by spike and recovery from ultrapure water, synthetic ocean water, and simulated denuder extracts used for collecting gaseous PFCAs. Recoveries for C2-C9 PFCAs ranged from 83-130 % for the majority of analytes and matrices. The instrument detection limits (IDLs) range from 8-220 fg per injection, and method detection limits (MDLs) range from 0.06-14.6 pg/mL for 500 mL aqueous samples, which are within an order of magnitude to conventional LC-MS/MS methods. The method was applied to the analysis of real samples of tap water, rainwater, ocean water, and annular denuder extracts. The overall method provides a cost-effective alternative to conventional LC-MS/MS methods, overcoming the typical GC-MS drawbacks of high detection limits and long sample preparation times, while being able to simultaneously analyze the complete spectrum of environmentally relevant PFCAs.Item Open Access Ab-initio investigation of Br-3d core-excited electronic structures of HBr and HBr+(AIP Publishing, 2019-01-30) Kobayashi, Yuki; Zeng, Tao; Neumark, Daniel M.; Leone, StephenUltrafast X-ray absorption spectroscopy is a powerful tool for real-time probing of chemical dynamics. Interpretation of the time-resolved absorption spectra requires knowledge of core-excited potentials, which necessitates assistance from high-level electronic-structure computations. In this study, we investigate Br-3d core-excited electronic structures of hydrogen bromide (HBr) using the spin-orbit general multiconfigurational quasidegenerate perturbation theory (SO-GMC-QDPT). Core-to-valence excitation energies and transition dipole moments are computed as functions of the internuclear distance for five electronic states of HBr (1Σ0+ , 3Π1, 1Π1, 3Π0+ , 3Π1) and two electronic states of HBr+ (2Π3/2, 2Σ1/2). The results illustrate the capabilities of the Br-3d edge probing to capture transitions of electronic-state symmetry as well as nonadiabatic dissociation processes evolving across avoided crossings. Furthermore, core-to-valence absorption spectra are simulated from the neutral and ionic ground states by numerically solving the time-dependent Schrodinger equation, which exhibit an excellent agreement with an experimental spectrum. The calculated comprehensive and quantitative picture of the core-excited potentials allows for transparent analyses of the core-to-valence absorption signals, filling the gap in the theoretical understanding of the Br-3d absorption spectra.Item Open Access "Adjacent" Substituted Phthalocyanines(Georg Thieme Verlag, 1997) Leznoff, C.C.; Hu, M.; Nolan, K.J.M.Item Open Access The Alkaline Decomposition of o-Phthalaldehyde Di-p-toluene Sulfonylhydrazone(NRC Research Press, 1968) Leznoff, Clifford C.Item Open Access An instrument to measure and speciate the total reactive nitrogen budget indoors: description and field measurements(Royal Society of Chemistry, 2023-01-26) Crilley, Leigh; Lao, Melodie; salehpoor, Leyla; VandenBoer, TrevorReactive nitrogen species (Nr), defined here as all N-containing compounds except N2 and N2O, have been shown to be important drivers for indoor air quality. Key Nr species include NOx (NO + NO2), HONO and NH3, which are known to have detrimental health effects. In addition, other Nr species that are not traditionally measured may be important chemical actors for indoor transformations (e.g. amines). Cooking and cleaning are significant sources of Nr, whose emission will vary depending on the type of activity and materials used. Here we present a novel instrument that measures the total gas-phase reactive nitrogen (tNr) budget and key species NOx, HONO, and NH3 to demonstrate its suitability for indoor air quality applications. The tNr levels were measured using a custom-built heated platinum (Pt) catalytic furnace to convert all Nr species to NOx, called the tNr oven. The measurement approach was validated through a series of control experiments, such that quantitative measurement and speciation of the total Nr budget are demonstrated. The optimum operating conditions of the tNr oven were found to be 800 °C with a sampling flow rate of 630 cubic centimetres per minute (ccm). Oxidized nitrogen species are known to be quantitatively converted under these conditions. Here, the efficiency of the tNr oven to convert reduced Nr species to NOx was found to reach a maximum at 800 °C, with 103 ± 13% conversion for NH3 and 79–106% for selected relevant amines. The observed variability in the conversion efficiency of reduced Nr species demonstrates the importance of catalyst temperature characterization for the tNr oven. The instrument was deployed successfully in a commercial kitchen, a complex indoor environment with periods of rapidly changing levels, and shown to be able to reliably measure the tNr budget during periods of longer-lived oscillations (>20 min), typical of indoor spaces. The measured NOx, HONO and basic Nr (NH3 and amines) were unable to account for all the measured tNr, pointing to a substantial missing fraction (on average 18%) in the kitchen. Overall, the tNr instrument will allow for detailed survey(s) of the key gaseous Nr species across multiple locations and may also identify missing Nr fractions, making this platform capable of stimulating more in-depth analysis in indoor atmospheres.Item Open Access Analysis of the role played by ligand-induced folding of the cocaine-binding aptamer in the photochrome aptamer switch assay(Elsevier, 2020-04-11) Shoara, Aron A.; Churcher, Zachary R; Steele, Terry W.J.; Johnson, Philip EThe Photochrome Aptamer Switch Assay (PHASA) relies on ligand binding by an aptamer to alter the local environment of a stilbene compound covalently attached to the 5’ end of the aptamer. We used the PHASA with both structure switching and non-structure switching versions of the cocaine-binding aptamer. We show that the largest change in fluorescence intensity and the lowest concentration limit of detection (CLooD) is obtained using the structure-switching cocaine-binding aptamer. Fluorescence anisotropy measurements were used to quantify the affinity of the conjugated aptamer to cocaine. We also used thermal melt analysis and Nuclear Magnetic Resonance (NMR) spectroscopy to show that the addition of the stilbene to the aptamer increases the melt temperature of the cocaine-bound structure-switching aptamer by (6.4 ± 0.3) °C compared to the unconjugated aptamer while the free form of the structure-switching aptamer-stilbene conjugate remains unfolded.Item Open Access Approaches Towards the Synthesis of a 2,9,16,23-Tetrasubstituted Phthalocyanine as a Pure Isomer(NRC Research Press, 1988) Leznoff, Clifford C.; Lever, A.B.P.; Greenberg, ShafriraItem Open Access Aptamers 2017 at Oxford(2018-02-12) Henri, Justin; McKeague, Maureen; Johnson, Philip E; Suess, Beatrix; Nakamura, Yoshikazu; Nilsen-Hamilton, Marit; Pastor, Fernando; Hahn, Ulrich; Bunka, David; Shigdar, SarahThe 4th annual symposium of the International Society on Aptamers, Aptamers 2017, was held in Oxford on the 11th and 12th April and was well attended, with presenters from Europe (Spain, Germany, Austria, and UK), North and South America, Asia, and Australasia presenting on a diverse range of topics, from enhancing SELEX, to diagnostic applications such as lateral flow devices or medical imaging, to therapeutic applications such as drug delivery. The conference was split into six sections in total, covering chemical modifications, disease, analysis/diagnostics, tools/selection/design, riboswitches, and computation with over 50 oral and poster presentations. The conference started with a welcome from both the Symposium Chair, Professor Dr Ulrich Hahn (University of Hamburg, Germany) and the President of the International Society on Aptamers, Dr Sarah Shigdar (Deakin University, Australia).Item Open Access Aptamers 2018 – a conference update(2018-06-29) Tanner, Julian A; Ismail, Said I; Shigdar, Sarah; DeRosa, Maria C; Hahn, Ulrich; Johnson, Philip E; Suess, Beatrix; McKeague, MaureenThe 5th annual symposium of the International Society on Aptamers, Aptamers 2018, was held in Oxford on the 11th and 12th April. We had a very diverse group of attendees and presenters from all over the world with representatives from both academia and industry. This year, the conference included a Lifetime Achievement Award presented to Emeritus Professor Dr Uli Hahn from the University of Hamburg and a very successful “Flash Talks” session.Item Open Access Aptamers 2019 – a conference update(2019-07-14) Shigdar, Sarah; Johnson, Philip; Pietruschka, Georg; Legen, Tjaša; Mayer, Günter; McKeague, MaureenThe International Society on Aptamers held Aptamers 2019, the sixth successful annual symposium at Oxford in April. The meeting was chaired by Professor Dr Günter Mayer. The participants, representing over 25 countries, included some familiar faces as well as several new ones (~40% PIs/ postdocs, 25% students, and 35% from the industry)! A wide range of topics were covered in in 25+ oral presentations, 15+ flash-talks and 45+ posters. Below, we have briefly discussed some of the highlights of the symposium.Item Open Access Asymmetric Induction in the Cycloaddition of 1,3-Butadienes to Polymer-Bound Chiral Acrylates(Elsevier, 1988) Leznoff, Clifford C.; McArthur, Colin R.; Corbridge, Michael D.Item Open Access Asymmetric Syntheses Towards (3Z,6R)-3-Methyl-6-isopropenyl-3,9-decadien-1-yl Acetate, a Component of the California Red Scale Pheromone(NRC Research Press, 1985) Leznoff, Clifford C.; McArthur, Colin R.; Whittaker, MarkItem Open Access Asymmetric Synthesis of 2-Alkylcyclohexanones on Solid Phases(Wiley-Blackwell, 1979) Leznoff, Clifford C.; McArthur, Colin R.; Worster, Paul M.Item Open Access The Asymmetric Synthesis of 4,4-Dimethyl-3-substitutedbutyrolactones(Taylor & Francis, 1986) Whittaker, Mark; McArthur, Colin R.; Leznoff, Clifford C.Item Open Access Attraction of Various Tortricine Moths to Blends Containing Cis-11-tetradecenal(Springer Verlag, 1978) Fyles, T.M.; Leznoff, C.C.; Werner, R.A.; Frech, D.; L.M., MacDonald; Grant, G.G.; Weatherston, J.Item Open Access BF3‑Catalyzed Intramolecular Fluorocarbamoylation of Alkynes via Halide Recycling(American Chemical Society, 2023-05-12) McKnight, E. Ali; Arora, Ramon; Pradhan, Ekadashi; Fujisato, Yuriko H.; Ajayi, Ayonitemi, J.; Lautens, Mark; Zeng, Tao; Le, Christine M.A BF3-catalyzed atom-economical fluorocarbamoylation reaction of alkyne-tethered carbamoyl fluorides is reported. The catalyst acts as both a fluoride source and Lewis acid activator, thereby enabling the formal insertion of alkynes into strong C–F bonds through a halide recycling mechanism. The developed method provides access to 3-(fluoromethylene) oxindoles and γ-lactams with excellent stereoselectivity, including fluorinated derivatives of known protein kinase inhibitors. Experimental and computational studies support a stepwise mechanism for the fluorocarbamoylation reaction involving a turnover-limiting cyclization step, followed by internal fluoride transfer from a BF3-coordinated carbamoyl adduct. For methylene oxindoles, a thermodynamically driven Z–E isomerization is facilitated by a transition state with aromatic character. In contrast, this aromatic stabilization is not relevant for γ-lactams, which results in a higher barrier for isomerization and the exclusive formation of the Z-isomer.Item Open Access Bifunctional Resins Applications to the Synthesis of Insect Sex Attractants(NRC Research Press, 1978) Weatherston, John; Leznoff, Clifford C.; Fyles, Thomas M.