DOCSLIB.ORG

Nitroxyl-Mediated Peroxide Modification of Polypropylene

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nitroxyl-Mediated Peroxide Modification of Polypropylene Nitroxyl-Mediated Peroxide Modification of Polypropylene by Benjamin Rhys Jones A thesis submitted to the Department of Chemical Engineering In conformity with the requirements for the degree of Master of Applied Science Queen’s University Kingston, Ontario, Canada (May 2021) Copyright ©Benjamin Rhys Jones, 2021 Abstract The thermal stability of alkoxyamine derivatives of polypropylene (PP) is examined through studies of model hydrocarbon systems and atactic-PP substrates. Primary, secondary and tertiary alkoxyamines are integral to modern techniques for modifying the architecture of linear PP materials, and detailed knowledge of their stability at polymer processing temperatures is needed to further understand the underlying principles of nitroxyl-based formulations. GC analysis of alkoxyamines derived from 2,4-dimethylpentane + TEMPO show that the tertiary regioisomer is susceptible to disproportionation to alkene + HOTEMPO at temperatures as low as 140 oC. Extension of these thermolysis experiments to atactic PP-g-HOTEMPO mirrored the model compound results, with appreciable extents of nitroxyl generation observed over a 20 min timescale at 180 oC. This reaction extent is not expected to dramatically alter the performance of nitroxyl-based formulations that modify the structure and composition of PP homopolymers. The yield of H-atom abstraction by peroxide-derived alkoxy radicals is another fundamental reaction that underlies polyolefin modifications. Indirect measures based on analysis of peroxide byproducts are supplemented with a fluorescence spectroscopy method that quantifies polymer- bound alkoxyamines. H-atom transfer from high density polyethylene (HDPE) and poly(ethylene-co-propylene) (EPR) was gained by using napthoyloxy-TEMPO, whose fluorophore supports a highly sensitive analytical method. This technique is extended to studies of reactive HDPE/EPR blending to ascertain the extent of peroxide migration from one phase to the other during the compounding process. The data indicates that mass transfer of the peroxide is competitive with the rate of peroxide breakdown, causing both polymers to incur structure modification irrespective of how the initiator is charged to the blend components. i Acknowledgements I would like to thank Dr. Scott Parent for his expertise and guidance through this new field of study for me. I would like to thank my lab mates: Mitch Sadler, Kyle Ford and Matt Hawrylow for making my time in the lab more enjoyable. I’d also like to thank all the other staff and students in the department who made these times memorable. Special shoutout to Andrew Sellathurai for keeping me sane during the COVID-19 pandemic. Lastly, I would like to thank my partner, Kylie, and my family, who were always there to support me. To my mother, who always encouraged me to continue my education, while only encouraging my brother, Craig, to eat more bacon. This is for you. ii Table of Contents Abstract…………………………………………………………………………………………….i Acknowledgements………………………………………………………………………………..ii List of Figures…………………………………………………………………………………….vi List of Tables…………………………………………………………………………………….vii List of Schemes…………………………………………………………………………………viii List of Equations………………………………………………………………………………….ix List of Abbreviations……………………………………………………………………………...x Chapter 1 Introduction………………………………………………………………………….…1 1.1 Polypropylene Degradation………..……………………………………………….....1 1.2 H-Atom Abstraction by Peroxide Initiators...………………………………………....2 1.3 Nitroxyl Trapping of Alkyl Radicals………………………..………………………...4 1.4 Alkoxyamine Instability………………………………..……………………………...7 1.5 Model Compounds…………………………………………………..………………...8 Chapter 2 Experimental Methods………………………………………………………………..10 2.1 Materials………………………………………………………………..…………....10 2.2 Instrumentation and Analysis……………………………..…………………………11 2.3 Synthesis of 1-methoxy-2,2,6,6-tetramethyl-1-piperidine (Me-TEMPO)…………...12 2.4 Synthesis of (2,2,6,6,-tetramethylpiperidine-N-oxyl)-2,4-dimethylpentane regioisomers (DMP-TEMPO isomers)……………………………………...…………...12 2.5 Synthesis of 1-(2,2,6,6-tetramethylpiperdine-N-oxyl)-cyclohexane (cyclohexane-g-TEMPO)...................................................................................................13 2.6 Thermolysis of cyclohexane and DMP alkoxyamines…………………………...…..14 iii 2.7 Synthesis of PPatactic-g-HOTEMPO…………………………………………..……...14 2.8 Thermolysis of PPatactic-g-HOTEMPO…………………………………………….....14 2.9 Synthesis of Model Compounds for AE Determinations……………………………15 2.10 Synthesis of 4-(1-Naphthoyloxy)-2,2,6,6-tetramethylpiperdine-1-oxyl (N- TEMPO)……………………………………………………………………………….....15 2.11 Synthesis of Dodecyloxy-(4-(1-Naphthoyloxy)-2,2,6,6-tetramethylpiperdine) (Dodecane-NTEMPO)……………………………………………………………….…..16 2.12 Synthesis of Polymer-g-NTEMPO samples (EPR/HDPE-g-NTEMPO)………...…17 2.13 Synthesis of EPR/HDPE-g-NTEMPO Polymer Mix……………………………….18 Chapter 3 –Tertiary Alkoxyamine Disproportionation…………………………………………..19 3.1 Introduction…………………………………………………………………..………19 3.2 Results and Discussion………………………………………………………..……..20 3.3 Conclusion………………………………………………………………………..….26 Chapter 4- Fluorescence Determination of Macroradical Yields in Polyolefin Melt Blends……………………………………………………………………………………………28 4.1 Introduction………………………………………………………………………..…28 4.2 Results and Discussion…………………………………………………………..…..31 4.2.1 Abstraction Efficiency Validations………………………………….…..…31 4.2.2 Independent HDPE and EPR Modifications……………………………….33 4.2.3 HDPE + EPR Blend Modifications…………………………….……….....38 4.3 Conclusion………………………………………………………………………..….41 Chapter 5 Future Work…………………………………………………………………………..42 5.1 Tertiary Alkoxyamine Instability…………………………..………………………………...42 iv 5.2 Peroxide Migration Trials………………………..…………………………………………..42 References………………………………………………………………………………………..42 Appendix…………………………………………………………………………………………49 Appendix A 1H NMR spectrum of dodecane-g-NTEMPO……………………………...49 Appendix B 1H NMR of PP-g-TEMPO………………………………………………….50 v List of Figures Figure 1. GC signal integrations from nitroxyl liberated by Cyclohexane-g-NTEMPO and DMP-g-NTEMPO at 140oC………………………………………………………………...……22 Figure 2. GC signal integrations from nitroxyl liberated by Cyclohexane-g-NTEMPO and DMP-g-NTEMPO after 20 min …………………………………………………………………23 Figure 3 H-atom abstraction efficiency measurements acquired with different analytical techniques………………………………………………………………………………………..33 Figure 4 Calibrations of dodecane-g-NTEMPO in cyclohexane (295nm excitation, 280-580nm emission at 20oc) and dodecane-g-NTEMPO in xylenes (295nm excitation, 315-430nm at 125oc) ……………………………………………………………………………………………35 Figure 5. Comparison of dodecane-g-NTEMPO and EPR-g-NTEMPO fluorescence spectra in cyclohexane (20oC, 295 excitation wavelength)..……………………………………………..36 Figure 6 Comparison of HDPE-g-NTEMPO and dodecane-g-NTEMPO fluorescence spectra in xylenes (125oC, 295 excitation wavelength)..………………………………………………...37 Figure 7. EPR-g-NTEMPO and HDPE-g-NTEMPO alkoxyamine yields……………………...38 Figure 8. Fluorescence spectra for EPR-g-NTEMPO isolated from the compounded blend and its parent material …………………………………………………………………………...40 Figure 9. Fluorescence spectra for HDPE-g-NTEMPO isolated from the compounded blend and its parent material……………………………………………………………………………40 vi List of Tables Table 1. Amount of nitroxyl liberated from PP-g-HOTEMPO at 140oC…………………….....25 Table 2. Amount of nitroxyl liberated from PP-g-HOTEMPO after 20 min …………………...25 Table 3. AE of DCP acting upon various model hydrocarbons at 160oC……………………….32 vii List of Schemes Scheme 1. Production and -scission of tertiary macroradicals …………………………………1 Scheme 2. Peroxide thermolysis and hydrogen abstraction……………………………………….2 Scheme 3. Nitroxyl trapping of alkyl radicals produced by peroxide initiator……………………5 Scheme 4. Disproportionation products of 4-TEMPO-2,4,6-trimethyl heptane…………………..8 Scheme 5. Model alkoxyamine studies…………………………………………………………..20 Scheme 6: Cumyloxyl scission and H-atom abstraction products of AE determinations……….29 Scheme 7. Structure of NTEMPO……………………………………………………………….30 viii List of Equations Equation 1. Abstraction Efficiency………………………………………………………………..3 Equation 2. Trapping Ratio………………………………………………………………………..5 Equation 3. Induction time provided by a nitroxyl formulation…………………………………..6 ix List of Abbreviations 1o – primary 2o - secondary 3o – tertiary AE – abstraction efficiency BDE – bond dissociation energy CDCl3 – deuterated chloroform DCP – dicumyl peroxide DMP – 2,4-dimethylpentane DMP-TEMPO – (2,2,6,6-tetramethylpiperidine) 2,4-dimethylpentane isomers DMSO – dimethylsulfoxide EPR – ethylene propylene rubber . FeSO4 7H2O – iron (II) sulfate heptahydrate g – gram GC – gas chromatography H2O – water H2O2 – hydrogen peroxide H2 – hydrogen HOTEMPO – 4-hydroxy-2,2,6,6-tetramethylpiperdine-N-oxyl HDPE – high density polyethylene k – rate constant L130 – 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne L231 – 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane Me-TEMPO - 1-methoxy-2,2,6,6-tetramethyl-1-piperidine MW – molecular weight N2 – nitrogen NaSO4 – sodium sulfate NMR – nuclear magnetic resonance x NTEMPO – 4-(1-Naphthoyloxy)-2,2,6,6-tetramethylpiperdine-1-oxyl Min – minutes MS – mass spectroscopy PE – polyethylene PIB – polyisobutylene PP – polypropylene ppm – parts per million t1/2 – initiator half lives tind – induction time TEMPO – 2,2,6,6-tetramethylpiperidine-N-oxyl TMIO - 1,1,3,3-Tetramethylisoindolin-2-yloxy TPE – Thermoplastic Elastomer TPV – Thermoplastic Vulcanizate VTES – vinyl triethoxy silane xi Chapter 1 Introduction 1.1 Polypropylene Degradation The mechanism
Load more

Recommended publications
  • A Biochemical Rationale for the Discrete Behavior of Nitroxyl and Nitric Oxide in the Cardiovascular System
    A biochemical rationale for the discrete behavior of nitroxyl and nitric oxide in the cardiovascular system Katrina M. Miranda*†‡, Nazareno Paolocci§, Tatsuo Katori§, Douglas D. Thomas*, Eleonora Ford¶, Michael D. Bartbergerʈ, Michael G. Espey*, David A. Kass§, Martin Feelisch**, Jon M. Fukuto¶, and David A. Wink*† *Radiation Biology Branch, Building 10, Room B3-B69, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892; §Division of Cardiology, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, MD 21287; ¶Department of Molecular and Medical Pharmacology, Center for the Health Sciences, University of California, Los Angeles, CA 90095; ʈDepartment of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095; and **Department of Molecular and Cellular Physiology, Louisiana State University Health Sciences Center, Shreveport, LA 71130 Edited by Louis J. Ignarro, University of California School of Medicine, Los Angeles, CA, and approved May 20, 2003 (received for review February 20, 2003) The redox siblings nitroxyl (HNO) and nitric oxide (NO) have often cellular thiol functions (14, 15). Conversely, NO reacts only indi- been assumed to undergo casual redox reactions in biological sys- rectly with thiols after RNOS formation (17). tems. However, several recent studies have demonstrated distinct Contrasting effects are also apparent in vivo or ex vivo,for pharmacological effects for donors of these two species. Here, infu- example in models of ischemia reperfusion injury. Exposure to NO sion of the HNO donor Angeli’s salt into normal dogs resulted in donors at the onset of reperfusion provides protection against elevated plasma levels of calcitonin gene-related peptide, whereas reperfusion injury in the heart and other organs (18–20).
    [Show full text]
  • Hidden Complexities in the Reaction of H2O2 and HNO Revealed by Ab Initio Quantum Chemical Cite This: Phys
    PCCP PAPER Hidden complexities in the reaction of H2O2 and HNO revealed by ab initio quantum chemical Cite this: Phys. Chem. Chem. Phys., 2017, 19, 29549 investigations† Daniel Beckett, Marc Edelmann, Jonathan D. Raff and Krishnan Raghavachari* Nitroxyl (HNO) and hydrogen peroxide have both been implicated in a variety of reactions relevant to environmental and physiological processes and may contribute to a unique, unexplored, pathway for the production of nitrous acid (HONO) in soil. To investigate the potential for this reaction, we report an in-depth investigation of the reaction pathway of H2O2 and HNO forming HONO and water. We find the breaking of the peroxide bond and a coupled proton transfer in the first step leads to hydrogen nitryl (HNO2) and an endogenous water, with an extrapolated NEVPT2 (multireference perturbation theory) barrier of 29.3 kcal molÀ1. The first transition state is shown to possess diradical character linking the far peroxide oxygen to the bridging, reacting, peroxide oxygen. The energy of this first step, when calculated using hybrid density functional theory, is shown to depend heavily on the amount of Hartree–Fock exchange in the functional, with higher amounts leading to a higher barrier and more diradical character. Additionally, high amounts of spin contamination cause CCSD(T) to significantly overestimate the TS1 barrier with a value of 36.2 kcal molÀ1 when using the stable UHF wavefunction as the reference wavefunction. However, when using the restricted Hartree–Fock reference wavefunction, the TS1 CCSD(T) energy is lowered to yield a barrier of 31.2 kcal molÀ1, in much better agreement with the Received 29th August 2017, NEVPT2 result.
    [Show full text]
  • Nitroaromatic Antibiotics As Nitrogen Oxide Sources
    Review biomolecules Nitroaromatic Antibiotics as Nitrogen Oxide Sources Review Allison M. Rice, Yueming Long and S. Bruce King * Nitroaromatic Antibiotics as Nitrogen Oxide Sources Department of Chemistry and Biochemistry, Wake Forest University, Winston-Salem, NC 27101, USA; Allison M. Rice , Yueming [email protected] and S. Bruce (A.M.R.); King [email protected] * (Y.L.) * Correspondence: [email protected]; Tel.: +1-336-702-1954 Department of Chemistry and Biochemistry, Wake Forest University, Winston-Salem, NC 27101, USA; [email protected]: Nitroaromatic (A.M.R.); [email protected] antibiotics (Y.L.) show activity against anaerobic bacteria and parasites, finding * Correspondence: [email protected]; Tel.: +1-336-702-1954 use in the treatment of Heliobacter pylori infections, tuberculosis, trichomoniasis, human African trypanosomiasis, Chagas disease and leishmaniasis. Despite this activity and a clear need for the Abstract: Nitroaromatic antibiotics show activity against anaerobic bacteria and parasites, finding usedevelopment in the treatment of new of Heliobacter treatments pylori forinfections, these conditio tuberculosis,ns, the trichomoniasis, associated toxicity human Africanand lack of clear trypanosomiasis,mechanisms of action Chagas have disease limited and their leishmaniasis. therapeutic Despite development. this activity Nitroaro and a clearmatic need antibiotics for require thereductive development bioactivation of new treatments for activity for theseand this conditions, reductive the associatedmetabolism toxicity can convert
    [Show full text]
  • On the Distinction Between Nitroxyl and Nitric Oxide Using Nitronyl Nitroxides
    Published on Web 05/26/2010 On the Distinction between Nitroxyl and Nitric Oxide Using Nitronyl Nitroxides Uri Samuni,† Yuval Samuni,‡ and Sara Goldstein*,§ Department of Chemistry and Biochemistry, Queens College, City UniVersity of New York, Flushing, New York 11367, and Department of Prosthodontics, School of Dental Medicine, and Institute of Chemistry, The Accelerator Laboratory, The Hebrew UniVersity of Jerusalem, Jerusalem 91904, Israel Received March 8, 2010; E-mail: [email protected] Abstract: A better understanding of the origins of NO and HNO and their activities and biological functions requires accurate methods for their detection and quantification. The unique reaction of NO with nitronyl nitroxides such as 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (C-PTIO), which yields the corresponding imino nitroxides, is widely used for NO detection (mainly by electron paramagnetic resonance spectroscopy) and for modulation of NO-induced physiological functions. The present study demonstrates that HNO readily reacts with nitronyl nitroxides, leading to the formation of the respective imino nitroxides and hydroxylamines via a complex mechanism. Through the use of the HNO donor Angeli’s salt (AS) with metmyoglobin as a competing agent, the rate constant for C-PTIO reduction by HNO has been determined to be (1.4 ( 0.2) × 105 M-1 s-1 at pH 7.0. This reaction yields the corresponding nitronyl • hydroxylamine C-PTIO-H and NO, which is trapped by C-PTIO to form NO2 and the corresponding imino • nitroxide, C-PTI. NO2 oxidizes the nitronyl and imino nitroxides to their respective oxoammonium cations, which decay mainly via comproportionation with the nitronyl and imino hydroxylamines.
    [Show full text]
  • Nitroxyl (Hno) and Carbonylnitrenes
    INVESTIGATION OF REACTIVE INTERMEDIATES: NITROXYL (HNO) AND CARBONYLNITRENES by Tyler A. Chavez A dissertation submitted to the Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy Baltimore, Maryland February 2016 © 2016 Tyler A. Chavez All rights reserved Abstract Membrane inlet mass spectrometry (MIMS) is a well-established method used to detect gases dissolved in solution through the use of a semipermeable hydrophobic membrane that allows the dissolved gases, but not the liquid phase, to enter a mass spectrometer. Interest in the unique biological activity of azanone (nitroxyl, HNO) has highlighted the need for new sensitive and direct detection methods. Recently, MIMS has been shown to be a viable method for HNO detection with nanomolar sensitivity under physiologically relevant conditions (Chapter 2). In addition, this technique has been used to explore potential biological pathways to HNO production (Chapter 3). Nitrenes are reactive intermediates containing neutral, monovalent nitrogen atoms. In contrast to alky- and arylnitrenes, carbonylnitrenes are typically ground state singlets. In joint synthesis, anion photoelectron spectroscopic, and computational work we studied the three nitrenes, benzoylnitrene, acetylnitrene, and trifluoroacetylnitrene, with the purpose of determining the singlet-triplet splitting (ΔEST = ES – ET) in each case (Chapter 7). Further, triplet ethoxycarbonylnitrene and triplet t-butyloxycarbonylnitrene have been observed following photolysis of sulfilimine precursors by time-resolved infrared (TRIR) spectroscopy (Chapter 6). The observed growth kinetics of nitrene products suggest a contribution from both the triplet and singlet nitrene, with the contribution from the singlet becoming more prevalent in polar solvents. Advisor: Professor John P. Toscano Readers: Professor Kenneth D.
    [Show full text]
  • Studies Toward the Synthesis of Photolabile HNO Donors–An
    STUDIES TOWARD THE SYNTHESIS OF PHOTOLABILE HNO DONORS – AN EXPLORATION OF SELECTIVITY FOR HNO GENERATION A thesis submitted to the Kent State University Honors College in partial fulfillment of the requirements for Departmental Honors by Zachary Alan Fejedelem August, 2015 Thesis written by Zachary Alan Fejedelem Approved by ________________________________________________________________, Advisor ________________________________________________________________, Advisor ________________________________________________________________, Chair, Department of Chemistry & Biochemistry Accepted by _____________________________________________________, Dean, Honors College ii TABLE OF CONTENTS LIST OF FIGURES……………………………………………………...…………….…vi LIST OF TABLES………………………………………………………………………..ix ACKNOWLEDGMENTS………………………………………………….......................x CHAPTER 1. INTRODUCTION……………………………………………………..….1 1.1 Introduction to HNO……………………………………………....1 1.1.1 The unique qualities of HNO……………………………………...1 1.1.2 Drawbacks and issues of HNO…………………………………....5 1.1.3 Importance of HNO donors……………………………….………6 1.2 Examples of HNO donors………………………………………...7 1.2.1 Angeli’s Salt (AS)………………………………………………...7 1.2.2 Piloty’s Acid (PA)………………………………………………...8 1.2.3 HNO-generating diazeniumdiolates…………………………..…12 1.2.4 Cyanamide…………………………………………………….…12 1.2.5 Nitrosocarbonyls…………………………………………………14 1.2.6 Hydroxylamine…………………………………………………..16 1.2.7 α-Acyloxy-C-nitroso compounds………………………………..16 1.2.8 Photolabile HNO and NO donors………………………………..17 1.3 Our research group’s family of current HNO donors…………....20 iii 1.3.1 Previous work on first family of photoactivatable HNO donors..20 1.3.2 Previous synthesis of target photolabile HNO donors…………..22 1.4 Photolysis results from HNO donors 22………………………....25 1.4.1 Photolysis results of first HNO donor 22a……………………....25 1.4.2 Proposed photolysis mechanism………………………………...27 1.5 Thesis project goal……………………………………………....29 1.5.1 Thesis project……………………………………………………29 1.5.2 Proposed photolysis mechanism………………………………...31 2.
    [Show full text]
  • Dynamic Nitroxyl Formation in the Ammonia Oxidation on Platinum Via Eley–Rideal Reactions† Cite This: Phys
    PCCP View Article Online PAPER View Journal | View Issue Dynamic nitroxyl formation in the ammonia oxidation on platinum via Eley–Rideal reactions† Cite this: Phys. Chem. Chem. Phys., 2016, 18, 29858 Yunxi Yao and Konstantinos P. Giapis* For over 90 years, nitroxyl (HNO) has been postulated to be an important reaction intermediate in the catalytic oxidation of ammonia to NO and its by-products (N2,N2O), but never proven to form or exist on catalytic surfaces. Here we show evidence from reactive ion beam experiments that HNO can form directly on the surface of polycrystalline Pt exposed to NH3 via Eley–Rideal abstraction reactions of + + adsorbed NH by energetic O and O2 projectiles. The dynamic formation of HNO in a single collision followed up by prompt rebound from the surface prevents subsequent reactive interactions with other Received 23rd September 2016, surface adsorbates and enables its detection. In addition to HNO, NO and OH are also detected as direct Accepted 14th October 2016 products in what constitutes the concurrent abstraction of three surface adsorbates, namely NH, N, and + DOI: 10.1039/c6cp06533c H, by O projectiles with entirely predictable kinematics. While its relation to thermal catalysis may Creative Commons Attribution-NonCommercial 3.0 Unported Licence. be tenuous, dynamic HNO formation could be important on grain surfaces of interstellar or cometary www.rsc.org/pccp matter under astrophysical conditions. Introduction mechanisms of nitroxyl and hydroxylamine may therefore be important not only for catalysis but also for astrochemistry. The catalytic oxidation of ammonia (NH3) to nitric oxide (NO) Detection of short-lived reaction intermediates is challeng- on Pt–Rh gauze (Ostwald process) is one of the oldest industrial ing but critical to revealing the correct elementary steps in reactions still in use today for manufacturing nitric acid.1 heterogeneous catalytic reactions.
    [Show full text]
  • Stable Bicyclic Functionalized Nitroxides: the Synthesis of Derivatives of Aza-Nortropinone–5-Methyl-3-Oxo-6,8-Diazabicyclo[3
    molecules Article Stable Bicyclic Functionalized Nitroxides: The Synthesis of Derivatives of Aza-nortropinone–5-Methyl-3-oxo-6,8- diazabicyclo[3.2.1]-6-octene 8-oxyls Larisa N. Grigor’eva, Alexsei Ya. Tikhonov *, Konstantin A. Lomanovich and Dmitrii G. Mazhukin * N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry SB RAS, Academician Lavrentiev Ave. 9, 630090 Novosibirsk, Russia; [email protected] (L.N.G.); [email protected] (K.A.L.) * Correspondence: [email protected] (A.Y.T.); [email protected] (D.G.M.); Tel.: +7-383-330-8867 (A.Y.T.); +7-383-330-6852 (D.G.M.) Abstract: In recent decades, bicyclic nitroxyl radicals have caught chemists’ attention as selective catalysts for the oxidation of alcohols and amines and as additives and mediators in directed C-H oxidative transformations. In this regard, the design and development of synthetic approaches to new functional bicyclic nitroxides is a relevant and important issue. It has been reported that imidazo[1,2- b]isoxazoles formed during the condensation of acetylacetone with 2-hydroxyaminooximes having a secondary hydroxyamino group are recyclized under mild basic catalyzed conditions to 8-hydroxy- 5-methyl-3-oxo-6,8-diazabicyclo[3.2.1]-6-octenes. The latter, containing a sterically hindered cyclic N-hydroxy group, upon oxidation with lead dioxide in acetone, virtually quantitatively form sta- ble nitroxyl bicyclic radicals of a new class, which are derivatives of both 2,2,6,6-tetramethyl-4- oxopiperidine-1-oxyl (TEMPON) and 3-imidazolines. Citation: Grigor’eva, L.N.; Tikhonov, A.Y.; Lomanovich, K.A.; Mazhukin, Keywords: bicyclic nitroxide; condensation; acetylacetone; base-catalyzed recyclization; 3-imidazoline D.G.
    [Show full text]
  • Nitroxyl (HNO): a Reduced Form of Nitric Oxide with Distinct Chemical, Pharmacological, and Therapeutic Properties
    Hindawi Publishing Corporation Oxidative Medicine and Cellular Longevity Volume 2016, Article ID 4867124, 15 pages http://dx.doi.org/10.1155/2016/4867124 Review Article Nitroxyl (HNO): A Reduced Form of Nitric Oxide with Distinct Chemical, Pharmacological, and Therapeutic Properties Mai E. Shoman and Omar M. Aly Department of Medicinal Chemistry, Faculty of Pharmacy, Minia University, Minia 61519, Egypt Correspondence should be addressed to Omar M. Aly; [email protected] Received 5 May 2015; Revised 14 August 2015; Accepted 1 September 2015 Academic Editor: Lezanne Ooi Copyright © 2016 M. E. Shoman and O. M. Aly. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Nitroxyl (HNO), the one-electron reduced form of nitric oxide (NO), shows a distinct chemical and biological profile from that of NO. HNO is currently being viewed as a vasodilator and positive inotropic agent that can be used as a potential treatment for heart failure. The ability of HNO to react with thiols and thiol containing proteins is largely used to explain the possible biological actions of HNO. Herein, we summarize different aspects related to HNO including HNO donors, chemistry, biology, and methods used for its detection. 1. Nitric Oxide (NO) cGMP in platelets, and this is thought to be the mechanism by which it inhibits platelet function [7]. In the vasculature, Biological activities associated with nitrogen oxide species are NO also prevents neutrophil/platelet adhesion to endothelial the subject of intense and current research interest.
    [Show full text]
  • Oxidative Coupling of Alkynes Mediated by Nitroxyl Radicals Under Sonogashira Conditions and Pd-Free Catalytic Approach to Stabl
    Available online at www.sciencedirect.com Tetrahedron Letters 48 (2007) 8246–8249 Oxidative coupling of alkynes mediated by nitroxyl radicals under Sonogashira conditions and Pd-free catalytic approach to stable radicals of 3-imidazoline family with triple bonds Sergei F. Vasilevsky,a,* Olga L. Krivenkoa and Igor V. Alabuginb,* aInstitute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Science, 630090 Novosibirsk, Russian Federation bDepartment of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306, United States Received 5 April 2007; accepted 4 September 2007 Available online 11 September 2007 Abstract—In the presence of Pd catalyst, 3-imidazoline nitroxyl radicals promote oxidative coupling (dimerization) of terminal alky- nes even in the absence of Cu(II) additives. On the other hand, the Pd-free CuI–PPh3–K2CO3–DMF catalytic system leads to the efficient cross-coupling of 1-hydroxy-4-[2-(p-iodophenyl)vinyl]-2,2,5,5-tetramethyl-3-imidazoline-3-oxide with terminal aryl- and hetarylacetylenes with the formation of 4-[2-(aryl/hetarylethynyl)phenyl)vinyl]-2,2,5,5-tetramethyl-3-imidazoline-3-oxide-1-oxyls in 70–75% yields. Ó 2007 Elsevier Ltd. All rights reserved. High stability of 3-imidazoline nitroxyl radicals and sen- chemical phenomena and for the construction of mole- sitivity of their EPR spectra to the environment account cular devices for practical applications. for rapidly emerging applications of these molecules in analytical chemistry, molecular biology, and biophys- Despite
    [Show full text]
  • Opposite Effects of Nitric Oxide and Nitroxyl on Postischemic Myocardial Injury
    Opposite effects of nitric oxide and nitroxyl on postischemic myocardial injury Xin L. Ma*†, Feng Gao*, Gao-Lin Liu*, Bernard L. Lopez*, Theodore A. Christopher*, Jon M. Fukuto‡, David A. Wink§, and Martin Feelisch¶ *Department of Surgery, Thomas Jefferson University, Philadelphia, PA 19107; ‡Department of Pharmacology, University of California School of Medicine, Los Angeles, CA 90024; §Radiation Biology Branch, National Cancer Institute, Bethesda, MD 20892; and ¶The Wolfson Institute for Biomedical Research, University College London, London, United Kingdom Edited by Louis J. Ignarro, University of California, Los Angeles, CA, and approved October 21, 1999 (received for review July 22, 1999) Recent experimental evidence suggests that reactive nitrogen ONOOϪ causes aggregation of platelets in buffer solution but oxide species can contribute significantly to postischemic myocar- inhibits aggregation of platelets in plasma (9). Administration of dial injury. The aim of the present study was to evaluate the role ONOOϪ to buffer solution-perfused rat hearts increases reperfu- -of two reactive nitrogen oxide species, nitroxyl (NO؊) and nitric sion injury whereas administration of ONOOϪ to whole blood ⅐ oxide (NO ), in myocardial ischemia and reperfusion injury. Rabbits perfused hearts significantly diminishes reperfusion injury (10). were subjected to 45 min of regional myocardial ischemia followed Moreover, Nossuli et al. (11) have recently reported that adminis- by 180 min of reperfusion. Vehicle (0.9% NaCl), 1 ␮mol͞kg S- tration of a low concentration of ONOOϪ in vivo attenuates rather ⅐ nitrosoglutathione (GSNO) (an NO donor), or 3 ␮mol͞kg Angeli’s than enhances reperfusion injury. These results suggest that the salt (AS) (a source of NO؊) were given i.v.
    [Show full text]
  • Arxiv:1510.07052V1 [Astro-Ph.EP] 23 Oct 2015 99 Lae Ta.20,Adrfrne Therein)
    A Chemical Kinetics Network for Lightning and Life in Planetary Atmospheres P. B. Rimmer1 and Ch Helling School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, United Kingdom ABSTRACT There are many open questions about prebiotic chemistry in both planetary and exoplane- tary environments. The increasing number of known exoplanets and other ultra-cool, substellar objects has propelled the desire to detect life and prebiotic chemistry outside the solar system. We present an ion-neutral chemical network constructed from scratch, Stand2015, that treats hydrogen, nitrogen, carbon and oxygen chemistry accurately within a temperature range between 100 K and 30000 K. Formation pathways for glycine and other organic molecules are included. The network is complete up to H6C2N2O3. Stand2015 is successfully tested against atmo- spheric chemistry models for HD209458b, Jupiter and the present-day Earth using a simple 1D photochemistry/diffusion code. Our results for the early Earth agree with those of Kasting (1993) for CO2, H2, CO and O2, but do not agree for water and atomic oxygen. We use the network to simulate an experiment where varied chemical initial conditions are irradiated by UV light. The result from our simulation is that more glycine is produced when more ammonia and methane is present. Very little glycine is produced in the absence of any molecular nitrogen and oxygen. This suggests that production of glycine is inhibited if a gas is too strongly reducing. Possible applications and limitations of the chemical kinetics network are also discussed. Subject headings: astrobiology — atmospheric effects — molecular processes — planetary systems 1. Introduction The input energy source and the initial chem- istry have been varied across these different ex- The potential connection between a focused periments.
    [Show full text]