DOCSLIB.ORG

Monitoring Oxidation Reactions by Photochemical Techniques

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Monitoring Oxidation Reactions by Photochemical Techniques Monitoring Oxidation Reactions by Photochemical Techniques by Hamdy Saad Sadek El–Sheshtawy A thesis submitted in partial fulfillment for the degree of Doctor of Philosophy in Chemistry Approved Thesis Committee: Prof. Dr. Werner M. Nau Jacobs University Bremen, Bremen Prof. Dr. Nikolai Kuhnert Jacobs University Bremen, Bremen Dr. Aurica Farcas “Petru Poni” Institute of Macromolecular Date of defense: November 7, 2011 Chemistry, Romania School of Engineering and Science Declaration of Authorship I, Hamdy El–Sheshtawy, declare that this thesis entitled, “ Monitoring Oxidation Reactions by Photochemical Techniques" and the work presented in it are my own. I confirm that: • This work was done wholly or mainly while in candidature for a doctoral degree in chemistry at Jacobs University. • Where I have consulted the published work of others, this is always clearly attributed. • Where I have quoted from the work of others, the source is always given with the exception of such quotations; this thesis is entirely my own work. • I have acknowledged all main sources of help. • Where the thesis is based on work done by myself jointly with others, I have made clear exactly what was done by others and what I have contributed myself. Signed: Date: ii Yesterday we obeyed kings and bent our necks before emperors. But today we kneel only to truth, follow only beauty, and obey only love. Khalil Gibran iii To my Parents iv Abstract PhD Thesis by Hamdy Saad El–Sheshtawy This doctoral thesis is devoted to monitor oxidation processes by photochemical techniques. Oxidation reactions play a crucial role in both environmental and biological systems. Therefore, my thesis started with the study of oxygen scavenging of aryl- substituted benzyl radicals. In this part of my work, a combination of experimental techniques (laser-flash photolysis) and theoretical calculations (DFT) was used to elucidate the mechanism of an elementary step in an oxidation process. The effect of substituents on the scavenging rate constants was studied in detail. Solvent effects on the reaction progress, as well as temperature effects were investigated. For the first time, a negative activation energy was observed: the scavenging rate constants of aryl–benzyl radicals in acetonitrile decreased at higher temperature. In the second part of my thesis, the effect of the solvent on H atom abstractions from C–H donors by oxygen-centered radicals (the cumoxyl radical) and n–π* excited molecules (2,3-diazabicyclo[2.2.2]oct–2–ene) was investigated. For this, theoretical calculations and experimental results were again combined to rationalize the solvent effects on the H atom abstraction from several C–H donors by the oxygen–centered radicals. The results are compared to those previously reported in the literature for H atom abstraction from O–H donors. In the last part, I developed a fluorescence-based supramolecular tandem assay to monitor a biologically important oxidation process, namely an enzymatic oxidation. When searching for a macrocyclic receptor (required for tandem assays) for the substrate of peroxidases, namely iodide, I found a novel interaction (halogen bonding) in v supramolecular host–guest complexes associated with cucurbit[n]urils (CBs), which is based on the encapsulation of molecular iodine (I2) inside the nanocavity of CB6. Halogen bonds have been found to play a crucial role in the complex stability in the case of CB6•I2, while for the CB7•I2 association complex the hydrophobic effect is dominant. Based on the encapsulation of I2 into the CB7 cavity, we developed a supramolecular tandem assay for monitoring the activity of peroxidases, namely myeloperoxidase (MPO), lactoperoxidase (LPO), and horseradish peroxidase (HRP). This assay has the advantage of using a small inorganic substrate (I–), in contrast to the previously employed organic compounds. In addition, the supramolecular tandem assay requires only µM concentrations of the substrate (I–), such that it overcomes the use of high substrate concentration (needed for other methods), which is known to adversely affect (inhibit) peroxidase activity. vi Acknowledgments I would like to thankfully acknowledge the enormous support, encouragement and guidance of my supervisor, Prof. Dr. Werner M. Nau, who provided me with a diverse playground of projects to develop upon. I want to thank Prof. Dr. Nikolai Kuhnert and Dr. Aurica Farcas for being kind enough to be committee members for my PhD thesis. I would also like to thank all members of the Nau research group for providing a stimulating environment, both socially as well as professionally. In particular, I thank Dr. Apurba L. Koner, Indrajit Ghosh for their fruitful discussions regards the wide variety of subjects and instruments in the laboratory. Special thanks go to Dr. Bassem Bassil for solving extremely complex supramolecular structures and being patient until good results were obtained. I want to also thank Dr. Vanya Uzunova for the ITC measurements, and Dr. Patrice Donfack for Raman spectroscopy measurements. Also I would like to extend my deepest thankful to Dr. Xiangyang Zhang for the preparation of the substituted dibenzylketones, which have been used during this study. I acknowledge the kind and generous financial support of the Egyptian Government, DFG, and NanoFun center at Jacobs University. Finally, to my wife, and our children Ahmed and Ayah, all I can say that I want to express my deep love for you. Your patience, love and encouragement have upheld me, particularly in those many days in which I spent more time with my lab than with you. vii Contents Abstract v Acknowledgements vii List of Figures x List of Tables xii 1 Introduction 2 1.1 Scope of the Thesis and Overview…………………………………………… 2 1.2 Environmental Oxidation Reactions ………………………….……………… 5 1.2.1 Oxidation Reactions in Combustion Chemistry……….……………….. 5 1.2.2 Oxidation Reactions in Atmospheric Chemistry……………………….. 7 1.2.3 The Benzyl Radical as a Model for Combustion and Atmospheric Radical Reactions………………………………………………………. 9 1.3 Oxidation Reactions in Biological Systems………………………………….. 11 1.3.1 An Overview…………………………………………………………… 11 1.3.2 Mechanism of Compound I Formation in Heme Peroxidases…………... 12 1.3.3 Halide Oxidation by Heme Peroxidases………………………………... 13 1.3.4 Defense Mechanisms Based on Halogen Oxidation…………………… 14 References…………………………………………………………………… 16 2 Oxygen Scavenging of Aryl–Substituted Benzyl Radicals 20 2.1 Introduction…………………………………………………………………... 20 2.2 Oxygen Scavenging Rate Constants…………………………………............. 22 2.3 Solvent Effect on the Scavenging Rate Constants…………………………… 28 2.4 Temperature Effect on the Scavenging Rate Constants……………………… 30 References………………………...………………………………….............. 34 viii 3 Solvent Polarity Affects H–Atom Abstractions from C–H Donors 36 3.1 Introduction…………………………………………………………………… 36 3.1.1 Intramolecular H–Atom Transfer (Isomerization)……………….......... 37 3.1.2 Solvent Effect on Intermolecular H–Atom Transfer…………………… 37 References…………………………………………………………………… 46 4 Catalytic Oxidation of Iodide by Peroxidases: A Supramolecular Tandem Assay for Monitoring Peroxidase Activity 49 4.1 Supramolecular Host–Guest Assemblies……………………………………… 49 4.2 Driving Forces for Host–Guest Interactions…………………………………... 49 4.2.1 Hydrogen Bond………………………………………………………….. 49 4.2.2 Halogen Bond………………………….………………………………... 50 4.3 Cucurbiturils…………………………………………………………………… 52 4.4 Iodine by the Barrel–On the Macrocyclic Recognition of an Element………... 55 4.4.1 Molecular Iodine Binding with Cucurbit[n]urils……………………….. 55 4.4.2 Halogen Bond in CB6•I2 Crystal Structure…………………………….. 59 4.4.3 Iodine as Solvatochromic Probe for Polarizability Inside Cucurbit[n]uril Cavity……………………………………………............. 61 4.4.4 Raman Spectroscopy of Iodine Encapsulated Inside Cucurbit[n]urils Cavity…………………………………………………... 66 4.5 Supramolecular Tandem Assays for Monitoring Peroxidase Activity……… 72 4.5.1 Supramolecular Tandem Assay……………………………………….. 72 4.5.2 Monitoring Heme Peroxidases Activity by Supramolecular Tandem Assays……………………………………………………….. 73 4.5.3 Peroxidase Inhibition by Melatonin…………………………………… 77 4.6 Storage of CBs•I2 in Gel Matrix…………………………………….............. 79 References…………………………………………………………………… 81 5 Appendices 85 Appendix I …………………………………………………………………….. 86 Appendix II …………………………………………………………………… 101 Appendix III……………………………………………………………………. 123 Appendix IV …………………………………………………………………… 164 ix List of Figures: 1.1 Mono–and–di substituted benzyl–type triplet diradicals used for the ΔD scale. 10 2.1 Transient absorption decay traces observed for benzyl radical………………... 23 2.2 Optimized transition state geometries of the substituted benzyl radicals ……... 25 2.3 Hammet relationship for the aryl–substituted benzyl radicals in n–hexane….. 27 2.4 Transient decay traces of benzyl radical in acetonitrile and in n–hexane……… 28 2.5 Transient absorption decay traces of benzyl radical at different temperatures… 30 2.6 Potential energy profile for unsubstituted benzyl radical………………………. 33 3.1 Transient absorption decays of cumyloxyl radicals in aerated CH3CN, EtOAc/CH3CN (50/50), and in EtOAc in the presence of hexamethylbenzene... 41 3.2 Fluorescence lifetime decays of DBO in deaerated CH3CN, EtOAc/CH3CN (50/50), and in EtOAc in the presence of 1,3–cyclohexadiene…………………. 41 3.3 Plots of log k versus the composition of a binary EtOAc/CH3CN mixture…….. 3.4 Optimized transition–state structures and solvation energies of the cumyloxyl radical and tert–butoxyl radical………………………………………………… 44 4.1 UV-Vis titrations of iodine
Load more

Recommended publications
  • Rate Constants for Reactions Between Iodine- and Chlorine-Containing Species: a Detailed Mechanism of the Chlorine Dioxide/Chlorite-Iodide Reaction†
    3708 J. Am. Chem. Soc. 1996, 118, 3708-3719 Rate Constants for Reactions between Iodine- and Chlorine-Containing Species: A Detailed Mechanism of the Chlorine Dioxide/Chlorite-Iodide Reaction† Istva´n Lengyel,‡ Jing Li, Kenneth Kustin,* and Irving R. Epstein Contribution from the Department of Chemistry and Center for Complex Systems, Brandeis UniVersity, Waltham, Massachusetts 02254-9110 ReceiVed NoVember 27, 1995X Abstract: The chlorite-iodide reaction is unusual because it is substrate-inhibited and autocatalytic. Because - analytically pure ClO2 ion is not easily prepared, it was generated in situ from the rapid reaction between ClO2 and I-. The resulting overall reaction is multiphasic, consisting of four separable parts. Sequentially, beginning with mixing, these parts are the (a) chlorine dioxide-iodide, (b) chlorine(III)-iodide, (c) chlorine(III)-iodine, and (d) hypoiodous and iodous acid disproportionation reactions. The overall reaction has been studied experimentally and by computer simulation by breaking it down into a set of kinetically active subsystems and three rapidly established - equilibria: protonations of chlorite and HOI and formation of I3 . The subsystems whose kinetics and stoichiometries were experimentally measured, remeasured, or which were previously experimentally measured include oxidation of - iodine(-1,0,+1,+3) by chlorine(0,+1,+3), oxidation of I by HIO2, and disproportionation of HOI and HIO2. The final mechanism and rate constants of the overall reaction and of its subsystems were determined by sensitivity analysis and parameter fitting of differential equation systems. Rate constants determined for simpler reactions were fixed in the more complex systems. A 13-step model with the three above-mentioned rapid equilibria fits the - -3 - -3 - - overall reaction and all of its subsystems over the range [I ]0 < 10 M, [ClO2 ]0 < 10 M, [I ]0/[ClO2 ]0 ) 3-5, pH ) 1-3.5, and 25 °C.
    [Show full text]
  • Measurement Report: Indirect Evidence for the Controlling Influence of Acidity on the Speciation of Iodine in Atlantic Aerosols
    Atmos. Chem. Phys., 21, 13067–13076, 2021 https://doi.org/10.5194/acp-21-13067-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Measurement report: Indirect evidence for the controlling influence of acidity on the speciation of iodine in Atlantic aerosols Alex R. Baker1 and Chan Yodle1,a 1Centre for Ocean and Atmospheric Sciences, School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK anow at: Department of Environmental Science, Faculty of Science and Technology, Chiang Mai Rajabhat University, Chiang Mai, 50300, Thailand Correspondence: Alex R. Baker ([email protected]) Received: 26 January 2021 – Discussion started: 26 April 2021 Revised: 22 July 2021 – Accepted: 10 August 2021 – Published: 2 September 2021 Abstract. The speciation of soluble iodine and major- 1 Introduction ion composition were determined in size-fractionated aerosols collected during the AMT21 cruise between Avon- mouth, UK, and Punta Arenas, Chile, in September– Iodine (I) plays a significant role in the destruction of ozone November 2011. The proportions of iodine species (iodide, (O3) in the atmosphere (Davis et al., 1996; Saiz-Lopez et iodate and soluble organic iodine (SOI)) varied markedly be- al., 2012), being responsible for ∼ 30 % of O3 loss in the tween size fractions and with the extent to which the samples marine boundary layer (MBL) (Prados-Roman et al., 2015). were influenced by pollutants. In general, fine mode aerosols Oceanic emission, principally of volatile I2 and hypoiodous (< 1 µm) contained higher proportions of both iodide and acid (HOI) formed through the reaction of O3 with iodide − SOI, while iodate was the dominant component of coarse (I ) at the sea surface (Carpenter et al., 2013), is the main (< 1 µm) aerosols.
    [Show full text]
  • United States Patent Office Patiented Sept
    2,904,470 United States Patent Office Patiented Sept. 15, 1959 1 2 tion with bacteria or other organic matter, thus pro longing the activity of the solution. It is known that when elemental iodine is dissolved in 2,904,470 water a minute quantity of hypoiodous acid is formed. DIATOMICIODINE-HYPOIODOUS ACID GEN 5 However, this quantity of hypoiodous acid is too small to :ERATING COMPOSITIONS provide any useful therapeutic effect. It should be noted Abraham Berliner and Benjamin Carroll, New York, N.Y. that the solutions of the present invention contain hy poiodous acid at a concentration greater than that pro "No Drawing. Application December 1, 1955 duced when iodine is dissolved in water. Also the solu Serial No. 550,463 0 tions are preferably essentially free from iodide and tri iodide ions. 7 Claims, (Cl. 167-70) We have further found that aqueous solutions of diatomic iodine and hypoiodous acid are relatively un stable and that if effective germicidal action is to be This invention relates to germicides and more par 5 achieved the solutions must be prepared under carefully -ticularly to a novel iodine containing composition that controlled conditions as described herein. Because of the is adapted to be dissolved in water to produce an aqueous comparative instability of the solutions, it is desirable solution of diatomic iodine and hypoiodous acid, which that they be prepared shortly before they are used and solution is also new and possesses improved germicidal accordingly the present invention contemplates the use properties. Germicidal iodine-containing solutions made 20 of a solid composition which is readily soluble in water according to the present invention may be used for either and contains all the ingredients necessary to produce the therapeutic purposes or as sterilizing agents for a variety desired germicidal solution.
    [Show full text]
  • ATOMIC ENERGY F F S L'energie ATOMIQUE of CANADA UMITED T
    AECL-6f)2 ATOMIC ENERGY ffS L'ENERGIE ATOMIQUE OF CANADA UMITED Tif T DU CANADA UMITEE ASSESSMENT OF IODINE BEHAVIOUR IN REACTOR CONTAINMENT BUILDINGS FROM A CHEMICAL PERSPECTIVE EVALUATION DU COMPORTEMENT CHIMIQUE DE L'lODE DANS L'ENCEINTE DE PROTECTION D'UN REACTEUR Robert J. Lemire', Jean Paquette, David F. Torgerson , David J. Wren1, J. Wallace Fletcher2 Whiteshell Nuclear Research Establishment Etablissement de Recherches Nucle'aires de Whiteshell * Chalk River Nuclear Laboratories Laboratoires Nucleaires de Chalk River Whiteshell Nuclear Research Etablissement de Recherches Establishment Nucle'aires de Whiteshell Pinawa, Manitoba ROE 1L0 June T981 juin ATOMIC ENERGY OF CANADA LIMITED ASSESSMENT OF IODINE BEHAVIOUR IN REACTOR CONTAINMENT BUILDINGS FROM A CHEMICAL PERSPECTIVt by Robert J. Lemire , Jean Paquette , David F. Torgersor) , 1 2 David J. Wren and J. Wallace Fletcher Research Chemistry Branch Whiteshell Nuclear Research Establishment Physical Chemistry Branch Chalk River Nuclear Laboratories Whiteshell Nuclear Research Establishment Pinawa, Manitoba ROE 1L0 1981 June AECL-6812 EVALUATION DU COMPORTEMENT CHIMIQUE DE L'IODE DANS L'ENCEINTE DE PROTECTION D'UN REACTEUR par Robert J. Lemire , Jean Paquet te , David F. ïorgerson , 1 2 David J. Wren et J. Wallace Fletcher RESUME Les paramètres thermodynamiques pour les espèces aqueuses, solides et gazeuses de l'iode à 25°C ont été obtenus à partir d'un examen de la littérature chimique. Ces données ont été rendues com- patibles avec la compilation du groupe CODATA. En utilisant les données thermodynamiques à 25°C, les valeurs de l'énergie libre de formation ont été évaluées en fonction de la température, jusqu'à 150°C, et ce pour toutes les espèces de l'iode.
    [Show full text]
  • 6. Potential for Human Exposure
    IODINE 233 6. POTENTIAL FOR HUMAN EXPOSURE 6.1 OVERVIEW The stable isotope of iodine, 127I, and two of its radioactive isotopes, 129I and 131I, have been identified in at least 8, 3, and 6, respectively, of the 1,636 hazardous waste sites that have been proposed for inclusion on the EPA National Priorities List (NPL) (HazDat 2004). However, the number of sites evaluated for iodine is not known. The frequency of these sites can be seen in Figures 6-1, 6-2, and 6-3. All of these sites are located within the United States. Iodine is a naturally occurring constituent of the earth’s crust and is the least abundant of the halogen elements (Straub et al. 1966). The stable isotope iodine, 127I, is ubiquitous throughout the earth’s surface. The concentration of 127I in the earth’s crust is approximately 0.5 ppm; in the oceans, the concentration is 45–60 µg/L, and in the atmosphere, the concentration ranges from 10 to 20 ng/m3. Concentrations of iodine in the environment throughout the United States vary depending on the proximity to the seacoast and the soil type. The concentration of iodine in bedrock varies between 0.5 and 380 ppm, depending on whether the rock is igneous or sedimentary. Iodine exists in many chemical forms (e.g., molecular iodine, iodide, iodate, periodate) and can undergo oxidation-reduction as well as microbial alkylation (mostly methyl iodide). Iodine has nine radioisotopes, of which 123I, 125I, 129I, and 131I are commonly encountered in acute or chronic exposures to human populations, due either to the life-times of the radioisotope in the environment, their production, and/or their use in industry, medicine, and research.
    [Show full text]
  • Identification of Promising Remediation Technologies for Iodine in the UP-1 Operable Unit
    PNNL-26934 RPT-DVZ-AFRI-050 Identification of Promising Remediation Technologies for Iodine in the UP-1 Operable Unit September 2017 CE Strickland CD Johnson BD Lee NP Qafoku JE Szecsody MJ Truex VR Vermeul PNNL-26934 RPT-DVZ-AFRI-050 Identification of Promising Remediation Technologies for Iodine in the UP-1 Operable Unit CE Strickland CD Johnson BD Lee NP Qafoku JE Szecsody MJ Truex VR Vermeul September 2017 Prepared for the U.S. Department of Energy under Contract DE-AC05-76RL01830 Pacific Northwest National Laboratory Richland, Washington 99352 Executive Summary Iodine-129 (129I) generated at the U.S. Department of Energy (DOE) Hanford Site during plutonium production was released to the subsurface, resulting in several large, though dilute, plumes in the groundwater, including the plume in the 200-UP-1 operable unit (OU). Because 129I is an uncommon contaminant, relevant remediation experience and scientific literature are limited, though work is under way to better understand the fate and transport of 129I in the environment and the effectiveness of potential remediation technologies. The recent UP-1 Evaluation Plan for Iodine1 and report on the Conceptual Model of Iodine Behavior in the Subsurface at the Hanford Site2 provide information on the history of contamination in the 200-UP-1 OU, relevant controlling processes (biological and geochemical), risk, the conceptual site model, and potential remedial options, which provided a foundation for this study. In this study, available information was compiled and used to categorize potential remediation technologies, culminating in a recommendation of promising technologies for further evaluation. Approaches to improve the technical information about promising technologies are also recommended in this study so that a subsequent evaluation of potential remediation alternatives can assess these technologies.
    [Show full text]
  • Post Treatment Alternatives for Stabilizing Desalinated Water
    University of Central Florida STARS Electronic Theses and Dissertations, 2004-2019 2009 Post Treatment Alternatives For Stabilizing Desalinated Water Susaye Douglas University of Central Florida Part of the Environmental Engineering Commons Find similar works at: https://stars.library.ucf.edu/etd University of Central Florida Libraries http://library.ucf.edu This Masters Thesis (Open Access) is brought to you for free and open access by STARS. It has been accepted for inclusion in Electronic Theses and Dissertations, 2004-2019 by an authorized administrator of STARS. For more information, please contact [email protected]. STARS Citation Douglas, Susaye, "Post Treatment Alternatives For Stabilizing Desalinated Water" (2009). Electronic Theses and Dissertations, 2004-2019. 4065. https://stars.library.ucf.edu/etd/4065 POST TREATMENT ALTERNATIVES FOR STABILIZING DESALINATED WATER by SUSAYE S DOUGLAS B.S. University of Central Florida, 2007 A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in the Department of Civil, Environmental, and Construction Engineering in the College of Engineering and Computer Science at the University of Central Florida Orlando, Florida Summer Term 2009 ©2009 Susaye S Douglas ii ABSTRACT The use of brackish water and seawater desalination for augmenting potable water supplies has focused primarily on pre-treatment, process optimization, energy efficiency, and concentrate management. Much less has been documented regarding the impact of post-treatment requirements with respect to distribution system. The goals of this study were to review current literature on post-treatment of permeate water, use survey questionnaires to gather information on post-treatment water quality characteristics, gather operation information, review general capital and maintenance cost, and identify appropriate “lessons learned” with regards to post-treatment from water purveyors participating in the Project.
    [Show full text]
  • Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013
    International Union of Pure and Applied Chemistry Division VIII Chemical Nomenclature and Structure Representation Division Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013. Prepared for publication by Henri A. Favre and Warren H. Powell, Royal Society of Chemistry, ISBN 978-0-85404-182-4 Chapter P-6 APPLICATIONS TO SPECIFIC CLASSES OF COMPOUNDS (continued) (P-66 to P-69) (continued from P-60 to P-65) P-60 Introduction P-61 Substitutive nomenclature: prefix mode P-62 Amines and imines P-63 Hydroxy compounds, ethers, peroxols, peroxides and chalcogen analogues P-64 Ketones, pseudoketones and heterones, and chalcogen analogues P-65 Acids and derivatives P-66 Amides, hydrazides, nitriles, aldehydes P-67 Oxoacids used as parents for organic compounds P-68 Nomenclature of other classes of compounds P-69 Organometallic compounds P-66 AMIDES, IMIDES, HYDRAZIDES, NITRILES, AND ALDEHYDES, P-66.0 Introduction P-66.1 Amides P-66.2 Imides P-66.3 Hydrazides P-66.4 Amidines, amidrazones, hydrazidines, and amidoximes (amide oximes) P-66.5 Nitriles P-66.6 Aldehydes P-66.0 INTRODUCTION The classes dealt with in this Section have in common the fact that their retained names are derived from those of acids by changing the ‘ic acid’ ending to a class name, for example ‘amide’, ‘ohydrazide’, ‘nitrile’, or ‘aldehyde’. Their systematic names are formed substitutively by the suffix mode using one of two types of suffix, one that includes the carbon atom, for example, ‘carbonitrile’ for –CN, and one that does not, for example, ‘-nitrile’ for –(C)N. Amidines are named as amides, hydrazidines as hydrazides, and amidrazones as amides or hydrazides.
    [Show full text]
  • NATURE August 3, 1957 Vol
    250 NATURE August 3, 1957 voL. 1ao absence of any change in the slight influence of a hypoiodous acid and iodide in equal amounts. (The nearby ionizing electron discharge upon the speed hypoiodous acid and iodide take part in an equili­ of pumping of the carbon monoxide {condensation brium to give a trace of iodine which is volatile.) coefficient), suggests that the gas molecules (neutral (3) The ratio of total iodine/chloride is higher in or ionized) are not taken up directly by the barium, warm, partly enclosed sea areas•. This is to be ex­ but are first dissociated into oxygen and carbon. pected from the effect of temperature upon the Thus the reaction is one of oxidation in the presence equilibria mentioned in (1) and (2) 2, which results of carbon, and so the qualitative similarity between in a. marked increase in the content of volatile iodine the behaviour of barium towards oxygen and carbon molecules when sea water is cooled. monoxide is to be expected. Whereas the hypothesis accounts for these findings, In some details, there are important differences it should be noted that iodate and not hypoiodous between the reactions in the two cases. In the case acid would be the thermodynamically stable form of of oxygen, it was found• that the first monolayer of oxidized iodine in the sea. However, it seems likely o1'-ygen was only taken up if there were nucleation that the rate of iodate formation from hypoiodous centres in the surface of the barium film. Ordinarily, acid, a third-order reaction in near-neutral solution', such centres always exist in the surface of getter will be slow at the very low hypoiodous acid con­ films deposited in a fraction of a minute and at centrations in sea water.
    [Show full text]
  • Chemistry 192 Problem Set 5 Spring, 2018 Solutions
    Chemistry 192 Problem Set 5 Spring, 2018 Solutions 1. In a titration experiment varying amounts of a 0.0100 M sodium hydroxide solution are added to 100. mL of 0.053 M hydrochloric acid. Determine the following: (a) the volume of the sodium hydroxide solution required to produce a solution of pH=7.0; Answer: + −1 moles of H3O = (0:053 mol L )(0:100 L) = 0:0053 mol 0:0053 mol V = = 0:53 L ≡ 530: mL 0:0100 mol L−1 (b) the pH of the solution if the amount of sodium hydroxide solution added is 10.0 mL less than the volume found in problem 1a; Answer: + −1 number of moles of H3O remaining = 0:0053 mol − (0:52 L)(0:0100 mol L ) = 0:00010 mol 0:00010 mol [H O+] = = 1:6 × 10−4 M 3 0:620 L −4 pH = − log10(1:6 × 10 ) = 3:79 (c) the pH of the solution if the amount of sodium hydroxide solution added is 10.0 mL more than the volume found in problem 1a. Answer: (0:010 L)(0:0100 mol L−1) [OH−] = = 1:6 × 10−4 M 0:640 L −4 pOH = − log10(1:6 × 10 ) = 3:81 pH = 14:00 − pOH = 10:19 1 2. In a titration experiment varying amounts of a 0.0100 M sodium hydroxide solution are added to 100. mL of 0.046 M benzoic acid (the pKa of benzoic acid is found on page 745 of your textbooks). Determine the following: (a) the volume of the sodium hydroxide solution required to reach the equivalence point; Answer: number moles benzoic acid = (0:046 mol L−1)(0:100 L) = 0:0046 mol = moles OH−needed 0:0046 mol V = = 0:46 L 0:0100 mol L−1 (b) the pH of the solution at the equivalence point; Answer: At the equivalence point, all benzoate is in the form of sodium benzoate.
    [Show full text]
  • Iodine As a Drinking Water Disinfectant
    Iodine as a drinking water disinfectant Draft Document 5.4 24 October 2016 Version for Public Review Contents Contents ............................................................................................................................................... i List of abbreviations ............................................................................................................................ 1 1 Introduction ......................................................................................................................................... 2 2 Disinfectant mode of action and efficacy ............................................................................................ 3 2.1 Chemistry basics ........................................................................................................................... 3 2.1.1 Water solubility, taste, odour and colour .............................................................................. 3 2.1.2 Chemical speciation of iodine in water and corresponding disinfection powers .................. 4 2.1.2.1 Effect of pH ..................................................................................................................... 5 2.1.2.2 Effect of temperature ..................................................................................................... 7 2.2 Efficacy of iodine ........................................................................................................................... 7 2.2.1 Bactericidal efficacy of iodine ...............................................................................................
    [Show full text]
  • Measurement of Iodine Species and Sulfuric Acid Using Bromide
    https://doi.org/10.5194/amt-2020-494 Preprint. Discussion started: 18 December 2020 c Author(s) 2020. CC BY 4.0 License. 1 Measurement of iodine species and sulfuric acid using bromide 2 chemical ionization mass spectrometers 3 4 Mingyi Wang1,2*, Xu-Cheng He3*#, Henning Finkenzeller4, Siddharth Iyer3, Dexian Chen1,5, Jiali 5 Shen3, Mario Simon6, Victoria Hofbauer1,2, Jasper Kirkby6,7, Joachim Curtius6, Norbert Maier8, 6 Theo Kurtén3,8, Douglas R. Worsnop3,9, Markku Kulmala3,10,11,12, Matti Rissanen3,13, Rainer 7 Volkamer4, Yee Jun Tham3#, Neil M. Donahue1,2,5,14, and Mikko Sipilä3 8 9 1Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, 15213, USA 10 2Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA, 15213, USA 11 3Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, 00014 Helsinki, Finland 12 4Department of Chemistry & CIRES, University of Colorado Boulder, Boulder, CO 80309, USA 13 5Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA 14 6Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, 60438 Frankfurt am Main, 15 Germany 16 7CERN, the European Organization for Nuclear Research, CH-1211 Geneve 23, Switzerland 17 8Department of Chemistry, University of Helsinki, 00014 Helsinki, Finland 18 9Aerodyne Research, Inc., Billerica, MA, 01821, USA 19 10Helsinki Institute of Physics, P.O. BoX 64 (Gustaf Hallstromin katu 2), FI-00014 University of Helsinki, Finland 20 11Joint International Research
    [Show full text]