Radicals in Flames
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Glossary Physics (I-Introduction)
1 Glossary Physics (I-introduction) - Efficiency: The percent of the work put into a machine that is converted into useful work output; = work done / energy used [-]. = eta In machines: The work output of any machine cannot exceed the work input (<=100%); in an ideal machine, where no energy is transformed into heat: work(input) = work(output), =100%. Energy: The property of a system that enables it to do work. Conservation o. E.: Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes. Equilibrium: The state of an object when not acted upon by a net force or net torque; an object in equilibrium may be at rest or moving at uniform velocity - not accelerating. Mechanical E.: The state of an object or system of objects for which any impressed forces cancels to zero and no acceleration occurs. Dynamic E.: Object is moving without experiencing acceleration. Static E.: Object is at rest.F Force: The influence that can cause an object to be accelerated or retarded; is always in the direction of the net force, hence a vector quantity; the four elementary forces are: Electromagnetic F.: Is an attraction or repulsion G, gravit. const.6.672E-11[Nm2/kg2] between electric charges: d, distance [m] 2 2 2 2 F = 1/(40) (q1q2/d ) [(CC/m )(Nm /C )] = [N] m,M, mass [kg] Gravitational F.: Is a mutual attraction between all masses: q, charge [As] [C] 2 2 2 2 F = GmM/d [Nm /kg kg 1/m ] = [N] 0, dielectric constant Strong F.: (nuclear force) Acts within the nuclei of atoms: 8.854E-12 [C2/Nm2] [F/m] 2 2 2 2 2 F = 1/(40) (e /d ) [(CC/m )(Nm /C )] = [N] , 3.14 [-] Weak F.: Manifests itself in special reactions among elementary e, 1.60210 E-19 [As] [C] particles, such as the reaction that occur in radioactive decay. -
High-Resolution Infrared Spectroscopy: Jet-Cooled Halogenated Methyl Radicals and Reactive Scattering Dynamics in an Atom + Polyatom System
HIGH-RESOLUTION INFRARED SPECTROSCOPY: JET-COOLED HALOGENATED METHYL RADICALS AND REACTIVE SCATTERING DYNAMICS IN AN ATOM + POLYATOM SYSTEM by ERIN SUE WHITNEY B.A., Williams College, 1996 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirement for the degree of Doctor of Philosophy Department of Chemistry and Biochemistry 2006 UMI Number: 3207681 Copyright 2006 by Whitney, Erin Sue All rights reserved. UMI Microform 3207681 Copyright 2006 by ProQuest Information and Learning Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. ProQuest Information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, MI 48106-1346 This thesis for the Doctor of Philosophy degree entitled: High resolution infrared spectroscopy: Jet cooled halogenated methyl radicals and reactive scattering dynamics in an atom + polyatom system written by Erin Sue Whitney has been approved for the Department of Chemistry and Biochemistry by David J. Nesbitt Veronica M. Bierbaum Date ii Whitney, Erin S. (Ph.D., Chemistry) High-Resolution Infrared Spectroscopy: Jet-cooled halogenated methyl radicals and reactive scattering dynamics in an atom + polyatomic system Thesis directed by Professor David J. Nesbitt. This thesis describes a series of projects whose common theme comprises the structure and internal energy distribution of gas-phase radicals. In the first two projects, shot noise-limited direct absorption spectroscopy is combined with long path-length slit supersonic discharges to obtain first high-resolution infrared spectra for jet-cooled CH2F and CH2Cl in the symmetric and antisymmetric CH2 stretching modes. -
Bimolecular Reaction Dynamics in the Phenyl - Silane System
Bimolecular Reaction Dynamics in the Phenyl - Silane System: Exploring the Prototype of a Radical Substitution Mechanism 1 1 1 1 2 Michael Lucas , Aaron M. Thomas , Tao Yang , Ralf I. Kaiser *, Alexander M. Mebel , Diptarka Hait3, Martin Head-Gordon3,4* 1 Department of Chemistry, University of Hawai’i at Manoa, Honolulu, HI 96822 2 Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199 3 Kenneth S. Pitzer Center for Theoretical Chemistry, Department of Chemistry, University of California, Berkeley, CA 94720 4 Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 *Email: [email protected] *Email: [email protected] Abstract We present a combined experimental and theoretical investigation of the bimolecular gas phase reaction of the phenyl radical (C6H5) with silane (SiH4) under single collision conditions to investigate the chemical dynamics of forming phenylsilane (C6H5SiH3) via a bimolecular radical substitution mechanism at a tetra-coordinated silicon atom. Verified by electronic structure and quasiclassical trajectory calculations, the replacement of a single carbon atom in methane by silicon lowers the barrier to substitution thus defying conventional wisdom that tetra-coordinated hydrides undergo preferentially hydrogen abstraction. This reaction mechanism provides funda- mental insights into the hitherto unexplored gas phase chemical dynamics of radical substitution reactions of mononuclear main group hydrides under single collision conditions and highlights -
Thermochemical Properties of Methyl and Chloro-Methyl Hyplochlorites and Ethers and Reaction of Methyl Radical with CLO
New Jersey Institute of Technology Digital Commons @ NJIT Theses Electronic Theses and Dissertations Spring 5-31-2000 Thermochemical properties of methyl and chloro-methyl hyplochlorites and ethers and reaction of methyl radical with CLO Dawoon Jung New Jersey Institute of Technology Follow this and additional works at: https://digitalcommons.njit.edu/theses Part of the Chemistry Commons Recommended Citation Jung, Dawoon, "Thermochemical properties of methyl and chloro-methyl hyplochlorites and ethers and reaction of methyl radical with CLO" (2000). Theses. 778. https://digitalcommons.njit.edu/theses/778 This Thesis is brought to you for free and open access by the Electronic Theses and Dissertations at Digital Commons @ NJIT. It has been accepted for inclusion in Theses by an authorized administrator of Digital Commons @ NJIT. For more information, please contact [email protected]. Copyright Warning & Restrictions The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specified conditions is that the photocopy or reproduction is not to be “used for any purpose other than private study, scholarship, or research.” If a, user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of “fair use” that user may be liable for copyright infringement, This institution reserves -
Carbon Kinetic Isotope Effect in the Oxidation of Methane by The
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 95, NO. D13, PAGES 22,455-22,462, DECEMBER 20, 1990 CarbonKinetic IsotopeEffect in the Oxidationof Methaneby the Hydroxyl Radical CttRISTOPHERA. CANTRELL,RICHARD E. SHE•, ANTHONY H. MCDANmL, JACK G. CALVERT, JAMESA. DAVIDSON,DAVID C. LOWEl, STANLEYC. TYLER,RALPH J. CICERONE2, AND JAMES P. GREENBERG AtmosphericKinetics and PhotochemistryGroup, AtmosphericChemistry Division, National Centerfor AtmosphericResearch, Boulder, Colorado The reactionof the hydroxylradical (HO) with the stablecafix)n isotopes of methanehas been studied as a functionof temperaturefrom 273 to 353 K. The measuredratio of the rate coefficientsfor reaction with•ZCHn relative to •3CH•(kn•/kn3) was 1.0054 (20.0009 at the95% confidence interval), independent of temperaturewithin the precisionof the measurement,over the rangestudied. The precisionof the present valueis muchimproved over that of previousstudies, and this resultprovides important constraints on the currentunderstanding of the cyclingof methanethrough the atmospherethrough the useof carbonisotope measurements. INTRODUCTION weightedaverage of the sourceratios must equal the atmospher- Methane (CH•) is an importanttrace gas in the atmosphere ic ratio, after correctionfor fractionationin any lossprocesses. [Wofsy,1976]. It is a key sink for the tropospherichydroxyl The primaryloss of CI-I4in the troposphereis the reactionwith radical. Methane contributesto greenhousewarming [Donner the hydroxylradical: and Ramanathan,1980]; its potentialwarming effects follow only CO2 and H20. Methaneis a primary sink for chlorine (R1) CHn + HO ---)CH3 + HzO atomsin the stratosphereand a majorsource of watervapor in the upper stratosphere. The concentrationof CI-I4 in the The rate coefficient for this reaction has been studied extensive- tropospherehas been increasing at a rateof approximately1% ly (seereview by Ravishankara[1988]), but dataindicating the per year, at leastover the pastdecade [Rasmussen and Khalil, effect of isotopesubstitution in methaneare scarce. -
Free Radical Reactions (Read Chapter 4) A
Chemistry 5.12 Spri ng 2003, Week 3 / Day 2 Handout #7: Lecture 11 Outline IX. Free Radical Reactions (Read Chapter 4) A. Chlorination of Methane (4-2) 1. Mechanism (4-3) B. Review of Thermodynamics (4-4,5) C. Review of Kinetics (4-8,9) D. Reaction-Energy Diagrams (4-10) 1. Thermodynamic Control 2. Kinetic Control 3. Hammond Postulate (4-14) 4. Multi-Step Reactions (4-11) 5. Chlorination of Methane (4-7) Suggested Problems: 4-35–37,40,43 IX. A. Radical Chlorination of Methane H heat (D) or H H C H Cl Cl H C Cl H Cl H light (hv) H H Cl Cl D or hv D or hv etc. H C Cl H C Cl H Cl Cl C Cl H Cl Cl Cl Cl Cl H H H • Why is light or heat necessary? • How fast does it go? • Does it give off or consume heat? • How fast are each of the successive reactions? • Can you control the product ratio? To answer these questions, we need to: 1. Understand the mechanism of the reaction (arrow-pushing!). 2. Use thermodynamics and kinetics to analyze the reaction. 1 1. Mechanism of Radical Chlorination of Methane (Free-Radical Chain Reaction) Free-radical chain reactions have three distinct mechanistic steps: • initiation step: generates reactive intermediate • propagation steps: reactive intermediates react with stable molecules to generate other reactive intermediates (allows chain to continue) • termination step: side-reactions that slow the reaction; usually combination of two reactive intermediates into one stable molecule Initiation Step: Cl2 absorbs energy and the bond is homolytically cleaved. -
Gas-Phase Chemistry of Methyl-Substituted Silanes in a Hot-Wire Chemical Vapour Deposition Process
University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2013-08-27 Gas-phase Chemistry of Methyl-Substituted Silanes in a Hot-wire Chemical Vapour Deposition Process Toukabri, Rim Toukabri, R. (2013). Gas-phase Chemistry of Methyl-Substituted Silanes in a Hot-wire Chemical Vapour Deposition Process (Unpublished doctoral thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/26257 http://hdl.handle.net/11023/891 doctoral thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY Gas-phase Chemistry of Methyl-Substituted Silanes in a Hot-wire Chemical Vapour Deposition Process by Rim Toukabri A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CHEMISTRY CALGARY, ALBERTA August, 2013 © Rim Toukabri 2013 Abstract The primary decomposition and secondary gas-phase reactions of methyl- substituted silane molecules, including monomethylsilane (MMS), dimethylsilane (DMS), trimethylsilane (TriMS) and tetramethylsilane (TMS), in hot-wire chemical vapour deposition (HWCVD) processes have been studied using laser ionization methods in combination with time of flight mass spectrometry (TOF-MS). For all four molecules, methyl radical formation and hydrogen molecule formation have been found to be the common decomposition steps on both tungsten (W) and tantalum (Ta) filaments. -
The Distribution of the Hydroxyl Radical in the Troposphere Jack
The Distribution of the Hydroxyl Radical in the Troposphere By Jack Fishman Paul J. Crutzen Department of Atmospheric Science Colorado State University Fort Collins, Colorado THE DISTRIBUTION OF THE HYDROXYL RADICAL IN THE TROPOSPHERE by Jack Fishman and Paul J. Crutzen Preparation of this report has been financially supported by Environmental Protection Agency Grant No. R80492l-0l Department of Atmospheric Science Colorado State University Fort Collins, Colorado January, 1978 Atmospheric Science Paper No. 284 Abstract A quasi-steady state photochemical numerical model is developed to calculate a two-dimensional distribution of the hydroxyl (OH) radical in the troposphere. The diurnally, seasonally averaged globaJ 5 3 value of OH derived by this model is 3 x 10 cm- which is several times lower than the number computed previously by other models, but is in good agreement with the value inferred from the analysis of the tropospheric distribution of methyl chloroform. Likewise, the effects of the computed OH distribution on the tropospheric budgets of ozone and carbon monoxide are not inconsistent with this lower computed value. One important result of this research is the detailed analysis of the distribution of tropospheric ozone in the Southern Hemisphere. Our work shows that there is a considerable difference in the tropospheric ozone patterns of the two hemispheres and that through the analysis of the likely photochemistry occurring in the troposphere, a significant source of tropospheric ozone may exist in the Northern Hemisphere due to carbon monoxide oxidation. Future research efforts will be devoted to the meteorological dynamics of the two hemispheres to try to distinguish if these physical processes are similarly able to explain the interhemispheric differences in tropospheric ozone. -
A Variationally Computed IR Line List for the Methyl Radical CH3 Arxiv
A Variationally Computed IR Line List for the Methyl Radical CH3 Ahmad Y. Adam,y Andrey Yachmenev,z Sergei N. Yurchenko,{ and Per Jensen∗,y yFakult¨atf¨urMathematik und Naturwissenschaften, Physikalische und Theoretische Chemie, Bergische Universit¨atWuppertal, D{42097 Wuppertal, Germany zCenter for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, D-22607 Hamburg, Germany, The Hamburg Center for Ultrafast Imaging, Universit¨atHamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany {Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom E-mail: [email protected] arXiv:1905.05504v1 [physics.chem-ph] 14 May 2019 1 Abstract We present the first variational calculation of a hot temperature ab initio line list for the CH3 radical. It is based on a high level ab initio potential energy surface and dipole moment surface of CH3 in the ground electronic state. The ro-vibrational energy lev- els and Einstein A coefficients were calculated using the general-molecule variational approach implemented in the computer program TROVE. Vibrational energies and vibrational intensities are found to be in very good agreement with the available ex- perimental data. The line list comprises 9,127,123 ro-vibrational states (J ≤ 40) and 2,058,655,166 transitions covering the wavenumber range up to 10000 cm−1 and should be suitable for temperatures up to T = 1500 K. Introduction The methyl radical CH3 is a free radical of major importance in many areas of science such as hydrocarbon combustion processes,1 atmospheric chemistry,2 the chemistry of semiconductor production,3 the chemical vapor deposition of diamond,4 and many chemical processes of current industrial and environmental interest. -
Glossary of Scientific Terms in the Mystery of Matter
GLOSSARY OF SCIENTIFIC TERMS IN THE MYSTERY OF MATTER Term Definition Section acid A substance that has a pH of less than 7 and that can react with 1 metals and other substances. air The mixture of oxygen, nitrogen, and other gasses that is consistently 1 present around us. alchemist A person who practices a form of chemistry from the Middle Ages 1 that was concerned with transforming various metals into gold. Alchemy A type of science and philosophy from the Middle Ages that 1 attempted to perform unusual experiments, taking something ordinary and turning it into something extraordinary. alkali metals Any of a group of soft metallic elements that form alkali solutions 3 when they combine with water. They include lithium, sodium, potassium, rubidium, cesium, and francium. alkaline earth Any of a group of metallic elements that includes beryllium, 3 metals magnesium, calcium, strontium, barium, and radium. alpha particle A positively charged particle, indistinguishable from a helium atom 5, 6 nucleus and consisting of two protons and two neutrons. alpha decay A type of radioactive decay in which a nucleus emits 6 an alpha particle. aplastic anemia A disorder of the bone marrow that results in too few blood cells. 4 apothecary The person in a pharmacy who distributes medicine. 1 atom The smallest component of an element that shares the chemical 1, 2, 3, 4, 5, 6 properties of the element and contains a nucleus with neutrons, protons, and electrons. atomic bomb A bomb whose explosive force comes from a chain reaction based on 6 nuclear fission. atomic number The number of protons in the nucleus of an atom. -
Oxidative Stress and Radical-Induced Signalling John R
part 2. mechanisms of carcinogenesis chapter 15. Oxidative stress and radical-induced signalling John R. Bucher PART 2 CHAPTER 15 Throughout evolution, aerobic An imbalance between the normal Pierre et al., 2002). Peroxisomes are organisms have developed mul- production of oxygen radicals and a source of H2O2, through reactions tiple defence systems to protect their capture and disposal by pro- involving acyl-CoA oxidase (which themselves against oxygen radicals tective enzyme systems and antiox- is involved in oxidation of long-chain (Benzie, 2000). One-, two-, and idants results in oxidative stress, and fatty acids), d-amino acid oxidase, three-electron reductions of molecu- this condition has been proposed and other oxidases (Schrader and lar oxygen give rise to, respectively, to be the basis of many deleterious Fahimi, 2006). • − superoxide (O2 ), hydrogen peroxide chronic health conditions and dis- When stimulated, inflammatory (H2O2, a radical precursor), and the eases, including cancer. cells such as neutrophils, eosino- highly reactive hydroxyl radical (•OH) phils, and macrophages produce ox- or equivalent transition metal–oxy- Sources of oxygen radicals ygen radicals during the associated gen complexes (Miller et al., 1990). respiratory burst (the rapid release of Reactions of oxygen radicals with Mitochondrial oxidative phosphor- reactive oxygen species from cells) cellular components can deplete an- ylation is a major source of oxy- that involves nicotinamide adenine tioxidants, can cause direct oxidative gen radicals of endogenous -
Chem 51B Chapter 15 Notes
Lecture Notes Chem 51B S. King Chapter 15 Radical Reactions I. Introduction A radical is a highly reactive intermediate with an unpaired electron. Radicals are involved in oxidation reactions, combustion reactions, and biological reactions. Structure: compare with: compare with: Stability: Free radicals and carbocations are both electron deficient and they follow a similar order of stability: R R H H , > R C > R C > R C > H C R H H H • like carbocations, radicals can be stabilized by resonance. H H H H C C C C H C CH3 H C CH3 H H • unlike carbocations, no rearrangements are observed in free radical reactions. Q. How are free radicals formed? A. Free radicals are formed when bonds break homolytically: 103 Look @ the arrow pushing: Notice the fishhook arrow! It shows movement of a single electron: Compare with heterolytic bond cleavage: A double-headed arrow shows movement of a pair of electrons: Nomenclature: bromide ion bromine atom Bromine (molecule) II. General Features of Radical Reactions Radicals are formed from covalent bonds by adding energy in the form of heat or light (hν). Some radical reactions are carried out in the presence of radical initiators, which contain weak bonds that readily undergo homolysis. The most common radical initiators are peroxides (ROOR), which contain the weak O−O bond. A. Common Reactions of Radicals: Radicals undergo two common reactions: they react with σ-bonds and they add to π-bonds. 1. Reaction of a Radical X• with a C−H bond A radical X• abstracts a H atom from a C−H bond to form H−X and a carbon radical: 104 2.