Heavy-Atom Kinetic Isotope Effects
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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 -
APPENDIX M SUMMARY of MAJOR TYPES of Carfg2 REFINERY
APPENDIX M SUMMARY OF MAJOR TYPES OF CaRFG2 REFINERY MODIFICATIONS Appendix M: Summan/ of Major Types of CaRFG2 Refinery Modifications: Alkylation Units A process unit that combines small-molecule hydrocarbon gases produced in the FCCU with a branched chain hydrocarbon called isobutane, producing a material called alkylate, which is blended into gasoline to raise the octane rating. Alkylate is a high octane, low vapor pressure gasoline blending component that essentially contains no olefins, aromatics, or sulfur. This plant improves the ultimate gasoline-making ability of the FCC plant. Therefore, many California refineries built new or modified existing units to increase alkylate production to blend and to produce greater amounts of CaRFG2. Alkylate is produced by combining C3, C4, and C5 components with isobutane (nC4). The process of alkylation is the reverse of cracking. Olefins (such as butenes and propenes) and isobutane are used as feedstocks and combined to produce alkylate. This process enables refiners to utilize lighter components that otherwise could not be blended into gasoline due to their high vapor pressures. Feed to alkylation unit can include pentanes from light cracked gasoline treaters, isobutanes from butane isomerization unit, and C3/C4 streams from delayed coking units. Isomerization Units - C4/C5/C6 A refinery that has an alkylation plant is not likely to have exactly enough is-butane to match the proplylene and butylene (olefin) feeds. The refiner usually has two choices - buy iso-butane or make it in a butane isomerization (Bl) plant. Isomerization is the rearrangement of straight chain hydrocarbon molecules to form branched chain products or to convert normal paraffins to their isomer. -
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 -
Kinetic Isotope Effects and Hydrogen Tunnelling in PCET Oxidations of Ascorbate: New Insights Into Aqueous Chemistry?
molecules Review Kinetic Isotope Effects and Hydrogen Tunnelling in PCET Oxidations of Ascorbate: New Insights into Aqueous Chemistry? Ana Karkovi´cMarkovi´c,Cvijeta Jakobuši´cBrala * , Viktor Pilepi´cand Stanko Urši´c* Faculty of Pharmacy and Biochemistry, University of Zagreb, A. Kovaˇci´ca1, 10 000 Zagreb, Croatia; [email protected] (A.K.M.); [email protected] (V.P.) * Correspondence: [email protected] (C.J.B.); [email protected] (S.U.); Tel.: +385-01-4870-267 (C.J.B.) Academic Editor: Poul Erik Hansen Received: 17 February 2020; Accepted: 21 March 2020; Published: 23 March 2020 Abstract: Recent experimental studies of kinetic isotope effects (KIE-s) and hydrogen tunnelling comprising three proton-coupled electron transfer (PCET) oxidations of ascorbate monoanion, (a) in aqueous reaction solutions, (b) in the mixed water-organic cosolvent systems, (c) in aqueous solutions of various salts and (d) in fairly diluted aqueous solutions of the various partial hydrophobes are reviewed. A number of new insights into the wealth of the kinetic isotope phenomena in the PCET reactions have been obtained. The modulation of KIE-s and hydrogen tunnelling observed when partially hydrophobic solutes are added into water reaction solution, in the case of fairly diluted solutions is revealed as the strong linear correlation of the isotopic ratios of the Arrhenius prefactors Ah/Ad and the isotopic differences in activation energies DEa (D,H). The observation has been proposed to be a signature of the involvement of the collective intermolecular excitonic vibrational dynamics of water in activation processes and aqueous chemistry. Keywords: kinetic isotope effects; ascorbate PCET reactions; hydrogen tunnelling; water vibrational dynamics; activation processes 1. -
Chapter 12 Lecture Notes
Chemical Kinetics “The study of speeds of reactions and the nanoscale pathways or rearrangements by which atoms and molecules are transformed to products” Chapter 13: Chemical Kinetics: Rates of Reactions © 2008 Brooks/Cole 1 © 2008 Brooks/Cole 2 Reaction Rate Reaction Rate Combustion of Fe(s) powder: © 2008 Brooks/Cole 3 © 2008 Brooks/Cole 4 Reaction Rate Reaction Rate + Change in [reactant] or [product] per unit time. Average rate of the Cv reaction can be calculated: Time, t [Cv+] Average rate + Cresol violet (Cv ; a dye) decomposes in NaOH(aq): (s) (mol / L) (mol L-1 s-1) 0.0 5.000 x 10-5 13.2 x 10-7 10.0 3.680 x 10-5 9.70 x 10-7 20.0 2.710 x 10-5 7.20 x 10-7 30.0 1.990 x 10-5 5.30 x 10-7 40.0 1.460 x 10-5 3.82 x 10-7 + - 50.0 1.078 x 10-5 Cv (aq) + OH (aq) → CvOH(aq) 2.85 x 10-7 60.0 0.793 x 10-5 -7 + + -5 1.82 x 10 change in concentration of Cv Δ [Cv ] 80.0 0.429 x 10 rate = = 0.99 x 10-7 elapsed time Δt 100.0 0.232 x 10-5 © 2008 Brooks/Cole 5 © 2008 Brooks/Cole 6 1 Reaction Rates and Stoichiometry Reaction Rates and Stoichiometry Cv+(aq) + OH-(aq) → CvOH(aq) For any general reaction: a A + b B c C + d D Stoichiometry: The overall rate of reaction is: Loss of 1 Cv+ → Gain of 1 CvOH Rate of Cv+ loss = Rate of CvOH gain 1 Δ[A] 1 Δ[B] 1 Δ[C] 1 Δ[D] Rate = − = − = + = + Another example: a Δt b Δt c Δt d Δt 2 N2O5(g) 4 NO2(g) + O2(g) Reactants decrease with time. -
Chapter 9. Atomic Transport Properties
NEA/NSC/R(2015)5 Chapter 9. Atomic transport properties M. Freyss CEA, DEN, DEC, Centre de Cadarache, France Abstract As presented in the first chapter of this book, atomic transport properties govern a large panel of nuclear fuel properties, from its microstructure after fabrication to its behaviour under irradiation: grain growth, oxidation, fission product release, gas bubble nucleation. The modelling of the atomic transport properties is therefore the key to understanding and predicting the material behaviour under irradiation or in storage conditions. In particular, it is noteworthy that many modelling techniques within the so-called multi-scale modelling scheme of materials make use of atomic transport data as input parameters: activation energies of diffusion, diffusion coefficients, diffusion mechanisms, all of which are then required to be known accurately. Modelling approaches that are readily used or which could be used to determine atomic transport properties of nuclear materials are reviewed here. They comprise, on the one hand, static atomistic calculations, in which the migration mechanism is fixed and the corresponding migration energy barrier is calculated, and, on the other hand, molecular dynamics calculations and kinetic Monte-Carlo simulations, for which the time evolution of the system is explicitly calculated. Introduction In nuclear materials, atomic transport properties can be a combination of radiation effects (atom collisions) and thermal effects (lattice vibrations), this latter being possibly enhanced by vacancies created by radiation damage in the crystal lattice (radiation enhanced-diffusion). Thermal diffusion usually occurs at high temperature (typically above 1 000 K in nuclear ceramics), which makes the transport processes difficult to model at lower temperatures because of the low probability to see the diffusion event occur in a reasonable simulation time. -
Kinetic Isotope Effect Lecture.Key
Kinetic Isotope Effect Chapter 8, sections 8.1.1-8.1.3 Isotope Effects • Traditional kinetics studies do not provide information as to what bonds are broken/formed and changes in hybridization that occur during the rate- limiting step of a reaction. • Isotope effects can provide this information. • Substituting one iosotope for another at or near an atom at which bonds are breaking or rehybridizing typically leads to a change in the rate of the reaction. • The effect of replacing H with D often is relatively large when the bonds being broken or formed involve H. This effect can be measured routinely. • The effects of isotope replacement for other elements have been studied, but the effects are typically small and sometimes difficult to quantify. Isotope Effects: Experimental • An isotope effect is measured to determine if the bond at which the isotopic substitution has been made changes in some manner during the rate-limiting step. • The isotope effect is expressed as a ratio of rate constants: the rate constant for the reaction with the natural abundance isotope over the rate constant for the reaction with the altered isotope. [ for H/D substitutions: kH/kD] • For a hydrogen isotope effect, typically a first order (or pseudo-first order) rate constant for the reaction of interest is determined. The natural abundance of deuterium (D) and tritium (T) [0.015% and 1x10-4% respectively] is so low that their contribution to the observed rate is negligible. • The magnitude of the isotope effect (deviation of kH/kD from unity) provides information about the reaction mechanism. -
Andrea Deoudes, Kinetics: a Clock Reaction
A Kinetics Experiment The Rate of a Chemical Reaction: A Clock Reaction Andrea Deoudes February 2, 2010 Introduction: The rates of chemical reactions and the ability to control those rates are crucial aspects of life. Chemical kinetics is the study of the rates at which chemical reactions occur, the factors that affect the speed of reactions, and the mechanisms by which reactions proceed. The reaction rate depends on the reactants, the concentrations of the reactants, the temperature at which the reaction takes place, and any catalysts or inhibitors that affect the reaction. If a chemical reaction has a fast rate, a large portion of the molecules react to form products in a given time period. If a chemical reaction has a slow rate, a small portion of molecules react to form products in a given time period. This experiment studied the kinetics of a reaction between an iodide ion (I-1) and a -2 -1 -2 -2 peroxydisulfate ion (S2O8 ) in the first reaction: 2I + S2O8 I2 + 2SO4 . This is a relatively slow reaction. The reaction rate is dependent on the concentrations of the reactants, following -1 m -2 n the rate law: Rate = k[I ] [S2O8 ] . In order to study the kinetics of this reaction, or any reaction, there must be an experimental way to measure the concentration of at least one of the reactants or products as a function of time. -2 -2 -1 This was done in this experiment using a second reaction, 2S2O3 + I2 S4O6 + 2I , which occurred simultaneously with the reaction under investigation. Adding starch to the mixture -2 allowed the S2O3 of the second reaction to act as a built in “clock;” the mixture turned blue -2 -2 when all of the S2O3 had been consumed. -
Kinetic Isotope Effect in the Hydrogenation and Deuteration of Graphene
Kinetic isotope effect in the hydrogenation GR-ThP3 and deuteration of graphene A. Nefedov, A. Paris, N. Verbitsky, Y. Wang, A. V. Fedorov, D. Haberer, M. Oehzelt, L. Petaccia, D. Usachov, D.V. Vyalikh, H. Sachdev, Ch. Wöll, M. Knupfer, B. Büchner, L. Calliari, L. V. Yashina, S. Irle, and A. Grüneis Motivation Sample preparation and layout of the experiment Experimental facilities: BESSY II and Elletra Kinetic isotope effects (KIEs), i.e. a different reaction constant for isotopes, are important phenomena in physical chemistry. They Ni(111),10 nm Graphene Experimental stations @ BESSY II ARPES @ Elletra have been studied for a long time in their relation to the activation and rate of chemical reactions. A significant contribution to KIE are vibrational zero-point energy (ZPE) effects that upshift the energy of a chemical bond by half the phonon frequency of its W(110) W(110) W(110) constituents. Hence, KIEs are easy to observe in the hydrogen isotopes (deuterium and tritium) due to their large relative mass Ni difference and were studied, even at the single-molecule level for hydrogen transfer in organic reactions including acid and base Sputtering, Flashing up to 1700°C, Ni evaporation, CVD from C3H6 catalysis, enzyme reactions and catalytic decomposition. Most of these reactions were carried out with H and D in a molecular Annealing in O2 at 1000°C Thickness control: QCM Characterization: LEED; XPS configuration and it was found that the reaction constant for the D compounds is lower than for the corresponding H compounds. Characterization: LEED, XPS Characterization: LEED These results are explained by the larger ZPE for H bonds, which results in a lower potential energy barrier to be overcome for H- bonds breaking as compared to D bonds. -
Eyring Equation
Search Buy/Sell Used Reactors Glass microreactors Hydrogenation Reactor Buy Or Sell Used Reactors Here. Save Time Microreactors made of glass and lab High performance reactor technology Safe And Money Through IPPE! systems for chemical synthesis scale-up. Worldwide supply www.IPPE.com www.mikroglas.com www.biazzi.com Reactors & Calorimeters Induction Heating Reacting Flow Simulation Steam Calculator For Process R&D Laboratories Check Out Induction Heating Software & Mechanisms for Excel steam table add-in for water Automated & Manual Solutions From A Trusted Source. Chemical, Combustion & Materials and steam properties www.helgroup.com myewoss.biz Processes www.chemgoodies.com www.reactiondesign.com Eyring Equation Peter Keusch, University of Regensburg German version "If the Lord Almighty had consulted me before embarking upon the Creation, I should have recommended something simpler." Alphonso X, the Wise of Spain (1223-1284) "Everything should be made as simple as possible, but not simpler." Albert Einstein Both the Arrhenius and the Eyring equation describe the temperature dependence of reaction rate. Strictly speaking, the Arrhenius equation can be applied only to the kinetics of gas reactions. The Eyring equation is also used in the study of solution reactions and mixed phase reactions - all places where the simple collision model is not very helpful. The Arrhenius equation is founded on the empirical observation that rates of reactions increase with temperature. The Eyring equation is a theoretical construct, based on transition state model. The bimolecular reaction is considered by 'transition state theory'. According to the transition state model, the reactants are getting over into an unsteady intermediate state on the reaction pathway. -
Estimation Of'hetrazan'in Body Fluids
No. 4183 December 31, 1949 NATURE II 35 strated by a coupled oxidation of alcohol in the blank value of about 1 (J.gm.fml. Further, trichlor presence of catalase6 • As an artificial ascorbic oxidase acetic acid precipitation removes about 20 per cent it had a Qo8 ((.Ll. oxygen per mgm. dry weight per hr.) of added 'Hetrazan'. Therefore, although it may at pH 7·2 and 39° C. of about 10,000. Hydrogen be more tedious, it is preferable to extract serum or cyanide inhibited this catalysed oxidation of ascorbic plasma. acid by combining with modified ferricytochrome c, Urines show a blank value of about 5 flgm.fml., thus preventing its reduction, while carbon monoxide, but occasionally, in concentrated urines, the blank by combining with modified ferrocytochrome c, may reach 20 vgm.jml. prevented its oxidation. The carbon monoxide The method is sufficiently sensitive to measure a inhibition was somewhat light-sensitive. This reaction blood concentration of 'Hetrazan' of 1 (J.gm.jml. Like was also inhibited by methyl isocyanide and nitroso most of these methods, it lacks specificity, but has benzene. Modified cytochrome c also catalysed the been found useful in following the concentration jn decomposition of hydrogen peroxide, being itself blood and urine after oral administration of the drug. destroyed in this reaction. Cyanide inhibited this A full account of the results of these experiments catalysed decomposition of hydrogen peroxide. will be published later. Typically, ingestion of The result of this experiment agrees with an 10 mgm.jkgm. body-weight of the hydrochloride observation of Keilin and Hartrees that when cyto results in a maximum plasma concentration of about chrome c is made autoxidizable it loses its catalytical 5-7 [lgm.jml., reached in three hours.