DOCSLIB.ORG

Characterization and Redox Chemistry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Characterization and Redox Chemistry Homobimetallic Cobalt Phosphinoamides: Characterization and Redox Chemistry. Master’s Thesis Presented to The Faculty of the Graduate School of Arts and Sciences Brandeis University Department of Chemistry Christine M. Thomas, Advisor In Partial Fulfillment of the Requirements for the Degree Master of Science in Chemistry by Ramyaa Mathialagan February 2014 Copyright by Ramyaa Mathialagan © 2014 Acknowledgement ü First of all, I want to thank my supervisor, Prof. Christine Thomas, for her excellent guidance, critiques, advice and support. Thank you Chris, for teaching me everything inside and outside chemistry. ü I would like to record my sincere thanks to Prof. Casey Wade for his constant support. ü I would like to convey my thanks to Prof. Bruce Foxman and Mark Bezpalko for their kind help to solve all my structures. ü My sincere thanks to my lab-mates for their co-operation and help during the course of study. ü My special thanks to faculties and chemistry department office staffs for their friendly support during my stay. ü My heartfelt thanks to all my friends who were encouraged me and gave me confidence at the beginning of my course at Brandeis. ü I would like to express my lovable thanks to my husband and my little MATHI, without their support I can’t imagine the work accomplished throughout this period. ü My parents and my brothers are the great source of inspiration for me. I would like to express my gratitude for their encouragement, love, care and affection. They bestowed and the freedom I enjoyed at every point in my life cannot be explainable with mere word. -Ramyaa Mathialagan iii Abstract Homobimetallic Cobalt Phosphinoamides: Characterization and Redox Chemistry. A thesis presented to the Department of Chemistry Graduate School of Arts and Sciences Brandeis University Waltham, Massachusetts By Ramyaa Mathialagan Homobimetallic dicobalt complexes featuring vastly different coordination environments have been synthesized, and their multielectron redox chemistry has been investigated. Treatment of CoX2 with K[MesNPiPr2] leads to self-assembly of [(THF)Co(MesNPiPr2)2(µ-X)CoX] [X = Cl (1), I (2)], with one Co center bound to two amide donors and the other bound to two phosphine donors. Upon two-electron reduction, a ligand rearrangement occurs to generate the symmetric species (PMe3)Co(MesNPiPr2)2Co(PMe3) (3), where each Co has an identical mixed P/N donor set. One-electron oxidation of 3 to generate a mixed valence species promotes a ligand rearrangement back to an asymmetric configuration in [(THF)Co(MesNPiPr2)2Co(PMe3)][PF6] (4). To construct rigid bimetallic cobalt complexes, a series of triply bridged phosphinoamide complexes been synthesized. Reaction of K[MesNPiPr2] with CoCl2 in THF results in the formation of a brown crystalline solid, Co(µ- i 2 i PrNPPh2)3Co(η - PrNPPh2) (6). The one electron bulk chemical reduction in the absence and iv i i presence of two-electron σ-donor ligands yields Co(µ- PrNPPh2)3Co( PrNHPPh2) (7) and Co(µ- i PrNPPh2)3Co(PMe3) (8). Treatment of 8 with organic azides results in the formation of two- i electron oxidized Co(µ- PrNPPh2)3Co≡NMes (9, Mes = 2,4,6-trimethylphenyl). In contrast to 9, the reaction of 8 with Ph2CN2 led to the formation of unexpected two-electron phosphine i oxidized product [Co(µ- PrNPPh2)2(µ-iPrNPPh2N2CPh2)Co] (11). Ligand substitution reactions i of 8 with Et4N-N3 and KOH resulted to the formation of [Co(µ- PrNPPh2)3Co(N3)][Et4N] (12) i and [Co(µ- PrNPPh2)3Co(OH)](KC12H24O6) (13), respectively. v Table of Contents Chapter 1 Introduction: History and Recent Development on Late Transition 01 Metal Homobimetallic Complexes Chapter 2 Metal−Metal Bonding in Low-Coordinate Dicobalt Complexes 12 Supported by Phosphinoamide Ligands Chapter 3 Triply Bridged Homobimetallic Cobalt Phosphinoamides: Syntheses, 37 Characterization and Reactivity vi List of Tables 1 MO diagrams of 3 and 4 22 2 X-ray Diffraction Experimental Details of 1 - 4 34 3 Interatomic distances (Å) and angles (degrees) of 6 - 8 47 4 Interatomic distances (Å) and angles (degrees) of 9 - 13 48 5 X-ray diffraction Experimental Details of Complexes 6 - 8 64 6 X-ray diffraction Experimental Details of Complexes 9 - 13 65 vii List of Figures 1 Displacement ellipsoid (50%) representations of 2, 3 and 4 18 2 Frontier molecular orbital diagram of 3 and 4 21 1 3 H NMR of [(THF)Co(MesNPiPr2)2(µ-Cl)CoCl] (1) 29 1 4 H NMR of [(THF)Co(MesNPiPr2)2(µ-I)CoI] (2) 29 1 5 H NMR of (PMe3)Co(MesNPiPr2)2Co(PMe3) (3) 30 1 6 H NMR of [(THF)Co(MesNPiPr2)2Co(PMe3)]PF6 (4) 30 1 7 H NMR of [Co(MesNPiPr2)(PMe3)3]PF6 (5) 31 8 CV of [(THF)Co(MesNPiPr2)2(µ-I)CoI] (2) 31 9 CV of (PMe3)Co(MesNPiPr2)2Co(PMe3) (3) 32 10 EPR Spectrum of [(THF)Co(MesNPiPr2)2Co(PMe3)]PF6 (4) 32 11 UV- vis-NIR spectra of 3 and 4 in THF solution 33 12 ORTEP plots of molecular structures of 6 – 8 45 13 ORTEP plots of molecular structures of 9 and 11-13 46 14 Computed MO diagrams of complexes 8 and 9 50 viii 1 i 2 i 15 H NMR of Co(µ- PrNPPh2)3Co(η - PrNPPh2) (6) 58 1 i i 16 H NMR of Co(µ- PrNPPh2)3Co( PrNHPPh2) (7) 58 1 i 17 H NMR of Co(µ- PrNPPh2)3Co(PMe3) (8) 59 1 i 18 H NMR of Co(µ- PrNPPh2)3Co(NMes) (9) 59 1 i 19 H NMR of [Co(µ- PrNPPh2)2(µ-iPrNPPh2N2CPh2)Co] (11) 60 1 i 20 H NMR of [Co(µ- PrNPPh2)3Co(OH)](KC12H24O6) (13) 60 1 i 21 H NMR of [Co(µ- PrNPPh2)3Co(N3)][Et4N] (12) 61 i i 22 CV of Co(µ- PrNPPh2)3Co( PrNPPh2) (6) 61 i 23 CV of Co(µ- PrNPPh2)3Co(PMe3) (8) 62 i 24 CV of Co(µ- PrNPPh2)3Co(NMes) (9) 62 25 UV- vis-NIR spectra of 6-13 in THF solution 63 ix List of Schemes 1 The first quadruple and quintuple bonded Re2 and Cr2 complexes 3 2 Multi-metallic clusters with different donor ligands 4 3 Homobimetallic Co complexes with different ligand framework 6 4 Selected metal-ligand multiple bond complexes from literature 7 5 Electronic differences between homo and heterobimetallic complexes 8 6 Synthesis of complex 1 and 2 14 7 Reduction of 1 and 2 15 8 One and Two electron Oxidation of complex 3 16 9 Formation of mixed valence di-cobalt complexes 7 and 8 41 10 Synthesis of 9 and attempted nitrene transfer reaction 43 11 Attempted synthesis of di-cobalt carbene species 43 - - 12 Displacement of PMe3 from 8 by reaction with OH and N3 44 x Chapter 1 Introduction: History and Recent Development on Late Transition Metal Homobimetallic Complexes. 1 History of Metal-Metal Multiple Bond. The first reported observation of metal-metal bonded complex was observed in K3(W2Cl9) with W-W distance of 2.41 Å, which is significantly shorter than the elemental tungsten distance of 2.74 Å, by Brosset in 1935. The short distance between the metal atoms was thought to be due to a strong interaction, however, the actual bond order of this complex could not be determined.1 In 1956, Figgis and Martin suggested that the weak interaction between metal atoms in a well-known diamagnetic Cr2(µ-O2CMe)4(H2O)2 complex could possibly have metal-metal multiple bond character.2 In 1964, Cotton and coworkers reported the first structural 2- 3,4 characterization of a quadruple bond between rhenium atoms in [Re2Cl8] . Since then, a number of multiply bonded bimetallic complexes have been reported in the literature.5 The majority of the metal-metal multiply bonded complexes consist of two similar metal atoms in the 2nd and 3rd row, although a number of exceptions include vanadium and chromium complexes.6,7 A metal-metal bond order greater than four was not characterized in any isolated bimetallic I 5 complexes until Power’s quintuply bonded Cr2 (Cr , d ) complex was reported in 2005 (Scheme 1). In this complex, all five d orbitals are involved in bonding since the sterically encumbered terphenyl ligand framework stabilizes the CrI centers with weak aryl π interactions.8 In recent years, quintuply bonded di-chromium complexes with diverse ligand frameworks have been reported and their reactivity towards small molecules has been explored.9 Unsupported metal- metal multiply bonded complexes are often targeted to achieve maximum bond order and to avoid complications from metal-ligand overlap. 2 2- Cl Cl Cl Cl Re Re Cr Cr Cl Cl Cl Cl 3,8 Scheme 1. The first quadruple and quintuple bonded Re2 and Cr2 complexes. Cotton and coworkers introduced bridging amidinato, triazenato and carboxylato framework to construct D3h symmetric trigonal lantern and D4h tetragonal lantern complexes with transition metals across the periodic table, including multiply bonded di-iron, di-cobalt and di- nickel derivatives.10 Computational investigations of high spin metal-metal bonded complexes are challenging and yet to be explored. Multiple bonds between two different transition metals are uncommon, and this has become an emerging area of research in past few years. Late Transition Metal Homobimetallic Complexes. In contrast to the 2nd and 3rd row transition metals, multiple bonds between two first row transition metal atoms, except for vanadium and chromium complexes,5,6 are challenging targets for synthetic chemists. The intermediate spin state and lower electron count of early metal atoms (vanadium and chromium) favor the arrangement of electrons only in bonding orbitals in the d- manifold, but in the case of late transition metals their high electron count and high spin nature populates anti-bonding orbitals, resulting in lower metal-metal bond orders.
Load more

Recommended publications
  • An Analysis of Electrophilic Aromatic Substitution: a “Complex Approach” PCCP
    Volume 23 Number 9 7 March 2021 Pages 5033–5682 PCCP Physical Chemistry Chemical Physics rsc.li/pccp ISSN 1463-9076 PERSPECTIVE Janez Cerkovnik et al . An analysis of electrophilic aromatic substitution: a “complex approach” PCCP View Article Online PERSPECTIVE View Journal | View Issue An analysis of electrophilic aromatic substitution: a ‘‘complex approach’’† Cite this: Phys. Chem. Chem. Phys., a a b 2021, 23, 5051 Nikola Stamenkovic´, Natasˇa Poklar Ulrih and Janez Cerkovnik * Electrophilic aromatic substitution (EAS) is one of the most widely researched transforms in synthetic organic chemistry. Numerous studies have been carried out to provide an understanding of the nature of its reactivity pattern. There is now a need for a concise and general, but detailed and up-to-date, overview. The basic principles behind EAS are essential to our understanding of what the mechanisms underlying EAS are. To date, textbook overviews of EAS have provided little information about the Received 5th October 2020, mechanistic pathways and chemical species involved. In this review, the aim is to gather and present the Accepted 21st December 2020 up-to-date information relating to reactivity in EAS, with the implication that some of the key concepts DOI: 10.1039/d0cp05245k will be discussed in a scientifically concise manner. In addition, the information presented herein suggests certain new possibilities to advance EAS theory, with particular emphasis on the role of modern Creative Commons Attribution-NonCommercial 3.0 Unported Licence. rsc.li/pccp
    [Show full text]
  • Nucleophilic Aromatic Substitution on Aryl-Amido Ligands Promoted by Oxidizing Osmium(IV) Centers
    Inorg. Chem. 2004, 43, 5804−5815 Nucleophilic Aromatic Substitution on Aryl-Amido Ligands Promoted by Oxidizing Osmium(IV) Centers Jake D. Soper, Erik Saganic, David Weinberg, David A. Hrovat, Jason B. Benedict,† Werner Kaminsky,† and James M. Mayer* Department of Chemistry, Campus Box 351700, UniVersity of Washington, Seattle, Washington 98195-1700 Received January 30, 2004 IV Addition of amine nucleophiles to acetonitrile solutions of the Os anilido complex TpOs(NHPh)Cl2 (1) [Tp ) hydrotris(1-pyrazolyl)borate] gives products with derivatized anilido ligands, i.e., TpOs[NH-p-C6H4(N(CH2)5)]Cl2 (2) from piperidine and TpOs[NH-p-C6H4N(CH2)4]Cl2 (3) from pyrrolidine. These materials are formed in ∼30% yield III under anaerobic conditions, together with ∼60% yields of the Os aniline complex TpOs(NH2Ph)Cl2 (5). Formation of the para-substituted materials 2 or 3 from 1 involves oxidative removal of two hydrogen atoms (two H+ and two - e ). The oxidation can be accomplished by 1, forming 5,orbyO2. Related reactions have been observed with other amines and with the 2-naphthylamido derivative, which gives an ortho-substituted product. Kinetic studies indicate an addition−elimination mechanism involving initial attack of the amine nucleophile on the anilido ligand. These are unusual examples of nucleophilic aromatic substitution of hydrogen. Ab initio calculations on 1 show that the LUMO has significant density at the ortho and para positions of the anilido ligand, resembling the LUMO of nitrobenzene. By analogy with nucleophilic aromatic substitution, 2 is quantitatively formed from piperidine and IV the p-chloroanilide TpOs(NH-p-C6H4Cl)Cl2 (7).
    [Show full text]
  • Intermolecular Forces
    Intermolecular Forces The intermolecular forces between molecules are important in the properties of all solid and liquid materials. They are key to reactions that take place in biological molecules. Proteins form their secondary and tertiary structures through hydrogen-bonding and London forces. DNA forms because of hydrogen bonding between base pairs. Enzymes function when molecules interact with the protein active site in these biological catalysts. Outline • Types of Intermolecular Forces • Entropy Considerations • Intermolecular Forces and DNA • Homework Types of Intermolecular Forces Solutions consist of a solvent and solute. There are gas, liquid, and solid solutions but in this unit we are concerned with liquids. The solvent then is a liquid phase molecular material that makes up most of the solution. Water is a good example of a solvent. The solute is a smaller quantity of anything that is dissolved in the solvent. It can be a gas (O2 in water), a liquid (water dissolved in ethanol), or a solid (NaCl dissolved in water). In any solution, the molecules or ions of the solute are randomly distributed among the molecules of the solvent. What are the intermolecular forces? They are listed in the table below along with covalent and ionic bonding for comparison. Notice that they have different dependence on the distance between the attracting particles, r. Materials dissolve in a solution when there are strong intermolecular forces between the solute and the solvent. London Dispersion Forces We could discount intermolecular interactions between gas-phase molecules because these molecules are mostly far apart and moving rapidly relative to each other. In the liquid phases, all molecules interact with one another.
    [Show full text]
  • Changes: Physical Or Chemical? by Cindy Grigg
    Changes: Physical or Chemical? By Cindy Grigg 1 If you have studied atoms, you know that atoms are the building blocks of matter. Atoms are so small they cannot be seen with an ordinary microscope. Yet atoms make up everything in the universe. Atoms can combine with different atoms and make new substances. Substances can also break apart into separate atoms. These changes are called chemical changes or reactions. Chemical reactions happen when atoms gain, lose, or share electrons. What about when water freezes into ice? Do you think that's a chemical change? 2 When water freezes, it has changed states. You probably already know about the four states of matter. They are solid, liquid, gas, and plasma. Plasma is the fourth state of matter and is the most common state in the universe. However, it is rarely found on Earth. Plasma occurs as ball lightning and in stars. Water is a common substance that everyone has seen in its three states of matter. Water in its solid state is called ice. Water in the liquid state is just called water. Water as a gas is called water vapor. We can easily cause water to change states by changing its temperature. Water will freeze at 32 degrees Fahrenheit (0 Celsius). However, no chemical change has occurred. The atoms have not combined or broken apart to make a different substance; it is still water or H2O. When we heat water to a temperature of 212 F. or 100 Celsius, it will change into a gas called water vapor. Changes in states of matter are just physical changes.
    [Show full text]
  • How Does Argumentation-Based Instruction Affect Pre-Service Science Teachers’ Conceptual Understanding of Organic Chemistry? the Case of Aromatic Compounds1
    Online Science Education Journal http://dergipark.gov.tr/ofed 2020; 5(1): 32 - 51. How Does Argumentation-based Instruction Affect Pre-service Science Teachers’ Conceptual Understanding of Organic Chemistry? The Case of Aromatic Compounds1 Gülten Şendur*, Dokuz Eylul University, Buca Faculty of Education, Department of Mathematics and Science Education, Chemistry Education Division, Izmir, Turkey Ezgi Kurt, Dokuz Eylul University, Institute of Educational Sciences, Izmir, Turkey Büşra Hekimoğlu, Ministry of National Education, Istanbul, Turkey *Corresponding Author: [email protected] Şendur, G., Kurt, E. & Hekimoğlu, B. (2020). How does argumentation-based instruction affect pre-service science teachers’ conceptual understanding of organic To cite this article chemistry? The case of aromatic compounds. Online Science Education Journal, 5(1): 32-51. Article Info Abstract Article History Aromatic compounds are one of the fundamental topics in Organic Chemistry. For this reason, creating learning environments that will contribute to pre-service Received: teachers’ meaningful understanding of aromatic compounds is of importance. The 04 May 2020 purpose of this study was to explore whether argumentation-based instruction has an effect on the conceptual understanding of pre-service science teachers in the Accepted: topic of aromatic compounds. In pursuit of this aim, the study was conducted in 05 June 2020 quasi-experimental, pre-test/post-test and control group design during the 2016- 2017 academic year at the Science Education Division of a state university in Keywords Turkey. Two classes were randomly selected as an experimental group (N=30) and a control group (N=35). The data collection instruments used in the study Argumentation Aromatic were pre- and post-tests, consisting of 10 open-ended questions.
    [Show full text]
  • Metal Carbonyls
    MODULE 1: METAL CARBONYLS Key words: Carbon monoxide; transition metal complexes; ligand substitution reactions; mononuclear carbonyls; dinuclear carbonyls; polynuclear carbonyls; catalytic activity; Monsanto process; Collman’s reagent; effective atomic number; 18-electron rule V. D. Bhatt / Selected topics in coordination chemistry / 2 MODULE 1: METAL CARBONYLS LECTURE #1 1. INTRODUCTION: Justus von Liebig attempted initial experiments on reaction of carbon monoxide with metals in 1834. However, it was demonstrated later that the compound he claimed to be potassium carbonyl was not a metal carbonyl at all. After the synthesis of [PtCl2(CO)2] and [PtCl2(CO)]2 reported by Schutzenberger (1868) followed by [Ni(CO)4] reported by Mond et al (1890), Hieber prepared numerous compounds containing metal and carbon monoxide. Compounds having at least one bond between carbon and metal are known as organometallic compounds. Metal carbonyls are the transition metal complexes of carbon monoxide containing metal-carbon bond. Lone pair of electrons are available on both carbon and oxygen atoms of carbon monoxide ligand. However, as the carbon atoms donate electrons to the metal, these complexes are named as carbonyls. A variety of such complexes such as mono nuclear, poly nuclear, homoleptic and mixed ligand are known. These compounds are widely studied due to industrial importance, catalytic properties and structural interest. V. D. Bhatt / Selected topics in coordination chemistry / 3 Carbon monoxide is one of the most important π- acceptor ligand. Because of its π- acidity, carbon monoxide can stabilize zero formal oxidation state of metals in carbonyl complexes. 2. SYNTHESIS OF METAL CARBONYLS Following are some of the general methods of preparation of metal carbonyls.
    [Show full text]
  • Chemical Changes What Is a Chemical Change?
    CHEMICAL CHANGES WHAT IS A CHEMICAL CHANGE? • Chemical Change- produces substances that have new and different properties. • Signs: a change in color, heat or light is given off, gas is produced, or powdery solid settles out of a liquid. • The mass of the matter does not change. • Compound- a chemical combination of 2 or more substances. • A compound has its own properties, different from that of the substances it is made of. Rust is one example of a chemical reaction and a compound. WHAT ARE CHEMICAL BONDS? • Chemical Bonds- the links that atoms or electronically charged particles can form with one another. • They result from electrical attraction between atoms. • When atoms of different elements bond together, compounds are formed. • Chemical Formula- the ratio in which atoms are bonded together in a compound. • A way of using letters and numbers to show how much of an element is in a substance. • Example: Water is made of 2 hydrogen atoms and 1 oxygen, so its chemical formula is 퐻2푂. TYPES OF CHEMICAL BONDS • There are 2 types of chemical bonds: • Covalent Bonds • Ionic Bonds HOW DO COVALENT BONDS FORM? • Covalent Bond- formed when two nuclei attract the same electrons. • In a covalent bond, 2 atoms share electrons. • Usually the elements that form covalent bonds are: • Nonmetals: hydrogen, oxygen, carbon, and nitrogen. • May form between atoms of the same element or different elements. • When atoms are identical, they share electrons equally. • When the atoms are different, one atom attracts electrons more strongly than the other. HOW DO IONIC BONDS FORM? • Ionic Bond- when a metal atom transfers and electrons to a nonmetal atom.
    [Show full text]
  • Physical and Chemical Changes W
    W 401 PHYSICAL AND CHEMICAL CHANGES Savannah Webb, Former 4-H Extension Agent, Maury County Jennifer Richards, Assistant Professor, 4-H Youth Development MANAGEMENT OF APHIDS AND BYD IN TENNESSEE WHEAT 1 Tennessee 4-H Youth Development Physical and Chemical Changes Skill Level Introduction to Content Beginner A physical change is any change in a Learner Outcomes substance’s form that does not change The learner will be able to: its chemical makeup. Examples of Explain the difference between a physical and chemical change. physical changes are breaking a stick or melting ice. Educational Standard(s) Supported 5.PS1.4: Evaluate the results of an A chemical change, or chemical reaction, experiment to determine whether the occurs when atoms of a substance are mixing of two or more substances result rearranged, and the bonds between the in a change of properties. atoms are broken or formed. During a chemical reaction, the structure or Success Indicator composition of the materials change. Learners will be successful if they: Identify the five factors that indicate a When a chemical change is complete, the chemical change has occurred. resulting substance(s) is/are different from Give at least two examples of a physical change. the original substance(s). As a result of a Classify a change as either physical chemical reaction, new substances with or chemical. new properties are formed. Time Needed Introduction to Methodology 15-20 Minutes In this lesson, students will learn about Materials List physical and chemical changes. Physical Playdough, M&M’s, 6 percent hydrogen changes will be demonstrated with peroxide, 16 oz.
    [Show full text]
  • CHEM 203 Summary of Topics to Be Covered in the Course INDEX A
    CHEM 203 Summary of Topics to be Covered in the Course INDEX A. Introduction p. 3 Lecture 1: Structural theory of organic chemistry p. 3 B. Aspects of the Electronic Theory of Organic Chemistry p. 5 Lecture 2: Electronic theory of organic chemistry p. 5 Lecture 3: Lewis acid-base interactions p. 11 C. Alkenes p. 14 Lecture 4: Bronsted acid-base equilibria, alkenes p. 14 Lecture 5: Electrophilic addition of H–X to alkenes p. 21 Lecture 6: Regioselective addition of H–X to alkenes p. 26 Lecture 7: Regioselective addition of H–X to alkenes, rearrangements p. 31 Lecture 8: Stereochemical aspects of H–X the additions to alkenes p. 35 Lecture 9: Hydration of alkenes p. 39 Lecture 10: Addition of "water-like" molecules to alkenes p. 42 Lecture 11: Halogenation of alkenes & stereochemical aspects p. 45 Lecture 12: Halogenation, halohydrins, stereochemical aspects p. 49 Lecture 13: Ozonolysis of alkenes p. 53 Lecture 14: Osmylation of alkenes p. 58 Lecture 15: Hydroboration of alkenes p. 61 Lecture 16: Hydrogenation of alkenes p. 66 Lecture 17: Radical addition to alkenes - I p. 70 Lecture 18: Radical addition to alkenes - II p. 75 D. Alkynes p. 79 Lecture 19: Chemistry of Alkynes p. 79 E. Alkyl Halides p. 83 Lecture 20: Alkyl halides - halogenation of C–H bonds p. 83 Lecture 21: SN2 reactions - I p. 88 Lecture 22: SN2 reactions - II p. 91 Lecture 23: SN2 vs. elimination reactions p. 94 Lecture 24: E2 reactions p. 98 Lecture 25: SN1 and E1 reactions p. 102 Lecture 26: SET reactions of alkyl halides: organometallics p.
    [Show full text]
  • The Electronic Theory of Organic Reactions, 1922-1953
    The Electronic Theory of Organic Reactions, 1922-1953 Thursday, October 14, 2010 A New Set of Issues for Organic Chemists • Can we explain chemical change? • What causes tautomerism? O O OH O OEt OEt • Why do conjugated systems behave so strangely? • Are physical methods relevant to organic chemistry? • Reductionism: How should chemistry be affected by the new model of the atom? Thursday, October 14, 2010 Robert Robinson (1886-1875) Thursday, October 14, 2010 Robinson and Residual Valences • Lapworth’s polarities • Thiele’s dotted affinities Br Br • Polarization of bonds in the intermediate complex • No “extra” affinities, but “split” or fractional bonds. Thursday, October 14, 2010 Robinson and Residual Valences Gertrude Maud Robinson and Robert Robinson, “Researches on Pseudo-Bases. Part II. Note on Some Berberine Derivatives and Remarks on the Mechanism of the Condensation Reactions of Pseudo-Bases,” Journal of the Chemical Society, 111 (1917): 958-69 Thursday, October 14, 2010 Robert Robinson, “The Conjugation of Partial Valencies,” Manchester Memoirs, 64 (1920), Thursday, October 14, 2010 Robert Robinson, “The Conjugation of Partial Valencies,” Manchester Memoirs, 64 (1920), Thursday, October 14, 2010 Robert Robinson, “The Conjugation of Partial Valencies,” Manchester Memoirs, 64 (1920), Thursday, October 14, 2010 Bernard Flürscheim (1874-1955) • Studied with Thiele and Werner • Royal Institution, London (1905-1907; 1925-1928) • Private laboratory • In carbon chains, strong and weak links would alternate. • Not charges, but affinities alternate. Thursday, October 14, 2010 Flürscheim’s “Affinity Demand” Model • Alternation of quantity of affinity • Affinity is continuously divisible (partly bound, partly free) • Atoms that can increase valency the most create the most “affinity demand” • Works well to explain the directive ability of most groups on aromatic rings.
    [Show full text]
  • Physical and Chemical Change
    For the audio file, click on the link physical vs. chemical change General Chemistry I – CHM1045 (Chapter 1) Physical vs. Chemical Change For the follow scenarios, identify whether the change is physical or chemical. Definition Physical Change: A change that alters only the state or appearance of a substance. This is typically exhibited through odor, taste, appearance, melting point, boiling point, and density. Chemical Change: A change to a substance that alters its composition into a different substance which can be achieved via reacting with other substances. This is typically exhibited through corrosion, flammability, acidity, or toxicity. Substance(s) Scenario Please place an “X” for the correct type of change. Physical (P) Chemical (C) 1. Sub Sandwich Eat it for Lunch 2. Milk Made into Yogurt 3. Balloon Inflated by a Machine 4. Rubbing Alcohol Evaporating 5. Leaves Change Color in the Fall 6. Leaves Shredded 7. Car Window Smashed by a Bat 8. Lamp Oil Burning 9. Fireworks Lite on Fourth of July 10. Cut Apples Turning Brown 11. Gold Melted into a Molds 12. Hair Bleached by Hydrogen Peroxide 13. Vanilla Ice Cream Dripping Down Your Hand 14. Egg Fry it for Breakfast 15. Fruits Blended with Yogurt 16. Water Vapor Frosting on a Window 17. Fireflies Glowing at Night 18. NaCl Dissolving on French Fries 19. Food Scraps Composted 20. Music Heard by your Neighbor This resource has been created by the Tallahassee Community College Learning Commons. General Chemistry I – CHM1045 (Chapter 1) Physical vs. Chemical Change Substance(s) Scenario Type of Change Explained This is a chemical change because the food undergoes the process of digestion.
    [Show full text]
  • Organic Chemistry ACCM
    Journal of Chemical Education Anchoring Concepts Content Map for Organic Chemistry Organic Chemistry Anchoring Concepts Content Map Jeffrey R. Raker,† Thomas Holme†* and Kristen Murphy‡ †Department of Chemistry, Iowa State University, Ames, Iowa 50011 United States; *[email protected] ‡Department of Chemistry and Biochemistry, University of Wisconsin–Milwaukee, Milwaukee, Wisconsin 53201 United States The outline below delineates the anchoring concepts content map for organic chemistry. I. Atoms: Matter consists of atoms that have internal structures that dictate their chemical and physical behavior. A. Atoms have unique chemical identities based on the number of protons in the nucleus. 1. The atomic number and mass number are used to determine average atomic weight and identify isotopes, which play a part in understanding techniques such as MS, NMR, or IR and rates of reactions via kinetic isotope effects. B. Electrons play the key role for atoms to bond with other atoms. 1. Electrons play a role in understanding the relative stability of resonance structures. a. Stabilization of anions helps to explain pKa values and relative acidities of protons. 2. Some reactions occur because molecules that are electrophilic are prone to react with regions where electron density is high. a. Electron-deficient atoms that seek electron-rich atoms are called electrophiles (meaning “electron seeking”). Electrophiles are commonly neutral or positively charged. b. Alkenes and alkynes are electron-rich and therefore are susceptible to electrophilic addition. Alcohols and alkyl halides are often formed from alkenes via electrophilic addition. 3. Some reactions occur because molecules that are nucleophilic are prone to react with regions where electron density is low.
    [Show full text]