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Brittain-DR-1965-Phd-Thesis.Pdf
POLYMETHYLENE PYRIDINES , A thesis submitted by David Robert Brittain in partial fulfilment of the requirements for the degree of DOCTOR OP PHILOSOPHY in the University of London Organic Chemistry Department, dune, 1965. Imperial College, LONDON, S.W.7. ABSTRACT This thesis describes a series of attempts to syn- thesise 2,5- and 1,4-polymethylene bridged pyridines. Nuclear magnetic resonance theory predicts that protons, which are held directly over an aromatic ring, will be abnormally shielded compared with protons in aliphatic straight-chain hydrocarbons. This prediction has been verified for the central methylene protons of paracyclo- phanes. The degree of shielding, expressed in terms of the distance from the aromatic ring, is a measure of the induced ring current and hence the aromaticity of the benzene ring. Similar measurements upon 2,5- or 1,4— polymethylene bridged pyridines would make it possible to determine the degree of aromaticity of the pyridine ring relative to benzene. A review of the subject of aromaticity is presented in which special reference has been made to its inter- pretation by nuclear magnetic resonance. The synthetic work has not been brougL.t to a truly satisfactory conclusion. However, the synthetic routes to 2,5-dialkylpyridines have been thoroughly investigated and a wide variety of such compounds prepared. The functional groups at the ends of the alkyl chains have been varied in an effort to produce a derivative which would cyclise to give a 2,5-bridged pyridine. The attempted intramolecular oxidative coupling of 2,5-dihex- 51 -ynylpyridine received much attention. In the attempts to obtain a 1,4-bridged pyridine, two tricyclic compounds, each containing two quaternised pyridine rings linked by polymethylene chains, were obtained. -
Syntheses and Eliminations of Cyclopentyl Derivatives David John Rausch Iowa State University
Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1966 Syntheses and eliminations of cyclopentyl derivatives David John Rausch Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Organic Chemistry Commons Recommended Citation Rausch, David John, "Syntheses and eliminations of cyclopentyl derivatives " (1966). Retrospective Theses and Dissertations. 2875. https://lib.dr.iastate.edu/rtd/2875 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been microfilmed exactly as received 66—6996 RAUSCH, David John, 1940- SYNTHESES AND ELIMINATIONS OF CYCLOPENTYL DERIVATIVES. Iowa State University of Science and Technology Ph.D., 1966 Chemistry, organic University Microfilms, Inc., Ann Arbor, Michigan SYNTHESES AND ELIMINATIONS OF CYCLOPENTYL DERIVATIVES by David John Rausch A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject: Organic Chemistry Approved : Signature was redacted for privacy. Signature was redacted for privacy. Head of Major Department Signature was redacted for privacy. Iowa State University Of Science and Technology Ames, Iowa 1966 ii TABLE OF CONTENTS VITA INTRODUCTION HISTORICAL Conformation of Cyclopentanes Elimination Reactions RESULTS AND DISCUSSION Synthetic Elimination Reactions EXPERIMENTAL Preparation and Purification of Materials Procedures and Data for Beta Elimination Reactions SUMMARY LITERATURE CITED ACKNOWLEDGEMENTS iii VITA The author was born in Aurora, Illinois, on October 24, 1940, to Mr. -
8.3 Bonding Theories >
8.3 Bonding Theories > Chapter 8 Covalent Bonding 8.1 Molecular Compounds 8.2 The Nature of Covalent Bonding 8.3 Bonding Theories 8.4 Polar Bonds and Molecules 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 8.3 Bonding Theories > Molecular Orbitals Molecular Orbitals How are atomic and molecular orbitals related? 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 8.3 Bonding Theories > Molecular Orbitals • The model you have been using for covalent bonding assumes the orbitals are those of the individual atoms. • There is a quantum mechanical model of bonding, however, that describes the electrons in molecules using orbitals that exist only for groupings of atoms. 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 8.3 Bonding Theories > Molecular Orbitals • When two atoms combine, this model assumes that their atomic orbitals overlap to produce molecular orbitals, or orbitals that apply to the entire molecule. 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 8.3 Bonding Theories > Molecular Orbitals Just as an atomic orbital belongs to a particular atom, a molecular orbital belongs to a molecule as a whole. • A molecular orbital that can be occupied by two electrons of a covalent bond is called a bonding orbital. 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. 8.3 Bonding Theories > Molecular Orbitals Sigma Bonds When two atomic orbitals combine to form a molecular orbital that is symmetrical around the axis connecting two atomic nuclei, a sigma bond is formed. • Its symbol is the Greek letter sigma (σ). -
Molecular Orbital Theory
Molecular Orbital Theory The Lewis Structure approach provides an extremely simple method for determining the electronic structure of many molecules. It is a bit simplistic, however, and does have trouble predicting structures for a few molecules. Nevertheless, it gives a reasonable structure for many molecules and its simplicity to use makes it a very useful tool for chemists. A more general, but slightly more complicated approach is the Molecular Orbital Theory. This theory builds on the electron wave functions of Quantum Mechanics to describe chemical bonding. To understand MO Theory let's first review constructive and destructive interference of standing waves starting with the full constructive and destructive interference that occurs when standing waves overlap completely. When standing waves only partially overlap we get partial constructive and destructive interference. To see how we use these concepts in Molecular Orbital Theory, let's start with H2, the simplest of all molecules. The 1s orbitals of the H-atom are standing waves of the electron wavefunction. In Molecular Orbital Theory we view the bonding of the two H-atoms as partial constructive interference between standing wavefunctions of the 1s orbitals. The energy of the H2 molecule with the two electrons in the bonding orbital is lower by 435 kJ/mole than the combined energy of the two separate H-atoms. On the other hand, the energy of the H2 molecule with two electrons in the antibonding orbital is higher than two separate H-atoms. To show the relative energies we use diagrams like this: In the H2 molecule, the bonding and anti-bonding orbitals are called sigma orbitals (σ). -
1St Year Students Lecture No. 5 Ahmed Mohamad Jawad
1st year students Lecture No. 5 Ahmed Mohamad Jawad Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) Out line 1- Dienes: Introduction of diene Nomenclature of diene Preparation of diene Reaction of diene 2- Alkyne Introduction of Alkyne Nomenclature of Alkyne Physical properties of alkyne Preparation of Alkyne Reaction of Alkyne Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) Introduction of diene Dienes are simply alkenes that contain two carbon-carbon double bonds. Dienes are divided into two major important classes according to the arrangement of the double bonds 1-Conjugated : Double bonds that alternate with single bonds are said to be conjugated. Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) Introduction of diene 2-Isolated double bonds that are separated by more than one single bond are said to be isolated Less stable than conjugated 3-Cumulated : contains cumulated double bonds Least one stable . Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) Nomenclature of diene Dienes are named by the IUPAC system in the same way as alkenes , except that the ending diene is used, with two numbers to indicate the position of the two double bonds. H2C C CH2 1,2-propadiene 1,3-butadiene 1,4-pentadiene This system is easily extended to compounds containing any number of double bonds. Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) Preparation of diene 1- by acid catalyzed double dehydration 2- By dehydrogenation of dihalides: Create PDF files without this message by purchasing novaPDF printer (http://www.novapdf.com) Reactions of Dienes In general terms, dienes undergo electrophilic addition reactions in a similar approach of alkenes Conjugated dienes undergo addition but the proximity of the conjugated C=C influences the reactions. -
Photoremovable Protecting Groups Used for the Caging of Biomolecules
1 1 Photoremovable Protecting Groups Used for the Caging of Biomolecules 1.1 2-Nitrobenzyl and 7-Nitroindoline Derivatives John E.T. Corrie 1.1.1 Introduction 1.1.1.1 Preamble and Scope of the Review This chapter covers developments with 2-nitrobenzyl (and substituted variants) and 7-nitroindoline caging groups over the decade from 1993, when the author last reviewed the topic [1]. Other reviews covered parts of the field at a similar date [2, 3], and more recent coverage is also available [4–6]. This chapter is not an exhaustive review of every instance of the subject cages, and its principal focus is on the chemistry of synthesis and photocleavage. Applications of indi- vidual compounds are only briefly discussed, usually when needed to put the work into context. The balance between the two cage types is heavily slanted to- ward the 2-nitrobenzyls, since work with 7-nitroindoline cages dates essentially from 1999 (see Section 1.1.3.2), while the 2-nitrobenzyl type has been in use for 25 years, from the introduction of caged ATP 1 (Scheme 1.1.1) by Kaplan and co-workers [7] in 1978. Scheme 1.1.1 Overall photolysis reaction of NPE-caged ATP 1. Dynamic Studies in Biology. Edited by M. Goeldner, R. Givens Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 3-527-30783-4 2 1 Photoremovable Protecting Groups Used for the Caging of Biomolecules 1.1.1.2 Historical Perspective The pioneering work of Kaplan et al. [7], although preceded by other examples of 2-nitrobenzyl photolysis in synthetic organic chemistry, was the first to apply this to a biological problem, the erythrocytic Na:K ion pump. -
IODINE Its Properties and Technical Applications
IODINE Its Properties and Technical Applications CHILEAN IODINE EDUCATIONAL BUREAU, INC. 120 Broadway, New York 5, New York IODINE Its Properties and Technical Applications ¡¡iiHiüíiüüiütitittüHiiUitítHiiiittiíU CHILEAN IODINE EDUCATIONAL BUREAU, INC. 120 Broadway, New York 5, New York 1951 Copyright, 1951, by Chilean Iodine Educational Bureau, Inc. Printed in U.S.A. Contents Page Foreword v I—Chemistry of Iodine and Its Compounds 1 A Short History of Iodine 1 The Occurrence and Production of Iodine ....... 3 The Properties of Iodine 4 Solid Iodine 4 Liquid Iodine 5 Iodine Vapor and Gas 6 Chemical Properties 6 Inorganic Compounds of Iodine 8 Compounds of Electropositive Iodine 8 Compounds with Other Halogens 8 The Polyhalides 9 Hydrogen Iodide 1,0 Inorganic Iodides 10 Physical Properties 10 Chemical Properties 12 Complex Iodides .13 The Oxides of Iodine . 14 Iodic Acid and the Iodates 15 Periodic Acid and the Periodates 15 Reactions of Iodine and Its Inorganic Compounds With Organic Compounds 17 Iodine . 17 Iodine Halides 18 Hydrogen Iodide 19 Inorganic Iodides 19 Periodic and Iodic Acids 21 The Organic Iodo Compounds 22 Organic Compounds of Polyvalent Iodine 25 The lodoso Compounds 25 The Iodoxy Compounds 26 The Iodyl Compounds 26 The Iodonium Salts 27 Heterocyclic Iodine Compounds 30 Bibliography 31 II—Applications of Iodine and Its Compounds 35 Iodine in Organic Chemistry 35 Iodine and Its Compounds at Catalysts 35 Exchange Catalysis 35 Halogenation 38 Isomerization 38 Dehydration 39 III Page Acylation 41 Carbón Monoxide (and Nitric Oxide) Additions ... 42 Reactions with Oxygen 42 Homogeneous Pyrolysis 43 Iodine as an Inhibitor 44 Other Applications 44 Iodine and Its Compounds as Process Reagents ... -
Inorganic Chemistry/Chemical Bonding/MO Diagram 1
Inorganic Chemistry/Chemical Bonding/MO Diagram 1 Inorganic Chemistry/Chemical Bonding/MO Diagram A molecular orbital diagram or MO diagram for short is a qualitative descriptive tool explaining chemical bonding in molecules in terms of molecular orbital theory in general and the Linear combination of atomic orbitals molecular orbital method (LCAO method) in particular [1] [2] [3] . This tool is very well suited for simple diatomic molecules such as dihydrogen, dioxygen and carbon monoxide but becomes more complex when discussing polynuclear molecules such as methane. It explains why some molecules exist and not others, how strong bonds are, and what electronic transitions take place. Dihydrogen MO diagram The smallest molecule, hydrogen gas exists as dihydrogen (H-H) with a single covalent bond between two hydrogen atoms. As each hydrogen atom has a single 1s atomic orbital for its electron, the bond forms by overlap of these two atomic orbitals. In figure 1 the two atomic orbitals are depicted on the left and on the right. The vertical axis always represents the orbital energies. The atomic orbital energy correlates with electronegativity as a more electronegative atom holds an electron more tightly thus lowering its energy. MO treatment is only valid when the atomic orbitals have comparable energy; when they differ greatly the mode of bonding becomes ionic. Each orbital is singly occupied with the up and down arrows representing an electron. The two AO's can overlap in two ways depending on their phase relationship. The phase of an orbital is a direct consequence of the oscillating, wave-like properties of electrons. -
Structure of Benzene, Orbital Picture, Resonance in Benzene, Aromatic Characters, Huckel’S Rule B
Dr.Mrityunjay Banerjee, IPT, Salipur B PHARM 3rd SEMESTER BP301T PHARMACEUTICAL ORGANIC CHEMISTRY –II UNIT I UNIT I Benzene and its derivatives 10 Hours A. Analytical, synthetic and other evidences in the derivation of structure of benzene, Orbital picture, resonance in benzene, aromatic characters, Huckel’s rule B. Reactions of benzene - nitration, sulphonation, halogenationreactivity, Friedelcrafts alkylation- reactivity, limitations, Friedelcrafts acylation. C. Substituents, effect of substituents on reactivity and orientation of mono substituted benzene compounds towards electrophilic substitution reaction D. Structure and uses of DDT, Saccharin, BHC and Chloramine Benzene and its Derivatives Chemists have found it useful to divide all organic compounds into two broad classes: aliphatic compounds and aromatic compounds. The original meanings of the words "aliphatic" (fatty) and "aromatic" (fragrant/ pleasant smell). Aromatic compounds are benzene and compounds that resemble benzene in chemical behavior. Aromatic properties are those properties of benzene that distinguish it from aliphatic hydrocarbons. Benzene: A liquid that smells like gasoline Boils at 80°C & Freezes at 5.5°C It was formerly used to decaffeinate coffee and component of many consumer products, such as paint strippers, rubber cements, and home dry-cleaning spot removers. A precursor in the production of plastics (such as Styrofoam and nylon), drugs, detergents, synthetic rubber, pesticides, and dyes. It is used as a solvent in cleaning and maintaining printing equipment and for adhesives such as those used to attach soles to shoes. Benzene is a natural constituent of petroleum products, but because it is a known carcinogen, its use as an additive in gasoline is now limited. In 1970s it was associated with leukemia deaths. -
Recent Advances on Mechanistic Studies on C–H Activation
Open Chem., 2018; 16: 1001–1058 Review Article Open Access Daniel Gallego*, Edwin A. Baquero Recent Advances on Mechanistic Studies on C–H Activation Catalyzed by Base Metals https:// doi.org/10.1515/chem-2018-0102 received March 26, 2018; accepted June 3, 2018. 1Introduction Abstract: During the last ten years, base metals have Application in organic synthesis of transition metal- become very attractive to the organometallic and catalytic catalyzed cross coupling reactions has been positioned community on activation of C-H bonds for their catalytic as one of the most important breakthroughs during the functionalization. In contrast to the statement that new millennia. The seminal works based on Pd–catalysts base metals differ on their mode of action most of the in the 70’s by Heck, Noyori and Suzuki set a new frontier manuscripts mistakenly rely on well-studied mechanisms between homogeneous catalysis and synthetic organic for precious metals while proposing plausible chemistry [1-5]. Late transition metals, mostly the precious mechanisms. Consequently, few literature examples metals, stand as the most versatile catalytic systems for a are found where a thorough mechanistic investigation variety of functionalization reactions demonstrating their have been conducted with strong support either by robustness in several applications in organic synthesis [6- theoretical calculations or experimentation. Therefore, 12]. Owing to the common interest in the catalysts mode we consider of highly scientific interest reviewing the of action by many research groups, nowadays we have a last advances on mechanistic studies on Fe, Co and Mn wide understanding of the mechanistic aspects of precious on C-H functionalization in order to get a deep insight on metal-catalyzed reactions. -
Reactions of Aromatic Compounds Just Like an Alkene, Benzene Has Clouds of Electrons Above and Below Its Sigma Bond Framework
Reactions of Aromatic Compounds Just like an alkene, benzene has clouds of electrons above and below its sigma bond framework. Although the electrons are in a stable aromatic system, they are still available for reaction with strong electrophiles. This generates a carbocation which is resonance stabilized (but not aromatic). This cation is called a sigma complex because the electrophile is joined to the benzene ring through a new sigma bond. The sigma complex (also called an arenium ion) is not aromatic since it contains an sp3 carbon (which disrupts the required loop of p orbitals). Ch17 Reactions of Aromatic Compounds (landscape).docx Page1 The loss of aromaticity required to form the sigma complex explains the highly endothermic nature of the first step. (That is why we require strong electrophiles for reaction). The sigma complex wishes to regain its aromaticity, and it may do so by either a reversal of the first step (i.e. regenerate the starting material) or by loss of the proton on the sp3 carbon (leading to a substitution product). When a reaction proceeds this way, it is electrophilic aromatic substitution. There are a wide variety of electrophiles that can be introduced into a benzene ring in this way, and so electrophilic aromatic substitution is a very important method for the synthesis of substituted aromatic compounds. Ch17 Reactions of Aromatic Compounds (landscape).docx Page2 Bromination of Benzene Bromination follows the same general mechanism for the electrophilic aromatic substitution (EAS). Bromine itself is not electrophilic enough to react with benzene. But the addition of a strong Lewis acid (electron pair acceptor), such as FeBr3, catalyses the reaction, and leads to the substitution product. -
Diels-Alder Reaction Between Naphthalene and N-Phenylmaleimide Under Ambient and High Pressure Conditions
Issue in Honor of Prof. Alexander I. Konovalov ARKIVOC 2004 (xii) 70-79 Diels-Alder reaction between naphthalene and N-phenylmaleimide under ambient and high pressure conditions Gulnara G. Iskhakova*, Vladimir D. Kiselev, Elena A. Kashaeva, Lubov’ N. Potapova, Evgeny A. Berdnikov, Dmitry B. Krivolapov, and Igor A. Litvinov A. M. Butlerov Chemical Institute, Kazan State University, Kremlevskaya str.18, 420008 Kazan, Russian Federation E-mail: [email protected] Dedicated to the 70th anniversary of Professor Alexander I. Konovalov (received 02 Nov 04; accepted 08 Jan 05; published on the web 05 Feb 05) Abstract The rate and equilibrium constants for the Diels-Alder reactions between benzene and naphthalene as dienes and tetracyanoethylene, maleic anhydride and N-phenylmaleimide as dienophiles at 25 °С were estimated from empirical rule. The highest yield of the adduct was predicted for the reaction of naphthalene with N-phenylmaleimide. The time of adduct formation in 50% yield exceeds 30 years. The use of gallium chloride as a catalyst affords the exo-adduct for seven days at room temperature. The rate ((2±0.5)•10-6 L mol-1 s-1) and equilibrium constants (5±2 L mol-1) of this reaction were determined. Under high pressure conditions (8 kbar) reaction occurs with formation of both stereo isomers at 100 °С during 80 hours. Keywords: Naphthalene, Diels-Alder reaction, catalysis, high pressure Introduction 1 Many dienes, including substituted benzenes and naphthalenes, are known to form molecular complexes of the π,π-type due to the interaction of the highest occupied π-orbital of a diene- donor with the lowest unoccupied π-orbital of a dienophile-acceptor.