DOCSLIB.ORG

Ethers and Epoxides

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

18.7 Cyclic Ethers: Epoxides Cyclic ethers behave like acyclic ethers, except if ring is 3-membered Dioxane, tetrahydrofuran (THF) and furan are used as solvents 1,4-dioxane tetrahydrofuran (THF) furan Epoxides (oxiranes) are three- membered cyclic ethers. The strain of the three-member ring of epoxides gives them unique chemical reactivity. 1 Nomenclature of Epoxides The nonsystematic name, –ene oxide, describes the method of formation. The systematic name, epoxy, describes the location of the epoxide ring. (nonsystematic) (nonsystematic) (systematic) (systematic) 2 Name the following A. B. C. H3C CH3 H3C HC CH O 2 H3C C C CH3 O O 3 Preparation of Epoxides The simplest and commercially most important example is ethylene oxide, manufactured from ethylene, air, and a silver catalyst. In the laboratory, epoxides are most commonly prepared from alkenes and organic peroxy acids. The reaction occurs in one step with syn stereochemistry. alkene peroxy acid epoxide carboxylic acid 4 Epoxides from Halohydrins Addition of HO-X to an alkene gives a halohydrin Treatment of a halohydrin with base gives an epoxide 1. Cl , H O Intramolecular Williamson ether synthesis 2 2 2. NaOH, H2O 5 18.8 Ring-Opening Reactions of Epoxides Water adds to epoxides with dilute acid at room temperature. Because of ring strain, epoxides react under milder conditions. Product is a 1,2-diol (glycol). Mechanism: acid protonates oxygen and water adds to opposite side (anti addition, trans product) 6 Ethylene Glycol 1,2-ethanediol from acid catalyzed hydration of ethylene oxide EG is primarily used as a raw material in the manufacture of polyester fibers and fabric industry, and polyethylene terephthalate resins (PET) used in bottling. Widely used as automobile antifreeze (lowers freezing point of water solutions) 7 18.8 Ring-Opening Reactions of O HO OH Epoxides (FormationH+ of 1,2-alkoxyalcohol) C C + H OH C C Other nucleophiles (such as alcohols)glycol add similarly to epoxides. O HO OR H+ C C R OH C C 2-alkoxyalcohol O R OMgX R OH H2O OrganometallicC C + R MreagentgX C C C C H+ R R' R R' H+ HC CH + R'' ONa HC CH O HO OR'' 8 HO OH OO HO OH H++ + H CC CC + HH OOHH CC CC 18.8 Ring-Opening Reactionsgglylyccool l of Epoxides O HO OR O + HO OR HH+ CC CC RR OOHH CC CC The reactions with organometallic reagents (RMgX and RLi) are useful two-carbon chain22-a--allengtheningklkooxxyyaalclcoohhool l reactions. R OMgX R OH OO R OMgX R OH ether HH2OO C C + R MgX C C 2 C C C C + R MgX C C + C C HH+ Halohydrins from Epoxides Anhydrous HF, HBr, HCl, or HI combines with an epoxide, gives trans product Where X = F, Br, Cl, or I H HX O ether H 9 Regiochemistry of Acid-Catalyzed Opening of Epoxides (2o vs 1o, 3o vs 1o) When both epoxide carbons are 1 or 2, halogen attack occurs primarily at the less hindered site. Secondary Primary O HCl H3C C C H ether H H When one epoxide carbon is 3, halogen attack occurs at the more highly substituted site. The mechanism is midway between SN2 and SN1. The reaction occurs by backside attack (SN2), but a positive charge is stabilized by a tertiary carbocation-like transition state (SN1). Tertiary O Primary HCl H3C C C H ether H3C H 10 Complete the following reactions. H+ A. H2C CH2 H C CH + HO CH3 2 2 O OH OCH3 H C CH OH 3 3 + HC CH H H3C O B. + CH HC O HO CH3 H C 3 CH3 CH3 HC CH2 + H Br C. HC CH2 + HC CH2 O OH Br Br OH major minor 11 Complete the following reactions. H3C CH3 + H3C CH3 D. H HC CH CH CH + H3C ONa O HO OCH3 H C CH H C CH 3 3 H+ 3 3 E. HC CH CH CH + H5C2 ONa O HO OC2H5 H O+ H2C CH2 3 + H3C CH2 CH2 CH2 MgBr H3C CH2 CH2 CH2 CH2 CH2 OH O F. 12 18.9 Crown Ethers Large cyclic ethers were discovered in 1960. Central cavity is electronegative and attracts cations They are named in the general format: X-crown-Y ether X= total atoms in ring Y= number of oxygens O O O O O O O O O O O O O O O O O O O O O O 30-Crown-10 ether 24-Crown-8 ether 13-Crown-4 ether 13 Uses of Crown Ethers Complexes between crown ethers and ionic salts are soluble in nonpolar organic solvents Creates reagents that are free of water that have useful properties Inorganic salts dissolve in organic solvents leaving the anion unassociated, enhancing reactivity 14 Crown Ethers Crown ethers are able to solvate metal cations, different size crown ethers solvate different size cations. O O O O O O + O + O + Li Na K MnO4 O O O O O O O 15 12-Crown-4 ether 15-Crown-5 ether 18-Crown-6 ether 18.10 Spectroscopy of Ethers IR Spectroscopy: Ethers are difficult to identify since many other types of absorptions occur at the 1050 – 1150 cm-1 range where ethers absorb. NMR: 13C NMR ether carbons absorb in 50 – 80 range. 1H NMR hydrogens on carbons next to an ether oxygen absorb in 3.4 – 4.5 range. Hydrogens on carbons next to an epoxide oxygen absorb near 2.5 – 3.5 , and –OH in 3 –8 range. 16 18.11 Thiols and Sulfides Sulfur is the element just below oxygen in the periodic table, and many oxygen-containing organic compounds have sulfur analogs. Thiols, R-SH, are sulfur analogs of alcohol Sulfides, R-S-R’, are sulfur analogs of ethers. 17 Thiol Nomenclature Thiols are named in a similar way as alcohols, in terms of the numbering of carbons, keep the terminal -e and add the suffix –thiol. The –SH group itself is referred to as the mercapto group when it is a lower priority (“capturer of mercury”). ethanethiol cyclohexanethiol m-mercaptobenzoic acid 18 Mercaptans Gases like hydrogen sulfide H2S are mixed to give natural gases their pungent smell. Mercaptans were in the news with the Porter Ranch, CA leaks (2015-16). Human noses can easily detect sulfur compounds that belong to the Thiol class. Other compounds like ethanethiol and propanethiol are added to increase the amount of smell that these gasses give. These compounds are called warning agents, because they help warn you of a gas leak. Besides utility companies need for mercaptan, there are other trades that use it. Industries use it for jet fuel, pharmaceuticals and livestock feed additives. It is used in many chemical plants. Mercaptan is less corrosive and less toxic than similar sulfur compounds and found naturally in rotten eggs, onions, garlic, skunks, and, of course, bad breath. In other words, forms of mercaptan can be found in things that smell. 19 Properties of Thiols Thiols have low boiling points (because of reduced hydrogen bonding. Thiols have a strong, disagreeable odor. It is added to natural gas, and is responsible for the odors of skunks. Thiols are easily oxidized but yield different products than their alcohol analogs. (Thiols form disulfides) 20 Skunks The family of chemicals that a skunk sprays are (E)-2-butene-1-thiol, 3-methyl-1-butanethiol and thioacetates. They're volatile, which means they disperse easily in the air, and they're easily picked up by the human nose. (E)-2-butene-1-thiol 3-methylbutane-1-thiol thioacetate 21 http://www.compoundchem.com/wp-content/uploads/2014/04/The- 22 Chemistry-of-Body-Odours-2015.png Sulfide Nomenclature Sulfides (R-S-R), are sulfur analogs of ethers Named by rules used for ethers, with sulfide in place of ether for simple compounds and alkylthio in place of alkoxy dimethyl sulfide methyl phenyl sulfide 3-(methylthio)cyclohexene 23 Problems: Draw the structures for the following: 2-butanethiol 2,2,6-trimethyl-4-heptanethiol ethyl methyl sulfide 24 Thiols: Formation and Reaction Formation of alkyl thiols is done by SN2 nucleophilic displacement with sulfhydryl ion. Yields are often poor unless excess nucleophile is used. R-X + SH CH3CH2Br + NaSH Thiourea can be used to get a better yield, RCH2Br RCH2SH 25 Oxidation of Thiols to Disulfides Thiols are easily oxidized to disulfide compounds by a mild oxidizing agent such as hydrogen peroxide, iodine or bromine. This reaction is reversible using Zn and Acid. I2, H2O 2 RSH thiol Zn, H+ 26 Thiol to Thiolate to Sulfide Thiols react with aqueous base (NaOH or NaH) to give thiolates, RSH + NaOH which can react with a 1, or 2 alkyl halide to form a sulfide by SN2 mechanism. CH3CH2SNa + CH3CH2I 27 Sulfides as Nucleophiles Preparation of Sulfides R-S + R’CH2Br Sulfur compounds are more nucleophilic than oxygen analogs due to the valence electrons on the sulfur being farther from the nucleus and less tightly held. Sulfides react with primary alkyl halides (SN2) to give + trialkylsulfonium salts (R3S ) THF S H3C I H3C CH3 + 28 Oxidation of Sulfides Sulfides are easily oxidized with H2O2 to a sulfoxide (R2SO) Oxidation of a sulfoxide with a peroxyacid yields a sulfone (R2SO2) Dimethyl sulfoxide (DMSO) is often used as a polar aprotic solvent 29 Preview of Carbonyl Compounds Your textbook has a preview of carbonyl compounds between chapters 18 & 19 on Pages 743 – 752. Be sure to review and study these pages to help you better understand the material to come. 30 Chapter 19. Aldehydes and Ketones: Nucleophilic Addition Reactions 31 Aldehydes and Ketones Aldehydes and ketones are characterized by the the carbonyl functional group (C=O) aldehyde ketone The compounds occur widely in nature as intermediates in metabolism and biosynthesis Aldehydes and ketones are bonded to substituents that cannot stabilize a negative charge and therefore cannot act as leaving groups.
Recommended publications
  • Recent Advances in Titanium Radical Redox Catalysis

    Recent Advances in Titanium Radical Redox Catalysis

    JOCSynopsis Cite This: J. Org. Chem. 2019, 84, 14369−14380 pubs.acs.org/joc Recent Advances in Titanium Radical Redox Catalysis Terry McCallum, Xiangyu Wu, and Song Lin* Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States ABSTRACT: New catalytic strategies that leverage single-electron redox events have provided chemists with useful tools for solving synthetic problems. In this context, Ti offers opportunities that are complementary to late transition metals for reaction discovery. Following foundational work on epoxide reductive functionalization, recent methodological advances have significantly expanded the repertoire of Ti radical chemistry. This Synopsis summarizes recent developments in the burgeoning area of Ti radical catalysis with a focus on innovative catalytic strategies such as radical redox-relay and dual catalysis. 1. INTRODUCTION a green chemistry perspective, the abundance and low toxicity of Ti make its complexes highly attractive as reagents and Radical-based chemistry has long been a cornerstone of 5 1 catalysts in organic synthesis. synthetic organic chemistry. The high reactivity of organic IV/III radicals has made possible myriad new reactions that cannot be A classic example of Ti -mediated reactivity is the reductive ring opening of epoxides. This process preferentially readily achieved using two-electron chemistry. However, the − high reactivity of organic radicals is a double-edged sword, as cleaves and functionalizes the more substituted C O bond, the selectivity of these fleeting intermediates can be difficult to providing complementary regioselectivity to Lewis acid control in the presence of multiple chemotypes. In addition, promoted epoxide reactions. The synthetic value of Ti redox catalysis has been highlighted by their many uses in total catalyst-controlled regio- and stereoselective reactions involv- 6−10 ing free-radical intermediates remain limited,2 and the synthesis (Scheme 1).
  • Unusual Regioselectivity in the Opening of Epoxides by Carboxylic Acid Enediolates

    Unusual Regioselectivity in the Opening of Epoxides by Carboxylic Acid Enediolates

    Molecules 2008, 13, 1303-1311 manuscripts; DOI: 10.3390/molecules13061303 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.org/molecules Communication Unusual Regioselectivity in the Opening of Epoxides by Carboxylic Acid Enediolates Luis R. Domingo, Salvador Gil, Margarita Parra* and José Segura Department of Organic Chemistry, Universitat de València, Dr. Moliner 50, 46100 Burjassot, Spain. Fax +34(9)63543831; E-mails: [email protected]; [email protected]; [email protected] * Author to whom correspondence should be addressed; E-mail: [email protected] Received: 29 May 2008; in revised form: 5 June 2008 / Accepted: 6 June 2008 / Published: 9 June 2008 Abstract: Addition of carboxylic acid dianions appears to be a potential alternative to the use of aluminium enolates for nucleophilic ring opening of epoxides. These conditions require the use of a sub-stoichiometric amount of amine (10% mol) for dianion generation and the previous activation of the epoxide with LiCl. Yields are good, with high regioselectivity, but the use of styrene oxide led, unexpectedly, to a mixture resulting from the attack on both the primary and secondary carbon atoms. Generally, a low diastereoselectivity is seen on attack at the primary center, however only one diastereoisomer was obtained from attack to the secondary carbon of the styrene oxide. Keywords: Lactones, lithium chloride, nucleophilic addition, regioselectivity, diastereoselectivity. Introduction Epoxides have been recognized among the most versatile compounds in organic synthesis, not only as final products [1] but as key intermediates for further manipulations. Accordingly, new synthetic developments are continuously being published [2]. Due to its high ring strain (around 27 Kcal/mol) its ring-opening, particularly with carbon-based nucleophiles, is a highly valuable synthetic strategy Molecules 2008, 13 1304 [3].
  • Highly Efficient Epoxidation of Olefins with Hydrogen Peroxide Oxidant Using Modified Silver Polyoxometalate Catalysts

    Highly Efficient Epoxidation of Olefins with Hydrogen Peroxide Oxidant Using Modified Silver Polyoxometalate Catalysts

    African Journal of Pure and Applied Chemistry Vol. 7(2), pp. 50-55, February 2013 Available online at http://www.academicjournals.org/AJPAC DOI: 10.5897/AJPAC12.060 ISSN 1996 - 0840 ©2013 Academic Journals Full Length Research Paper Highly efficient epoxidation of olefins with hydrogen peroxide oxidant using modified silver polyoxometalate catalysts Emmanuel Tebandeke 1*, Henry Ssekaalo 1 and Ola F. Wendt 2 1Department of Chemistry, Makerere University, P. O. Box 7062 Kampala, Uganda. 2Organic Chemistry, Department of Chemistry, Lund University, P. O. Box 124, 221 00 Lund, Sweden. Accepted 31 January, 2013 The catalytic epoxidation of olefins is an important reaction in chemical industry since epoxides are versatile and important intermediates in the synthesis of fine chemicals and pharmaceuticals. The current epoxidation procedures often use stoichiometric organic and sometimes toxic inorganic oxidants that are less favourable from an environmental and economical point of view. In contrast to such processes, catalytic epoxidation processes employing H2O2 oxidant are preferred for green processing. Herein is reported a highly efficient green process for the epoxidation of olefins using H2O2 oxidant and modified silver polyoxometalate catalysts at 65°C. The preparation and activity of the catalysts are described. The method enjoys >90% conversion and ≥99% selectivity to the epoxide for a variety of cyclic and linear olefins including terminal ones. The catalysts are easily recovered by filtration and are reusable several times. Key words: Epoxidation, olefins, hydrogen peroxide, polyoxometalate, silver catalysts. INTRODUCTION The catalytic epoxidation of olefins is very important in compared to organic peroxides and peracids (Jones, the chemical industry since epoxides are versatile and 1999; Lane and Burgess, 2003).
  • Part I. the Total Synthesis Of

    Part I. the Total Synthesis Of

    AN ABSTRACT OF THE THESIS OF Lester Percy Joseph Burton forthe degree of Doctor of Philosophy in Chemistry presentedon March 20, 1981. Title: Part 1 - The Total Synthesis of (±)-Cinnamodialand Related Drimane Sesquiterpenes Part 2 - Photochemical Activation ofthe Carboxyl Group Via NAcy1-2-thionothiazolidines Abstract approved: Redacted for privacy DT. James D. White Part I A total synthesis of the insect antifeedant(±)-cinnamodial ( ) and of the related drimanesesquiterpenes (±)-isodrimenin (67) and (±)-fragrolide (72)are described from the diene diester 49. Hydro- boration of 49 provided the C-6oxygenation and the trans ring junction in the form of alcohol 61. To confirm the stereoselectivity of the hydroboration, 61 was convertedto both (t)-isodrimenin (67) and (±)-fragrolide (72) in 3 steps. A diisobutylaluminum hydride reduction of 61 followed by a pyridiniumchlorochromate oxidation and treatment with lead tetraacetate yielded the dihydrodiacetoxyfuran102. The base induced elimination of acetic acid preceded theepoxidation and provided 106 which contains the desired hydroxy dialdehydefunctionality of cinnamodial in a protected form. The epoxide 106 was opened with methanol to yield the acetal 112. Reduction, hydrolysis and acetylation of 112 yielded (t)- cinnamodial in 19% overall yield. Part II - Various N- acyl- 2- thionothiazolidineswere prepared and photo- lysed in the presence of ethanol to provide the corresponding ethyl esters. The photochemical activation of the carboxyl function via these derivatives appears, for practical purposes, to be restricted tocases where a-keto hydrogen abstraction and subsequent ketene formation is favored by acyl substitution. Part 1 The Total Synthesis of (±)-Cinnamodial and Related Drimane Sesquiterpenes. Part 2 Photochemical Activation of the Carboxyl Group via N-Acy1-2-thionothiazolidines.
  • Epoxidation of Olefins Using Molecular Oxygen

    Epoxidation of Olefins Using Molecular Oxygen

    Epoxidation of Olefins Using Molecular Oxygen Zhongxing Huang Sep 16th, 2015 1 Major Challenge in Catalysis Key points . Low temperature . Selective May 31st, 1993, C&EN News. 2 Most Ancient Chemistry-Oxygenase Monooxygenase catalyzes the incorporation of one atom of oxygen into the product Iron-Containing Enzymes, RSC Publishing, 2011. 3 Most Ancient Chemistry-Oxygenase Dioxygenase incorporates both oxygen atoms into the product Shen, B.; Gould, S. J. Biochemistry 1991, 30, 8936. Gould, S. J.; Kirchmeier, M. J.; LaFever, R. E. J. Am. Chem. Soc. 1996, 118, 7663. 4 Most Ancient Chemistry-Oxygenase Monooxygenase catalyzes the incorporation of one atom of oxygen into the product . Ideal system should avoid use of reductants Dioxygenase incorporates both oxygen atoms into the product 5 Most Ancient Chemistry-Oxygenase Monooxygenase catalyzes the incorporation of one atom of oxygen into the product . Ideal system should avoid use of reductants Dioxygenase incorporates both oxygen atoms into the product Ideal Dioxygenase incorporates both oxygen atoms into the epoxide 6 Most Ancient Chemistry-Oxygenase Monooxygenase catalyzes the incorporation of one atom of oxygen into the product . Ideal system should avoid use of reductants Dioxygenase incorporates both oxygen atoms into the product Ideal Dioxygenase incorporates both oxygen atoms into the epoxide 7 Industrial Process- EO and PO . Top chemicals produced in US (2004,103 ton) 1 sulfuric acid 35954 2 nitrogen 30543 3 ethylene 25682 4 oxygen 25568 5 propylene 15345 6 chlorine 12166 7 ethylene dichloride 12163 8 phosphoric acid 11463 9 ammonia 10762 10 sodium hydroxide 9508 11 benzene 7675 12 nitric acid 6703 13 ammonium nitrate 6021 14 ethylbenzene 5779 15 urea 5755 16 styrene 5394 17 hydrochloric acid 5012 18 ethylene oxide 3772 19 cumene 3736 20 ammonium sulfate 2643 8 Industrial Process- EO and PO .
  • Alcohol Oxidation

    Alcohol Oxidation

    Alcohol oxidation Alcohol oxidation is an important organic reaction. Primary alcohols (R-CH2-OH) can be oxidized either Mechanism of oxidation of primary alcohols to carboxylic acids via aldehydes and The indirect oxidation of aldehyde hydrates primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an aldehyde hydrate (R- CH(OH)2) by reaction with water. The oxidation of a primary alcohol at the aldehyde level is possible by performing the reaction in absence of water, so that no aldehyde hydrate can be formed. Contents Oxidation to aldehydes Oxidation to ketones Oxidation to carboxylic acids Diol oxidation References Oxidation to aldehydes Oxidation of alcohols to aldehydes is partial oxidation; aldehydes are further oxidized to carboxylic acids. Conditions required for making aldehydes are heat and distillation. In aldehyde formation, the temperature of the reaction should be kept above the boiling point of the aldehyde and below the boiling point of the alcohol. Reagents useful for the transformation of primary alcohols to aldehydes are normally also suitable for the oxidation of secondary alcohols to ketones. These include: Oxidation of alcohols to aldehydes and ketones Chromium-based reagents, such as Collins reagent (CrO3·Py2), PDC or PCC. Sulfonium species known as "activated DMSO" which can result from reaction of DMSO with electrophiles, such as oxalyl chloride (Swern oxidation), a carbodiimide (Pfitzner-Moffatt oxidation) or the complex SO3·Py (Parikh-Doering oxidation). Hypervalent iodine compounds, such as Dess-Martin periodinane or 2-Iodoxybenzoic acid. Catalytic TPAP in presence of excess of NMO (Ley oxidation). Catalytic TEMPO in presence of excess bleach (NaOCl) (Oxoammonium-catalyzed oxidation).
  • BIO 1: Enzymatic Biodiesel Chairs: H.C

    BIO 1: Enzymatic Biodiesel Chairs: H.C

    Abstracts 105th AOCS Annual Meeting & Expo May 4-May 7, 2014 BIO 1: Enzymatic Biodiesel Chairs: H.C. Holm, Novozymes A/S, Denmark; and R. Burton, MARC-IV, Inc., USA Technical Considerations for Biodiesel Production feedstocks. The recent results from a commercial Using Enzyme Catalysis. R. Burton, MARC-IV, Inc., continuous unit for the enzymatic production of Pittsboro, NC, USA. biodiesel using high FFA’s multiple feedstocks will The search for alternative catalysts for the also be presented. production of biodiesel has been of significant interest to industry. Enzyme Catalyzed Biodiesel Using Liquid Lipases. One primary reason to replace conventional P.M. Nielsen, Novozymes A/S, Bagsvaerd, Denmark. alkaline catalysis is to eliminate soap waste streams During the last year the enzymatic in commercial production. Furthermore, utilizing transesterification using liquid lipase (the BioFAME enzymes in the processing of fatty acid esters can process) has been proven in full production scale in eliminate waste water streams, enhance the co- two plants in USA. The learnings from these plants product quality of glycerol, and provide the ability to are shared in this presentation in the discussion of use lower quality feedstocks. These low quality how to control the process to get biodiesel from feedstocks like yellow grease with higher free fatty used cooking oil and DDGS corn oil. The most acid (FFA) content are largely underutilized for important parameters have been: biodiesel due to the difficulty of processing these Securing correct pretreatment to keep the types of oils. This paper will evaluate the real world enzyme stable experiences of an enzymatic biodiesel plant.
  • How Is Alcohol Metabolized by the Body?

    How Is Alcohol Metabolized by the Body?

    Overview: How Is Alcohol Metabolized by the Body? Samir Zakhari, Ph.D. Alcohol is eliminated from the body by various metabolic mechanisms. The primary enzymes involved are aldehyde dehydrogenase (ALDH), alcohol dehydrogenase (ADH), cytochrome P450 (CYP2E1), and catalase. Variations in the genes for these enzymes have been found to influence alcohol consumption, alcohol-related tissue damage, and alcohol dependence. The consequences of alcohol metabolism include oxygen deficits (i.e., hypoxia) in the liver; interaction between alcohol metabolism byproducts and other cell components, resulting in the formation of harmful compounds (i.e., adducts); formation of highly reactive oxygen-containing molecules (i.e., reactive oxygen species [ROS]) that can damage other cell components; changes in the ratio of NADH to NAD+ (i.e., the cell’s redox state); tissue damage; fetal damage; impairment of other metabolic processes; cancer; and medication interactions. Several issues related to alcohol metabolism require further research. KEY WORDS: Ethanol-to­ acetaldehyde metabolism; alcohol dehydrogenase (ADH); aldehyde dehydrogenase (ALDH); acetaldehyde; acetate; cytochrome P450 2E1 (CYP2E1); catalase; reactive oxygen species (ROS); blood alcohol concentration (BAC); liver; stomach; brain; fetal alcohol effects; genetics and heredity; ethnic group; hypoxia The alcohol elimination rate varies state of liver cells. Chronic alcohol con- he effects of alcohol (i.e., ethanol) widely (i.e., three-fold) among individ- sumption and alcohol metabolism are on various tissues depend on its uals and is influenced by factors such as strongly linked to several pathological concentration in the blood T chronic alcohol consumption, diet, age, consequences and tissue damage. (blood alcohol concentration [BAC]) smoking, and time of day (Bennion and Understanding the balance of alcohol’s over time.
  • 20 More About Oxidation–Reduction Reactions

    20 More About Oxidation–Reduction Reactions

    More About 20 Oxidation–Reduction Reactions OOC n important group of organic reactions consists of those that O A involve the transfer of electrons C from one molecule to another. Organic chemists H OH use these reactions—called oxidation–reduction reactions or redox reactions—to synthesize a large O variety of compounds. Redox reactions are also important C in biological systems because many of these reactions produce HH energy. You have seen a number of oxidation and reduction reactions in other chapters, but discussing them as a group will give you the opportunity to CH3OH compare them. In an oxidation–reduction reaction, one compound loses electrons and one com- pound gains electrons. The compound that loses electrons is oxidized, and the one that gains electrons is reduced. One way to remember the difference between oxidation and reduction is with the phrase “LEO the lion says GER”: Loss of Electrons is Oxi- dation; Gain of Electrons is Reduction. The following is an example of an oxidation–reduction reaction involving inorganic reagents: Cu+ + Fe3+ ¡ Cu2+ + Fe2+ In this reaction,Cu+ loses an electron, so Cu+ is oxidized. Fe3+ gains an electron, so Fe3+ is reduced. The reaction demonstrates two important points about oxidation– reduction reactions. First, oxidation is always coupled with reduction. In other words, a compound cannot gain electrons (be reduced) unless another compound in the reaction simultaneously loses electrons (is oxidized). Second, the compound that is oxidized (Cu+) is called the reducing agent because it loses the electrons that are used to reduce the other compound (Fe3+). Similarly, the compound that is reduced (Fe3+) is called the oxidizing agent because it gains the electrons given up by the other compound (Cu+) when it is oxidized.
  • Reactions of Epoxides with Neighbouring Nucleophiles

    Reactions of Epoxides with Neighbouring Nucleophiles

    REACTIONS OF EPOXIDES WITH NEIGHBOURING NUCLEOPHILES A thesis presented for the degree of Doctor o.f Philosophy in Chemistry in the University of Canterbury, Christchurch, New Zealand. by W.H. Swallow 1972 CONTENTS ABSTRACT INTRODUCTION 1 Acid catalysed reactions of epoxides 1 (i) Mechanism of acid catalysed reactions of epoxides with nucleophiles 4 (ii) Ring formation by acid catalysed intramolecular nucleophilic attack of epoxides 10 (iii) Mechanism of acid catalysed rearrangements of epoxides to give carbonyl compounds. 14 Objectives and work undertaken 26 NEIGHBOURING HYDROXYL GROUPS 28 Preparation of the epoxyalcohols 28 The acid catalysed reactions of the epoxyalcohols 36 Rearrangements of epoxyheptanols (26,32) and epoxy- hexanols (24,30) 37 Mechanism of rearrangements of epoxyheptanols (26,32} and epoxyhexanols (24,30) 40 Rearrangements of epoxypentanols (22,28} 42 Mechanism of rearrangements of epoxypentanols (22,28) 44 THE ACID CATALYSED REARRANGEMENTS OF EPOXIDES WITH NEIGHBOURING ACETATE GROUPS 53 Introduction 53 Mechanisms of the acid catalysed reactions of epoxides with neighbouring ester groups 54 The acid catalysed reactions of epoxyacetates 59 Rearrangements of epoxypentanol acetates {23,29) 60 Rearrangements of epoxyhexanol acetates (25,31} 61 Rearrangements of epoxyheptanol acetates (27,33) 64 18 Rearrangements of o enriched epoxyacetates 65 Mechanism of formation of tetrahydrofuranol derivatives from epoxyacetates 66 Mechanism of formation of fluorohydrins and carbonyl compounds from epoxyacetates 73 EXPERIMENTAL 76 REFERENCES 109 ABSTRACT The syntheses and acid catalysed rearrangements of cis- and trans-3,4-epoxypentan-1-ols (28,22), 4,5-epoxyhexan-1-ols (30,24) and 5,6-epoxyheptan-1-ols (32,26) have been described. Isomerizations of these compounds gave cyclic ether derivatives as the major products.
  • Ruthenium Tetroxide and Perruthenate Chemistry. Recent Advances and Related Transformations Mediated by Other Transition Metal Oxo-Species

    Ruthenium Tetroxide and Perruthenate Chemistry. Recent Advances and Related Transformations Mediated by Other Transition Metal Oxo-Species

    Molecules 2014, 19, 6534-6582; doi:10.3390/molecules19056534 OPEN ACCESS molecules ISSN 1420-3049 www.mdpi.com/journal/molecules Review Ruthenium Tetroxide and Perruthenate Chemistry. Recent Advances and Related Transformations Mediated by Other Transition Metal Oxo-species Vincenzo Piccialli Dipartimento di Scienze Chimiche, Università degli Studi di Napoli ―Federico II‖, Via Cintia 4, 80126, Napoli, Italy; E-Mail: [email protected]; Tel.: +39-081-674111; Fax: +39-081-674393 Received: 24 February 2014; in revised form: 14 May 2014 / Accepted: 16 May 2014 / Published: 21 May 2014 Abstract: In the last years ruthenium tetroxide is increasingly being used in organic synthesis. Thanks to the fine tuning of the reaction conditions, including pH control of the medium and the use of a wider range of co-oxidants, this species has proven to be a reagent able to catalyse useful synthetic transformations which are either a valuable alternative to established methods or even, in some cases, the method of choice. Protocols for oxidation of hydrocarbons, oxidative cleavage of C–C double bonds, even stopping the process at the aldehyde stage, oxidative cleavage of terminal and internal alkynes, oxidation of alcohols to carboxylic acids, dihydroxylation of alkenes, oxidative degradation of phenyl and other heteroaromatic nuclei, oxidative cyclization of dienes, have now reached a good level of improvement and are more and more included into complex synthetic sequences. The perruthenate ion is a ruthenium (VII) oxo-species. Since its introduction in the mid-eighties, tetrapropylammonium perruthenate (TPAP) has reached a great popularity among organic chemists and it is mostly employed in catalytic amounts in conjunction with N-methylmorpholine N-oxide (NMO) for the mild oxidation of primary and secondary alcohols to carbonyl compounds.
  • Synthesis and Polymerization of Several Ester Substituted Epoxides. John, Muggee University of Massachusetts Amherst

    Synthesis and Polymerization of Several Ester Substituted Epoxides. John, Muggee University of Massachusetts Amherst

    University of Massachusetts Amherst ScholarWorks@UMass Amherst Doctoral Dissertations 1896 - February 2014 1-1-1982 Synthesis and polymerization of several ester substituted epoxides. John, Muggee University of Massachusetts Amherst Follow this and additional works at: https://scholarworks.umass.edu/dissertations_1 Recommended Citation Muggee, John,, "Synthesis and polymerization of several ester substituted epoxides." (1982). Doctoral Dissertations 1896 - February 2014. 670. https://scholarworks.umass.edu/dissertations_1/670 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Doctoral Dissertations 1896 - February 2014 by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. SYNTHESIS AND POLYMERIZATION OF SEVERAL ESTER SUBSTITUTED EPOXIDES A Dissertation Presented By JOHN MUGGEE Submitted to the Graduate School of the University of Massachusetts in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Pebtuary 1982. Polymer Science and Engineering SYNTHESIS AND POLYMERIZATION OF SEVERAL ESTER SUBSTITUTED EPOXIDES A Dissertation Presented By JOHN MUGGEE Approved as to style and content by: Otto Vogl,/ Chairpd^rson of Committee R. S. Stein, Member Polymer Science and Engineering 11( JOHN MUGGEE All rights reserved . ACKNOWLEDGMENTS The author would like to offer his deepest thanks and gratitude to his parents for their love and guidance thoughout his life, and to Professor Otto Vogl for his friendship and professional guidance during the course of this research. The efforts and helpful suggestions con- tributed by Professors Richard S. Stein and James C. W. Chien are also appreciated. The author would also like to thank his laboratory coworkers for making this an interest ing and productive period of his life.