DOCSLIB.ORG

Oxidation and Reduction in Organic Chemistry

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Oxidation and Reduction in Organic Chemistry OXIDATION AND REDUCTION IN ORGANIC CHEMISTRY In ionic and free radical reactions, oxidation and reduction are defined as processes by which an element undergoes a net loss or gain of electrons, respectively. The concept as applied to organic covalent compounds, where elements share electrons rather than losing or gaining them is the same, but it’s frequently simplified and narrowed down to make it easier to recognize these processes. Therefore it must be kept in mind that, while the following definition is grossly simplified, it serves the goal of quickly identifying oxidation and reduction processes in many organic reactions. In reference to organic molecules, oxidation is a process by which a carbon atom gains bonds to more electronegative elements, most commonly oxygen. Reduction is a process by which a carbon atom gains bonds to less electronegative elements, most commonly hydrogen. The following chart summarizes these concepts when applied to organic transformations. [ox] stands for oxidation, and [red] stands for reduction. OXIDATION H [ox] H [ox] O [ox] O [ox] H C H H C OH C C O C O H H H OH H [red] H [red] [red] [red] (CO2) carboxylic carbon alkane alcohol aldehyde acid dioxide Most highly Most highly reduced state REDUCTION oxidized state Some points must be noted. First, a gain or loss of bonds means simply more or less bonds. The double bond counts as two bonds and the triple bond counts as three bonds. Thus in the carbonyl group (C=O) carbon is considered to have two bonds to oxygen. Therefore, this carbon has a higher oxidation state than the alcohol carbon, which has only one bond to oxygen. In routine terminology, it is said that the aldehyde is a more highly oxidized functional group than the alcohol. Oxidation reactions are therefore those in which the central carbon of a functional group is transformed into a more highly oxidized form, and reduction reactions are those in which the central carbon is transformed into a more highly reduced form. Second, there can be several functional groups where the central carbon has the same oxidation state. For example, the carbons bonded to oxygen in alcohols and ethers have the same oxidation state. Likewise for aldehydes and their hydrated forms, and for carboxylic acids and their derivatives. However, most references to oxidation and reduction reactions in organic chemistry textbooks involve the functional groups presented in the chart above. H H H OH O H C OH H C O C H H C H C H H H H H OH alcohol ether aldehyde aldehyde hydrate The chart presented before shows the oxidation and reduction states for a molecule that contains only one carbon. But most organic compounds contain more than one carbon. The maximum oxidation state that a particular carbon can attain depends on how many other carbons it must remain attached to. For example, a molecule with two carbon atoms could not be oxidized all the way to carbon dioxide because the carbon atom in CO2 must have four bonds to oxygen, leaving no room for bonds to other carbons. The maximum oxidation state that a carbon can attain decreases gradually as the number of bonds to other carbons increases. Thus, the maximum oxidation state possible for a carbon that’s bonded to one other carbon is the carboxylic acid stage, and so on. The following chart illustrates this idea. ONE SINGLE CARBON H [ox] H [ox] O [ox] O [ox] H C H H C OH C C O C O H H H OH H [red] H [red] [red] [red] alkane alcohol aldehyde carboxylic carbon dioxide (methane) acid (CO2) CARBON BONDED TO ONE OTHER CARBON H [ox] H [ox] O [ox] O H3C C H H3C C OH C C H C H H C OH H [red] H [red] 3 [red] 3 alkane 1o alcohol aldehyde carboxylic acid (1o carbon) CARBON BONDED TO TWO OTHER CARBONS H [ox] OH [ox] O H3C C CH3 H3C C CH3 C H C CH H [red] H [red] 3 3 alkane 2o alcohol ketone (2o carbon) CARBON BONDED TO THREE OTHER CARBONS CH3 [ox] CH3 H3C C CH3 H3C C CH3 H [red] OH alkane 3o alcohol (3o carbon).
Load more

Recommended publications
  • Direct Β‑Functionalization of Cyclic Ketones with Aryl Ketones Via the Merger of Photoredox and Organocatalysis Filip R
    Communication pubs.acs.org/JACS Direct β‑Functionalization of Cyclic Ketones with Aryl Ketones via the Merger of Photoredox and Organocatalysis Filip R. Petronijevic,́† Manuel Nappi,† and David W. C. MacMillan* Merck Center for Catalysis at Princeton University, Princeton, New Jersey 08544, United States *S Supporting Information ABSTRACT: The direct β-coupling of cyclic ketones with aryl ketones has been achieved via the synergistic combination of photoredox catalysis and organocatalysis. Diaryl oxymethyl or aryl−alkyl oxymethyl radicals, transiently generated via single-electron reduction of ketone precursors, readily merge with β-enaminyl radical species, generated by photon-induced enamine oxidation, to produce γ-hydroxyketone adducts. Experimental evidence indicates that two discrete reaction pathways can be operable in this process depending upon the nature of the ketyl radical precursor and the photocatalyst. he direct β-functionalization of saturated ketones and T aldehydes is an important yet elusive goal in organic chemistry.1 While carbonyl groups are readily amenable to ipso- and α-carbon substitution with a range of nucleophiles and electrophiles respectively,2,3 activation at the β-methylene position poses a significant synthetic challenge. With a few notable exceptions,1,4 carbonyl β-functionalization has tradition- ally been restricted to the conjugate addition of soft nucleophiles are accessed via carbene catalysis,9,10 nucleophilic addition of into α,β-unsaturated carbonyl systems. As such, the development acetal-protected Grignard reagents,11 or stoichiometric metal- 5 − of a general catalytic platform for the direct β-functionalization activated homoenolate equivalents.12 16 of saturated ketones or aldehydes would represent a conceptual Drawing from the mechanistic insights gained in the course of and practical advance for the field.
    [Show full text]
  • Aldehydes and Ketones
    12 Aldehydes and Ketones Ethanol from alcoholic beverages is first metabolized to acetaldehyde before being broken down further in the body. The reactivity of the carbonyl group of acetaldehyde allows it to bind to proteins in the body, the products of which lead to tissue damage and organ disease. Inset: A model of acetaldehyde. (Novastock/ Stock Connection/Glow Images) KEY QUESTIONS 12.1 What Are Aldehydes and Ketones? 12.8 What Is Keto–Enol Tautomerism? 12.2 How Are Aldehydes and Ketones Named? 12.9 How Are Aldehydes and Ketones Oxidized? 12.3 What Are the Physical Properties of Aldehydes 12.10 How Are Aldehydes and Ketones Reduced? and Ketones? 12.4 What Is the Most Common Reaction Theme of HOW TO Aldehydes and Ketones? 12.1 How to Predict the Product of a Grignard Reaction 12.5 What Are Grignard Reagents, and How Do They 12.2 How to Determine the Reactants Used to React with Aldehydes and Ketones? Synthesize a Hemiacetal or Acetal 12.6 What Are Hemiacetals and Acetals? 12.7 How Do Aldehydes and Ketones React with CHEMICAL CONNECTIONS Ammonia and Amines? 12A A Green Synthesis of Adipic Acid IN THIS AND several of the following chapters, we study the physical and chemical properties of compounds containing the carbonyl group, C O. Because this group is the functional group of aldehydes, ketones, and carboxylic acids and their derivatives, it is one of the most important functional groups in organic chemistry and in the chemistry of biological systems. The chemical properties of the carbonyl group are straightforward, and an understanding of its characteristic reaction themes leads very quickly to an understanding of a wide variety of organic reactions.
    [Show full text]
  • Aldehydes and Ketone
    ALDEHYDES AND KETONE www.gneet.com ALDEHYDES AND KETONES In aldehydes, the carbonyl group is linked to either two hydrogen atom or one hydrogen atom and one carbon containing group such as alkyl, aryl or aralkyl group Examples * In ketones, the carbonyl group is linked to two carbon containing groups which may be same or different alkyl, aryl group. If two R and R’ groups are same, the ketone is called simple or symmetrical ketone and if R and R’ are different, then ketone is known as mixed or an unsymmetrical ketone. STRUCTURE Carbonyl carbon of both aldehyde and ketones is sp2 – hybridised, One of the three sp2 hybridised orbital get involved in σ- bond formation with half –filled p-orbital of oxygen atom whereas rest of the two are consumed in σ-bond formation with hydrogen and carbon depending on the structure of aldehyde or ketone. Unhybridised p-orbital of carbonyl carbon form π-bond with another half-filled p-orbital of oxygen atom by sideways overlapping. ISOMERISM IN ALDEHYDES AND KETONES (a) Chain isomerism: Aldehydes ( with 4 or more carbon atoms) and ketone ( with 5 or more carbon atoms) show chain isomerism. Example i) C4H8O CH3-CH2-CH2-CHO ( butanal) 1 ALDEHYDES AND KETONE www.gneet.com ii) C5H10O (b) Position isomerism: aliphatic aldehydes do not show position isomerism, because –CHO group is always present at the end of carbon chain. Aromatic aldehyde show position isomerism. Example (c) Metamerism: Higher ketones show metamerism due to presence of different alkyl groups attached to the same functional group C5H10O (d) Functional isomerism : Aldehydes and ketones show functional isomerism in them.
    [Show full text]
  • Chapter 14 – Aldehydes and Ketones
    Chapter 14 – Aldehydes and Ketones 14.1 Structures and Physical Properties of Aldehydes and Ketones Ketones and aldehydes are related in that they each possess a C=O (carbonyl) group. They differ in that the carbonyl carbon in ketones is bound to two carbon atoms (RCOR’), while that in aldehydes is bound to at least one hydrogen (H2CO and RCHO). Thus aldehydes always place the carbonyl group on a terminal (end) carbon, while the carbonyl group in ketones is always internal. Some common examples include (common name in parentheses): O O H HH methanal (formaldehyde) trans-3-phenyl-2-propenal (cinnamaldehyde) preservative oil of cinnamon O O propanone (acetone) 3-methylcyclopentadecanone (muscone) nail polish remover a component of one type of musk oil Simple aldehydes (e.g. formaldehyde) typically have an unpleasant, irritating odor. Aldehydes adjacent to a string of double bonds (e.g. 3-phenyl-2-propenal) frequently have pleasant odors. Other examples include the primary flavoring agents in oil of bitter almond (Ph- CHO) and vanilla (C6H3(OH)(OCH3)(CHO)). As your book says, simple ketones have distinctive odors (similar to acetone) that are typically not unpleasant in low doses. Like aldehydes, placing a collection of double bonds adjacent to a ketone carbonyl generally makes the substance more fragrant. The primary flavoring agent in oil of caraway is just a such a ketone. 2 O oil of carraway Because the C=O group is polar, small aldehydes and ketones enjoy significant water solubility. They are also quite soluble in typical organic solvents. 14.2 Naming Aldehydes and Ketones Aldehydes The IUPAC names for aldehydes are obtained by using rules similar to those we’ve seen for other functional groups (e.g.
    [Show full text]
  • Oxidation State Slides.Key
    Oxidation States Dr. Sobers’ Lecture Slides The Oxidation State Also known as the oxidation number The oxidation state is used to determine whether an element has been oxidized or reduced. The oxidation state is not always a real, quantitative, physical constant. The oxidation state can be the charge on an atom: 2+ - MgCl2 Mg Cl Oxidation State: +2 -1 2 The Oxidation State For covalently bonded substances, it is not as simple as an ionic charge. A covalent bond is a sharing of electrons. The electrons are associated with more than one atomic nuclei. This holds the nuclei together. The electrons may not be equally shared. This creates a polar bond. The electronegativity of a covalently bonded atom is its ability to attract electrons towards itself. 3 Example: Chlorine Sodium chloride is an ionic compound. In sodium chloride, the chloride ion has a charge and an oxidation state of -1. The oxidation state of sodium is +1. 4 Example: Chlorine In a chlorine molecule, the chlorine atoms are covalently bonded. The two atoms share electrons equally and the oxidation state is 0. 5 Example: Chlorine The two atoms of a hydrogen chloride molecule are covalently bonded. The electrons are not shared equally because chlorine is more electronegative than hydrogen. There are no ions but the oxidation state of chlorine in HCl is -1 and the oxidation state of hydrogen is +1. 6 7 Assigning Oxidation States See the handout for the list of rules. Rule 1: Free Elements Free elements have an oxidation state of zero Example Oxidation State O2(g) 0 Fe(s) 0 O3(g) 0 C(graphite) 0 C(diamond) 0 9 Rule 2: Monatomic Ions The oxidation state of monatomic ions is the charge of the ion Example Oxidation State O2- -2 Fe3+ +3 Na+ +1 I- -1 V4+ +4 10 Rule 3: Fluorine in Compounds Fluorine in a compound always has an oxidation state of -1 Example Comments and Oxidation States NaF These are monatomic ions.
    [Show full text]
  • 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.
    [Show full text]
  • Structure-Property Relationships of Layered Oxypnictides
    AN ABSTRACT OF THE DISSERTATION OF Sean W. Muir for the degree of Doctor of Philosophy in Chemistry presented on April 17, 2012. Title: Structure-property Relationships of Layered Oxypnictides Abstract approved:______________________________________________________ M. A. Subramanian Investigating the structure-property relationships of solid state materials can help improve many of the materials we use each day in life. It can also lead to the discovery of materials with interesting and unforeseen properties. In this work the structure property relationships of newly discovered layered oxypnictide phases are presented and discussed. There has generally been worldwide interest in layered oxypnictide materials following the discovery of superconductivity up to 55 K for iron arsenides such as LnFeAsO1-xFx (where Ln = Lanthanoid). This work presents efforts to understand the structure and physical property changes which occur to LnFeAsO materials when Fe is replaced with Rh or Ir and when As is replaced with Sb. As part of this work the solid solution between LaFeAsO and LaRhAsO was examined and superconductivity is observed for low Rh content with a maximum critical temperature of 16 K. LnRhAsO and LnIrAsO compositions are found to be metallic; however Ce based compositions display a resistivity temperature dependence which is typical of Kondo lattice materials. At low temperatures a sudden drop in resistivity occurs for both CeRhAsO and CeIrAsO compositions and this drop coincides with an antiferromagnetic transition. The Kondo scattering temperatures and magnetic transition temperatures observed for these materials can be rationalized by considering the expected difference in N(EF)J parameters between them, where N(EF) is the density of states at the Fermi level and J represents the exchange interaction between the Ce 4f1 electrons and the conduction electrons.
    [Show full text]
  • 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.
    [Show full text]
  • Effects of Ketone Bodies on Brain Metabolism and Function In
    International Journal of Molecular Sciences Review Effects of Ketone Bodies on Brain Metabolism and Function in Neurodegenerative Diseases Nicole Jacqueline Jensen 1,* , Helena Zander Wodschow 1, Malin Nilsson 1 and Jørgen Rungby 1,2 1 Department of Endocrinology, Bispebjerg University Hospital, 2400 Copenhagen, Denmark; [email protected] (H.Z.W.); malin.sofi[email protected] (M.N.); [email protected] (J.R.) 2 Copenhagen Center for Translational Research, Copenhagen University Hospital, Bispebjerg and Frederiksberg, 2400 Copenhagen, Denmark * Correspondence: [email protected] Received: 4 November 2020; Accepted: 18 November 2020; Published: 20 November 2020 Abstract: Under normal physiological conditions the brain primarily utilizes glucose for ATP generation. However, in situations where glucose is sparse, e.g., during prolonged fasting, ketone bodies become an important energy source for the brain. The brain’s utilization of ketones seems to depend mainly on the concentration in the blood, thus many dietary approaches such as ketogenic diets, ingestion of ketogenic medium-chain fatty acids or exogenous ketones, facilitate significant changes in the brain’s metabolism. Therefore, these approaches may ameliorate the energy crisis in neurodegenerative diseases, which are characterized by a deterioration of the brain’s glucose metabolism, providing a therapeutic advantage in these diseases. Most clinical studies examining the neuroprotective role of ketone bodies have been conducted in patients with Alzheimer’s disease, where brain imaging studies support the notion of enhancing brain energy metabolism with ketones. Likewise, a few studies show modest functional improvements in patients with Parkinson’s disease and cognitive benefits in patients with—or at risk of—Alzheimer’s disease after ketogenic interventions.
    [Show full text]
  • Plasma 'Ketone' Levelin the Diagnosis and Treatment of Diabetic Acidosis
    Postgrad. med. J. (October 1968) 44, 799-802. Postgrad Med J: first published as 10.1136/pgmj.44.516.799 on 1 October 1968. Downloaded from Plasma 'ketone' level in the diagnosis and treatment of diabetic acidosis M. S. KNAPP MARGARET E. HORN M.D., M.R.C.P. M.B., M.R.C.P. Lecturer in Medicine, University ofBristol Medical Registrar, Bristol Royal Hospital All patients in possible diabetic acidosis admit- Summary ted to one of the medical firms at the Bristol A simple method of estimating the plasma Royal Infirmary over a 3-year period had an 'ketone' level with 'Acetest' tablets has been used estimation of the plasma 'ketone' level performed in the diagnosis and treatment of diabetic acid- by the clinical staff in the ward side-room. In osis. The method is valuable when used in those patients treated for a moderate or severe association with full biochemical facilities, but it diabetic keto-acidosis the estimation was is especially useful in situations where these can- repeated, usually every four hours. The second not be easily obtained. and subsequent doses of insulin were based to a considerable extent on the plasma 'ketone' titre. Introduction If the titre had not fallen or had risen, an in- In a patient suspected of having diabetic keto- creased dose of insulin was given. A fall in titre acidosis it is useful to be able to rapidly confirm indicated a satisfactory response and either a Protected by copyright. the diagnosis. In this situation we have used a similar dose or a smaller one was used, depending simple side-room method for the detection of on previous blood sugar results.
    [Show full text]
  • Chapter 19 the Chemistry of Aldehydes and Ketones. Addition Reactions
    Instructor Supplemental Solutions to Problems © 2010 Roberts and Company Publishers Chapter 19 The Chemistry of Aldehydes and Ketones. Addition Reactions Solutions to In-Text Problems 19.1 (b) (d) (e) (g) 19.2 (a) 2-Propanone (d) (E)-3-Ethoxy-2-propenal (f) 4,4-Dimethyl-2,5-cyclohexadienone 19.3 (b) 2-Cyclohexenone has a lower carbonyl stretching frequency because its two double bonds are conjugated. 19.4 (b) The compound is 2-butanone: (c) The high frequency of the carbonyl absorption suggests a strained ring. (See Eq. 19.4, text p. 897.) In fact, cyclobutanone matches the IR stretching frequency perfectly and the NMR fits as well: 19.6 The structure and CMR assignments of 2-ethylbutanal are shown below. The two methyl groups are chemically equivalent, and the two methylene groups are chemically equivalent; all carbons with different CMR chemical shifts are chemically nonequivalent. INSTRUCTOR SUPPLEMENTAL SOLUTIONS TO PROBLEMS • CHAPTER 19 2 19.7 (a) The double bonds in 2-cyclohexenone are conjugated, but the double bonds in 3-cyclohexenone are not. Consequently, 2-cyclohexenone has the UV spectrum with the greater lmax. 19.9 Compound A, vanillin, should have a p T p* absorption at a greater lmax when dissolved in NaOH solution because the resulting phenolate can delocalize into the carboxaldehyde group; the resulting phenolate from compound B, isovanillin, on the other hand, can only delocalize in the aromatic ring. 19.11 The mass spectrum of 2-heptanone should have major peaks at m/z = 43 (from a-cleavage), 71 (from inductive cleavage), and 58 (from McLafferty rearrangement).
    [Show full text]
  • Plutonium Is a Physicist's Dream but an Engineer's Nightmare. with Little
    Plutonium An element at odds with itself lutonium is a physicist’s dream but an engineer’s nightmare. With little provocation, the metal changes its density by as much as 25 percent. It can Pbe as brittle as glass or as malleable as aluminum; it expands when it solidi- fies—much like water freezing to ice; and its shiny, silvery, freshly machined surface will tarnish in minutes. It is highly reactive in air and strongly reducing in solution, forming multiple compounds and complexes in the environment and dur- ing chemical processing. It transmutes by radioactive decay, causing damage to its crystalline lattice and leaving behind helium, americium, uranium, neptunium, and other impurities. Plutonium damages materials on contact and is therefore difficult to handle, store, or transport. Only physicists would ever dream of making and using such a material. And they did make it—in order to take advantage of the extraordinary nuclear properties of plutonium-239. Plutonium, the Most Complex Metal Plutonium, the sixth member of the actinide series, is a metal, and like other metals, it conducts electricity (albeit quite poorly), is electropositive, and dissolves in mineral acids. It is extremely dense—more than twice as dense as iron—and as it is heated, it begins to show its incredible sensitivity to temperature, undergoing dramatic length changes equivalent to density changes of more than 20 percent. Six Distinct Solid-State Phases of Plutonium Body-centered orthorhombic, 8 atoms per unit cell Face-centered cubic, 4 atoms per unit cell Body-centered monoclinic, Body-centered cubic, 8 34 atoms per unit cell 2 atoms per unit cell δ δ′ ε Contraction on melting 6 γ L L 4 β Monoclinic, 16 atoms per unit cell Anomalous Thermal Expansion and Phase Instability of Plutonium Length change (%) 2 Pure Pu Pure Al α 0 200 400 600 800 Temperature (°C) 16 Los Alamos Science Number 26 2000 Plutonium Overview Table I.
    [Show full text]