DOCSLIB.ORG

Summary of Alkene Reactions, Ch. 8. Memorize Reaction, Orientation Where Appropriate, Stereochemistry Where Appropriate, and Mechanism Where Appropriate

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Summary of Alkene Reactions, Ch. 8. Memorize Reaction, Orientation Where Appropriate, Stereochemistry Where Appropriate, and Mechanism Where Appropriate Chem 350 Jasperse Ch. 8 Handouts 1 Summary of Alkene Reactions, Ch. 8. Memorize Reaction, Orientation where Appropriate, Stereochemistry where Appropriate, and Mechanism where Appropriate. -all are drawn using 1-methylcyclohexene as a prototype alkene, because both orientation and stereochemistry effects are readily apparent. Orientation Stereo Mechanism 1 HBr Br Markovnikov None Be able to (no peroxides) draw completely 2 CH3 HBr H Anti-Markovnikov Nonselective. Be able to Both cis draw peroxides Br both cis and trans and trans propagation steps. 3 + CH3 H2O, H OH Markovnikov None Be able to draw completely 4 CH3 1. Hg(OAc)2, H2O OH Markovnikov None Not 2. NaBH4 responsible 5 CH3 1. BH3•THF H Anti-Markovnikov Cis Not 2. H2O2, NaOH responsible OH 6 CH3 1. Hg(OAc)2, ROH OR Markovnikov None Not 2. NaBH4 responsible 7 CH3 H , Pt 2 H None Cis Not D H responsible D Chem 350 Jasperse Ch. 8 Handouts 2 Orientation Stereo Mechanism CH 8 Br 3 2 Br None Trans Be able to (or Cl2) H draw Br completely CH 9 Br , H O 3 2 2 OH Markovnikov Trans Be able to (or Cl2) H draw Br completely 10 CH3 PhCO3H O None Cis Not responsible H 11 CH3 Be able to CH3CO3H OH None Trans draw H2O H acid- OH catalyzed epoxide hydrolysis 12 CH OsO , H O 3 4 2 2 OH None Cis Not OH responsible H 13 1. O3 O None None Not H 2. Me2S responsible H O Note: H-bearing alkene carbon ends up as aldehyde. 14 KMnO4 O None None Not H responsible OH O H-bearing alkene carbon ends as carboxylic acid Chem 350 Jasperse Ch. 8 Handouts 3 Summary of Mechanisms, Ch. 7 + 8. Alkene Synthesis and Reactions. 1 HBr Br (no peroxides) Note: For unsymmetrical alkenes, H Br Br Br protonation occurs at the less H substituted alkene carbon so that H Protonate Cation H H the more stable cation forms Capture H (3º > 2º > 1º), in keeping with the + Br product stability-reactivity principle CH3 CH3 vs. H H H H 3º 2º 2 CH3 HBr H peroxides Br both cis and trans Br H Br H Note 2: Hydrogenation of the radical comes from either Br + Br H Brominate Hydrogen Br face, thus cis/trans H mixture results Transfer H CH3 H Note 1: For unsymmetrical alkenes, top Br bromination occurs at the less CH3 CH3 substituted alkene carbon so that cis H vs. Br the more stable radical forms bottom Br Br H (3º > 2º > 1º), in keeping with the H H CH product stability-reactivity principle 3º H 3 2º Br trans H 3 + CH3 H2O, H OH H H OH2 O OH H -H H H Protonate Cation H H Deprotonate H Capture H H Note: For unsymmetrical alkenes, protonation again occurs at the less substituted end of the alkene, in order to produce the more stable radical intermediate (3º > 2º > 1º) Chem 350 Jasperse Ch. 8 Handouts 4 4 1. Hg(OAc) , H O CH3 2 2 OH 2. NaBH4 H HgOAc OH2 O OH HgOAc H -H H HgOAc HgOAc Cation Deprotonate - OAc H Capture H H NaBH4 Hg(OAc)2 OH H H 5 CH3 1. BH3•THF H 2. H O , NaOH 2 2 OH CH Notes 3 H2O2, NaOH CH3 H H H a. concerted addition of B-H across C=C -explains the cis stereochemistry BH2 BH2 OH b. the B-H addition is Markovnikov; the B is !+, the H is !- c. The H2O2, NaOH process is complex, but replaces the B with OH with complete retention of stereochem -the explains why the cis stereochemistry established in step one is preserved in step 2. 6 CH3 1. Hg(OAc)2, ROH OR 2. NaBH4 H HgOAc HOCH3 O OCH3 HgOAc CH3 -H H HgOAc HgOAc Cation Deprotonate - OAc H Capture H H NaBH4 Hg(OAc)2 OCH3 H H Chem 350 Jasperse Ch. 8 Handouts 5 8 CH3 Br2 Br (or Cl2) H Br 3 Notes Br Br Br Br Br 1. Cation intermediate is cyclic H Br bromonium (or chloronium) ion Cation 2. The nucleophile captures the H H Capture bromonium ion via backside attack -this leads to the trans stereochemistry 3. The nucleophile attacks the bromonium ion at the *more* substituted carbon 9 CH3 Br2, H2O OH (or Cl2) H Br H Br Br OH2 O Br H -H OH H Cation Br Br H Capture H H 4 Notes 1. Cation intermediate is cyclic bromonium (or chloronium) ion 2. The nucleophile captures the bromonium ion via backside attack (ala SN2) -this leads to the trans stereochemistry 3. The nucleophile attacks the bromonium ion at the *more* substituted carbon -this explains the orientation (Markovnikov) a. There is more + charge at the more substituted carbon b. The Br-C bond to the more substituted carbon is a lot weaker H O More H -H OH Substituted Br Br End H CH3 H Br Less H Substituted End Br Br H -H O OH H H H 4. Alcohols can function in the same way that water does, resulting in an ether OR rather than alcohol OH. Chem 350 Jasperse Ch. 8 Handouts 6 10 CH3 PhCO3H O H #+ ONE CH3 " H O " STEP! ! O ! ! + ! O ! ! No Ph #$ ions " Ph Ph Carbonyl-hydrogen Hydrogen-bonded reactant Notes 1. Complex arrow pushing 2. No ions required 3. The carbonyl oxygen picks up the hydrogen, leading directly to a neutral carboxylic acid -The peracid is already pre-organized for this' via internal H-bonding between carbonyl and H 11 CH CO H CH3 3 3 OH H2O H OH H ONE CH3 CH3 H OH2 O H STEP! -H OH O O OH H O OH O No Cation OH ions H H Capture H H CH3 Notes: a. The nucleophile (water) attacks from the more substituted end of the protonated epoxide . More δ+ charge there . The C-O bond to the more substituted end is much weaker b. The nucleophile adds via SN2-like backside attack. Inversion at the top stereocenter, but not the bottom, explains the trans stereochemistry. 12 CH3 OsO4, H2O2 OH OH H Concerted CH H2O CH 3 O 3 O O O cis addition O OH HO Os + Os Os (VI) Os O O OH HO O O O Osmate H Ester H H O Osmium Os (VIII) Os (VI) Hydrolysis 2 2 Reoxidation O O + H O Os 2 O O Os (VIII) Chem 350 Jasperse Ch. 8 Handouts 7 Chapter 7 Reactions and Mechanisms, Review E2 Br Br Mech: CH On NaOCH 3 R-X, 3 (Normal + H OCH3 H Normal OCH3 base) H + H OCH3 + Br Base Notes 1. Trans hydrogen required for E2 2. Zaytsev elimination with normal bases 3. For 3º R-X, E2 only. But with 2º R-X, SN2 competes (and usually prevails) 4. Lots of “normal base” anions. E2, Br NEt or Mech: Br H2 3 NEt3 On KOC(CH ) C + Et NH Br 3 3 H 3 R-X, Bulky (Bulky Base bases) Notes: 1. Hoffman elimination with Bulky Bases 2. E2 dominates over SN2 for not only 3º R-X but also 2º R-X 3. Memorize NEt3 and KOC(CH3)3 as bulky bases. Acid- OH Catalyzed H2SO4 + H OH E1- Elimination Of Mech Alcohols OH2 OH H2SO4 -H O 2 Deprotonation Protonation H + HSO Elimination H H 4 HSO4 + H2SO4 + OH2 Notes: 1. Zaytsev elimination 2. Cationic intermediate means 3º > 2º > 1º 3. 3-Step mechanism Chem 350 Jasperse Ch. 8 Handouts 8 Ch. 8 Reactions of Alkenes 8-1,2 Introduction CH CH 3 3 B + A B Addition Reaction A H H 1. Thermodynamics: Usually exothermic . 1 π + 1 σ 2 σ bonds 2. Kinetics: π bond is exposed and accessible Generic Electrophilic Addition Mechanism CH3 CH3 CH3 CH3 Cation Cation A B B A + B vs !+ !" Formation A Capture A B H H H H A B E F or CH3 CH3 CH3 A Doesn't Happen B Because + B A Inferior Cation A H C Product H H E Forms D 2 Steps: Cation formation and cation capture • Cation formation is the slow step o Cation stability will routinely determine the orientation in the first step . Which is preferred, A B or A C? • Often the cation is a normal cation B. Sometimes 3-membered ring cations D will be involved. • In some cases, the cation will be captured by a neutral species (like water), in which case an extra deprotonation step will be involved 4 Aspects to Watch For 1. Orientation • Matters only if both of two things are true: a. The alkene is unsymmetrical, and b. The electrophile is unsymmetrical 2. Relative Stereochemistry o Matters only if both the first and the second alkene carbons are transformed into chiral centers 3. Mechanism 4. Relative Reactivity of Different Alkenes o Stability of cation formed is key Chem 350 Jasperse Ch. 8 Handouts 9 8.3 H-X Hydrogen Halide Addition: Ionic/Cationic Addition in the Absence of Peroxides (Reaction 1) H X H X General: C C C C Orientation Stereo Mechanism 1 HBr Br Markovnikov None Be able to (no peroxides) draw completely Markovnikov’s Rule (For Predicting Products): When H-X (or any unsymmetrical species Aδ+Bδ-) adds to an unsymmetrical alkene: o the H+ (or Aδ+) adds to the less substituted carbon (the one with more H’s) o the X- (or Bδ-) adds to the more substituted carbon (the one with more non-H’s). o Note: Markovnikov’s rule does not apply if either the alkene or the atoms that are adding are symmetrical Examples, Predict the Products.
Load more

Recommended publications
  • The Origin of the Peculiarities of the Vietnamese Alphabet André-Georges Haudricourt
    The origin of the peculiarities of the Vietnamese alphabet André-Georges Haudricourt To cite this version: André-Georges Haudricourt. The origin of the peculiarities of the Vietnamese alphabet. Mon-Khmer Studies, 2010, 39, pp.89-104. halshs-00918824v2 HAL Id: halshs-00918824 https://halshs.archives-ouvertes.fr/halshs-00918824v2 Submitted on 17 Dec 2013 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Published in Mon-Khmer Studies 39. 89–104 (2010). The origin of the peculiarities of the Vietnamese alphabet by André-Georges Haudricourt Translated by Alexis Michaud, LACITO-CNRS, France Originally published as: L’origine des particularités de l’alphabet vietnamien, Dân Việt Nam 3:61-68, 1949. Translator’s foreword André-Georges Haudricourt’s contribution to Southeast Asian studies is internationally acknowledged, witness the Haudricourt Festschrift (Suriya, Thomas and Suwilai 1985). However, many of Haudricourt’s works are not yet available to the English-reading public. A volume of the most important papers by André-Georges Haudricourt, translated by an international team of specialists, is currently in preparation. Its aim is to share with the English- speaking academic community Haudricourt’s seminal publications, many of which address issues in Southeast Asian languages, linguistics and social anthropology.
    [Show full text]
  • Prebiological Evolution and the Metabolic Origins of Life
    Prebiological Evolution and the Andrew J. Pratt* Metabolic Origins of Life University of Canterbury Keywords Abiogenesis, origin of life, metabolism, hydrothermal, iron Abstract The chemoton model of cells posits three subsystems: metabolism, compartmentalization, and information. A specific model for the prebiological evolution of a reproducing system with rudimentary versions of these three interdependent subsystems is presented. This is based on the initial emergence and reproduction of autocatalytic networks in hydrothermal microcompartments containing iron sulfide. The driving force for life was catalysis of the dissipation of the intrinsic redox gradient of the planet. The codependence of life on iron and phosphate provides chemical constraints on the ordering of prebiological evolution. The initial protometabolism was based on positive feedback loops associated with in situ carbon fixation in which the initial protometabolites modified the catalytic capacity and mobility of metal-based catalysts, especially iron-sulfur centers. A number of selection mechanisms, including catalytic efficiency and specificity, hydrolytic stability, and selective solubilization, are proposed as key determinants for autocatalytic reproduction exploited in protometabolic evolution. This evolutionary process led from autocatalytic networks within preexisting compartments to discrete, reproducing, mobile vesicular protocells with the capacity to use soluble sugar phosphates and hence the opportunity to develop nucleic acids. Fidelity of information transfer in the reproduction of these increasingly complex autocatalytic networks is a key selection pressure in prebiological evolution that eventually leads to the selection of nucleic acids as a digital information subsystem and hence the emergence of fully functional chemotons capable of Darwinian evolution. 1 Introduction: Chemoton Subsystems and Evolutionary Pathways Living cells are autocatalytic entities that harness redox energy via the selective catalysis of biochemical transformations.
    [Show full text]
  • Chapter 3 • Ratio: Cnh2n+2
    Organic Chemistry, 5th Edition Alkane Formulas L. G. Wade, Jr. • All C-C single bonds • Saturated with hydrogens Chapter 3 • Ratio: CnH2n+2 Structure and Stereochemistry • Alkane homologs: CH3(CH2)nCH3 of Alkanes • Same ratio for branched alkanes H H H H H H CH H C C C C H H H H C CCH Jo Blackburn H H H H H H Richland College, Dallas, TX H => Butane, C4H10 Dallas County Community College District Chapter 3Isobutane, C H 2 © 2003, Prentice Hall 4 10 Common Names Pentanes H H H H H H H CH • Isobutane, “isomer of butane” H C C C C C H H H • Isopentane, isohexane, etc., methyl H H H H H H H C CCC H branch on next-to-last carbon in chain. H H H H • Neopentane, most highly branched n-pentane, C5H12 isopentane, C5H12 • Five possible isomers of hexane, CH3 18 isomers of octane and 75 for H3C C CH3 decane! CH3 => => neopentane, C5H12 Chapter 3 3 Chapter 3 4 Longest Chain IUPAC Names • The number of carbons in the longest • Find the longest continuous carbon chain determines the base name: chain. ethane, hexane. (Listed in Table 3.2, • Number the carbons, starting closest to page 81.) the first branch. • If there are two possible chains with the • Name the groups attached to the chain, same number of carbons, use the chain using the carbon number as the locator. with the most substituents. • Alphabetize substituents. H3C CH CH CH • Use di-, tri-, etc., for multiples of same 2 3 CH3 substituent.
    [Show full text]
  • Organoboranes in Organic Syntheses Including Suzuki Coupling Reaction
    HETEROCYCLES, Vol. 80, No. 1, 2010 15 HETEROCYCLES, Vol. 80, No. 1, 2010, pp. 15 - 43. © The Japan Institute of Heterocyclic Chemistry DOI: 10.3987/COM-09-S(S)Summary ORGANOBORANES IN ORGANIC SYNTHESES INCLUDING SUZUKI COUPLING REACTION Akira Suzuki In 1962 I had a lively interest in Wacker reaction [the oxidation of ethylene to acetaldehyde in the presence of palladium chloride and cupric chloride (Angew. Chem. 1959, 71, 176)] and began a literature survey. One Saturday afternoon during that time, I went a bookstore in Sapporo to look at new chemistry books and found a red and black two-tone colored book on the shelf that did not look like a chemistry book. The book was "Hydroboration" written by Professor Herbert C. Brown of Purdue University. It seemed to be an interesting book, so, I bought it. This book changed the course of my career, and my fascination with the chemistry of hydroboration reaction and organoboron compounds thus prepared by hydroboration began after reading the book. I immediately wrote to Professor Brown requesting to work as a postdoctoral research fellow. At that time Professor Brown was at Heidelberg in Germany as a visiting professor. He kindly wrote me a letter of acceptance, and I began a study of the stereochemistry of hydroboration reaction at Purdue (1963-65). Through this work I came to understand hydroboration and the interesting characteristics of organoboranes. My family (wife and two small girls) and I had a very good time there and made good friends. Of course I enjoyed chemistry. After a stay of about two years at Purdue, I returned to Japan with my family at the end of March 1965.
    [Show full text]
  • Stereochemistry of Alkanes and Cycloalkanes
    STEREOCHEMISTRY OF ALKANES AND CYCLOALKANES CONFORMATIONAL ISOMERS 1 CONFORMATIONAL ISOMERS • Stereochemistry concerned with the 3-D aspects of molecules • Rotation is possible around C-C bonds in open- chain molecules • A conformation is one of the many possible arrangements of atoms caused by rotation about a single bond, and a specific conformation is called a conformer (conformational isomer). 2 SOME VOCABULARY • A staggered conformation is the conformation in which all groups on two adjacent carbons are as far from each other as possible. • An eclipsed conformation is the conformation in which all groups on two adjacent carbons are as close to each other as possible. • Dihedral angle is angle between the substituents on two adjacent carbons; changes with rotation around the C-C bond 3 MORE VOCABULARY • Angle strain is the strain caused by the deformation of a bond angle from its normal value. • Steric strain is the repulsive interaction caused by atoms attempting to occupy the same space. • Torsional strain is the repulsive interaction between two bonds as they rotate past each other. Torsional strain is responsible for the barrier to rotation around the C-C bond. The eclipsed from higher in energy than the staggered form. 4 CONFORMATION OF ETHANE • Conformation- Different arrangement of atoms resulting from bond rotation • Conformations can be represented in 2 ways: 5 TORSIONAL STRAIN • We do not observe perfectly free rotation • There is a barrier to rotation, and some conformers are more stable than others • Staggered- most stable:
    [Show full text]
  • Chemical Kinetics HW1 (Kahn, 2010)
    Chemical Kinetics HW1 (Kahn, 2010) Question 1. (6 pts) A reaction with stoichiometry A = P + 2Q was studied by monitoring the concentration of the reactant A as a function of time for eighteen minutes. The concentration determination method had a maximum error of 6 M. The following concentration profile was observed: Time (min) Conc (mM) 1 0.9850 2 0.8571 3 0.7482 4 0.6549 5 0.5885 6 0.5183 7 0.4667 8 0.4281 9 0.3864 10 0.3557 11 0.3259 12 0.3037 13 0.2706 14 0.2486 15 0.2355 16 0.2188 17 0.2111 18 0.1930 Determine the reaction order and calculate the rate constant for decomposition of A. What can be said about the mechanism or molecularity of this reaction? Question 2. (4 pts) Solve problem 2 on pg 31 in your textbook (House) using both linear and non-linear regression. Provide standard errors for the rate constant and half-life based on linear and non-linear fits. Below is the data set for your convenience: dataA = {{0, 0.5}, {10, 0.443}, {20,0.395}, {30,0.348}, {40,0.310}, {50,0.274}, {60,0.24}, {70,0.212}, {80,0.190}, {90,0.171}, {100,0.164}} Question 3. (3 pts) Solve problem 3 on pg 32 in your textbook (House). Question 4. (7 pts) The authors of the paper “Microsecond Folding of the Cold Shock Protein Measured by a Pressure-Jump Technique” suggest that the activated state of folding of CspB follows Hammond- type behavior.
    [Show full text]
  • 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.
    [Show full text]
  • Chemistry 301-301A - Hour Examination #3, December 11, 2003
    Chemistry 301-301A - Hour Examination #3, December 11, 2003 “.....as we know, there are known unknowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns - the ones we don't know we don't know.” Donald Rumsfeld (winner of a British award given to the worst mangler of the English language in 2003) “I know, a proof is a proof. What kind of a proof is a proof? A proof is a proof and when you have a good proof it's because it's proven." Jean Chrétien (hon. mention for the same award) 1[18 points] (a) Acid-catalyzed addition of water to 3-methyl-1-butene (1) results in formation of large amounts of a rearranged alcohol (2), in addition to the expected alcohol (3). Explain, with excellent arrow formalisms. H2O + H O+ 3 OH OH 1 3 2 (b) On the other hand hydroboration of 1, followed by oxidation, does not lead to any rearranged product. Only alcohol 4 is formed. Explain. Detailed mechanisms are not needed here, but a drawing of the transition state for the hydroboration step is. 1. BH3 OH 2. HOOH/HO – 1 4 (c) But there are some strange things that happen in hydroboration. For example when 2-methyl-2-butene (5) is hydroborated at high temperature, then treated with HOOH/HO–, alcohol 4 is still one of the products. Explain mechanistcally. Hint: at high temperature hydroboration is reversible.
    [Show full text]
  • Chapter 4: Stereochemistry Introduction to Stereochemistry
    Chapter 4: Stereochemistry Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C7H16: CH3 CH3 2-methylhexane 3-methylhexane Me Me Me C Me H Bu Bu Me Me 2-methylhexane H H mirror Me rotate Bu Me H 2-methylhexame is superimposable with its mirror image Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C7H16: CH3 CH3 2-methylhexane 3-methylhexane H C Et Et Me Pr Pr 3-methylhexane Me Me H H mirror Et rotate H Me Pr 2-methylhexame is superimposable with its mirror image Introduction To Stereochemistry Consider two of the compounds we produced while finding all the isomers of C7H16: CH3 CH3 2-methylhexane 3-methylhexane .Compounds that are not superimposable with their mirror image are called chiral (in Greek, chiral means "handed") 3-methylhexane is a chiral molecule. .Compounds that are superimposable with their mirror image are called achiral. 2-methylhexane is an achiral molecule. .An atom (usually carbon) with 4 different substituents is called a stereogenic center or stereocenter. Enantiomers Et Et Pr Pr Me CH3 Me H H 3-methylhexane mirror enantiomers Et Et Pr Pr Me Me Me H H Me H H Two compounds that are non-superimposable mirror images (the two "hands") are called enantiomers. Introduction To Stereochemistry Structural (constitutional) Isomers - Compounds of the same molecular formula with different connectivity (structure, constitution) 2-methylpentane 3-methylpentane Conformational Isomers - Compounds of the same structure that differ in rotation around one or more single bonds Me Me H H H Me H H H H Me H Configurational Isomers or Stereoisomers - Compounds of the same structure that differ in one or more aspects of stereochemistry (how groups are oriented in space - enantiomers or diastereomers) We need a a way to describe the stereochemistry! Me H H Me 3-methylhexane 3-methylhexane The CIP System Revisited 1.
    [Show full text]
  • The Arene–Alkene Photocycloaddition
    The arene–alkene photocycloaddition Ursula Streit and Christian G. Bochet* Review Open Access Address: Beilstein J. Org. Chem. 2011, 7, 525–542. Department of Chemistry, University of Fribourg, Chemin du Musée 9, doi:10.3762/bjoc.7.61 CH-1700 Fribourg, Switzerland Received: 07 January 2011 Email: Accepted: 23 March 2011 Ursula Streit - [email protected]; Christian G. Bochet* - Published: 28 April 2011 [email protected] This article is part of the Thematic Series "Photocycloadditions and * Corresponding author photorearrangements". Keywords: Guest Editor: A. G. Griesbeck benzene derivatives; cycloadditions; Diels–Alder; photochemistry © 2011 Streit and Bochet; licensee Beilstein-Institut. License and terms: see end of document. Abstract In the presence of an alkene, three different modes of photocycloaddition with benzene derivatives can occur; the [2 + 2] or ortho, the [3 + 2] or meta, and the [4 + 2] or para photocycloaddition. This short review aims to demonstrate the synthetic power of these photocycloadditions. Introduction Photocycloadditions occur in a variety of modes [1]. The best In the presence of an alkene, three different modes of photo- known representatives are undoubtedly the [2 + 2] photocyclo- cycloaddition with benzene derivatives can occur, viz. the addition, forming either cyclobutanes or four-membered hetero- [2 + 2] or ortho, the [3 + 2] or meta, and the [4 + 2] or para cycles (as in the Paternò–Büchi reaction), whilst excited-state photocycloaddition (Scheme 2). The descriptors ortho, meta [4 + 4] cycloadditions can also occur to afford cyclooctadiene and para only indicate the connectivity to the aromatic ring, and compounds. On the other hand, the well-known thermal [4 + 2] do not have any implication with regard to the reaction mecha- cycloaddition (Diels–Alder reaction) is only very rarely nism.
    [Show full text]
  • NEW TANDEM REACTIONS INVOLVING NUCLEOPHILIC AROMATIC SUBSTITUTION by JAMES ERVIN SCHAMMERHORN III Associates of Science Murray
    NEW TANDEM REACTIONS INVOLVING NUCLEOPHILIC AROMATIC SUBSTITUTION By JAMES ERVIN SCHAMMERHORN III Associates of Science Murray State College Tishomingo, Oklahoma 2003 Bachelor of Science in Chemistry Oklahoma State University Stillwater, Oklahoma 2006 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY May, 2011 1 NEW TANDEM REACTIONS INVOLVING NUCLEOPHILIC ARMOMATIC SUBSTITUTION Thesis Approved: Dr. Richard Bunce Thesis Adviser Dr. K. Darrell Berlin Dr. Ziad El-Rassi Dr. Nicholas Materer Dr. Andrew Mort Dr. Mark E. Payton Dean of the Graduate College ii ACKNOWLEDGMENTS I would like to express my sincere gratitude to Dr. R. A. Bunce, my research advisor, my graduate committee chairman and my friend. I have learned many valuable lessons working alongside him in his research laboratory. His ability to teach both organic theory and laboratory techniques have been instrumental in my research at Oklahoma State University. I am immensely thankful for his support, guidance and patience to me during the course of this research. His unique sense of humor always makes me laugh and makes it a joy to come to lab. I would also like to thank my committee members, Drs. K. D. Berlin, Z. El Rassi, N. F. Materer, and A. J. Mort their acceptance to be on my committee. Their insights into research and graduate life have been invaluable during my graduate career. I am especially grateful to Dr. Berlin for sharing his wealth of organic chemistry knowledge with me during the course of my research. Also, to Dr.
    [Show full text]
  • Aromatic Compounds
    OCR Chemistry A Aromatic Compounds Aromatic Compounds Naming Aromatic compounds contain one or more benzene rings (while aliphatic compounds do not contain benzene rings). Another term for a compound containing a benzene ring is arene. The basic benzene ring, C6H6 is commonly represented as a hexagon with a ring inside. You should be aware that there is a hydrogen at each corner although this is not normally shown. N.B. it is OK to use benzene in this form in structural formulae too! Arenes occur naturally in many substances, and are present in coal and crude oil. Aspirin, for example, is an aromatic compound, an arene: HO O O CH 3 O Naming of substances based on benzene follows familiar rules: CH Br NO 3 2 benzene methylbenzene bromobenzene nitrobenzene Numbers are needed to identify the positions of substituents. The carbons around the ring are numbered from 1-6 consecutively and the name which gives the lowest number(s) is chosen: CH3 CH3 Cl Br Cl Br 2-bromomethylbenzene 4-bromomethylbenzene 1,2-dichlorobenzene Cl Cl Cl 1,3,5-trichlorobenzene Page 1 OCR Chemistry A Aromatic Compounds Determining the structure of benzene (historical) 1825 – substance first isolated by Michael Faraday, who also determined its empirical formula as CH 1834 – RFM of 78 and molecular formula of C6H6 determined H H H C C C Much speculation over the structure. Many suggested structures like: C C C H H H 1865 – Kekulé publishes suggestion of a ring with alternating double and single bonds: H H C H C C displayed C C skeletal H C H H This model persisted until 1922, but not all chemists accepted the structure because it failed to explain the chemical and physical properties of benzene fully: if C=C bonds were present as Kekulé proposed, then benzene would react like alkenes.
    [Show full text]