DOCSLIB.ORG

The Chemistry of Alkynes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Chemistry of Alkynes 14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 644 14 14 The Chemistry of Alkynes An alkyne is a hydrocarbon containing a carbon–carbon triple bond; the simplest member of this family is acetylene, H C'C H. The chemistry of the carbon–carbon triple bond is similar in many respects toL that ofL the carbon–carbon double bond; indeed, alkynes and alkenes undergo many of the same addition reactions. Alkynes also have some unique chem- istry, most of it associated with the bond between hydrogen and the triply bonded carbon, the 'C H bond. L 14.1 NOMENCLATURE OF ALKYNES In common nomenclature, simple alkynes are named as derivatives of the parent compound acetylene: H3CCC' H L L methylacetylene H3CCC' CH3 dimethylacetyleneL L CH3CH2 CC' CH3 ethylmethylacetyleneL L Certain compounds are named as derivatives of the propargyl group, HC'C CH2 , in the common system. The propargyl group is the triple-bond analog of the allyl group.L L HC' C CH2 Cl H2CA CH CH2 Cl L L LL propargyl chloride allyl chloride 644 14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 645 14.1 NOMENCLATURE OF ALKYNES 645 We might expect the substitutive nomenclature of alkynes to be much like that of alkenes, and it is. The suffix ane in the name of the corresponding alkane is replaced by the suffix yne, and the triple bond is given the lowest possible number. H3CCC' H CH3CH2CH2CH2 CC' CH3 H3C CH2 C ' CH L L L L L L L propyne 2-heptyne 1-butyne H3C CH C ' C CH3 HC' C CH2 CH2 C' C CH3 L L L L 1,5-heptadiyneLL L "CH3 4-methyl-2-pentyne Substituent groups that contain a triple bond (called alkynyl groups) are named by replac- ing the final e in the name of the corresponding alkyne with the suffix yl. (This is exactly anal- ogous to the nomenclature of substituent groups containing double bonds; see Sec. 4.2A.) The alkynyl group is numbered from its point of attachment to the main chain: HC' C HC' C CH2 L LL ethynyl group 2-propynyl group (ethyne yl) + OH 1 " 2 ` 12 3 CH C ' CH $ 2 3-(2-propynyl)cyclohexanol position of triple bond within the substituent position of the 2-propynyl group on the ring As with alkenes, groups that can be cited as principal groups, such as the OH group in the following example (as well as in the previous one), are given numerical precedenceL over the triple bond. (See Appendix I for a summary of nomenclature rules.) OH HC' C CH2 "CH CH3 5 43L L 2L 1 4-pentyn-2-ol OH group receives numerical priority When a molecule contains both double and triple bonds, the bond that has the lower num- ber at first point of difference receives numerical precedence. However, if this rule is ambigu- ous, a double bond receives numerical precedence over a triple bond. 14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 646 646 CHAPTER 14 • THE CHEMISTRY OF ALKYNES 123 45 54 3 2 1 12345 HC C CH CHCH3 CH3CC CH CH2 H2C CHCH2C CH 1-pentyn-3-ene 1-penten-3-yne 1-penten-4-yne precedence is given to the bond that has precedence is given to the double bond lower number at first point of difference when numbering is ambiguous PROBLEMS 14.1 Draw a Lewis structure for each of the following alkynes. (a) isopropylacetylene (b) cyclononyne (c) 4-methyl-1-pentyne (d) 1-ethynylcyclohexanol (e) 2-butoxy-3-heptyne (f) 1,3-hexadiyne 14.2 Provide the substitutive name for each of the following compounds. Also provide common names for (a) and (b). (a) CH3CH2CH2CH2C'CH (b) CH3CH2CH2CH2C'CCH2CH2CH2CH3 (c) OH (d) HC ' CCHCH2CH2CH3 H3CC"C C ' CH3 H2C H LL L "CH3 CC H CH2OCH3 (e) OH HC C CH CH CH2 14.2 STRUCTURE AND BONDING IN ALKYNES Because each carbon of acetylene is connected to two groups—a hydrogen and another car- bon—the H C'C bond angle in acetylene is 180 (Sec. 1.3B); thus, the acetylene molecule is linear. L ° 1.20 Å HHCC'' LL 180° 1.06 Å The C'C bond, with a bond length of 1.20 Å, is shorter than the CAC and C C bonds, which have bond lengths of 1.33 Å and 1.54 Å, respectively. L Because of the 180 bond angles at the carbon–carbon triple bond, cis–trans isomerism cannot occur in alkynes.° Thus, although 2-butene exists as cis and trans stereoisomers, 2-bu- tyne does not. Another consequence of this linear geometry is that cycloalkynes smaller than cyclooctyne cannot be isolated under ordinary conditions (see Problem 14.3). The hybrid orbital model for bonding provides a useful description of bonding in alkynes. We learned in Secs. 1.9B and 4.1A that carbon hybridization and geometry are correlated: tetrahedral carbon is sp3-hybridized, and trigonal planar carbon is sp2-hybridized. The linear geometry found in alkynes is characterized by a third type of carbon hybridization, called sp hybridization. Imagine that the 2s orbital and one 2p orbital (say, the 2px orbital) on carbon mix to form two new hybrid orbitals. Because these two new orbitals are each one part s and one part p, they are called sp hybrid orbitals. Two of the 2p orbitals (2py and 2pz) are not in- cluded in the hybridization..
Load more

Recommended publications
  • 14.8 Organic Synthesis Using Alkynes
    14_BRCLoudon_pgs4-2.qxd 11/26/08 9:04 AM Page 666 666 CHAPTER 14 • THE CHEMISTRY OF ALKYNES The reaction of acetylenic anions with alkyl halides or sulfonates is important because it is another method of carbon–carbon bond formation. Let’s review the methods covered so far: 1. cyclopropane formation by the addition of carbenes to alkenes (Sec. 9.8) 2. reaction of Grignard reagents with ethylene oxide and lithium organocuprate reagents with epoxides (Sec. 11.4C) 3. reaction of acetylenic anions with alkyl halides or sulfonates (this section) PROBLEMS 14.18 Give the structures of the products in each of the following reactions. (a) ' _ CH3CC Na| CH3CH2 I 3 + L (b) ' _ butyl tosylate Ph C C Na| + L 3 H3O| (c) CH3C' C MgBr ethylene oxide (d) L '+ Br(CH2)5Br HC C_ Na|(excess) + 3 14.19 Explain why graduate student Choke Fumely, in attempting to synthesize 4,4-dimethyl-2- pentyne using the reaction of H3C C'C_ Na| with tert-butyl bromide, obtained none of the desired product. L 3 14.20 Propose a synthesis of 4,4-dimethyl-2-pentyne (the compound in Problem 14.19) from an alkyl halide and an alkyne. 14.21 Outline two different preparations of 2-pentyne that involve an alkyne and an alkyl halide. 14.22 Propose another pair of reactants that could be used to prepare 2-heptyne (the product in Eq. 14.28). 14.8 ORGANIC SYNTHESIS USING ALKYNES Let’s tie together what we’ve learned about alkyne reactions and organic synthesis. The solu- tion to Study Problem 14.2 requires all of the fundamental operations of organic synthesis: the formation of carbon–carbon bonds, the transformation of functional groups, and the establish- ment of stereochemistry (Sec.
    [Show full text]
  • “Alkenyl Nonaflates from Carbonyl Compounds: New Synthesis, Elimination Reactions, and Systematic Study of Heck and Sonogashira Cross-Couplings”
    “Alkenyl nonaflates from carbonyl compounds: New synthesis, elimination reactions, and systematic study of Heck and Sonogashira cross-couplings” A thesis submitted to the Freie Universität Berlin for the degree of Dr. rer. nat. Faculty of Chemistry and Biochemistry 2009 Michael Alexander Kolja Vogel Department of Biology, Chemistry and Pharmacy FU Berlin 1. Gutachter: Prof. Dr. C. B. W. Stark 2. Gutachter: Prof. Dr. H.-U. Reißig Promotionsdatum: 19.06.2009 Contents Contents Contents 3 Abbreviations 7 Declaration and Copyright Statement 9 The Author 12 Acknowledgements 13 Abstract / Zusammenfassung 14 Introduction and Objective 16 Chapter 1 Alkenyl nonaflates from enolizable carbonyl precursors – 25 methodology, preparation, and elimination reactions 1.1. Purification of NfF and compatibility experiments with bases 26 1.2. Application of the internal quenching protocol for the 30 preparation of cyclic alkenyl nonaflates 1.3. Reactions of acyclic ketones with NfF and phosphazene bases 36 1.3.1 General remarks 36 1.3.2. Synthesis of alkynes: reactivity and selectivity 38 1.4. The formation of allenes 45 1.5. Conversion of aldehydes with NfF and phosphazene bases 50 1.5.1. Alkenyl nonaflate formation 50 1.5.2. Formation of terminal alkynes 52 1.6. Conclusions 54 Chapter 2 The alkenyl nonaflates in the Heck reaction – 56 methodology and reactivity 3 Contents 2.1. General remarks 57 2.2. Methodology and initial experiments 59 2.3. Systematic investigations 61 2.3.1. The solvent effect 61 2.3.2. The effect of different bases 65 2.3.3. The effect of additives 66 2.3.4. The effect of triphenylphosphine 71 2.3.5.
    [Show full text]
  • Fundamental Studies of Early Transition Metal-Ligand Multiple Bonds: Structure, Electronics, and Catalysis
    Fundamental Studies of Early Transition Metal-Ligand Multiple Bonds: Structure, Electronics, and Catalysis Thesis by Ian Albert Tonks In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2012 Defended December 6th 2011 ii 2012 Ian A Tonks All Rights Reserved iii ACKNOWLEDGEMENTS I am extremely fortunate to have been surrounded by enthusiastic, dedicated, and caring mentors, colleagues, and friends throughout my academic career. A Ph.D. thesis is by no means a singular achievement; I wish to extend my wholehearted thanks to everyone who has made this journey possible. First and foremost, I must thank my Ph.D. advisor, Prof. John Bercaw. I think more so than anything else, I respect John for his character, sense of fairness, and integrity. I also benefitted greatly from John’s laissez-faire approach to guiding our research group; I’ve always learned best when left alone to screw things up, although John also has an uncanny ability for sensing when I need direction or for something to work properly on the high-vac line. John also introduced me to hiking and climbing in the Eastern Sierras and Owens Valley, which remain amongst my favorite places on Earth. Thanks for always being willing to go to the Pizza Factory in Lone Pine before and after all the group hikes! While I never worked on any of the BP projects that were spearheaded by our co-PI Dr. Jay Labinger, I must also thank Jay for coming to all of my group meetings, teaching me an incredible amount while I was TAing Ch154, and for always being willing to talk chemistry and answer tough questions.
    [Show full text]
  • Chapter 8 - Alkynes: an Introduction to Organic Synthesis
    Chapter 8 - Alkynes: An Introduction to Organic Synthesis Draw structures corresponding to each of the following names. 1. ethynylcyclopropane Answer: CCH 2. 3,10-dimethyl-6-sec-butylcyclodecyne Answer: 3. 4-bromo-3,3-dimethyl-1-hexen-5-yne CH3 Br Answer: H 2C CH C CH C C H CH3 4. acetylene Answer: H CCH Provide names for each compound below. CH3 5. CH3C CCHCH2CH2CH3 Answer: 4-methyl-2-heptyne CH 3 6. CCH Answer: 1-ethynyl-2-methylcyclopentane Test Items for McMurry’s Organic Chemistry, Seventh Edition 59 The compound below has been isolated from the safflower plant. Consider its structure to answer the following questions. H H CCCCCCCC H H3C C C C H H C H H 7. What is the molecular formula for this natural product? Answer: C13H10 8. What is the degree of unsaturation for this compound? Answer: We can arrive at the degree of unsaturation for a structure in two ways. Since we know that the degree of unsaturation is the number of rings and/or multiple bonds in a compound, we can simply count them. There are three double bonds (3 degrees) and three triple bonds (six degrees), so the degree of unsaturation is 9. We can verify this by using the molecular formula, C13H10, to calculate a degree of unsaturation. The saturated 13-carbon compound should have the base formula C13H28, so (28 - 10) ÷ 2 = 18 ÷ 2 = 9. 9. Assign E or Z configuration to each of the double bonds in the compound. Answer: H H E CCCCCCCCE H H3C C C C H H C H H 10.
    [Show full text]
  • Chemical Bonding Valence Electrons Are the Outer Shell Electrons of an Atom
    Chapter 8 Chemical Bonding Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that participate in chemical bonding. Group e- configuration # of valence e- 1 ns1 1 2 ns2 2 13 ns2np1 3 14 ns2np2 4 15 ns2np3 5 16 ns2np4 6 17 ns2np5 7 Lewis Dot Symbols for the Representative Elements & Noble Gases Lewis dot symbol consists of the symbol of the element and one dot for each valence electron in an atom of each element The Ionic Bond Ionic bond = the electrostatic force that holds ions Li + F Li+ F - together in an 2 1 2 2 5 [He]2[Ne]2 2 6 ionic compound 1s 2s1s 2s 2p 1s1s 2s 2p Li Li+ + e- e- + F F - Lithium fluoride, LiF Li+ + F - Li+ F - Ionic Bonds 3Mg (s) + N2 (g) → Mg3N2 (s) .. .. 2 3 3 Mg2 N 3Mg 2: N : (Mg3N2 ) . .. Electrostatic (Lattice) Energy Lattice energy (E) is the energy required to completely separate one mole of a solid ionic compound into gaseous ions. Coulomb’s Law: the potential energy between 2 ions is directly proportional to the product of their charges and inversely proportional to the distance of separation between them Q+ is the charge on the cation Q Q E = k + - Q is the charge on the anion r - r is the distance between the ions cmpd lattice energy MgF2 2957 Q= +2,-1 Lattice energy (E) increases MgO 3938 Q= +2,-2 as Q increases and/or as r decreases. LiF 1036 r F- < r Cl- LiCl 853 Born-Haber Cycle for Determining Lattice Energy The Born-Haber cycle relates lattice energies of ionic compounds to ionization energies, electron affinities, and other atomic & molecular properties o o o o o o DHoverall = DH1 + DH2 + DH3 + DH4 + DH5 Born-Haber cycle for lithium fluoride 1.
    [Show full text]
  • Basic Concepts of Chemical Bonding
    Basic Concepts of Chemical Bonding Cover 8.1 to 8.7 EXCEPT 1. Omit Energetics of Ionic Bond Formation Omit Born-Haber Cycle 2. Omit Dipole Moments ELEMENTS & COMPOUNDS • Why do elements react to form compounds ? • What are the forces that hold atoms together in molecules ? and ions in ionic compounds ? Electron configuration predict reactivity Element Electron configurations Mg (12e) 1S 2 2S 2 2P 6 3S 2 Reactive Mg 2+ (10e) [Ne] Stable Cl(17e) 1S 2 2S 2 2P 6 3S 2 3P 5 Reactive Cl - (18e) [Ar] Stable CHEMICAL BONDSBONDS attractive force holding atoms together Single Bond : involves an electron pair e.g. H 2 Double Bond : involves two electron pairs e.g. O 2 Triple Bond : involves three electron pairs e.g. N 2 TYPES OF CHEMICAL BONDSBONDS Ionic Polar Covalent Two Extremes Covalent The Two Extremes IONIC BOND results from the transfer of electrons from a metal to a nonmetal. COVALENT BOND results from the sharing of electrons between the atoms. Usually found between nonmetals. The POLAR COVALENT bond is In-between • the IONIC BOND [ transfer of electrons ] and • the COVALENT BOND [ shared electrons] The pair of electrons in a polar covalent bond are not shared equally . DISCRIPTION OF ELECTRONS 1. How Many Electrons ? 2. Electron Configuration 3. Orbital Diagram 4. Quantum Numbers 5. LEWISLEWIS SYMBOLSSYMBOLS LEWISLEWIS SYMBOLSSYMBOLS 1. Electrons are represented as DOTS 2. Only VALENCE electrons are used Atomic Hydrogen is H • Atomic Lithium is Li • Atomic Sodium is Na • All of Group 1 has only one dot The Octet Rule Atoms gain, lose, or share electrons until they are surrounded by 8 valence electrons (s2 p6 ) All noble gases [EXCEPT HE] have s2 p6 configuration.
    [Show full text]
  • Early- Versus Late-Transition-Metal-Oxo Bonds: the Electronlc Structure of VO' and Ruo'
    J. Phys. Chem. 1988, 92, 2109-2115 2109 Early- versus Late-Transition-Metal-Oxo Bonds: The Electronlc Structure of VO' and RuO' Emily A. Cartert and William A. Goddard III* Arthur Amos Noyes Laboratory of Chemical Physics,$ California Institute of Technology, Pasadena, California 91125 (Received: July 9, 1987; In Final Form: November 3, 1987) From all-electron ab initio generalized valence bond calculations (GVBCI-SCF) on VO+ and RuO', we find that an accurate description of the bonding is obtained only when important resonance configurations are included self-consistently in the wave function. The ground state of VO+('Z-) has a triple bond similar to that of CO, with D,""(V-O) = 128.3 kcal/mol [DFptl(V-O) = 1.31 * 5 kcal/mol], while the ground state of RuO+(~A)has a double bond similar to that of Oz, with D,CS'cd(Ru-O) = 67.1 kcal/mol. Vertical excitation energies for a number of low-lying electronic states of VO+ and RuO' are also reported. These results indicate fundamental differences in the nature of the metal-oxo bond in early and late metal oxo complexes that explain the observed trends in reactivity (e.g., early metal oxides are thermodynamically stable whereas late metal oxo complexes are highly reactive oxidants). Finally, we have used these results to predict the ground states of MO' for other first-row transition-metal oxides. I. Introduction TABLE I: First-Row Transition-Metal-Oxo Bond Strengths While the electronic structure of neutral transition-metal oxides (kcal/mol)' has been examined by several authors,' the only cationic tran- metal Do(M+-O) Do(M-0) metal Do(M+-O) Do(M-0) sition-metal oxide (TMO) which has been studied with correlated 3 Mn 3 wave functions is2 CrO+.
    [Show full text]
  • The Molecular Level Modification of Surfaces: from Self-Assembled Monolayers to Complex Molecular Assemblies
    University of Wollongong Research Online Australian Institute for Innovative Materials - Papers Australian Institute for Innovative Materials 1-1-2011 The molecular level modification of surfaces: From self-assembled monolayers to complex molecular assemblies J Justin Gooding University of New South Wales, [email protected] Simone Ciampi University of New South Wales, [email protected] Follow this and additional works at: https://ro.uow.edu.au/aiimpapers Part of the Engineering Commons, and the Physical Sciences and Mathematics Commons Recommended Citation Gooding, J Justin and Ciampi, Simone, "The molecular level modification of surfaces: From self- assembled monolayers to complex molecular assemblies" (2011). Australian Institute for Innovative Materials - Papers. 1853. https://ro.uow.edu.au/aiimpapers/1853 Research Online is the open access institutional repository for the University of Wollongong. For further information contact the UOW Library: [email protected] The molecular level modification of surfaces: From self-assembled monolayers to complex molecular assemblies Abstract The modification of surfaces with self-assembled monolayers (SAMs) containing multiple different molecules, or containing molecules with multiple different functional components, or both, has become increasingly popular over the last two decades. This explosion of interest is primarily related to the ability to control the modification of interfaces with something approaching molecular level control and to the ability to characterise the molecular constructs by which the surface is modified. Over this time the level of sophistication of molecular constructs, and the level of knowledge related to how to fabricate molecular constructs on surfaces have advanced enormously. This critical review aims to guide researchers interested in modifying surfaces with a high degree of control to the use of organic layers.
    [Show full text]
  • Arxiv:1406.7034V1 [Astro-Ph.SR] 26 Jun 2014 Abn PH)Aecmol Noe Stercarrier
    Draft version July 13, 2018 A Preprint typeset using LTEX style emulateapj v. 5/2/11 CARBON-RICH DUST PAST THE ASYMPTOTIC GIANT BRANCH: ALIPHATICS, AROMATICS, AND FULLERENES IN THE MAGELLANIC CLOUDS G. C. Sloan1, E. Lagadec1, A. A. Zijlstra2, K. E. Kraemer3, A. P. Weis4,5, M. Matsuura6, K. Volk7, E. Peeters8,9, W. W. Duley10, J. Cami8,9, J. Bernard-Salas11, F. Kemper12, & R. Sahai13 Draft version July 13, 2018 ABSTRACT Infrared spectra of carbon-rich objects which have evolved off the asymptotic giant branch reveal a range of dust properties, including fullerenes, polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons, and several unidentified features, including the 21 µm emission feature. To test for the presence of fullerenes, we used the position and width of the feature at 18.7–18.9 µm and examined other features at 17.4 and 6–9 µm. This method adds three new fullerene sources to the known sample, but it also calls into question three previous identifications. We confirm that the strong 11 µm features seen in some sources arise primarily from SiC, which may exist as a coating around carbonaceous cores and result from photo-processing. Spectra showing the 21 µm feature usually show the newly defined Class D PAH profile at 7–9 µm. These spectra exhibit unusual PAH profiles at 11–14 µm, with weak contributions at 12.7 µm, which we define as Class D1, or show features shifted to ∼11.4, 12.4, and 13.2 µm, which we define as Class D2. Alkyne hydrocarbons match the 15.8 µm feature associated with 21 µm emission.
    [Show full text]
  • Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc
    Metal-Metal (MM) Bond Distances and Bond Orders in Binuclear Metal Complexes of the First Row Transition Metals Titanium Through Zinc Richard H. Duncan Lyngdoh*,a, Henry F. Schaefer III*,b and R. Bruce King*,b a Department of Chemistry, North-Eastern Hill University, Shillong 793022, India B Centre for Computational Quantum Chemistry, University of Georgia, Athens GA 30602 ABSTRACT: This survey of metal-metal (MM) bond distances in binuclear complexes of the first row 3d-block elements reviews experimental and computational research on a wide range of such systems. The metals surveyed are titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, and zinc, representing the only comprehensive presentation of such results to date. Factors impacting MM bond lengths that are discussed here include (a) n+ the formal MM bond order, (b) size of the metal ion present in the bimetallic core (M2) , (c) the metal oxidation state, (d) effects of ligand basicity, coordination mode and number, and (e) steric effects of bulky ligands. Correlations between experimental and computational findings are examined wherever possible, often yielding good agreement for MM bond lengths. The formal bond order provides a key basis for assessing experimental and computationally derived MM bond lengths. The effects of change in the metal upon MM bond length ranges in binuclear complexes suggest trends for single, double, triple, and quadruple MM bonds which are related to the available information on metal atomic radii. It emerges that while specific factors for a limited range of complexes are found to have their expected impact in many cases, the assessment of the net effect of these factors is challenging.
    [Show full text]
  • Chemical Reviews
    Chemical Reviews Volume 84, Number 5 October 1984 Three-Carbon Homologating Agents JOHN C. STOWELL aaperhrsnf of chemlsbj'. ulhraslly 01 Flsw (Maam, Lake Fmt, New mns,LOUL&M 70148 Rscslvad NoVembsr 7, 1983 (Uevk4 MamcrW Receivad Juw, 27. 19W contents I. Introduction 409 11. Nucleophilic Reagents 410 A. Reagents Providing Functknal Chains wlth 410 Saturated a-. 8-. and y-Carbons 1. Ethers and Alcohols 410 2. Amines 41 1 3. Bromldes 41 1 4. Propionaldehyde Homoenolate 413 Equivalents 5. Propionate Homenolate Equivalents 419 E. Reagents Rovidlng the Terminal Acetylene 421 Function C. Reagents Rovldlng a.@-Unsatuated 422 Functionality 1. Allylic Alcohols and Halides 422 2. a,@-UnsaturatedAldehydes 422 3. a,@-UnsaturatedCarboxylic Aclds. 424 John C. Stowel was bom in Passaic. NJ. in 1938. and received Esters, and Lactones hls B.S. degee h chemlsby from Rutgers UnivmW in 1960. Hls D. Reagents Providing a.@-Acetylenk 425 W.D. wee in Qganlc chemistry was granted by Massachusetts Functionality Insmule of Tedrmqly h 1964 where he waked WMDr. Frm 1. a.@-Acatylenk Alcohols 425 D. Greene on freeradical termination reactions and prepared the first diaziridinone. He pined the Central Research division of 3M 2. a,@-AcetylenicAldehydes 426 Company in St. Paul. MN. for 4 years. In 1969 he became a 3. a,@-Acetylenic Carboxylic Aclds and 426 postdoctoral fellow at The Ohio State University with Dr. Leo A. Esters Paquette. He prepared and sWIW various (CH),, and benzo (CH),, E. Reagents providing B.yUnsahmted 426 cwnpounds including Umrmal and sihw-catalyred rearrangements. Functionality In 1970 he jokd the faculty of me University of New Ohms.
    [Show full text]
  • Variation of Aromaticity by Twisting Or Expanding the Ring Content*
    Pure Appl. Chem., Vol. 82, No. 4, pp. 769–800, 2010. doi:10.1351/PAC-CON-09-11-07 © 2010 IUPAC, Publication date (Web): 26 March 2010 Variation of aromaticity by twisting or expanding the ring content* Remi Chauvin‡, Christine Lepetit, Valérie Maraval, and Léo Leroyer Laboratory of Coordination Chemistry (LCC), CNRS, 205, Route de Narbonne, F-31077 Toulouse, France; Université de Toulouse; UPS, INPT; LCC; F-31077 Toulouse, France Abstract: Generalization of the Hückel rule predicts that the (anti)aromaticity of a neutral ring is qualitatively reverted upon a single twist of the π-orbital array (Möbius interconver- sion), and is preserved upon expansion of all the bonds by single C2 units (ring carbo-mer- ization). These opposite effects are addressed from quantitative theoretical and experimental standpoints, respectively. (i) According to most resonance energy (RE) schemes, the RE value of a Möbius ring is not the opposite of that of the Hückel version. This also applies to the Aihara’s and Trinajstic’s topological resonance energy (TRE), where a non-aromatic ref- erence in the topological limit is defined as being “as identical as possible” to the parent ring but just “acyclic”. In spite of its conceptual merits, the computing complexity and fictitious character of the TRE acyclic reference resulted in a disuse of TRE as a current energetic aro- maticity index. Both the calculation and interpretation of TRE have been revisited in light of a cross-reference between the Hückel and Möbius rings within the Hückel molecular orbital (HMO) framework. Whereas the topological influence of triple bonds is currently neglected in the first-level HMO treatment of π-conjugated systems, a graph-theoretical analysis allows one to differentiate the TRE value of a [3n]annulene from those of the corresponding carbo- [n]annulene.
    [Show full text]