1871-52-9Relevant academic research and scientific papers
Electronic and Molecular Structure of the C8H10+. Valence Isomers 1,3,5-Cyclooctatriene+. and Bicycloocta-2,4-diene+. from their Electronic Absorption Spectra in Freon Glasses
Bally, Thomas,Roth, Kuno,Straub, Rolf
, p. 73 - 82 (1989)
The molecular cations of 1,3,5-cyclooctatriene (COT+.) and bicycloocta-2,4-diene (BCO+.) can be observed intact in γ-irradiated Freon glasses, as opposed to Ar matrices where ionization is accompanied by extensive rearrangements.This proves the superiority of the Freon-glass method for the generation of metastable primary cations.The electronic absorption (EA) spectra reveal a that a previous analysis of the BCO+. electronic structure on the basis of the ultraviolet photoelectron (UP) spectrum of BCO was incomplete, and b that COT undergoes planarization upon ionization, in accord with qualitative expectations and MNDO calculations.A previously proposed LCBO model was used to assess the influence of the above geometry change on the electronic structure of COT+..
Heats fo Formation of Solvated Annulene and Substituted Azaannulene Dianions
Stevenson, Gerald R.,Schock, Laurel E.,Reiter, Richard C.
, p. 5417 - 5419 (1984)
It was found that the heat of solution of the potassium salt of the cyclooctatetraene (COT) dianion in tetrahydrofuran (-11.1 kcal/mol) measured calorimetrically is very different from the heat of solution determined from solubility data.This is attributed to the existence of a partially solvated solid salt (K+2COT2-*nTHF), which is the form of the COT dianion lowest in energy yet generated.This stable form of the annulene dianion is lower in energy by 393.5 kcal/mol than the gas-phase dianion with two potassium cations.Both solvation and lattice effects are rsponsible for this tremendous stabilization.Substitution of a nitrogen atom for one of the carbon atoms in the eight-member ring system results in an increase in the energy of the THF solvated dianion relative to the metal and neutral organic compound due to an increase in the electron-electron repulsion energy in the dianion.
Fragmentation Patterns in the Gas-Phase Pyrolysis of Some Bi- and Tri-cyclic Sulfolanes Related to the 8-Thiabicyclonon-3-ene 8,8-Dioxide Ring System
Aitken, R. Alan,Cadogen, J. I. G.,Gosney, Ian,Newlands, Stephen
, p. 2301 - 2308 (2007/10/02)
Depending upon the degree of ring strain, the thermal breakdown of cis-8-thiabicyclonon-3-ene 8,8-dioxide 5 and related ring systems in the gas phase follows widely differing pathways.Decomposition of 5 occurs only under forcing conditions, resulting in complete fragmentation of the sulfolane ring to give a benzene and toluene, while pyrolysis of the 2,5-bridged analogues 6-8 proceeds by a retro-Diels-Alder reaction at much lower temperatures to give 1,3-dienes and the decomposition products of 3-sulfolene, buta-1,3-diene and SO2.Epoxidation of the double bond in the compounds results in a marked change in their thermal fragmentation behaviour; only SO2 is lost to produce novel divinyl epoxides.The corresponding N-ethoxycarbonylaziridines, formed by photolysis of the unsaturated sulfones in ethyl azidoformate, undergo extensive decomposition on pyrolysis and do not yield any useful products.The saturated sulfone 28 gives an expected octa-1,7-diene upon flash vacuum pyrolysis (FVP), but only under relatively severe conditions.Three isomeric diene sulfones 30-32 have also been examined and show a varied pattern of reactivity under FVP conditions.
9-Oxabicyclononynes
Mayer, Winfried,Meier, Herbert
, p. 509 - 518 (2007/10/02)
Semiempirical quantum mechanics (MNDO) and force field calculations (MM 2) reveal that two diastereomeric conformations a and b of low energy exist for each of the three isomeric cis-9-oxabicyclononynes 1 - 3.Synthetically, the highly strained comp
STRAINED CYCLOALKENYNES
Meier, Herbert,Hanold, Norbert,Molz, Thomas,Bissinger, Hans Joachim,Kolshorn, Heinz,Zountsas, Johannes
, p. 1711 - 1720 (2007/10/02)
Presently known strained cycloalkynes with one, two or three additional cis- or trans-configurated double bonds are summarized in Table 3.The main topics of the article are the geometrical ring strain, the preparation or in situ generation of these compounds by fragmentation of the corresponding 1,2,3-selendiazoles, and the thermal isomerisation processes performed at room temperature or in flash pyrolysis experiments at 440-640 deg C.
Cycloaddition of Singlet Oxygen and 4-Phenyl-4H-1,2,4-triazole-3,5-dione to 7-Substituted 1,3,5-Cyclooctatrienes
Adam, Waldemar,Gretzke, Nanette,Hasemann, Ludwig,Klug, Guenter,Peters, Eva-Maria,et al.
, p. 3357 - 3379 (2007/10/02)
The cycloaddition of the 7-substituted (X; Y) 1,3,5-cyclooctatrienes 3 (N3; H), 4 (OAc; H), 5 (OEt; OEt), 6 (Me; H), and 7 (iPr; H) with singlet oxygen (1O2) and 4-phenyl-4H-1,2,4-triazole-3,5-dione (PTAD) was investigated.Singlet oxygen gave w
The Symmetrical Cyclooctadienynes: 1,5-Cyclooctadien-3-yne and 1,3-Cyclooctadien-6-yne
Echter, Toni,Meier, Herbert
, p. 182 - 197 (2007/10/02)
Starting with 1,5-cycloctadiene (1) and cyclooctatetraene (2), respectively, the title compounds 16 and 17, highly strained members of the C8H8-series, can be generated in six or seven steps and isolated in pure state.Their stability and their chemical behaviour is discussed.Di- and oligomerisations on the one hand and Diels-Alder reactions on the other are mainly concerned. 16 and 17 are very reactive dienophiles; moreover 17 can also be used as a diene.
The Reductive Decyclizations of Semibullvalene
Goldstein, Melvin J.,Wenzel, Timothy T.
, p. 1654 - 1655 (2007/10/02)
Reduction of semibullvalene (5) with potassium more closely resembles deprotonation of tetrahydropentalenes by n-butyl-lithium-potassium t-pentoxide than it does the reduction of (5) with lithium; the former processes both provide the cyclo-octatetraenyl dianion (4), plausibly via the intermediate bicyclooctadienediyl dianion (3).
An Azocine Anion Radical and Heats of Formation of Azocine Dianions
Stevenson, Gerald R.,Schock, Laurel E.,Reiter, Richard C.,Hansen, John F.
, p. 6078 - 6082 (2007/10/02)
3,8-Dimethyl-2-methoxyazocine was reduced to its anion radical in hexamethylphosphoramide (HMPA).The ESR spectrum of the DMMA anion radical resembles one recorded from a monosubstituted cyclooctatetraene anion radical where the substituent is an electron-withdrawing group.Calorimetric techniques were utilized to study the thermodynamic stability of the DMMA dianion.This dianion is more stable relative to the metal and neutral molecule than is either the cycloocatetraene (COT) or tert-butoxycycloocatetraene dianion.The unexpected stability of DMMA2- is attributed to strong interactions between the cation (Na+) with the oxygen and/or nitrogen atoms.This same interaction shifts the disproportionation of DMMA-. to the right in solvents where ion association is prevalent.
The Metallation-Elimination Reaction, II. Monocyclic Anions and Polyanions
Wilhelm, Dieter,Clark, Timothy,Friedl, Thomas,Schleyer, Paul von Rague
, p. 751 - 760 (2007/10/02)
Equimolar mixtures of n-butyllithium and potassium tert-amyloxide effect metallation and metal hydride elimination of cyclic olefins directly to give conjugated anions and polyanions in a single operation. 1-Methyl-1-cycloalkenes or methylenecycloalkanes are particularly well suited and give highly unsaturated products.Odd-membered rings eliminate better than their even-membered counterparts, and eight-membered rings eliminate particularly slowly.Reactions with methyl iodide and trimethylsilyl chloride proceed smoothly in high yield.
