Showing papers on "Cyclopropane published in 1983"
TL;DR: In this article, a 500 W Oriel focused-beam mercury lamp was used to generate hydrido alkyl iridium complexes (HRIr) in saturated hydrocarbons.
Abstract: Irradiation of (eta/sup 5/-pentamethylcyclopenta-dienyl)(trimethyl phosphine) dehydroiridium (eta/sup 5/-C/sub 5/Me/sub 5/)(PMe/sub 3/)IrH/sub 2/ in saturated hydrocarbons using a 500 W Oriel focused-beam mercury lamp leads to extrusion of hydrogen and production of the hydrido alkyl iridium complexes (----HRIr). Competition experiments were used to measure relative rates at which the intermediate formed on hydrogen loss reacts with different types of C-H bonds. Relative to cyclohexane (1), these rates are: benzene (4), cyclopropane (2.65), cyclopentane (1.6), neopentane (1.14), cyclodecane (.23), and cyclooctane (.09). Reductive elimination of hydrocarbon occurs at elevated temperature, regenerating the intermediate, which may then react with another hydrocarbon acting as solvent. The factors which presumed to influence the rates of reaction of transition-metal complexes with saturated C-H bonds are discussed.
342 citations
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01 Jun 1983TL;DR: In this paper, an optically active cyclopropane was obtained from the reaction of diethyl fumarate with tetracarbonylchromium. But no free carbene was involved in the mechanism for the reaction.
Abstract: By using an optically active metal-carbene complex we were able to isolate an optically active cyclopropane from the reaction of diethyl fumarate with [(−) (R)-methylphenylpropylphosphine] (phenylmethoxycarbene) tetracarbonylchromium. In addition to being synthetically useful for the preparation of cyclopropanes of optical activity, this reaction demonstrates that no free carbene is involved in the mechanism for the reaction.
134 citations
TL;DR: In this article, photoelectron spectroscopy has proven an informative and valuable extension to other methods, since orbital interactions are involved in most intramolecular effects of this kind.
Abstract: Classical structural formulas often convey the impression only those relationships between the atoms are of importance which hold a molecule together as symbolized by the chemical bonds. However, many interactions between atoms or groups of atoms are not adequately denoted in this manner. Nevertheless, their existence can have important consequences for ground state energies (cis-difluoroethylene is more stable than trans-difluoroethylene), conformations (the syn form of methyl vinyl ether is more stable than the anti form), reactivities (an endo cyclopropane ring in 7-anti-norbornyl derivatives accelerates solvolysis by a factor of 1014), UV spectra (“superposition” of the π-systems of acridine and purine-bonded through a four-membered chain-results in hypochromism), CD spectra (the inherently symmetrical but dissymmetrically perturbed chromophore of 2-deuterionorbornadiene allows the observation of three transitions in the near UV), and ESR spectra (the long-range coupling with H-4 in the bridgehead bicyclo[2.1.1]hex-1-yl radical equals 22.5 G). Since orbital interactions are involved in most intramolecular effects of this kind, photoelectron spectroscopy has proven an informative and valuable extension to other methods.
130 citations
TL;DR: In this article, a molecular orbital theory has been used to study the ionization of methane, ethane, propane, n-butane, isobutane, cyclopropane and cyclobutanes.
Abstract: Ab initio molecular orbital theory has been used to study the ionization of methane, ethane, propane, n-butane, isobutane, cyclopropane and cyclobutane. For methane radical cation, the preferred structure has C20 symmetry and a pair of long C—H bonds, resembling a complex of CH+2 with H2. This appears to be the only significant minimum on the CH+4 surface. For the remaining acyclic systems, the calculated structures of lowest energy (e.g., CH3-CH2—CH+3, CH3-CH2—CH2-CH+3) are characterized by the extreme lengthening of a single C—C bond. However, alternative structures with two or more elongated C—C bonds have very low relative energies. The main structural conclusion for the alkane and cycloalkane radical cations is that the potential energy surface connecting various possible isomeric structures is generally very flat. Facile wide amplitude distortions and scrambling processes are therefore expected in these ions. The large structural changes which accompany ionization are manifested in large differences between vertical and adiabatic ionization potentials.
90 citations
TL;DR: This value represents a discontinuity in the positional dependence of the molecular order parameter for the sn-2 chain of PDSPC, indicating that the cyclopropane ring provides a rigid barrier separating the lipid bilayer into two regions: an ordered region from the bilayer surface to the site of the cycling ring and a much more disordered region thereafter to the center of the bilayers.
58 citations
TL;DR: γ-Stannyl tertiary alcohols and γ-stannyl benzyl alcohols form cyclopropanes stereospecifically on treatment with acid, with inversion of configuration at both carbon atoms as mentioned in this paper.
51 citations
TL;DR: Determination par une methode ab initio des constantes de force, frequences de vibration and conformation d'une serie de composes cycliques satures a 3 chainons as mentioned in this paper.
Abstract: Determination par une methode ab initio des constantes de force, frequences de vibration et conformation d'une serie de composes cycliques satures a 3 chainons
49 citations
40 citations
TL;DR: On etudie les reactions des ions Ni + avec l'oxiranne, le cyclopropane, l'ethylene and plusieurs hydrocarbures fluores en utilisant un appareil ionique as mentioned in this paper.
35 citations
35 citations
TL;DR: A series of radical cations have been generated from various cyclopropane derivatives by photoinitiated electron transfer to chloranil as discussed by the authors, and nuclear spin polarization effects observed during these reactions have been interpreted as evidence for the structure of these intermediates.
Abstract: A series of radical cations has been generated from various cyclopropane derivatives by photoinitiated electron transfer to chloranil. Nuclear spin polarization effects observed during these reactions have been interpreted as evidence for the structure of these intermediates. Tri- and tetraalkylsubstituted cyclopropanes (1, 3, 4) form "trimethylene" radical cations in which the most highly substituted carbon–carbon bond is broken (or weakened). The benzocyclopropanorbomene (12) forms a radical cation in which spin and charge are located in the benzenoid ring; the tertiary cyclopropane protons are coupled by a homohyperconjugative interaction; otherwise, the cyclopropane ring is unaffected. To the radical cation derived from bis-methanoparacyclophane (17) a trimethylene structure is assigned in which the benzylic carbons are pyramidal. Finally, benzonorcaradiene (20) forms a radical cation in which the two secondary–tertiary bonds are lengthened and in which the methylene group bears spin density.
TL;DR: The applicability of the u.v.n.i.r. transmission technique in surface studies has been explored using the sorption of propene, trans-butene and cyclopropane in activated zeolites CoNaY and HM as discussed by the authors.
Abstract: The applicability of the u.v.–vis.–n.i.r. transmission technique in surface studies has been explored using the sorption of propene, trans-butene and cyclopropane in activated zeolites CoNaY and HM. On CoNaY, after dehydration, near-tetrahedral Co2+ complexes remain, which are approached by the hydrocarbons without change of coordination number or symmetry. In HM at room temperature and in CoNaY at slightly elevated temperatures the appearance of new bands proves that allylic and dienylic carbenium ions are formed in an isomerization–oligomerization reaction. Mechanisms for the formation of these carbocations via Lewis or Bronsted acid sites are discussed.
TL;DR: In this paper, a 5-ring annulation sequence for 1-trimethylsilyl-cyclopropyl (1-Silyl)-1-phenyl-thiocyclopropane was proposed.
TL;DR: In this article, the authors employed the 4-31G basis set to evaluate the strain energies of gem-difluoro derivatives of cyclopropane and found that the increased strain energy of these molecules account for the relative ease of their thermal rearrangements.
TL;DR: In this article, the Flygare-Balle pulsed beam Fourier transform spectrometer was used to detect cyclopropane-HCN complex rotational transitions.
Abstract: Microwave rotational transitions for the cyclopropane‐HCN complex were observed using the Flygare–Balle pulsed beam Fourier transform spectrometer. The 111→212, 101→202, 110→211, 212→313, 202→303, 211→312, 313→414, 303→404, 312→413, 414→515, 404→505, and 413→514 transitions were observed. The rotational constants obtained are A=20 243±1344 MHz, B=1384.209±0.001 MHz, and C=1327.901±0.001 MHz. The distortion constants are DJ=1.53±0.03 kHz and DJK=50.9±1.1 kHz. The nitrogen quadrupole coupling strength is eQqaa=−4.38±0.01 MHz with eQqbb−eQqcc= 0.002±0.003 MHz. The cyclopropane carbon atoms and HCN lie in a plane. The most reasonable bond distance is obtained with the HCN hydrogen atom bonding to the midpoint between two of the cyclopropane carbon atoms. The separation of the centers of mass of HCN and cyclopropane is Rcm= 4.472±0.002 A. The HCN carbon atom is RCC–C=3.476±0.002 A from the cyclopropane carbon–carbon bond. The stretching force constant is ks=0.062 mdyn/A and the approximate bonding energy is 86...
TL;DR: Les radicaux cationiques de tri-and tetraalkyl cyclopropanes sont generes par transfert d'electron induit par la lumiere a partir du chloranile and du fluoranile as discussed by the authors.
Abstract: Les radicaux cationiques de tri- et tetraalkyl cyclopropanes sont generes par transfert d'electron induit par la lumiere a partir du chloranile et du fluoranile. Les effets CIDNP observes au cours de ces reactions sont compatibles avec les radicaux cationiques dans lesquels la liaison cyclopropane la plus substituee est coupee ou affaiblie
TL;DR: In this article, it was shown that cyclopropane cations exhibit a static distortion from D3h to C2v symmetry in a matrix at 4.2 K; the 3e′(D3h) highest occupied degenerate orbital splits into 6a1 and 3b1(C2v) orbitals, giving dominant spin densities on the two basal carbon atoms.
Abstract: E.s.r. evidence has been obtained that cyclopropane cations exhibit a static distortion from D3h to C2v symmetry in a matrix at 4.2 K; the 3e′(D3h) highest occupied degenerate orbital splits into 6a1 and 3b1(C2v) orbitals and the unpaired electron occupies 6a1, giving dominant spin densities on the two basal carbon atoms.
TL;DR: In this article, an intramolecular proton abstraction by the transient electron-rich enoxy double bond was proved for cyclopropane cleavage in tricyclo[3.3.0 2,8 ] octan-3-one (1a ) is increasingly directed towards the maximum bond overlap site in the following order of reagents.
TL;DR: Quinoxalines and 1,5-,1.6-, 1.7-and 1.8-naphthyridines react easily with N,N-dialkyl chloromethanesulfonamides in the presence of base to give tetracyclic bisaziridines and cyclopropae-aziridine derivatives as mentioned in this paper.
Patent•
08 Nov 1983TL;DR: Novel isomers and mixtures thereof of cyclopropane carboxylic acid derivatives with a 3-unsaturated side chain of the formula ##STR1## are known.
Abstract: Novel isomers and mixtures thereof of cyclopropane carboxylic acid derivatives with a 3-unsaturated side chain of the formula ##STR1## The double bond having Z or E geometry and having insecticidal and nematocidal activity as well as plant and animal acaricidal activity.
TL;DR: In this article, the nature of the one-electron two-centre bond in the cyclopropane and 1,2-divinylcyclopropane radical cations is elucidated by use of abinitio self consistent field (SCF) molecular orbital (MO) calculations.
Abstract: The nature of the one-electron two-centre bond in the cyclopropane and 1,2-divinylcyclopropane radical cations is elucidated by use of abinitio self consistent field (SCF) molecular orbital (MO) calculations. The charge and spin distributions in the 90,90 and 90,0 conformations are compared at the STO-3G and 4-31G basis set levels. From energy differences between the radical cations in the 90,90 conformation and the 90,0 (transition state) conformation, the activation barriers for cis–trans isomerization in the 2A1 state of C3H6,+ and of the 1,2-divinylcyclopropane radical cation are estimated. These results are compared to previous calculations and experimental data where possible.
TL;DR: In this article, the spectre microonde de the transformee de Fourier was utilised for the determination of cyclopropane-HCl and cycloprocessane-HCN.
Abstract: Utilisation du spectre microonde de la transformee de Fourier, pulse pour etudier l'effet Zeeman de rotation sur les complexes cyclopropane-HCl et cyclopropane-HCN. Determination pour le complexe cyclopropane-HCl du moment quadripolaire moleculaire, des elements tensoriels de susceptibilite magnetique, des contributions diamagnetiques et paramagnetiques et du second moment de la distribution de charge electronique. Calcul de constantes de Zeeman
TL;DR: In this paper, the CC band spectra of cyclopropane in front of S 1 cations were analyzed and a concerted reaction mechanism was concluded, i.e. cations and sulphur dioxide act as Lewis acids polarizing the π-electron system of cyclophane, thus activating the sorbed molecules for isomerization.
TL;DR: The photooxygenation of electron-rich 1,2-diarylcyclopropanes such as 1, 2-bis(4-methoxyphenyl)cyclopropane and 1, 4methoxycyclopropane in the presence of 9,10-dicyanoanthracene(DCA) as a sensitizer in acetonitrile affords trans- and cis-3,5-diminearl-1,2dioxolanes in high yields.
Abstract: The photooxygenation of electron-rich 1,2-diarylcyclopropanes such as 1,2-bis(4-methoxyphenyl)cyclopropane and 1-(4-methoxyphenyl)-2-phenylcyclopropane in the presence of 9,10-dicyanoanthracene(DCA) as a sensitizer in acetonitrile affords trans- and cis-3,5-diaryl-1,2-dioxolanes in high yields. This photooxygenation is initiated by the electron transfer from 1,2-diarylcyclopropanes to the excited singlet DCA, involving the cation radical of cyclopropanes as a key intermediate.
TL;DR: The title compounds were hydrogenolyzd over PdO or Raney nickel, and the C2-C3 bond of the cyclopropane ring underwent cleavage exclusively over the both catalysts as discussed by the authors.
Abstract: The title compounds were hydrogenolyzd over PdO or Raney nickel. The C2–C3 bond of the cyclopropane ring underwent cleavage exclusively over the both catalysts. The contribution of the fluorine substituent to the lengthening and weakening the C2–C3 bond of the cyclopropane ring seems to become a dominant factor in the regioselectivity.
TL;DR: The catalytic activity of SnO2+SO42− for the isomerization of cyclopropane at 100°C was found to be higher than 100 times that of simple SnO 2 for the same reaction at 300°C as discussed by the authors.
Abstract: The addition of about 3 wt% of sulfate ion to SnO2 caused the enhancement in the acid strength from H0=+3.3 to −8.2. The catalytic activity of SnO2+SO42− for the isomerization of cyclopropane at 100°C was found to be higher than 100 times that of simple SnO2 for the same reaction at 300°C. The effect of sulfate ion was remarkable also for the dehydration of 2-butanol.