Showing papers on "Double bond published in 1983"
407 citations
IBM1
TL;DR: In this paper, the carbon-carbon bond lengths in polyacetylene have been directly measured with use of nutation NMR spectroscopy, and the results showed that 1.36 and 1.44 \AA{} were found for the double and single bonds, respectively, in trans-${(mathrm{CH})}_{x}$, and 1.,37 \ AA{} was found for double bond in the cis isomer.
Abstract: The carbon-carbon bond lengths in polyacetylene have been directly measured with use of nutation NMR spectroscopy. 1.36 and 1.44 \AA{} were found for the double and single bonds, respectively, in trans-${(\mathrm{CH})}_{x}$, and 1.37 \AA{} was found for the double bond in the cis isomer. Over the temperature range 4.2-300 K, the dynamical single-double bond interchange predicted for chains in trans-${(\mathrm{CH})}_{x}$ containing a mobile soliton defect was not observed.
282 citations
265 citations
TL;DR: In this article, electron energy loss vibrational spectroscopy (EELS), XPS, thermal desorption and work function measurements were compared for the surface states with known acetonitrile coordination complexes.
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TL;DR: In this paper, the V=O-Doppelbindungen in V2O5 wird demonstriert, das die M-O-Bindungen von (katalytisch aktiven) Metalloxiden vomTragermaterial beeinflus werden.
Abstract: Am Beispiel der V=O-Doppelbindungen in V2O5 wird demonstriert, das die M-O-Bindungen von (katalytisch aktiven) Metalloxiden vomTragermaterial beeinflus werden.
97 citations
TL;DR: In this article, the authors used a combination of photochemical and spectroscopic techniques, the latter including absorption, fluorescence fluorescence excitation, medium-induced circular dichroism, and proton magnetic resonance.
Abstract: Bilirubin and biliverdin dimethyl esters (BRE and BVE, respectively) and related linear tetrapyrroles have been studied using a combination of photochemical and spectroscopic techniques, the latter including absorption, fluorescence fluorescence excitation, medium-induced circular dichroism, and proton magnetic resonance. Both types of tetrapyrroles form mixtures of different topological isomers in very dilute solutions. In the case of the bilirubins the heterogeneity of the solutions is caused by two coexisting conformers with different orientations of the A/B and C/D pyrromethenone moieties with repect to each other. The spectral properties of one conformer resemble the isolated parent pyrromethenone, whereas those of the other result from electronic coupling of the two subchromophores presumably held in a “ridge tile” -like orientation. CC rotations at the C-5 and C-15 bridges substantially compete in both components with the photochemical channels (EZ isomerization and lumirubin formation) for the radiationless deactivation of the excited singlet state. The more rigid “ridge tile” component additionally undergoes hydrogen bond-mediated deactivation, and it photoisomerizes more efficiently. The situation is markedly more complex with the biliverdins. In order to obtain a more detailed insight into the mechanisms of the radiationless excited-state processes, time-resolved optoacoustic spectroscopy and ultrafast absorption (pump-probe) and fluorescence detection (single-photon-timing) techniques were used to supplement the stationary methods. The solution mixtures are composed of a (family of) helically coiled all-Z, all-syn species, and of species differing from the former by stretched arrangements of the rings B and C around the central C-10 bridge (E-anti, E-syn, and Z-anti). Two excited singlet states with picosecond lifetimes are attributed to either one or two coiled ground-state forms, and two remarkably long-lived nanosecond excited states arise each from a stretched ground state. The radiationless deactivation of the shorter-lived of the picosecond states is brought about by ultrafast intramolecular proton transfer between the B/C nitrogen atoms, in addition to the CC rotational modes operative in both. ZE photoisomerization is also an appreciable deactivation channel of excited biliverdin dimethyl ester. It is confined to the central C-10 double bond and selectively affords a stretched isomer (10E-anti), which thermally reforms the coiled starting meterial at room temperature via a sequence of tautomerization and CC rotation. Heating or ultrasonic treatment can reverse this sequence and drive it farther to populate another stretched isomer (10E-syn) which is thermally stable at room temperature. This stretched form aggregates (presumably to dimers) already at concentrations at which the coiled species still appears to be fully monomeric.
TL;DR: In this article, two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones.
Abstract: Two general methods for the preparation of β-silyl-substituted divinyl ketones have been developed starting from either α, β-unsaturated aldehydes or simple ketones. Anhydrous FeCl3 induces the cyclization to cyclopentenones under mild conditions and in good yields with predictable and complete control over the position of the double bond in the five-membered ring. The observed effects of substituents on rate can be explained by a rate-determining cationic electrocyclization. Silyl substitution has been shown to retard the reaction.
TL;DR: In addition to the natural formation of epoxy-bearing oils, the double-bond functionality in ordinary triglyceride oils can be epoxidized as discussed by the authors, enabling the easy formation of polyesters and polyurethanes.
Abstract: Although most triglyceride oils contain only double bond functionality, a few oils such as castor oil, vernonia oil, lesquerella oil, etc., contain other functional groups. These functional groups include hydroxy and epoxy groups, permitting the easy formation of polyesters and/or polyurethanes. In addition to the natural formation of epoxy-bearing oils, the double bond functionality in ordinary triglyceride oils can be epoxidized. When these oils are polymerized to form polyesters or polyurethanes in the presence of polystyrene to synthesize interpenetrating polymer networks (IPN), a new class of tough plastics is formed.
TL;DR: Subpicosecond time resolved multiphoton ionization is demonstrated to be a useful technique for probing unimolecular dynamics in vapor phase samples in this paper, where cis-stilbene molecules are observed to decay out of their initially prepared S1 state with a single exponential time constant of 0.32 ps.
Abstract: Subpicosecond time resolved multiphoton ionization is demonstrated to be a useful technique for probing unimolecular dynamics in vapor phase samples. Vapor phase cis‐stilbene molecules are observed to decay out of their initially prepared S1 state with a single exponential time constant of 0.32 ps. This decay, thought to correspond to a rapid twisting of the molecule about the ethylenic double bond, occurs in roughly one c=c double bond torsional vibrational period.
TL;DR: The microstructure of polyphenylacetylenes prepared with MoCl5 and WCl6 catalysts under different reaction conditions was determined by 200 MHz 1H-NMR spectroscopy as discussed by the authors.
Abstract: The microstructure of polyphenylacetylenes prepared with MoCl5 and WCl6 catalysts under different reaction conditions was determined by 200 MHz 1H-NMR spectroscopy Cis, trans and cyclohexadiene sequences were evidenced in all polymers Two mechanisms are responsible for the polymer microstructure: isomerization prior to double bond formation, and thermal isomerization after double bond formation When trans sequences are formed mainly through the first mechanism, the polymer is almost void of cyclohexadiene structural units and its molecular weight is very high This can be explained through a unimolecular termination mechanism, ie, intramolecular cyclization of the cis-polymer chain end The control of polyphenylacetylene microstructure by these two mechanisms explains why a cis-cisoidal polymer could not be obtained by using MoCl5 or WCl6 catalysts
Patent•
20 Jun 1983
TL;DR: The co-metathesis reaction of triglycerides having fatty acid esters containing isolated carbon-carbon double bonds and ethylene produces modified triglycerides and alpha-olefins as mentioned in this paper.
Abstract: The co-metathesis reaction of triglycerides having fatty acid esters containing isolated carbon-carbon double bonds and ethylene produces modified triglycerides and alpha-olefins. The reaction occurs at an ethylene partial pressure of about 200 to 550 psig in the presence of a catalytically effective amount of a metathesis catalyst at a temperature of about 100° F. to 500° F.
TL;DR: In this paper, the nitrogen rule and the formula for calculating the number of rings plus double bonds of any common organic compound were presented. But they were based on the same formula as in this paper.
Abstract: This article wishes to demonstrate the nitrogen rule and the formula for calculating the number of rings plus double bonds of any common organic compound.
TL;DR: Synthese du dithioxo tri-t-butyl-2,4,6 phenyl phosphorane par reaction de la dimethylaminomethylene tri-T,t,butyl 2,4 6 phenylosphine avec le soufre S 8
TL;DR: In this article, a laser-based chemical kinetics technique has been demonstrated in studies of the reaction of OH with C2H4, which is dominated by electrophilic addition of OH to the double bond at low temperatures, and by increasingly rapid decomposition of the thermalized adduct HOC 2H4 back to reactants as the temperature is raised.
TL;DR: In this paper, an intram olecular ureidoselenenylation of double bonds followed by allylative de-selenenylization accomplishes a net ureidoallylation.
TL;DR: In this article, the potential of carbonyl carbene complexes is demonstrated upon their reactions with alkynes, based on the electrophilicity of the carbene car- hon atom and the facile substitution of carbon monoxide.
Abstract: Abstract — The synthetic potential of carbonyl carbene complexes is demonstrated upon their reactions with alkynes. Both the electrophilicity of the carbene car— hon atom and the facile substitution of carbon monoxide are used for selective carbon carbon bond formation. Nucleophilic alkynes (ynamines) add to the carbene carbon atom and then undergo insertion into the metal carbene bond. Chromium(O) is effective as a template in the annulation of carbene ligands bearing aromatic or vinylic side chains: Metal—assisted carbene transfer or both carbene and carbonyl transfer to alkynes are observed to yield indenes or l,4—hydroquinones. The hydro— quinome formation occurs regioselectively with respect to the alkyne incorporation and the annulation of diarylcarbene ligands. The synthetic utility of this reaction is exemplified by the synthesis of vitamins K and E.
TL;DR: In homogeneous catalyst systems in which the metal is likely to be in a relatively high oxidation state, such as molybdenum(VI) or tungsten(VI), metal-carbon multiple bonds may play an important role.
Abstract: Several well-characterized transition metal catalysts contain a metal-carbon double bond or a metal-carbon triple bond. In other homogeneous (or heterogeneous) catalyst systems in which the metal is likely to be in a relatively high oxidation state, such as molybdenum(VI) or tungsten(VI), metal-carbon multiple bonds may play an important role. Some recent results suggest that even supposedly well understood reactions such as ethylene polymerization may actually involve catalysts that behave as if they contained a metal-carbon double bond instead of a metal-carbon single bond. The chemistry of metal-carbon double and triple bonds should eventually complement and perhaps. overlap the known chemistry of complexes containing metal-oxygen double bonds or metal-nitrogen triple bonds, respectively; unique catalytic reactions involving carbon, nitrogen, and oxygen ligands multiply bonded to transition metals are therefore possible.
TL;DR: In this paper, the resonance Raman spectra of ethylene were obtained with 212.8 and 193.4 nm excitation frequencies, and strong enhancement of the even overtones of the torsional coordinate was found.
Abstract: The resonance Raman spectra of ethylene obtained with 212.8 and 193.4 nm excitation are presented. With these excitation frequencies, on the red edge of the N → V absorption system, strong enhancement of the even overtones of the torsional coordinate is found. In addition, scattering to the carbon–carbon double bond stretching and the symmetric CH2 scissors modes show enhancement. These results demonstrate that the CH2 groups lie in mutually perpendicular planes in the nuclear equilibrium configuration of the V state, while the C–C bond distance has been lengthened and the HCH angles reduced relative to those of the ground state. These results are discussed within the context of the G16(2) dynamic point group and recent calculations.
Patent•
22 Feb 1983
TL;DR: In this paper, a process for the hydrogenation of carbon-carbon double bonds of an unsaturated polymer is described, which consists of combining a polymer in latex form with an oxidant selected from the group consisting of oxygen, air and hydroperoxides; a reducing agent selected from a group of hydrazine and hydrates thereof; and a metal ion initiator.
Abstract: There is disclosed a process for the hydrogenation of carbon-carbon double bonds of an unsaturated polymer which comprises (a) combining an unsaturated polymer in latex form with (1) an oxidant selected from the group consisting of oxygen, air and hydroperoxides; (2) a reducing agent selected from the group of hydrazine and hydrates thereof; and (3) a metal ion initiator; (b) heating the mixture to a temperature from 0° C. to the reflux temperature of the reaction mixture.
TL;DR: In this article, the microstructure of polyphenylacetylenes prepared with MoCl5 and WCl6 catalysts in several solvents was studied by 13C-NMR spectroscopy.
Abstract: The microstructure of polyphenylacetylenes prepared with MoCl5 and WCl6 catalysts in several solvents was studied by 13C-NMR spectroscopy. Use of 13{1H} INEPT (insensitive nuclei enhanced by polarization transfer) experiment aids the resonance assignments of cis, trans and cyclohexadiene structural units. The NMR spectral data confirm our previous findings regarding the roles of isomerization prior to double bond formation and thermal isomerization after double bond formation in the mechanism responsible for the control of polymer microstructure and molecular weight.
TL;DR: In this article, internal double bonds were determined by oxidative cleavage in fractions of a commercial suspension PVC and experimental PVC samples obtained at subsaturation conditions (U-PVC) and the changes in molecular weight were measured by g.p.m. and viscometry.
TL;DR: Investigations described here have established, through the use of an isotope-trapping technique and the same organism, that the C α -derived product is the aromatic aldehyde (R-C α HO), which is rapidly reduced in cultures to the corresponding alcohol.
TL;DR: In this article, the complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 710; DOI:10.1002/anie.198307100
Abstract: The complete manuscript of this communication appears in: Angew. Chem. Suppl. 1983, 710. DOI:10.1002/anie.198307100