Showing papers on "Benzophenone published in 1986"
TL;DR: Preparation en particulier de difluoro-6,6 undecane, diffluoro-12,12 tricosane and cyclododecane is described in this paper.
Abstract: Preparation en particulier de difluoro-6,6 undecane, difluoro-12,12 tricosane, d'α,α-difluorotoluenes, difluoro-3,3 cholestane, difluoro-1,1 cyclododecane
144 citations
TL;DR: Water-soluble derivatives of benzophenone are readily reduced to the pinacol or alcohol upon irradiation with near-ultraviolet light in aqueous solution.
Abstract: Water-soluble derivatives of benzophenone are readily reduced to the pinacol or alcohol upon irradiation with near-ultraviolet light in aqueous solution. The hydrogen donor can be a simple organic compound (e.g. methane, alcohol, aldehyde, amine, amide, sulphide, ether, carboxylic acid etc.) but not water. In most cases the photochemistry proceeds rapidly with high quantum yield. If an active Pt colloidal catalyst is added to the solution, the intermediary radicals can be used to reduce water to H2 on the metallic surface. Thus the organic substrate is effectively dehydrogenated under ambient conditions. In some cases the reaction can be used for synthesis of useful organic materials.
83 citations
76 citations
TL;DR: Asymmetric carbon-carbon bond formation was obtained in optical yields up to 57 % in allylic alkylations using benzophenone imine of glycine methyl ester 1 as a prochiral nucleophile.
63 citations
TL;DR: Morphologie des spherulites et des monocristaux obtenus a partir de solutions dans l'α-chloronaphtalene and la benzophenone.
Abstract: Morphologie des spherulites et des monocristaux obtenus a partir de solutions dans l'α-chloronaphtalene et la benzophenone
63 citations
62 citations
TL;DR: In this article, two temporally distinct processes are observed for ketyl radical anion formation in benzophenone triplet quenching by triethylamine (TEA) at high concentrations in alkaline aqueous acetonitrile.
Abstract: In the course of benzophenone triplet quenching by triethylamine (TEA) at high concentrations in alkaline aqueous acetonitrile, two temporally distinct processes are observed for ketyl radical anion formation. The fast component occurs on a nanosecond time scale, has kinetics sensitive to basicity and water content of the medium, and is ascribed to the deprotonation of the diphenylhydroxymethyl radical initially produced as a result of subnanosecond intra-ion-pair proton transfer. The slow process occurs on a microsecond time scale and is characterized by pseudo-first-order rate constants linearly dependent on ketone ground-state concentration; this is assigned to the one-electron reduction of the ketone by the methyl(diethylamino)methyl radical (derived from TEA). Substituent effects on the kinetics of the two processes follow trends expected from those of the acidity of diarylhydroxymethyl radicals and of the behavior of diaryl ketones as oxidants. Neither of the two processes is observed with N,N-dimethylaniline (DMA) and 1,4-diazabicyclo(2.2.2)octane (DABCO) as quenchers. The electron or hydrogen transfer yields in the course of diaryl ketone triplet quenching by the three amines are all close to unity, suggesting that the back electron transfer in the triplet ion pairs is relatively unimportant.
60 citations
TL;DR: In this paper, the authors investigated the crystallization behavior via annealing of PEEK using FTIR spectroscopy and found that predominantly amorphous PEEK follows two distinct mechanisms when it is annealed.
Abstract: The crystallization behavior, via annealing, of PEEK was investigated using FTIR spectroscopy. It was found that predominantly amorphous PEEK (e.g., quenched polymer) follows two distinct mechanisms when it is annealed. One is a lower energy relaxation process that involves the partial rotation of the ether linkages, allowing the molecular chains in the disordered phase to become better packed, and occurs from 50 to 140°C (slightly below Tg). This relaxation process is also observed by dynamic mechanical analyses. The other process is a crystallization that takes place above the glass transition, with its onset characterized by the rotation of the benzophenone linkages near Tg. Isothermal crystallization kinetics data on PEEK can be described by an Avrami equation with an Avrami constant n of about 1.
49 citations
TL;DR: Etude de la benzophenone, de lacetyl-2 naphtalene, de methoxy-3' acetophenone and de l'acetyl 2 naphtaline as mentioned in this paper.
Abstract: Etude de la benzophenone, de l'acetophenone, de la methoxy-3' acetophenone et de l'acetyl-2 naphtalene
44 citations
TL;DR: In this article, a broad band piezoelectric PVF 2 detector was used for time-resolved detection of the pressure wave in the benzophenone triplet with various concentrations of KI as quencher.
42 citations
TL;DR: The benzophenone molecule has been treated in MNDO, MNDOC, and MINDO/3 approximation as a function of the twist angle α of the phenyl rings.
Abstract: The benzophenone molecule has been treated in MNDO, MNDOC, and MINDO/3 approximation as a function of the twist angle α of the phenyl rings. Calculated were (i) the energies of S0 and T1 state, (ii) delocalization of the n and π* orbitals involved in the 3nπ* state, (iii) net atomic charges,(iv) the force constants of the C=O vibration in the S0 and T1 state, respectively, (v) vertical transition energies for T1←S0 and S1←S0, and (vi) the position of upper triplet states. The results are discussed in relation to the spectroscopic properties of the T1 state of a vitreous benzophenone phase. It is concluded that diagonal disorder is due to a significant fluctuation of α causing both a spread of the site energies of the glass‐forming molecules and a variation of spin‐orbit coupling.
TL;DR: The photochemistry of eight aromatic carbonyl based photopolymerisation initiators is examined and compared using u.v. absorption, phosphorescence, micro-second flash photolysis, steady-state photolyisation and photopolymersisation rates for n-butyl methacrylate as discussed by the authors.
TL;DR: In this paper, photolysis of benzophenone oxime esters, prepared with aliphatic carboxylic acids, was performed in benzene and pyridine, in order to generate various primary, secondary and tertiary ALH radicals selectively, and corresponding alkylbenzenes and alkylpyridines.
TL;DR: Le radical intermediaire est identifie en tant que cetyle benzophenone qui est reduit en benzhydrolate de lithium par enlevement d'hydrogene-β a partir de l'alcoolate of lithium as discussed by the authors.
Abstract: Le radical intermediaire est identifie en tant que cetyle benzophenone qui est reduit en benzhydrolate de lithium par enlevement d'un atome d'hydrogene-β a partir de l'alcoolate de lithium
TL;DR: In this paper, the sensitivity of jet-cooled benzophenone to the S/sub 1/(n,..pi../sup */) transition has been measured and it was found that the spectrum consists exclusively of several long progressions of 60 cm/sup -1/ which is the in-phase torsional mode of the phenyl rings.
Abstract: The sensitized phosphorescence excitation spectrum of jet-cooled benzophenone due to the S/sub 1/(n,..pi../sup */) produced from S/sub 0/ transition has been measured. It was found that the spectrum consists exclusively of several long progressions of 60 cm/sup -1/ which is the in-phase torsional mode of the phenyl rings. The vibrational analysis and the potential calculation shows that the in the S/sub 1/(n,..pi../sup */) state great geometry changes occur in the dihedral angle between the phenyl rings, the C=O bond distance, and the C-C bonds adjacent to the C=O bond.
TL;DR: Reverse micelle photopolymerization of acrylamide has been investigated in the presence of ionic benzophenones and the results are discussed in terms of the processes involved in the excited states and observed through time resolved laser spectroscopy.
TL;DR: In this article, a 1,3-disubstituted imidazo[l,5-a]pyridines have been effected by treatment of ketimines derived from di-2-pyride ketone with LDA and benzophenone.
TL;DR: The hydrogen-donatability of coal-related model compounds such as benzophenone, trans-stilbene, anthracene, and 9-benzylphenanthrene is investigated in this paper.
15 Aug 1986
TL;DR: In this paper, the electronic properties and reaction mechanisms of triplet carbenes and diradicals have been investigated by solid state spectroscopy, and an energy level system including reaction pathways, activation energies and the final product of the carbene reaction is deduced from line positions and kinetics of the spectra.
Abstract: Electronic properties and reaction mechanisms of triplet carbenes and diradicals have been investigated by solid state spectroscopy. The model systems are represented by diphenylmethylene DPM (monocarbene) and para-phenyl-bis-(phenylmethylene) PPPM molecules embedded in a benzophenone host crystal. The correlation of the ESR and optical spectra leads to a consistent description of the carbene reaction and properties. An energy level system including reaction pathways, activation energies and the final product of the carbene reaction is deduced from line positions and kinetics of the spectra. The ESR results of the DPM and PPPM system are discussed in the light of recent results concerning the electronic structures of carbenes and diradicals in diacetylene oligomer systems. The electron wavefunctions are calculated using a configuration model. The parameters of the model are given by the radical electron transfer interaction and the energy difference of the benzenoid and quinoid configurations.
TL;DR: In this paper, the authors propose an approach for the formation (par desilylation des composes du titre) d'azolemethanures-1 via the formation of carbanions methyl-1 azolures-5.
Abstract: Obtention principalement d'azoleethanols-1 via la formation (par desilylation des composes du titre) d'azolemethanures-1; obtention egalement de methyl-1 azolemethanols-5 via les carbanions methyl-1 azolures-5
TL;DR: In this paper, the Wittig-type reaction of an intermediate methyleneborane 2 with the ketone was used to explain the olefin formation of fluoro(tetramethylpiperidino)[(trimethylsilyl)organyl]boranes.
Abstract: Contributions to the Chemistry of Boron, 181. Methyleneboranes as Intermediate of an Olefin Synthesis
Gas phase pyrolysis of fluoro(tetramethylpiperidino)[(trimethylsilyl)organyl]boranes 1 at ≥ 460°C yields (CH3)3SiF, but no methyleneborane 2 could be detected. In solution, (CH3)3SiF is produced at 285°C, and in the presence of benzophenone olefins are obtained. The olefin formation is explained by a Wittig-type reaction of an intermediate methyleneborane 2 with the ketone.
TL;DR: On etudie les reactions des enolates de Li de la pinacolone de la dimethyl-2,2 pentanone-3 and de la trimethyl- 2,2,4 pentane-3 avec la benzophenone et ses derives as mentioned in this paper.
Abstract: On etudie les reactions des enolates de Li de la pinacolone de la dimethyl-2,2 pentanone-3 et de la trimethyl-2,2,4 pentanone-3 avec la benzophenone et ses derives
TL;DR: In this article, a lanthanoid metal ester homoenolate (β-lanthanoid metaminer substituted ester) was proposed as a reaction intermediate for β-bromopropionate.
Abstract: γ-Lactones were easily prepared from the direct reaction of methyl β-bromopropionate with ketones mediated by lanthanoid metals; a lanthanoid metal ester homoenolate (β-lanthanoid metal substituted ester) is postulated as a reaction intermediate.