scispace - formally typeset
Search or ask a question

Showing papers on "Benzophenone published in 1992"


Journal ArticleDOI
TL;DR: Dimeric chloro-bridged ortho-palladated complexes of general formula [PdCl{C 6 H 4 (CR=NOH)-2}] 2, where R=H, Me, Et, and Ph, were prepared via the ligand-exchange reaction starting from aryl oximes and cyclopalladation complexes of N,N-dimethylbenzylamine, ((dimethylamino)methyl)ferrocene, or benzophenone oxime) as mentioned in this paper.
Abstract: Dimeric chloro-bridged ortho-palladated complexes of general formula [PdCl{C 6 H 4 (CR=NOH)-2}] 2 , where R=H, Me, Et, and Ph, were prepared via the ligand-exchange reaction starting from aryl oximes and cyclopalladated complexes of N,N-dimethylbenzylamine, ((dimethylamino)methyl)ferrocene, or benzophenone oxime. By reaction with various pyridine (Zpy), the dimers were converted into the corresponding monomers [PdCl{C 6 H 4 (CR=NOH)2}(Zpy)]

85 citations


Journal ArticleDOI
TL;DR: In this paper, the reactions of α-tocopherol with various radicals and ketone triplets in solution were studied using laser flash photolysis and competitive techniques, and the results showed that the deuterium lunetic isotope effects are frequently very small, reflecting the expected lack of selectivity of fast reactions.
Abstract: Laser flash photolysis and competitive techniques have been employed to study the reactions of α-tocopherol with various radicals and ketone triplets in solution. For example benzophenone triplets abstract hydrogen with rate constants of 5.1×10 9 and 3.7×10 9 M -1 s -1 in benzene and benzene/1.3 M methanol. Similar near-diffusion-controlled values were obtained for several other ketone triplets, as well as tert-butoxyl and 4-methoxybenzoyloxyl radicals. Deuterium lunetic isotope effects are frequently very small, reflecting the expected lack of selectivity of fast reactions

68 citations


Journal ArticleDOI
TL;DR: A laser flash photolysis study at 355 nm has been carried out on acetonitrile-water (4:1 v/v) mixtures of the methoxy naphthale-benzophenone-H 2 SO 4 system as mentioned in this paper.
Abstract: A laser flash photolysis study at 355 nm has been carried out on acetonitrile-water (4:1 v/v) mixtures of the methoxy naphthale-benzophenone-H 2 SO 4 system. It is found that the proton-assisted photoionization reaction of 2-methoxynaphtalenes (ROMe) produced by triplet sensitization of benzophenone (BP) effectively occurs to produce c corresponding methoxynaphthlene cation radical (ROMe +. ) and benzophenone ketyl radical (>COH)

64 citations


Journal ArticleDOI
TL;DR: In this article, the hydrogen atom abstraction reaction of triplet benzophenone from 2-propanol and 1-4-cyclohexadiene in supercritical CO 2 was studied.
Abstract: Laser flash photolysis studies of the hydrogen atom abstraction reaction of triplet benzophenone from 2-propanol and 1,4-cyclohexadiene in supercritical CO 2 reveal unusual pressure effects on absolute rate constants. Monitoring reactivity close to the critical temperature (T c ) revealed that bimolecular rate constants increase sharply with a decrease in pressure, approaching the critical point. Kinetic investigations along an isotherm further removed from T c and predictive calculations on the pressure effect expected in supercritical CO 2 indicate that enhanced reactivity is due to local substrate clustering

61 citations


Journal ArticleDOI
TL;DR: In this article, it was shown that overreduction occurs and no organofluorine products are obtained with these substrates, however, it appears that no organophosphate products can be obtained with those substrates.
Abstract: Perfluorocycloaliphatic compounds are reduced by solutions of the sodium benzophenone radical anion to give perfluorinated and highly fluorinated aromatic compounds. Perfluorocycloalkanes containing tertiary carbon centers are much more reactive than perfluorocyclohexane. Reduction of perfluoroalkanes and perfluorocycloalkanes that contain perfluoroalkyl substituents proceeds easily; however, it appears that overreduction occurs and no organofluorine products are obtained with these substrates

61 citations



Journal ArticleDOI
TL;DR: In this paper, aryl and alkylhydrazones are transformed to 1-chloroalkylazo compounds with tert-butyl hypochlorite, which are intercepted as 3H-1,2.
Abstract: Aryl- and alkylhydrazones 1 of alkyl ketones and propanal are transformed to 1-chloroalkylazo compounds 2 with tert-butyl hypochlorite. Compounds 2 react with antimony(V) chloride or aluminum(III) chloride to give 1-aza-2-azoniaallene salts 3 as reactive intermediates, which are intercepted as 3H-1,2.4-triazolium salts 5 with nitriles. In most cases these salts rearrange spontaneously to form the corresponding 1H-triazolium salts 6. Benzophenone arylhydrazone 1x reacts with ter-butyl hypochlorite

47 citations


Journal ArticleDOI
TL;DR: The solvatochromisms of Michler's ketone and the iron-II complex Fe(phen)2(CN)2 (2) have been investigated in 73 solvents of different polarity as mentioned in this paper.

43 citations


Journal ArticleDOI
TL;DR: In this article, two kinds of spin-adducts are detected and identified by ESR spectroscopy: a tertiary carbon radical and a secondary carbon radical which ere formed by eddition of the spin traps (ND or BNB) to two polymer radicals.
Abstract: Radical intermediates formed by UV irradiation of LDPE in the presence of benzophenone (BP) as a photoinitiator have been trapped by using 2,3,5,6-tetramethylnitrosobenzene (ND) end 2,4,6-tri-tert-butylnitrosobenzene (BNB) as spin-trapping reagents. Two kinds of spin-adducts are detected and identified by ESR spectroscopy: a tertiary carbon radical and a secondary carbon radical which ere formed by eddition of the spin traps (ND or BNB) to two polymer radicals. These intermediates are produced by hydrogen abstraction of the BP excited state from branch points and methylene groups of the LDPE chain

43 citations



Journal ArticleDOI
TL;DR: In this article, femtosecond-picosecond laser photolysis and time-resolved transient absorption spectroscopy were used to study the photoreduction process of benzophenone (BP)-N-methyldiphenylamine (MDPA) system in acetonitrile solution.
Abstract: Photoreduction process of benzophenone (BP)-N-methyldiphenylamine (MDPA) system in acetonitrile solution was studied by means of femtosecond-picosecond laser photolysis and time-resolved transient absorption spectroscopy. The reaction process including the formation of geminate ion pain (IP) by electron transfer (ET) between BP * and MDPA at encounter followed by intra-IP proton transfer giving the ketyl radical (BPH * ) were clearly observed in both the triplet and singlet excited states, while the IP produced by excitation of the CT complex between BP and MDPA formed in the ground state did not give BPH *

Journal ArticleDOI
TL;DR: In this paper, a cyclic formation of alkaline earth acetate followed by decomposition was used to convert acetic acid selectively into acetone in a fixed-bed flow system.
Abstract: Silica-supported alkaline earth oxides revealed excellent activity to convert acetic acid selectively into acetone in a vapor-phase fixed-bed flow system. Acetone was obtained through the cyclic formation of alkaline earth acetate followed by decomposition. Magnesium oxide should be supported on the silica surface without formation of magnesium silicate, which was inactive for the present reaction. Attempted syntheses of benzophenone and acetophenone are also described.

Journal ArticleDOI
TL;DR: In this paper, the initial radical reactions in photoinitiated cross-linking of n-paraffins (lignocerane and dodecane) and tertiary (isooctane and 3-ethylhexane) hydrocarbons as LDPE model compounds were studied using 2,4,6-tert-butylnitrosobenzene (BNB) as a spin trap.
Abstract: The initial radical reactions in the photoinitiated cross-linking of n-paraffins (lignocerane and dodecane) and tertiary (isooctane and 3-ethylhexane) and unsaturated (1-hexene, cis- and tans-3-hexene) hydrocarbons as LDPE model compounds in the presence of benzophenone (BP) as photoinitiator have been studied using 2,4,6-tert-butylnitrosobenzene (BNB) as a spin trap. Several kinds of initial radicals were identified. These photoinitiated radicals, which combine to form cross-links, are of tertiary, secondary and primary carbon types formed by hydrogen abstraction from the model compounds by the excited triplet state of BP

Journal ArticleDOI
TL;DR: In this article, the treatment of 1 equiv. of Yb metal with benzophenone in tetrahydrofuran-hexamethylphosphoramide (hmpa) gave a YbII-benzophenone dianion complex, which on treatment with 2,6-di-tert-butyl-4-methylphenol produces [Yb(OC6H2But2-2-6-me-4)2(hmpaa)2
Abstract: Treatment of 1 equiv. of Yb metal with benzophenone in tetrahydrofuran–hexamethylphosphoramide (hmpa) gives a YbII–benzophenone dianion complex, [{Yb(OCPh2)(hmpa)2}2]1 which on treatment with 2,6-di-tert-butyl-4-methylphenol produces [Yb(OC6H2But2-2,6-Me-4)2(hmpa)2]2; both 1 and 2 are structurally characterized by X-ray crystallography.

Journal ArticleDOI
TL;DR: In this article, a novel dianhydride, 2,2′-dichloro-4,4′, 5,5,5′-benzophenone tetracarboxylic diyanhydride (DCBTDA), was synthesized.
Abstract: We have synthesized a novel dianhydride, 2,2′-dichloro-4,4′,5,5′-benzophenone tetracarboxylic dianhydride (DCBTDA). Polyimides were synthesized with DCBTDA or 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and several relatively rigid meta- and para- substituted mononuclear diamines. The BTDA based systems were insoluble in dipolar, aprotic solvents whereas the DCBTDA based polymers displayed enhanced solubility in these solvents. The thermal stability of these polyimides was excellent as measured by 5% weight loss decomposition. The Tg's of the polymers were all above 290°C.

Journal ArticleDOI
TL;DR: In this paper, the photochemical dimerization of methyl methoxycinnamates was studied and both unsensitized and sensitized reactions showed a high stereoselectivity.

Journal ArticleDOI
TL;DR: In this article, photosensitized electron transfer oxygenation of several aralkyl ketones and aldehydes such as 1,2,2-triphenylethanone and diphenyl-and triphenylthanal has been carried out with 2,4,6triphenylpyrylium tetrafluoroborate (TPP + BF 4 - ) in dichloromethane.
Abstract: Photosensitized electron transfer oxygenation of several aralkyl ketones and aldehydes such as 1,2,2-triphenylethanone and diphenyl- and triphenylethanal has been carried out with 2,4,6-triphenylpyrylium tetrafluoroborate (TPP + BF 4 - ) in dichloromethane. The carbonyl compounds underwent C-C bond cleavage through they cation radicals, generated via electron transfer to the excited singlet state of the pyrylium salt. For example, diphenylethanal afforded benzophenone in 80% yield

Journal ArticleDOI
TL;DR: The effects of incorporating a benzophenone stabilizer into the structure of Disperse Red 167 have been investigated in this article, where four different substituents in the parent dye structure were substituted sequentially to build the desired stabilizer moiety into the backbone of the prototype dye.


Journal ArticleDOI
TL;DR: In this paper, the synthesis of 1,4-diol from dimethyl-L-tartrate and benzophenone has been reported, which has a preferred conformation with OH⋯Ph interactions which are different from related compounds.
Abstract: We report the synthesis of the 1,4-diol 2 (4R,5R)-α,α,α′,α′-2,2-hexaphenyl-4,5-dimethanol-1,3-dioxolane from dimethyl-L-tartrate and benzophenone. The X-ray and the IR structural studies on 2 show that this compound has a preferred conformation with OH⋯Ph interactions which are different from related compounds.

Journal ArticleDOI
TL;DR: In this article, the geminate recombination kinetics of ketyl-phenoxyl radical pairs (RP) produced by quenching of triplet benzophenone by 4-phenylphenol and in corresponding perdeuteriated system in micellar solutions of sodium octyl (SOS) or dodecyl sulfates (SDS) in D 2 O have been examined by using the laser flash technique under an external magnetic field up to 0.43 T.
Abstract: The geminate recombination kinetics of ketyl-phenoxyl radical pairs (RP) produced by quenching of triplet benzophenone by 4-phenylphenol and in corresponding perdeuteriated system in micellar solutions of sodium octyl (SOS) or dodecyl sulfates (SDS) in D 2 O have been examined by using the laser flash technique under an external magnetic field up to 0.43 T. The recombination rate and magnetic isotope effect (MIE) in zero magnetic field increase as the micellar size is described

Journal Article
TL;DR: 2-Phenylpyridine shows a unique spectrum, previously not observed with cytochrome P-450, that has components of both type I and type II spectra and in contrast, 2-, 3-, and 4-benzoylpyridines exhibited complex kinetic behavior from which inhibition constants could not be obtained.
Abstract: The binding to human placental aromatase cytochrome P-450 and resulting extent of inhibition was examined for pyridine, pyridines substituted at the 2-, 3-, or 4-positions with phenyl or benzoyl groups, and the nonpyridinic structural analogs biphenyl and benzophenone. Spectral binding studies with partially purified aromatase indicated that pyridine, 3- and 4-phenylpyridines, and 3- and 4-benzoylpyridines interact at the active site via ligation of the pyridinic nitrogen to heme iron, as judged by the type II difference spectra. The apparent dissociation constants for these compounds are 2.1, 0.11, 0.09, 2.6, and 0.27 mM, respectively. Biphenyl, benzophenone, and 2-benzoylpyridine show exclusively a hydrophobic interaction in the presence of the substrate, androst-4-ene-3,17-dione, to give reverse type I difference spectra, with apparent spectral dissociation constants of 0.14, 0.42, and 1.8 mM, respectively. 2-Phenylpyridine shows a unique spectrum, previously not observed with cytochrome P-450, that has components of both type I and type II spectra. As measured by tritium ion release from [1 beta-3H]androst-4-ene-3,17-dione, competitive inhibition of human microsomal aromatase activity was observed with pyridine, 2-, 3-, and 4-phenylpyridines, biphenyl, and benzophenone, with Ki values of 320, 62, 1.48, 0.36, 750, and 130 microM, respectively. In contrast, 2-, 3-, and 4-benzoylpyridines exhibited complex kinetic behavior from which inhibition constants could not be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Journal ArticleDOI
TL;DR: In this article, the photoinduced graft copolymerization of acrylamide (AM) onto styrene-butadiene-acrylonitrile (ABS) copolymers in chloroform and in the presence of benzophenone was investigated.
Abstract: The photoinduced graft copolymerization of acrylamide (AM) onto styrene—butadiene—acrylonitrile (ABS) copolymer in chloroform and in the presence of benzophenone was investigated. UV irradiation was used in the range 310–460 nm. The grafting parameters, such as weight conversion, grafting percentage and grafting efficiency, were determined as a function of the irradiation time and the concentrations of monoruer, substrate and initiator. The combinations of benzophenone with some mines, such as n -butylamine, trimethylamine and triethylamine, were examined as photoinitiating systems. The IR spectrum of the ABS-g-AM graft copolymer shows the disappearance of the double bond at 1630 cm −1 and the appearance of a new peak at 1685 cm −1 which indicates the presence of polyacrylamide chains in the ABS backbone. The rate of copolymerization of AM onto ABS was determined ( R p = 0.85% min −1 ). The mechanism of formation of grafted chains in the presence of different photoinitiating systems is discussed.

Journal ArticleDOI
TL;DR: In this article, the hydrogen-bonded 1:1 complex is formed by the association or benzophenone ketyl radical (BPH) and TEA in nonpolar solvents at room temperature (298 K).
Abstract: Transient absorption experiments in the benzophenone-triethylamine (TEA) system have revealed that the hydrogen-bonded 1:1 complex is formed by the association or benzophenone ketyl radical (BPH) and TEA in nonpolar solvents at room temperature (298 K). The complex exhibits a broad visible absorption band with an absorption coefficient or 4000 M -1 cm -1 at the peak (555 nm). The equilibrium constants for complex formation are determined to be 99±6 M -1 in cyclohexane and 37±4 M -1 in benzene. The complex is round to be nonfluorescent, although bare BPH is known as an emissive radical

Journal ArticleDOI
TL;DR: In this paper, two-step photo-absorption processes of benzophenone and photodissociation of the highly-excited triplet state have been investigated in solution by the time-resolved thermal lensing technique.
Abstract: Two-step photo-absorption processes of benzophenone and photodissociation of the highly-excited triplet state have been investigated in solution by the time-resolved thermal lensing technique. Two-step absorption processes at 308 nm are found to be composed of the first S1 ← S0 absorption followed by a rapid intersystem crossing to T1 and the second Tn ← T1 absorption. The quantitative analysis of time-resolved thermal lensing signals leads to an unexpected result that only 51 ± 6 % of the photon energy absorbed by the molecule in T1 has been detected as the heat released back to the system. This observation could be explained by a model that a fast photodissociation of benzophenone takes place from Tn. The chemical evidence and energy consideration support the dissociation into two phenyl radicals and a carbon monoxide molecule.

Journal ArticleDOI
TL;DR: In this article, the authors used the pulse radiolytic pump-probe technique to measure the time-dependent benzophenone anion absorption spectra in several different solvents ranging from linear alcohols to branched alcohols.
Abstract: The solvation of the benzophenone anion has been studied at room temperature using the pulse radiolytic pump-probe technique. The time-dependent benzophenone anion absorption spectra have been monitored in several different solvents ranging from linear alcohols to branched alcohols to acetonitrile. The maximum of the steady-state spectrum shifts to the red as the solvent is changed from linear alcohols to branched alcohols to acetonitrile. Computer Monte Carlo simulations indicate that the observed spectral shift can be assigned to the position and the orientation of the dipole functional group. The experimental dynamics of the anion solvation were also studied. By fitting the time-dependent absorption data to a multistate evolution kinetic model, the solvation time for these systems is obtained. 26 refs., 8 figs., 1 tab.

Journal ArticleDOI
TL;DR: In this article, the dipole-moment change determined from the solvatochromic shift is 4.0 D in alcohols and 10.4 D in polar aprotic solvents.

Journal ArticleDOI
TL;DR: In this article, the photoinduced polymerization of butanediol-1,4 dimethacrylate was investigated in the presence of various linear sulfides and cyclic dithioacetals.
Abstract: The photoinduced polymerization of butanediol-1,4 dimethacrylate was investigated in the presence of various linear sulfides and cyclic dithioacetals. Benzophenone was used as a sensitizer. It was found that the addition of small amounts of sulfides to the polymerization mixture causes, depending on the sulfide structure and concentration, reduction or full elimination of an induction period as well as an increase in the reaction rate and yield both in air and argon-saturated systems. The explanation of the obtained results is based on the propensity of sulfides to act as hydrogen donors, chain-transfer agents, and highly oxidizable compounds.

Journal ArticleDOI
TL;DR: In this article, the benzophenone-mediated photosensitization of 2-deoxyguanosine (dG) and thymidylyl-(3′-5′)-2−deoxy-D-ribono-1,4lac...
Abstract: Benzophenone-mediated photosensitization of 2′-deoxyguanosine (dG) and thymidylyl-(3′-5′)-2′-deoxyguanosine (d(TpG)) at 350 nm in oxygen-saturated aqueous solution produces 2-deoxy-D-ribono-1,4-lac...

Journal ArticleDOI
TL;DR: In this article, the laser flash photolysis study at 155 nm in the 1-naphthol (ROH) and benzophenone (BP) system with and without H 2 SO 4 has been carried out in acetonitrile-water (4:1 v/v) or methanol at 290 K
Abstract: The laser flash photolysis study at 155 nm in the 1-naphthol (ROH) and benzophenone (BP) system with and without H 2 SO 4 has been carried out in acetonitrile-water (4:1 v/v) or methanol at 290 K