Showing papers on "Benzophenone published in 1980"
TL;DR: In this article, the authors used time resolved laser flash spectroscopy to study the photophysical and photochemical properties of the lowest triplet of benzophenone in water and acetonitrile and obtained new estimates for the triplet extinction coefficient, unimolecular and bimolecular rate constant of decay in both solvents, as well as a determination of the quantum yield of ketyl formation in pure water and the rate constants of hydrogen abstraction from various lactams.
Abstract: The technique of time resolved laser flash spectroscopy has been used to study the photophysical and photochemical properties of the lowest triplet of benzophenone in water and acetonitrile. New estimates have been obtained for the triplet extinction coefficient, unimolecular and bimolecular rate constant of decay in both solvents, as well as a determination of the quantum yield of ketyl formation in pure water and the rate constants of hydrogen abstraction from various lactams in both solvents. Evidence for hydrogen abstraction from water by a triplet of benzophenone is found. Correlation between rate constants of hydrogen abstraction from lactams by the lowest benzophenone triplet and their ionization potential is discussed. Reversibility of these hydrogen abstractions is considered.
188 citations
103 citations
Patent•
05 Sep 1980TL;DR: In this paper, a photopolymerizable composition, element and method of photopolyming the composition or element are disclosed wherein the composition comprises an addition polymerizable compound containing ethylenic unsaturation and a co-initiator including an activator and a photosensitizer.
Abstract: A photopolymerizable composition, element and method of photopolymerizing the composition or element are disclosed wherein the composition comprises an addition polymerizable compound containing ethylenic unsaturation and a co-initiator including a photopolymerization activator and a photosensitizer. In one aspect of the invention, the photosensitizer is selected to be a coumarin having an absorption maximum between about 250 and about 550 nm, and a ##STR1## substituent in the 3-position wherein R1 is alkyl or alkenyl having 1-12 carbon atoms, or a carbocyclic or heterocyclic group having 5-20 nuclear carbon and hetero atoms, the coumarin and the activator being present in an amount sufficient to provide, when the composition is coated, dried and exposed to a medium-pressure mercury light source, a speed which is at least about one-fifth that of the same composition coated, dried and exposed identically except with a co-initiator consisting of Michler's ketone and benzophenone. In another aspect of the invention, the activator is selected to have the structure: ##STR2## wherein: J is -O-, -S- or a carbon-to-carbon bond; J1, J2, and J3 are each independently hydrogen; alkyl, alkoxy, or alkylthio having from 1 to 5 carbon atoms; aryloxy having from 6 to 10 carbon atoms; halogen; or any two of J1, J2, and J3 taken together comprise the atoms necessary to complete a 5- or 6-membered fused heterocyclic or aromatic ring; and Z is the number of atoms necessary to complete a heterocyclic or aromatic ring of from 4 to 6 ring atoms.
97 citations
TL;DR: In this paper, the magnetic field effect on the decay rate of the benzophenone ketyl radical in micellar solution was studied via nanosecond laser photolysis, and the rate constant of the slow component was found to decrease from 1.6 × 10 6 s − 1 at zero field to 9 × 10 5 s −1 at 700 G.
79 citations
TL;DR: In this article, a possible mechanism for semiconductors (TiO 2 and CdS) suspended in organic solvents containing 1,1-diphenylethylene and its derivatives under oxygen afforded the corresponding epoxides and benzophenone.
68 citations
TL;DR: In this paper, photolysis of benzophenone in the presence of an amine transferred an electron to an excited triplet state, forming an ion pair that is stable relative to diffusional separation.
Abstract: Studies were initiated utilizing picosecond (ps) absorption spectroscopy, to directly monitor the dynamics of electron transfer from 1,4-diazabicyclo(2.2.2)octane (Dabco) to the excited states of benzophenone and fluorenone. These two systems were chosen because of their contrasting photochemistry. The quantum yield for photoreduction of benzophenone in polar solvents is generally greater than 0.1, while that of fluorenone is zero. In polar solvents, the proposed mechanism dictates that an electron is transferred to the excited singlet state fluorenone, which then back-transfers the electron, regenerating ground-state fluorenone and amine. Photolysis of benzophenone in the presence of an amine transfers an electron to an excited triplet state, forming an ion pair that is stable relative to diffusional separation. The results of this study verify this proposal.
64 citations
57 citations
TL;DR: In this article, the extinction coefficients for the triplet absorption of benzophenone and naphthalene in benzene solution, and of anthracene in ethanol and cyclohexane solutions were determined.
56 citations
TL;DR: The results of laser flash photolysis studies of the primary reaction of benzophenone triplet with aliphatic amines in benzene solution were reported in this article, where the quantum yield of formation of benzphenone ketyl radical was 0.9 - 1.0.
Abstract: Results of laser flash photolysis studies of the primary reaction of benzophenone triplet with aliphatic amines in benzene solution are reported. Quantum yield of formation of benzophenone ketyl radical was 0.9 - 1.0. Quantum yields for reduction of ketone also were determined for various amines, and the effects of tert-butyl alcohol on radical formation was investigated. Data indicated that H is not abstracted from -CH/sub 3/ but is abstracted efficiently from -NH/sub 2/. The very high quantum yields observed with tertiary and secondary amines were thought to imply exciplex formation, but lower quantum yields with primary amines were conditionally attributed to higher ionization potentials. (BLM)
52 citations
TL;DR: The authors showed conclusively that the primary photochemical act involves hydrogen abstraction from benzhydrol by the n,π* uncomplexed triplet state of benzophenone to give a triplet radical pair which does not couple to a measurable extent within the solvent cage.
41 citations
TL;DR: In this paper, fast spectroscopy experiments have been performed upon the photoinitiation process of a vinyl polymerization with the benzophenone-amine derivative system and the rate constants of the processes in the excited states have been determined.
Abstract: Fast spectroscopy experiments have been performed upon the photoinitiation process of a vinyl polymerization with the benzophenone-amine derivative system. The rate constants of the processes in the excited states have been determined. The results make it possible to discuss the rate constant of the polymerization and to deduce the efficiency of the initiating radicals.
TL;DR: In this paper, an empirical approach is developed for the assessment of the importance of merostabilization in influencing the n,π* triplet energies of unsymmetrically substituted benzophenones.
Abstract: An empirical approach is developed for the assessment of the importance of merostabilization in influencing the n,π* triplet energies of unsymmetrically substituted benzophenones.
TL;DR: The reversal of the carbonyl activity of benzophenone, serving as electron donor in single-electron transfer processes and acting as a proton acceptor through the carbon atom, is observed upon η2-complexation to zirconocene.
TL;DR: The thermal decomposition of CoH(CO) 4 in solution to Co 2 (CO) 8 and H 2 is catalyzed by Co 2 CO 8 ; the effect of the latter is proportional to the square root of the concentration of CO 4 · radical is involved in the process as mentioned in this paper.
Patent•
03 Mar 1980TL;DR: The pendant benzophenone chromophores protect the acrylic backbone and when photoexcited do not degrade the ester side chain, nor abstract hydrogen from the backbone.
Abstract: Photostable and weather stable absorping copolymers have been prepared from acrylic esters such as methyl methacrylate containing 0.1 to 5% of an 2-hydroxy-allyl benzophenone, preferably the 4,4' dimethoxy derivative thereof. The pendant benzophenone chromophores protect the acrylic backbone and when photoexcited do not degrade the ester side chain, nor abstract hydrogen from the backbone.
TL;DR: In this paper, Nanosecond laser spectroscopy is applied to the determination of the rate constants of several processes involved in the photochemistry of a series of substituted benzophenones.
Abstract: Nanosecond laser spectroscopy is applied to the determination of the rate constants of several processes involved in the photochemistry of a series of substituted benzophenones. The results allow the initiation of a vinyl monomer polymerization to be discussed and reveal a peculiarity of the benzene/THF system.
TL;DR: In this paper, the mechanism of benzophenone ketyl radical formation in acid methanol, ethanol, and 2-propanol was studied by using pulse-radiolysis and rigid-matrix techniques.
Abstract: The mechanism of the benzophenone ketyl radical formation in acid methanol, ethanol, and 2-propanol was studied by using pulse-radiolysis and rigid-matrix techniques. When a 0.1 M ethanol solution of benzophenone containing hydrogen chloride (1.2 M) was irradiated at 77 K by ..gamma.. rays from /sup 60/Co, the absorption spectrum of the trapped intermediates was ascribed solely to benzophenone ketyl radicals. The pulse-radiolysis study of the solution at 100 K revealed that the ketyl radicals are produced by protonation of presolvated benzophenone anion radicals. At 153 K, the ketyl radicals were observed to be produced also by hydrogen-atom transfer from CH/sub 3/CHOH and CH/sub 3/CH(OH)CH/sub 3/ to benzophenone; the temperature dependence of the transfer rate constant was studied.
TL;DR: On the other hand, irradiation of 2,4-dimethylthiazole with acetophenone led to the formation of a dimeric material and 4-methylisothiazole gave an oxetane but rather a hydroxyphenyl derivative.
TL;DR: In this article, it was shown that the wavelength of light does not determine the character, but only the concentrations of the products formed, and that the reduced form of chlordiazepoxide and a conjugate are formed.
Abstract: By labelling chlordiazepoxide and diazepam with14C it was possible to follow quantitatively the photochemical decomposition of these compounds. It was found for chlordiazepoxide that the wavelength of light does not determine the character, but only the concentrations of the products formed. On irradiation of chlordiazepoxide, dissolved in methanol or methanol-water (pH=7.4), an oxaziridine is formed, which is subsequently converted into a quinoxaline and a benzoxadiazocine derivative. However, by irradiation in the presence of glutathione, the rate of decomposition is increased and the scheme is completely changed. Instead of the quinoxaline and the benzoxadiazocine derivative, the reduced form of chlordiazepoxide and a conjugate are formed. It was established that the oxaziridine, the first photoproduct of chlordiazepoxide, reacts spontaneously with glutathione at room temperature without light. On irradiation of diazepam, dissolved in methanolwater (pH=7.4), with light of 300 nm a benzophenone derivative is the only decomposition product, while with light of 254 nm also a quinazoline derivative is formed as a minor product. With methanol as solvent (λ=254 nm) the concentration of the products formed is strongly influenced, quinazoline derivatives become the main products and the benzophenone derivative a minor product.
TL;DR: In this article, it was shown that the 3-ketone triplet with the quadricyclene gives 1: 1-adducts with endo-orientation.
TL;DR: A series of N-methyl-substituted aromatic polyamides derived from the secondary aromatic diamines 4,4′-bis(methylamino)diphenylmethane, 3,3′-bimide-dimethylpoly(methylpolydimide) dicarboxylic acid dichloride was prepared by high-temperature solution polymerization in s-tetrachloroethane as mentioned in this paper.
Abstract: A series of N-methyl-substituted aromatic polyamides derived from the secondary aromatic diamines 4,4′-bis(methylamino)diphenylmethane, 3,3′-bis(methylamino)diphenylmethane, 4,4′-bis(methylamino)benzophenone or 3,3′-bis(methylamino)benzophenone and isophthaloyl dichloride, and terephthaloyl dichloride or 3,3′-diphenylmethane dicarboxylic acid dichloride was prepared by high-temperature solution polymerization in s-tetrachloroethane. Compared with analogous unsubstituted and partly N-methylated aromatic polyamides, the full N-methylated polyamides exhibited significantly lower glass transition temperatures (Tg), reduced crystallinity, improved thermal stability, and good solubility in chlorinated solvents.
TL;DR: In this paper, the electronic effect of the methyl group and steric effect of o -groups on the average tilt of a phenyl ring with respect to the plane of the carbonyl function was investigated.
TL;DR: The reaction of alkyl-lithium compounds, possessing α-hydrogens, or benzylmagnesium chloride with aromatic nitriles, followed by hydrolysis, gives ketones, E- and Z-N1-(1-arylalk-1-enyl)benzamidines, 2-alkyl-2,4,6-triaryldihydro-1,3,5-triazines, and 2, 4, 6-triaryl- 1, 3, 5-triazine as discussed by the authors.
Abstract: The reaction of alkyl-lithium compounds, possessing α-hydrogens, or benzylmagnesium chloride with aromatic nitriles, followed by hydrolysis, gives ketones, E- and Z-N1-(1-arylalk-1-enyl)benzamidines, 2-alkyl-2,4,6-triaryldihydro-1,3,5-triazines, and 2,4,6-triaryl-1,3,5-triazines. Conditions for preparing the enamidines in useful yields were established. t-Butyl-lithium and phenyl-lithium with benzonitrile gave only the ketones and dihydrotriazines. Phenylmagnesium bromide gave only benzophenone.
TL;DR: In this article, the photoprimary processes of intramolecular exciplex systems of benzophenone and N,N-dimethylaniline were studied by means of laser spectroscopy.
TL;DR: The reaction of 2,5-ditertiarybutylfuran with singlet oxygen has been used as a monitor to show that the quenching of triplet benzophenone by oxygen gives singleton oxygen with considerably less than unit efficiency as discussed by the authors.
TL;DR: Although the vibrational spectrum of benzophenone has been analyzed to some extent (1,2), and an attempt to calculate the normal vibrations was also made (3), a full systematization of the fundamentals of this molecule is not reached yet as mentioned in this paper.
Abstract: Although the vibrational spectrum of benzophenone has been analysed to some extent (1,2), and an attempt to calculate the normal vibrations was also made (3), a full systematization of the fundamentals of this molecule is not reached yet.
TL;DR: In this article, a 6,6-Dimethyl-6-silafulvene generated from (allyl)cyclopentadienyl)dimethylsilane reacts with a trapping reagent such as methanol, benzaldehyde, and benzophenone to give (cyclopentadiyl)(methoxy)dimmethylsilane, 6-phenylfulvenes, and 6-6diphenyl-silane, respectively.
Abstract: 6,6-Dimethyl-6-silafulvene generated from (allyl)(cyclopentadienyl)dimethylsilane reacts with a trapping reagent such as methanol, benzaldehyde, and benzophenone to give (cyclopentadienyl)(methoxy)dimethylsilane, 6-phenylfulvene, and 6,6-diphenylfulvene, respectively. Without a trapping reagent, the silafulvene undergoes dimerization.
TL;DR: In this paper, the influence of prior thermally generated hydroperoxides and added benzophenone on the photo-stabilising action of a hindered piperidine compound, bis[2,2,6,6-tetramethyl-4-piperidinyl]-sebacate, was examined.
TL;DR: In this paper, a photostationary state (p.s.) ratio of 3.5 ± 0.2 for xanthone, benzophenone, and 1- and 2-acetonaphthone was investigated.
Abstract: The photosensitized (E)-β-ionone (1)–α-pyran (2) isomerization in benzene as a solvent has been studied in some detail. For xanthone, benzophenone, and 1- and 2-acetonaphthone the (1) : (2) photostationary state (p.s.s.) ratio is 3.5 ± 0.2, whereas for the series of aromatic hydrocarbons studied and the ketones fluoren-9-one and benzanthrone it is 0.37 ± 0.07, both for a total substrate concentration of ca. 0.1M. The low {[(1)] : [(2)]} p.s.s. values observed with the second group of sensitizers are not the result of additional singlet sensitization. They are ascribed to a specific additional route of isomerization for the α-pyran via singlet exciplex formation which route is almost negligible for (E)-β-ionone. This explanation is in line with both the Stern–Volmer plots for the quenching of the fluorescence of fluoren-9-one by the α-pyran and by (E)-β-ionone [the quenching being far less with (E)-β-ionone than the α-pyran], and by the dependence of {[(1)]/[(2)]} p.s.s. on the total substrate concentration in the case of fluoren-9-one as a sensitizer. From the dependence of the photostationary state for the triplet photosensitized isomerization on the triplet energy of the sensitizer, it was concluded that the triplet energies of (E)-β-ionone and the isomeric α-pyran (2) are 54–56 and < 54 kcal mol–1, respectively.
TL;DR: In this article, the effects of hyperconjugation and charge delocalization in the charge transfer complex (CTC) and the role of charge complexation and of disproportionation and dissociation to free ions as light-wasting processes are discussed.