Showing papers on "Benzophenone published in 1971"
TL;DR: In this article, the triplet-triplet extinction coefficients of seventeen compounds have been determined in cyclohexane and benzene at room temperature by a method involving energy transfer, assuming no change of oscillator strength with solvent.
Abstract: The triplet-triplet extinction coefficients of seventeen compounds have been determined in cyclohexane and benzene at room temperature by a method involving energy transfer. Large changes in extinction coefficient at the wavelength maximum Iµ(λmax) were observed upon changing solvent from cyclohexane to benzene. Values of Iµ(λmax) were determined relative to a value of Iµ(λmax) for the ketyl radical (ϕ2ĊOH) of 3220 M–1 cm–1 in water, assuming no change of oscillator strength with solvent. A number of triplet transfer rates, and other reactivities of benzophenone triplet and ketyl radicals, were also estimated.
392 citations
TL;DR: In this article, the reduction of a wide series of p- and m-substituted benzophenones and 2-substantituted fluorenones is studied in dimethylformamide.
91 citations
TL;DR: In this paper, a detailed kinetic analysis suggests that this order results from decreasing rates (in the given order) of self dimerization of the semipinacol radicals.
85 citations
TL;DR: The rare earth series consists of the elements 57, lanthanum, through 71, lutetium, and Yttrium, and is also found to occur with these elements in nature and to display similar chemical behavior as discussed by the authors.
Abstract: Publisher Summary The replacement of the tedious fractional crystallization method of separation by the ion-exchange techniques used commercially today has made most of the lanthanide elements available in large-scale quantities of high purity. The increased availability of these metals and their compounds in the past few years has in turn promoted research which has resulted in new commercial applications. The rare earth series consists of the elements 57, lanthanum, through 71, lutetium. Yttrium, element 39, is also found to occur with these elements in nature and to display similar chemical behavior and is therefore generally classified with them. All four compounds are pyrophoric, rather thermally stable, and give positive tests with Michler's ketone. Reactions with mercuric chloride, carbon dioxide, and benzophenone give, respectively, phenyl mercuric chloride, benzoic acid, and triphenylcarbinol in good yields. A polymeric formulation has been suggested to explain the involatility and insolubility of the dried products, the initially isolated solids being benzene soluble, possibly as the result of monomer stabilization by tetrahydrofuran coordination.
47 citations
41 citations
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35 citations
TL;DR: In this article, the benzophenone-sensitised photo-oxidation of primary, secondary, and tertiary aliphatic amines and N-alkylanilines was investigated.
Abstract: Product studies are reported on the benzophenone-sensitised photo-oxidation of primary, secondary, and tertiary aliphatic amines and N-alkylanilines. Aliphatic amines gave aldehydes and imines, whereas N-alkylanilines were dealkylated but did not give imines. Amines which are known physical quenchers of singlet oxygen were efficiently oxidised. The reactivity of these compounds, and the type of products formed in the reaction, are explainable in terms of a mechanism in which hydrogen atom abstraction from the amine by triplet ketone is the primary chemical reaction. The results are not in accord with the participation of singlet oxygen. Quantum yield measurements of oxygen uptake, amine disappearance, and product formation are consistent with the proposed mechanism.
31 citations
TL;DR: In this article, the authors established the thermally activated delayed fluorescence process and observed a large temperature effect on the rate constant for nonradiative decay from the lowest triplet state to the ground singlet state.
29 citations
Patent•
29 Jul 1971TL;DR: A positive-acting printing plate having a coating containing a naphthoquinone-(1,2)-diazide-(2)-5-sulphonic acid derivative, the printing life of which has been improved by the inclusion of a polymeric carboxylic acid as mentioned in this paper.
Abstract: A positive-acting printing plate having a coating containing a naphthoquinone-(1,2)-diazide-(2)-5-sulphonic acid derivative, the printing life of which has been improved by the inclusion of a polymeric carboxylic acid. Specific derivatives are 2,3,4trihydroxy benzophenone tris- and 2,4-dihydroxy benzophenone bis(naphthoquinone-(1,2)-diazide-(2)-5-sulphonate). The coating includes a resin in particular an alkali-soluble novolak resin. The polymeric carboxylic acid is preferably present in an amount of 2 - 50 percent by weight based on the combined weight of said derivative and said resin. The invention makes possible the use of naphthoquinone-(1,2)-diazide-(2)-5-sulphonic acid derivatives hitherto unusable because of bad printing life of the plate.
28 citations
TL;DR: In this paper, a number of quinones have been found to photosensitize the decarboxylation of acids of the type R1XCH2·CO2H (where X = O, S, and NH).
Abstract: Benzophenone and a number of quinones have been found to photosensitize the decarboxylation of acids of the type R1XCH2·CO2H (where X = O, S, and NH). The yields of substituted hydrocarbons (R1XCH3) formed by hydrogen abstraction by the alkyl radicals (R1XĊH2) and of addition products formed by reaction of the radicals with tetrachloro-p-benzoquinone as well as reduction products of the quinones have been determined. The yields of substituted hydrocarbons were often considerably increased by the inclusion of the good hydrogen donor, thiophenol, in the reaction mixture. The amino-acid studied, was found to give a substantial yield of the related aniline as well as the expected N-methylaniline. The benzophenone-sensitized reactions were retarded by oxygen whereas those sensitized by quinones were not. Addition of acetic acid was found to retard the reaction of phenoxyacetic acid with tetrachloro-p-benzoquinone.
TL;DR: In this paper, the dipole moments of the lowest 3 nπ ∗ and 1 nπ∗ excited states of benzophenone have been determined by optical spectroscopic methods and are 1.79 D and 1.46 D respectively.
TL;DR: In this article, a selective attack of the excited carbonyl oxygen to the 4 position of N-methylimidazoles is proposed, which is in accord with results of simple Huckel calculations on N-methyl-methylidazole.
Patent•
06 Jul 1971
TL;DR: In this article, the authors present a procedure for PREPARING SUCH SOLUTIONS and for converting them to POLYIMIDES and TO POLYAMIC ACID PRECURSORS.
Abstract: MONOMERIC, RESINOID, SOLID STATE SOLUTIONS OF CERTAIN AROMATIC DIAMINES IN DERIVATIVES OF BENZOPHENONETETRACARBOXYLIC ACID. PROCESS FOR PREPARING SUCH SOLUTIONS AND FOR CONVERTING THEM TO POLYIMIDES AND TO POLYAMIC ACID PRECURSORS.
Patent•
22 Jan 1971TL;DR: An active sunscreen ingredient comprised of 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, neutralized with triethanolamine, and formulated with various compatible vehicles to produce effective sunscreens for human use is presented in this article.
Abstract: An active sunscreen ingredient comprised of 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, neutralized with triethanolamine, and formulated with various compatible vehicles to produce effective sunscreens for human use.
TL;DR: The photochemical reactions of some 2-alkyl-1,3-dioxolanes and 2-kioxolane in CFCl 3 in the presence of benzophenone yield exclusively the open 2-chloroethyl carboxylic esters and S -2-chlorosyl thiocarboxyl esters respectively as mentioned in this paper.
TL;DR: The reaction of AlkMgBr with Ph4SbF gives Ph 4SbAlk (Alk = CH3, C2H5) as discussed by the authors.
TL;DR: In this article, the authors present the results of an experimental study of the radiative decay of the lowest excited singlet state of the isolated benzophenone molecule, which exhibits predominantly the characteristics of strong singlet-triplet coupling.
Patent•
02 Feb 1971
TL;DR: In this article, a process of bleaching carboxylic acid esters and/or epoxy compounds by irradiating the esters with ultraviolet light in the presence of ketone is described.
Abstract: A process of bleaching carboxylic acid esters and/or epoxy compounds by irradiating the esters and/or epoxy compounds with ultraviolet light in the presence of ketone. The preferred compounds bleached are the epoxidized higher fatty acid esters. Benzophenone, acetophenone, and acetone are examples of some suitable ketones.
TL;DR: By observing electron spin resonance spectra during photolysis at room temperature, kinetic behaviors of short-lived free radicals are studied in photoreduction of benzophenone in alcohols, especially in ethanol, with and without sodium methoxide.
Abstract: By observing electron spin resonance spectra during photolysis at room temperature, kinetic behaviors of short-lived free radicals are studied in photoreduction of benzophenone in alcohols, especially in ethanol, with and without sodium methoxide In neutral solution, diphenylhydroxymethyl radicals and hydroxyethyl radicals are observed simultaneously This is a firm evidence, obtained from ESR, of hydrogen abstraction of excited benzophenone from ethanol Results indicate that (1) free radicals are the most efficiently generated by the light of ∼350 nm, (2) hydroxyethyl radicals transform into diphenylhydroxymethyl radicals if the concentration of benzophenone is high, and (3) the latter radicals disappear following the second order reaction In the presence of sodium methoxide, diphenylhydroxymethyl radicals transform into benzophenone ketyl anions Rate constants are determined, being 3×107 and ∼104 mole−1·1·sec−1 for the combination reaction between diphenylhydroxymethyl radicals and the proton transf
TL;DR: In this article, the electron spin resonance (e.s.r.) spectrum was interpreted due to the triphenylsiloxydiphenylmethyl radical, Ph2ĊOSiPh3.
Abstract: Thermal reaction of benzophenone with triphenylsilane at 400 °K produced an electron spin resonance (e.s.r.) spectrum which is interpreted due to the triphenylsiloxydiphenylmethyl radical, Ph2ĊOSiPh3.
Patent•
04 Oct 1971TL;DR: In this article, a class of stabilizers called N,N'-bis (3,5-di-t-butyl-4-hydroxybenzyl)3,4,3',4'-tetracarboxylic acid-diimide is described.
Abstract: Benzophenonetetracarboxylic acid diimides of 3,5-dialkyl-4-hydroxyphenylsubstituted amines of this invention effectively stabilize organic materials against the effects of heat and oxygen. The diimides of this invention are prepared by reacting the appropriate 3,5-dialkyl-4-hydroxyphenylsubstituted amine with benzophenone-3,4,3',4'-tetracarboxylic acid dianhydride or diimide. An example of this class of stabilizers is N,N'-bis(3,5-di-t-butyl-4-hydroxybenzyl)3,4,3',4'-tetracarboxylic acid-diimide.
TL;DR: In this article, the authors studied the effect of pressure on the defect phosphorescence of benzophenone crystals, and showed that squeezing the crystal irreversibly replaces exciton phosphorescence by defect phosphores, characterized by a ∼ 1000 cm−1 trap depth and lifetime of 3.7 msec.
Abstract: The phosphorescence from benzophenone crystals has been studied as a function of pressure at 77°K. Squeezing the crystal irreversibly replaces exciton phosphorescence by defect phosphorescence, characterized by a ∼ 1000‐cm−1 trap depth and a lifetime of 3.7 msec. The pressure effect on the defect phosphorescence is Δν = − 490 cm−1 and Δτ = − 0.5 msec for ΔP = 30 kbar.
TL;DR: In this article, the decay rates of benzophenone triplets were measured using laser flash photolysis in highly purified benzene, [2H6]benzene, and hexafluorobenzene.
Abstract: Decay rates of benzophenone triplets have been measured using laser flash photolysis in highly purified benzene, [2H6]benzene, and hexafluorobenzene; the results indicate a very small deuterium isotope effect, and enhanced rate of decay in hexafluorobenzene, and are most consistent with reversible triplet addition to the ring as the process responsible for the short triplet life-time.
TL;DR: Ozonolysis of tetraphenylethylene in acetone, methyl ethyl ketone or benzophenone yielded the corresponding ozonides 6a−c as discussed by the authors.
Abstract: Durch Ozonisierung von Tetraphenylathylen in Aceton, Methylathylketon oder Benzophenon lassen sich die Ozonide 6a–c darstellen
Preparation of Some Simple Ketozonides
Ozonolysis of tetraphenylethylene in acetone, methyl ethyl ketone or benzophenone yielded the corresponding ozonides 6a–c
Patent•
02 Dec 1971
TL;DR: A transition metal completex of 3,3''-METHYLENE-BIS-(5TERT.-BUTYL-2,4-DIHYDROXY BENZOPHENONE) was used to stabilize POLYOLEFINS against ULTRAVIOLET LIGHT as mentioned in this paper.
Abstract: A TRANSITION METAL COMPLEX OF 3,3''-METHYLENE-BIS-(5TERT.-BUTYL-2,4-DIHYDROXY BENZOPHENONE). THE COMPLEX CAN BE USED TO STABILIZE POLYOLEFINS AGAINST ULTRAVIOLET LIGHT.
TL;DR: The photochemical loss of cyanide from Mo(CN)84− is shown to be sensitized by common organic triplet donors naphthalene, phenanthrene, anthraquinone, and benzophenone, but not by biacetyl.
Abstract: The photochemical loss of cyanide from Mo(CN)84− is shown to be sensitized by common organic triplet donors naphthalene, phenanthrene, anthraquinone, and benzophenone, but not by biacetyl. This suggests that the reactive state may be 3B1, not the lower lying 3A2. The quantum yields for sensitized photolysis (near 0.25) are larger than for the direct reaction (near 0.15). This is unlike the behavior of Co(CN)63− where the similarity of the two yields leads to the conclusion that higher excited states are efficiently converted to "the lowest triplet".Naphthalene irradiated at 286 nm leads to a quantum yield of 0.4 which is, perhaps, associated with a new process involving sensitized production of a solvated electron.Thermal solvolysis rates in several media are also reported. The medium dependence of solvolysis is small.