Showing papers on "Xanthene published in 1986"

Photopolymerizable composition containing a certain xanthene or thioxanthene dyestuff

Abstract: Disclosed is a photopolymerizable composition which is very sensitive to visible light The composition comprises a polymerizable compound and a photopolymerization initiator wherein the photopolymerization initiator comprises (a) a particular xanthene or thioxanthene dyestuff, (b) a photosensitizer selected from the group consisting of N-phenylglycine, 2,4,6-tris(trichloromethyl)-1,3,5-triazine, and a mixture of p-dimethylaminobenzoic acid isopentyl ester and 2,4-diisopropylthioxanthone, and (c) a peroxide

Thermospray ionization and tandem mass spectrometry of dyes

Abstract: Sixteen commercial dye samples and three liquid wastes from organic pigment and dye manufacture have been characterized without prior chromatography by thermospray ionization and low energy collision-activated dissociation of protonated molecules using a triple quadrupole mass spectrometer. Many samples contained precursors of the dyes and other by-products of the synthesis. Many of these components were identified by collision-activated dissociation experiments and by inspection of the chemistry of dye manufacture. Detection limits of 20–200 ng in the positive ion mode were obtained for seven dyes of the anthraquinone, triarylmethane, xanthene, coumarin, azo and sulfonated azo dye classes. Under conditions of negative ionization, detection limits for an anthraquinone dye and a sulfonated azo dye were about one order of magnitude higher.

Surface enhanced resonance Raman study on fluorescein dyes

Abstract: Fluorescein and its derivatives fluoresceinamine and diiodofluoresceiniodoacetamide have been studied by surface enhanced resonance Raman spectroscopy (SERRS). Adsorption of the dyes at the silver/electrolyte interface requires attractive interactions between polar side groups (such as NH2, OH and COOH) with the metal as a prerequisite for Raman enhancement and fluorescence quenching. It was possible to characterize two prototropic forms of fluorescein and fluoresceinamine by their SERR spectra. Only vibrations of the chromophoric part (xanthene) of the molecule contribute to the measured spectra. Substituents in the phenyl ring influence only the ability of adsorption and the structure of the adsorbed molecules.

CIDEP studies of the formation of benzyl-type radicals in the photoreduction of flavones

Abstract: The photochemical hydrogen abstraction reactions of flavone and its derivatives with some hydrogen donors in 2-propanol solutions were investigated at room temperature with the aid of a chemically induced dynamic electron polarization technique. When xanthene and N,N-diethylaniline were used as hydrogen donors, the ketyl radical of flavone was obtained through the n..pi..* character and charge-transfer interaction of the triplet state, respectively. When tri-n-butyltin hydride and sodium borodeuteride were used as hydrogen donors, the benzyl-type radicals of flavones were obtained through the ..pi pi..* character of the triplet states.

Stabilization of oil-in-water emulsions by gums

Abstract: Etude d'emulsions modele additionnees de gomme xanthane, de carboxymethylcellulose ou de methylcellulose

Quantitative extraction and concentration of synthetic water-soluble acid dyes from aqueous media using a quinine-chloroform solution

Abstract: Twenty-one water-soluble acid dyes, including eleven azo, five triphenylmethane four xanthene, one naphthol derivatives, used at practical concentrations for food coloration, were quantitatively extracted from water and various carbonated beverages into a 0.1 M quinine-chloroform solution in the presence of 0.5 M boric acid by brief shaking. Quantitative extraction of these dyes was also accomplished by the 0.1 M quinine-chloroform solution made conveniently from chloroform, quinine hydrochloride, and sodium hydroxide added successively to water or beverages containing boric acid. Quinine acted as a countercation on the dyes having sulfonic and/or carboxylic acid group(s) to form chloroform-soluble ion-pair complexes. The diacidic base alkaloid interacted with each acid group of mono-, di-, tri-, and tetrasulfonic acid dyes approximately in the ratio 0.8-0.9 to 1. The dyes in the chloroform solution were quantitatively concentrated into a small volume of sodium hydroxide solution also by brief shaking. The convenient quinine-chloroform method was applicable to the quantitative extraction of a mixture of 12 dyes from carbonated beverages, which are all currently used for food coloration. A high-pressure liquid chromatographic method is also presented for the systematic separation and determination of these 12 dyes following their concentration into the aqueous alkaline solution. The chromatogram was monitoredmore » by double-wavelength absorptiometry in the visible and ultraviolet ray regions.« less

Mechanism for triplet-state concentration quenching in xanthene dyes

Abstract: This paper studies the mechanism for the concentration self-quenching of the triplet states in the luminophores containing the internal heavy atoms. Two xanthene dyes have been chosen as objects of the study: eosin (FlBr/sup 2 -//sub 4/) and erythrosin (FlI/sup 2 -//sub 4/). The delayed fluorescence dependences, optical density changes, and phosphorescence intensity on dye concentration in the ground state are presented at room temperature. The identical values of the rate constants for erythrosin at low concentrations indicate that the annihilation is less effective than the triplet deactivation route as compared to eosin.

Thermal cycloaddition reaction of xanthene-9-thione with allenes: An ESR study

Abstract: During the parallel (2 + 2)- and (4 + 2)-cycloaddition reactions of aromatic thiones such as xanthene-9-thione with substituted allenes XCHCCH2 (X = OR, SR, NMe2, Ph), a strong ESR signal is observed. This signal is associated with the (4 + 2)-cycloaddition reaction, affording thiopyran derivatives 3,11b-dihydro-2-(X-methylene)-2H-thiopyrano[4,3,2-kl]xanthene F or 3,11b-dihydro-3X-2-methylene-2H-thiopyrano[4,3,2-kl]xanthene E. Computer analyses of this signal made possible its identification as emanating from a 9-xanthenyl radical substituted at the 1- and 9-positions. The type of xanthenyl radical that is formed in the thermal reaction E rad or F rad depends on the nature of the substituent X at the allenic system H2CCCHX. This investigation shows that where X = Ph and NMe2, xanthenyl radicals of structure E rad are produced, and where X = O-t-Bu and S-t-Bu xanthenyl radicals of structure F rad are produced. It is striking that this production is so selective. On irradiation (λ>254nm), the production of xanthenyl radicals is enhanced. The conformation of xanthenyl radicals E rad and the role of E rad and F rad in the formation of addition products E and F are discussed.