Search results for "Hydroquinone"

Transformation of monuron photosensitized by soil extracted humic substances: energy or hydrogen transfer mechanism?

1997

The humic and fulvic acids extracted from a Ranker type soil sensitize the transformation of monuron. When monuron is irradiated at 365 nm in the presence of the fulvic acid, its degradation is faster in deoxygenated medium than in air-saturated solution. Chloride ions are released, and the para-hydroxylated derivative is formed as upon direct photolysis. It is deduced that the consumption of monuron observed in the absence of oxygen is due to an energy transfer from reactive triplet states of the fulvic acid to monuron. Energy transfer reactions also take place when hydroquinone or acetophenone are used as sensitizers, showing that the energy level of the triplet state of monuron is lower …

Chemoenzymatic synthesis of a poly(hydroquinone)

1999

Chemoenzymatic synthesis of a poly(hydroquinone) was achieved by enzymatic oxidative polymerization of 4-hydroxyphenyl benzoate, followed by alkaline hydrolysis of the resulting polymer. The polymerization of 4-hydroxyphenyl benzoate was performed using a peroxidase and hydrogen peroxide as catalyst and oxidizing agent, respectively, in an aqueous organic solvent. Soybean peroxidase afforded the polymer in good yields. IR analysis of the polymer showed the formation of the polymer consisting of a mixture of phenylene and oxyphenylene units. By alkaline hydrolysis of the resulting polymer, benzoate moiety was completely removed to give poly(hydroquinone).

Phytochemical constituents and chemosystematic significance of Pulicaria jaubertii E.Gamal-Eldin (Asteraceae)

2018

Abstract The chemical characterization of methylene chloride/methanol (1:1) extract of the air-dried whole medicinal plant, Pulicaria jaubertii E. Gamal-Eldin, led to isolation and identification of two new hydroquinone compounds; 2-(2-acetoxy propyl), 5-methyl hydroquinone (1) and 2-(2-hydroxy propyl), 5-methyl hydroquinone-4-O-β-D-glucopyranoside (2), four known flavonols (3-6) and 7 known dihydroflavonols (7-13). The structures were established depending upon comprehensive analysis of the NMR, IR and HR/EI-MS data. Herein, compounds 6, and 10-13 were isolated for the first time from this plant. The chemotaxonomic significance of the isolated flavonoids from P. jaubertii comparing with th…

Über die cyclopolymerisation einiger bis-(N-vinyl)-verbindungen

1966

Durch Umsetzung von Vinylisocyanat mitAthylenglykol, Butandiol-1,4, Hexandiol-1,6, Octandiol-1,8, Brenzcatechin, Resorcin, Hydrochinon, cis- und trans-Chinit sowie Piperazin wurden die entsprechenden Bis-(N-vinyl)-Verbindungen hergestellt. Diese Monomeren werden unter gleichen Bedingungen radikalisch polymerisiert. Der Gehalt an seitenstandigen N-Vinylgruppen ergibt sich aus der bei saurer Hydrolyse gebildeten Menge Acetaldehyd. Der auf 0% Umsatz berechnete Doppelbindungsgehalt und damit der Cyclisierungsgrad hangt von der Struktur der Monomeren ab. Die Ergebnisse stimmen uberein mit der Ringbildungstendenz bei niedermolekularen Verbindungen (z. B. Ansaverbindungen) und werden an Hand von M…

Die zweifache unterdrückung der polymerisation einiger bis(methacrylsäureester) mittels radikalischer additionsreaktionen

1973

Aus Hydrochinon, Resorcin, Dihydroxydiphenylen und Dihydroxynaphthalinen wurden mit Methacrylsaurechlorid Bis(methacrylsaureester) hergestellt. Setzte man diese in siedendem Benzol mit groser Verdunnung gelosten Ester dem Angriff von Radikalen aus α.α′-Azoisobuttersauredinitril (Primarradikale) aus, dessen Uberschus in Beziehung zum Ester mindestens zwanzigfach molar war, so erhielt man mittels saulenchromatographischer Trennung Verbindungen, bei denen je olefinische Doppelbindung zwei Primarradikale addiert waren (unterdruckte Polymerisation). Die Struktur dieser Produkte wurde mittels Elementaranalyse, Molekulargewichtsbestimmung, IR- und 1H-NMR-Spektren bewiesen. Demnach kann die Polymer…

Cyclic esters of aliphatic diacids with pyrocatechol and hydroquinone

1985

Cyclic esters of adipic acid, suberic acid and sebacic acid were prepared by reaction of the acid dichlorides and pyrocatechol or hydroquinone in benzene under high dilution conditions. While only the cyclic dimers could be obtained from hydroquinone, pyrocatechol formed cyclic monomers as well as cyclic dimers (and also a cyclic dimer with succinic acid). The structure of all compounds was confirmed by1H-NMR- and mass spectra. The crystal structures of the pyrocatechol esters were determined by single crystal X-ray analysis.

ChemInform Abstract: High-Yield Formation of Arbutin from Hydroquinone by Cell-Suspension Cultures of Rauwolfia serpentina.

2010

ChemInform Abstract: Cyclic Esters of Aliphatic Diacids with Pyrocatechol and Hydroquinone.

1986

Cyclic esters of adipic acid, suberic acid and sebacic acid were prepared by reaction of the acid dichlorides and pyrocatechol or hydroquinone in benzene under high dilution conditions. While only the cyclic dimers could be obtained from hydroquinone, pyrocatechol formed cyclic monomers as well as cyclic dimers (and also a cyclic dimer with succinic acid). The structure of all compounds was confirmed by1H-NMR- and mass spectra. The crystal structures of the pyrocatechol esters were determined by single crystal X-ray analysis.

Total Synthesis of Lavendamycin by a [2+2+2] Cycloaddition

2011

The total synthesis of the bacterial-derived, pentacyclic, antitumor antibiotic lavendamycin has been achieved through a highly convergent strategy. The key step of this synthesis is a ruthenium-catalyzed [2+2+2] cycloaddition of an electron-deficient nitrile to an alkynyl-ynamide to prepare the carboline scaffold. The elaborate cycloaddition substrate is obtained in few steps by an N-ethynylation using alkynyliodonium salt chemistry and two palladium-catalyzed cross-coupling reactions. An efficient synthesis of a halogenated quinoline-5,8-dione building block starting from hydroquinone is presented.