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Rose Bengal sensitized photooxidation

Baeckstrom and coworkers utilized the enhanced selectivity of singlet oxygen towards different types of double bonds, as the key step for the synthesis of trani-Sabinene . By using the method of simultaneous oxidation and reduction (Rose Bengal sensitized photooxidation in the presence of tetrabutylammonium borohydride) they managed to isolate compound 166 by a total conversion of 164 (Scheme 61). Compound 165 remained... [Pg.890]

Risk labels, lATA/ICAO, 751-3 Risk phrases, 621, 748, 749 River water, peroxide determination, 642 RNA, ozone disinfection, 616 ROS see Reactive oxygen species Rose Bengal sensitized photooxidation, 890 Rotational barriers, regioselective allylic hydroperoxide formation, 836, 847-9 Rotational isomers, peroxynitrous add, 8-9 Rotational spectra, ozonides, 721, 722-3 RP-HPLC, hydrogen peroxide determination, 627... [Pg.1487]

Figure 2. Quantum yields of the Rose Bengal sensitized photooxidation of Q shown in a plot derived from Equation 39. Figure 2. Quantum yields of the Rose Bengal sensitized photooxidation of Q shown in a plot derived from Equation 39.
Such a process can produce 02( Ag) with 80% efficiency and similar reactions involving peroxide decomposition have been documented [21]. Of particular interest is the use of the decomposition of the endoperoxides of aromatic compounds, which, when appropriately substituted can be used in water [22] and of water soluble phosphite/ozone adducts [23]. Such chemical methods can provide a critical control for reactions in which photoexcitation of a sensitizer is suspected of doing more than just produce 02(1Ag). A prime example involves the rose bengal sensitized photooxidation of relatively unreactive alkenes [24],... [Pg.220]

Recently, scale-up of photochemical reactions has significantly advanced, thanks to the development of microreactor technology. In the field of singlet oxygen, the first example in 2002 was the rose bengal-sensitized photooxidation of a-terpinene in a glass microchip [54]. Eighty percent conversion was obtained... [Pg.383]

Hatsui, T. and Takeshita, H., Rose Bengal-sensitized photooxidation of quadricyclane. A [2a + 2a -I- In] cycloaddition of singlet oxygen, Chem. Lett., 129-132,1993. [Pg.369]

Among the more interesting applications of polymer Rose Bengal is that of a sensitizer in studying the oxidation of other polymeric substrates [301]. Rose Bengal immobilized on Sepharose has been reported as a sensitizer for protein photooxidation [302], The oxygen uptake by the amino acids cysteine, hisitidine, methionine, tryptophan, and tyrosine was reported to be about 20% as much from the immobilized dye as from the free dye in aqueous solution. [Pg.373]

A number of workers have looked at the effect of photooxidation and photodynamic sensitizers on DNA. Rose Bengal photosensitizes strand breaks in double-stranded, supercoiled, pBR322 DNA the effect follows first-order kinetics with respect to light fluence and dye concentration. The reaction is substantially more efficient in the absence of oxygen, but the quantum yield of strand breaks in air is only 10 8. The results are consistent with the initiation of chain scission by Rose Bengal triplet, with some additional mechanism coming into play in the presence of oxygen. [Pg.374]

Substituent effects in the dye-sensitized (Rose Bengal or methylene blue) singlet oxygen photooxidation of a wide variety of furans have been investigated.287 Solvents effects on the value of p, which became less negative as polarity of the medium was increased was indicative of... [Pg.45]

The results of several control experiments made it clear that polymer rose bengal was an authentic singlet oxygen sensitizer.1 Photooxidation of typical singlet oxygen acceptors in non-polar... [Pg.225]

Photooxidation of alcohols to ketones in high yields is performed at room temperature with oxygen in the presence of at least 1 mol of a base (Na, NaH, NaOH, KOH, or terr-BuOK) under irradiation with rose bengal as a sensitizer [45]. [Pg.133]

Lead dioxide will oxidise 4,4 -(trimethylene)bis(2,6-di-t-butylphenol) leading to formation of a dispiro-compound by intramolecular cyclisation at the 4,4 -positions, and irradiation of this compound in a methylcyclohexane matrix at — 150°C gives 4,4 -(trimethylene)bis(2,6-di-t-butylphenoxy) diradical as a stable triplet species. Rose Bengal photooxidation of 2,3-dihydroxy-naphthalene and 2,7-dihydroxynaphthalene in basic aqueous solution gives the l,r-dimeric products by coupling of the radicals formed by electron transfer either to the excited sensitizer or to 02( Ag). ° The dimer which originates from 2,7-dihydroxynaphthalene is subject to further oxidation to 6,7-dihydroxyperylene-l,12-quinone. Irradiation of the dimethoxyphenol (82) under constant current electrolysis leads via (83) to formation of the substituted tricyclo[5.4.0.0 ]undec-8-ene (84) which can be converted into ( )-isoitalicene (85 R = Me, R = H). ... [Pg.218]

In the presence of Rose Bengal as sensitizer and under either aerobic or anaerobic conditions, proline is photodecarboxylated to A -pyrroline, and under similar conditions the methyl ester yields an equimolar mixture of A -and A -pyrroline-2-carboxylic acid methyl esters. These observations suggest that the reaction proceeds by a Type I photooxidation. [Pg.221]

The photooxidation of oxopurines such as caffeine, theophylline, theobromine, and 1,3,7-trimethyluric acid using Rose Bengal as sensitizer occurs by a type II mechanism. 3-Methyl-5-(methylamine)-l,5-dehydrohydantoin has been characterised as a reaction product, and evidence is presented which suggests that the initial exciplex formed between 02( Ag) and the oxopurine evolves into a zwitterionic transition state. [Pg.223]

Type II photooxidations involve energy transfer from triplet sensitizers to 302 to form what is now recognized as 02. Dyes such as rose bengal and methylene blue [187] and metal complexes such as ruthenium(bipyr)3 [188—189] are very efficient sensitizers in visible light with quantum efficiencies close to 1. The process is generally described by the reactions... [Pg.78]

Photooxidation Rose bengal (anionic) or methylene blue (cationic) as sensitizer... [Pg.352]


See other pages where Rose Bengal sensitized photooxidation is mentioned: [Pg.968]    [Pg.968]    [Pg.94]    [Pg.129]    [Pg.412]    [Pg.766]    [Pg.391]    [Pg.968]    [Pg.968]    [Pg.94]    [Pg.129]    [Pg.412]    [Pg.766]    [Pg.391]    [Pg.374]    [Pg.437]    [Pg.853]    [Pg.853]    [Pg.914]    [Pg.640]    [Pg.226]    [Pg.640]    [Pg.350]    [Pg.35]    [Pg.349]    [Pg.355]    [Pg.914]    [Pg.153]    [Pg.350]    [Pg.294]    [Pg.304]    [Pg.319]    [Pg.295]    [Pg.25]    [Pg.116]    [Pg.208]    [Pg.134]    [Pg.376]    [Pg.334]   
See also in sourсe #XX -- [ Pg.890 ]




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Bengal

Photooxidation Rose Bengal

Photooxidation sensitized

Photooxidation sensitizers

Rose Bengal-sensitized

Rose bengale

Sensitizer rose bengale

Sensitizing rose bengal

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