Sensitizing rose bengal

Since the sensitizer Rose Bengal is recyclable, relatively high concentrations (5 10 M) can be used without raising cost issues and optical detection problems [21]. Under these conditions, it was shovm that molecules at any position in the micro channel have a similar photon flux. 

Sensitizer rose bengal. b Sensitizer methylene blue. 

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... 

Until the beginning of this work, little was known about the effect of the polymer on the behavior of the sensitizer, rose bengal. In this paper we shall establish that the polymer is indeed an extremely important component of the chemistry of polymeric derivatives of rose bengal. 

An earlier report by Maruyama et al. described the formation of dimers (439) from the direct irradiation of the acetylquinone (440). In the presence of an electron-donating sensitizer (Rose Bengal) irradiation of the same quinone yields a different dimer assigned structure (441). A further account of the regio- and stereo-specific dimerization of the quinones (442) to yield (443) has been reported. The possibility of the involvement of an enol intermediate was considered. In one example, that of (444), dimerization failed and the cyclobutene derivative (455) was obtained via a Norrish Type II reaction. 

Recently, Ferroud et al. [154] found another dye sensitizer. Rose Bengal, highly effective as a visible light photoredox catalyst in the direct enantioselective a-alkylation of aldehydes with stabilized dimethyl 2-bromomalonate (132) (Scheme 8.40). The reaction proceeded smoothly under visible light irradiation at room temperature and with short reaction times when co-catalyst (LiCl) was used, providing a-alkylated aldehydes in high yields (up to quantitative yield) with high enantioselectivity (up to 85% ee). 

The role of rose bengal and other sensitizer dyes in the photodimerization of 2-acet5i-l,4-benzoquinone [1125-55-9] involves electron transfer but not singlet oxygen (42) (see Dyes, SENSITIZING). 

Dye-Sensitized Photoisomerization. One technological appHcation of photoisomerization is in the synthesis of vitamin A. In a mixture of vitamin A acetate (all-trans stmcture) and the 11-cis isomer (23), sensitized photoisomerization of the 11-cis to the all-trans molecule occurs using zinc tetraphenylporphyrin, chlorophyU, hematoporphyrin, rose bengal, or erythrosin as sensitizers (73). Another photoisomerization is reported to be responsible for dye laser mode-locking (74). In this example, one metastable isomer of an oxadicarbocyanine dye was formed during flashlamp excitation, and it was the isomer that exhibited mode-locking characteristics. 

Lee, P.C.C. and Rodgers, M.A.J. (1987). Laser flash photoki-netic studies of rose bengal sensitized photodynamic interactions of nucleotides and DNA. Photochem. Photobiol. 45, 79-86. 

The photosensitized transformation of carotenoids has been studied using several sensitizer molecules, such as chlorophylls, iodine, rose bengal (RB), and methylene blue (MB) and in general terms isomerization is the major pathway of reaction. 

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... 

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... 

With rose bengal and erythrosin as xanthene dye sensitizers, the... 

Competitive photooxygenation of the substrate pair 1-methyl-cyclopentene (AJ/l-methylcyclohexene (A2) was studied by Kopecky and Reich.123 Using rose bengal, erythrosin, and eosin, as well as methylene blue and hematoporphyrin as sensitizers, the ratio kg1/kg2 was found to be independent of the nature of the sensitizer used, in agreement with the assumption that singlet oxygen is the oxygenating intermediate. 

Oa-Consumption, in milliliters of 02 per minute, in Rose Bengal-Sensitized Photooxygenation of a-Terpinene in Different Solvents as a Function of Temperature (from ref. 124) ... 

---