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Photooxidation phenothiazine

Photolysis reactions often are associated with oxidation because the latter category of reactions frequently can be initiated by light. The photooxidation of phenothiazines with the formation of N- and S-oxides is typical. But photolysis reactions are not restricted to oxidation. In the case of sodium nitroprusside, it is believed that degradation results from loss of the nitro-ligand from the molecule, followed by electronic rearrangement and hydration. Photo-induced reactions are common in steroids [36] an example is the formation of 2-benzoylcholestan-3-one following irradiation of cholest-2-en-3-ol benzoate. Photoadditions of water and of alcohols to the electronically excited state of steroids have also been observed [37],... [Pg.150]

Phenothiazine (PTZ) and ferrocene (Fc), both of which have a small reorganization energy associated to the electron transfer, are the first comediators that have been considered. Each has a potential that falls between 0.22 and 0.75 V versus SCE, respectively, the potential of the Co(DTB)33+/2+ and of the dye [Ru(H2DCB)-(dnbpy)(NCS)2]+/0. Because of the facile electron transfer, the photooxidized dye would be predominantly reduced by the comediator. Its oxidized form (PTZ+ and Fc +) can then be rapidly intercepted by Co(II), preventing the direct charge recombination between the oxidized comediator and the electrons in the 2. Nanosecond... [Pg.551]

A photochromic system based on the reversible photooxidation of the leuco forms of certain organic dyes has been described (B-76MI11401). Under appropriate conditions compounds such as the phenothiazine (150) can exist in different oxidation states (Scheme 17), each having significantly different absorption spectra. [Pg.387]

Organic Systems. The photooxidation and reduction reactions for most organic compounds require two electron processes and are generally irreversible. However, several phenothiazine dyes, such as Thionine and Methylene Blue, function as reversible two electron redox systems. The reversible photobleaching of chlorophyll may also involve a one or two electron process although the exact mechanism is still in doubt. One electron redox processes for organic molecules are possible... [Pg.294]

The identification of the major products of the photooxidation of phenothiazine upon its direct excitation does not support the idea of a N-hydroperoxy intermediate (Equation 5) (11). In fact, phenothia-zine-5-oxide (A) which has been first identified by comparing Rf values in thin layer chromatography of isolated and separately prepared samples (11) represents the best evidence of a singlet oxygen reaction (Equation 9) (12). [Pg.80]

Benzophenone (BP) sensitized photooxidation of phenothiazine leads mainly to the formation of products A and B (17). In view of the many data available from the literature and from our own experiments the published interpretation needs, however, some revision provided 3H-phenothiazine-3-ones are not products of a singlet oxygen reaction with ground state phenothiazine (c.f. methylphenothiazine), formation of products A and B implies two different oxidation mechanisms. Since singlet oxygen sensitization by benzophenone (Equations 10 to 12) is known to be very inefficient, reaction sequence (10), (13), (14), and (9)... [Pg.81]

Indeed, photooxidation of MPT in water/ethanol (1/2) leads, as expected from similar experiments with PTH (v. supra), to a complex mixture of products. The main components of the mixture have been separated and identified (22). 3-Hydroxy-10-methyl-phenothiazine (E) is not formed in a singlet oxygen reaction (26) in analogy to the products from the photooxidation of directly excited phenothiazine, the formation of E may be explained by a recombination of the products of reaction 23,... [Pg.85]

Our hypothesis is based on the observation that the photooxidation upon direct excitation of F yields G as well as a hydroxylated sulfone, too (28). Again, this reaction must involve oxidants other than singlet oxygen, for no reaction has been observed between the latter and ground state 10-methyl-phenothiazine-5-oxide (F). [Pg.86]

Photooxidation to 5-oxides was noticed when aqueous solutions of some phenothiazine drugs were exposed to light. ... [Pg.452]

There has been intensive study of the photooxidation of, mainly, phenothiazine systems. Allusion has already been made to the formation of both 251 and 252 upon photolysis of phenothiazine in ethanol in the previous section. [Pg.137]

Among this array of somewhat conflicting evidence on the photooxidation of phenothiazine lies a truth which accounts for the initial confusion of 251 and 252. There are several reports that the stable ultimate product of the photooxidation of phenothiazine is the sulfoxide although... [Pg.139]

The photooxidation of 10-substituted phenothiazines, in particular the drug chlorpromazine, has been investigated, again with conflicting conclusions about mechanisms. The sulfoxide is again a principal... [Pg.139]

C02Me) in the presence of 2,4,6-triphenylpyrylium tetrafluoroborate as sensitizer gives cyclopropenes together with 2H-pyrroles which arise by solvent addition to the 1,3-radical cation intermediate. Phenylmercaptotetrazole has been photo-catalytically oxidised on aerated Ti02 dispersions (Xjn- >330 nm) and a mechanism suggested which involves the formation of CO2, S04, NOa, and NH4. Photooxidation of phenothiazine in either benzene or cyclohexane in the presence of molecular oxygen has been shown by EPR experiments to give the phenothiazine nitroxyl radical rather than the radical cation. These observations are supported by the results of AMI calculations. The photooxidation of Azure A (81) as well as its fluorescence properties have been studied in the presence of P-cyclodextrin, and this has enabled an induced fluorimetric method to be developed for the determination of (81). ... [Pg.218]

Barium acrylate may be polymerized in solution by dye-sensitized photoinitiation in the presence of a reducing agent. Typical dyes are phenothiazine dye photooxidants such as methylene blue or thionine. The reducing agent may be a sulfinic acid such asp-toluenesulfinic acid [111]. [Pg.343]


See other pages where Photooxidation phenothiazine is mentioned: [Pg.81]    [Pg.87]    [Pg.89]    [Pg.19]    [Pg.138]    [Pg.138]    [Pg.139]    [Pg.362]    [Pg.2005]    [Pg.119]    [Pg.261]   
See also in sourсe #XX -- [ Pg.79 , Pg.80 , Pg.81 ]




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Phenothiazine-5-oxide, photooxidation

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