Photolysis in aqueous solutions

Evidence for the existence of a ketene intermediate was first obtained by Nakamura et al. (1972) in a study of the photolysis of 2,1-diazonaphthoquinone-5-sulfonic acid by flash photolysis in aqueous solution. An intermediate with a strong absorption at 350 nm and a lifetime of approximately 2 ms was found. 

Certain aromatic N-oxides undergo rearrangement by a process equivalent to that observed in nitrones to give the corresponding lactam. This is illustrated by the conversion of 2,5-dimethylpyrazine 1-oxide (179) into the lactam (180) by photolysis in aqueous solution.150... 

The photoaddition of water to a variety of naturally occurring pyrimidine derivatives has been reported. Photolysis in aqueous solution of uracil (224 R = H), uridine (224 R=ribosyl), and uridylic acid results in the formation of the corresponding 6-hydroxy-5,6-dihydropyrimidine (225)208-210 these structures have been established by independent synthesis.209 Analogous photoadditions have been observed in 1,3-dimethyluracil211 and 5-fluorouracil.212 These additions are reversible. 

The quantum yield for this process at 3130 A. has been determined to be of the same order of magnitude in the vapor phase, in the pure liquid and in methyl pentane solution (29). The significance of this surprising result is difficult to assess at present since the data are sparse. In photolysis in aqueous solution a reaction has been observed (17) which bears resemblance to both eq. 18 and 52. It leads to the formation of caproic acid, the net reaction being the addition of a molecule of water and cleavage of the ring in the ketone molecule. 

Candeias LP, Steenken S (1992b) Ionizing purine nucleosides and nucleotides and their components by 193-nm laser photolysis in aqueous solution model studies for oxidative damage of DNA. J Am Chem Soc 114 699-704... 

Mossoba MM, Rosenthal I, Riesz P (1981) ESR and spin-trapping studies of dihydropyrimidines, y-Radiolysis in the polycrystalline state and UV photolysis in aqueous solution. Int J Radiat Biol 40 541-552... 

Marciniec B. Photochemical decomposition of phenazone derivatives. Part 3 kinetics of photolysis in aqueous solutions. Pharmazie 1984 39 103-106. 

From these results and others from UV-vis absorption spectroscopy and differential pulse polarography (data not shown), Garbin et al. (2007) concluded that HS can act as photocatalyst to pesticide photolysis in aqueous solution only for specific ranges of concentration (as seen in Figure 16.12), which in turn depended on the HS and pesticide chemical characteristics. Under ultraviolet and visible radiation, this photocatalysis is based on photogeneration of -OH radicals, and the susceptibility of pesticide molecules to -OH attacks defines the efficiency of the photocatalysis. 

Indirect Photolysis in Aqueous Solution Involving Energy Transfer... 

Scheme 4 Products of 2-haIoaniline photolysis in aqueous solution...

Einschlag FG, Feliz MR, Capparelli AL (1997) Effect of Temperature on Hydrogen Peroxide Photolysis in Aqueous Solutions, J. Photochem. Photobiol. A Chem. 110 235-242. 

Gurol MD, Akata a (1996) Kinetics of Ozone Photolysis in Aqueous Solution, Am. Inst. Chem. EngJ. 42, No. 11 3283-3292. 

Surface water u = (14.5 0.3) min for direct photolysis in aqueous solutions (Peijnenburg et al. 1992). Ground water ... 

The fact that the quantum yields determined in the condensed phase are lower than those obtained in the vapour phase may be due to (i) efficient deactivation of the excited acetone molecules, or ( ) recombination of the CH3CO and CH3 radicals in the solvent cage . A decision between these alternatives might be made by studying the solvent effect. Namely, the lowest quantum yields are expected to occur in the photolysis of liquid acetone or in the photolysis in aqueous solution if efficient deactivation or if the cage effect, respectively, were responsible for the low quantum yields in condensed phase. On the basis of the results presented in Table 18, as well as on those of Pieck and Steacie made with mixtures of liquid acetone and acetone-rfg, the quenching hypothesis seems to be more likely. However, probably both effects play some role. 

Primary Amines. The photolysis of neat primary amines was undertaken relatively recently by Pfordte and Leuschner (212) in 1961, but some earlier studies by Booth and Norrlsh (213), and later studies by Pouyet (214) and Niu (124) and Stenberg et al, (215) have been carried out in hydrocarbon solvents. Pouyet (216) investigated their photolysis in aqueous solutions. 

A few years later the author noticed a report by Kraeutler that stated that methylcobalamine is stable under photolysis in aqueous solution in the absence of radical scavengers, but that the presence of CO in moderate concentration (0.03 M) leads to acetylcobalamine in high yield.11 The explanation (Scheme 7) was again unusual in view of the known propensity of methyl and acetyl radicals for rapid coupling reactions. 

West has recently reported intramolecular [4 + 4] cycloadditions of furan and 2-pyrone under photolysis in aqueous solution [49]. The exo and endo adducts are obtained in varying ratios when 31 bearing a variety of substituents is photolyzed in an aqueous solution of LiCl, Eq. 21. 

Pawlaczyck, J. and Turowska, W., 1976, Identification of certain photoproducts of sulfanilamide photolysis in aqueous solutions, Arch. Pol. Pharm. 33, 505-509. 

It is interesting that, on the other hand, paraquat does not undergo photolysis in aqueous solution (Slade, 1966), but adsorbed on silica gel or at the leaf surface, depending on the intensity of light, 25-50% is photolysed into 4-carboxyl-1-methylpyridinium chloride and methylamine within three weeks (Calderbank, 1968) ... 

The photochemical behaviour of BrO differs from that of other oxyhalo-anions XO -.457 Thus photolysis in NaOH glasses at 77 and flash photolysis in aqueous solution provided evidence for participation of reactions (94) and (95) but not for O7 or 0(8P) production. The absence of O7 is attributed to the low stability of Br03. The photolysis of powdered samples of NaC103, both with and without previous y-irradiation, has been investigated.458... 

PROBABLE FATE photolysis slow photolysis in aqueous solution, but fast in atmosphere is the principle fate, atmospheric and aqueous photolytic half-lives 0.5-1 hr oxidation not an important process, photooxidation half-life in air 25.4 hrs-10.6 days hydrolysis does not occur under natural conditions, relatively resistant to hydrolysis, one study reports a half-life of 3 weeks in aerobic soils under laboratory conditions volatilization too slow to be an important process, if released to the surface of warm, wet soils, it will quickly volatilize sorption does not occur biological processes no bioaccumulation, resistant to biodegradation under natural conditions... 

The formation of the ketene derived from 12 has been reported to be complete within 10 ns following laser photolysis in aqueous solution [110b]. For a microsecond TRIR study of 12, see S. Oishi, Y. Watanabe, Y. Kuriyama, Chem. Lett. 1994, 2187. Picosecond transient absorption experiments have indicated that the carbene derived from 13 (R=H) has a lifetime of 20 ps in methanol however, the ketene growth rate could not be determined due to overlap with carbene absorption J.J.M, Vleggaar, A. H. Huizer, P. A. Kraakman, W. P. M. Nijssen, R. J. Visser, C. A. G. O., Varma, J. Am. Chem. Soc. 1994, 116, 11754. See also Ref. 110a. 

The ionisation of purine nucleotides by 193 nm laser photolysis in aqueous solution has been... 

I) Ozone photolysis in aqueous solution results in the direct production of hydrogen peroxide... 

Iridium(ni).— Photochemical studies analogous to those described above have also appeared for the [Ir(NH3)8Na] + ion. In this case the quantum yields are again wavelength-dependent and appreciable for excitation in the ligand-field bands. An unidentified intermediate is also observed upon irradiating the complex in a glass at 77 K, or upon flash photolysis in aqueous solution. This intermediate is postulated to arise from a reaction between the nitrene complex, [Ir(NH8)5N] +, and the solvent water. In perchlorate, chloride, and sulphite media the observed reactions of the nitrene are... 

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