Photolysis of aqueous solutions

By observation of its absorption spectrum [12], the production of ejq has been demonstrated in the flash photolysis of aqueous solutions of inorganic ions, e.g. 

Efficient production of hydrated electrons can be observed in these systems using radiation of 254 nm. More recently, Boyle et al. [13] have identified eaq as a product of the direct photoionization of water at 195 nm. 

Photolysis of an alkaline solution saturated with hydrogen provides a good source of eeq. The reactions occurring are 

Photolysis of aqueous solutions of certain organic substrates also produces e q. 

Studies of aromatic compounds show that photoionization in aqueous solution occurs for benzene derivatives with electron donating substituents, e.g. amines and carboxylic acids [14]. 

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The multiplicity of products produced in the photolysis of aqueous solutions of bromouracil and l,3-dimethyl-5-bromouracil has been thoroughly investigated by Ishihara and Wang.67 The products, which in neither case included the cyclobutane-type dimer or the hydrate, are shown in Tables IV and V. 

The possibly complex composition of the dimer formed in pTpT photolysis68 is indicated by the observation that at least two different chromatographically separable dimers are formed in the photolysis of aqueous solutions of TpT11-69 (16a, R = H) along with two other photoproducts. For a process of such complexity, simple measurement of absorbance changes as a function of dose or other variable does not... 

In practice, however, photolysis of aqueous solutions of [Ru(bipy)3]2+ produces neither hydrogen nor oxygen in the absence of added catalyst, and despite initial claims106 to the contrary, this is also true for irradiation of monolayers of analogous cationic complexes containing surfactant bipyridyl ligands.107"109... 

Other derivatives of [Ru(bipy)3]2+ have also been used in reductive cycles178 180 and thus photolysis of aqueous solutions containing tris(2,2 -bipyrazinyl)Run ([RuL 3]2+) or tris(2,2 -bipyrimidyl)Run ([RuL"3]2+) with TEOA and MV24 leads to formation of MV+ with quantum yields of 0.77 and 0.44 respectively. These yields are increased to 0.98 and 0.85 if the solutions are degassed by freeze-pump-thaw cycles.181 At first sight, these reactions would appear to proceed by the oxidative route described in Section 61.5.4.2.2 but comparison of fcq (MV24-) and kq (TEOA) reveals that a reductive mechanism operates with MV2+ being reduced by [RuL 3]+ or [RuL"3]+. 

Following the classical observation of Lewis and his school (29, 30, 34) of the photoionization of aromatic molecules in rigid solvents, Land, Porter and Strachan (25) proved such processes in the flash photolysis of aqueous solutions of phenols. It was suggested (7, 15, 25, 38) that the primary photochemical act involves electron ejection. 

Barat F, Hickel B, Sutton J (1969) Flash photolysis of aqueous solutions of azide and nitrate ions. Chem Commun 125-126... 

I. Chemical mechanism. J Phys Chem A 107 1313-1324 Yu X-Y, Bao ZC, Barker JR (2004) Free radical reactions involving Cl", Cb-", and SCV" in the 248 nm photolysis of aqueous solutions containing S2082"and Cl". J Phys Chem A 108 295-308 Zehavi D, Rabani J (1972) The oxidation of the bromide ion by hydroxyl radicals. J Phys Chem 76 312-319... 

Direct photolysis of aqueous solutions of the 2-chloro-.v-iriaz.ine herbicides (atrazine, simazine, propazine) proceeds via excitation of the triazine molecule, followed mainly by dechlorination and hydroxylation to form the corresponding hydroxytriazine (Pape and Zabik, 1970 Khan and Schnitzer, 1978 Chan et al, 1992 Lai et al, 1995 Schmitt et al, 1995 Sanlaville et al, 1997 Torrents et al, 1997 Texier et al, 1999b Hequet et al, 2001). This observation - plus the fact that when 2-chloro-v-triazine herbicides are photolyzed in methanol, ethanol, and n-butanol, the respective 2-alkoxy derivatives are formed - indicates a mechanism involving photochemical solvolysis rather than the involvement of hydroxyl radicals. This conclusion is supported by the fact that the rate of oxidation of atrazine was unaffected by the presence of either bicarbonate ion (Beltran et al, 1993) or ferf-butanol (Torrents et al, 1997), both strong hydroxyl radical scavengers. 

Table 23.2 Identified photolysis products3 resulting from photolysis of aqueous solutions of several triazine herbicides... 

Well studied primary reactive species in radiation- or photo-initiated reactions of auxiliary oxidants in an aqueous phase are hydrated electrons (eaq), hydrogen atoms (H ) and hydroxyl radicals ( OH), the last being by far the most important ones in photo-initiated AOPs. The formation and reactivity of ejq and of H were described by Hart and Anbar (1970) and by Buxton et al. (1988). Hydrated electrons can be produced by VUV photolysis of water, by photolysis of aqueous solutions of [FelCNlq]" or of V with formation of [Fe(CN)5] and il2, respectively (cf. Buxton et al, 1988). 

Gonzalez MC, Braun AM (1996) Vacuum UV Photolysis of Aqueous Solutions of Nitrate. Effect of Organic Matter. II. Methanol,/. Photochem. Photobiol. A Chem. 95 67-72. 

Gonzalez MC, Braun AM (1995) VUV Photolysis of Aqueous Solutions of Nitrate... 

Braun AM (1995) Oxidative Degradation of Nitrogen-containing Organic Compounds Vacuum-Ultraviolet (VUV) Photolysis of Aqueous Solutions of 3-Amino-5-Methylisoxazole, Fresenius /. Anal. Chem. 

The formation of saturated acids via ketenes by photolysis of aqueous solutions of steroid ketones is a general process. It has been demonstrated for C(s) , C(6> C(i2)- and... 

The irradiation of the phenoxazin-3-one dye, resazurin (21), in the presence of tertiary amines results in its efficient deoxygenation via the triplet state, forming the dye resorufin (22). The radiolysis/photolysis of aqueous solutions of pyrimidines produces radicals which are the result, in general, of 1-electron reduction involving hydrated electrons. The structures of the radicals were assigned on the basis of their by EPR spectra. The study included 2-hydroxypyrimidine... 

Oxidative deamination is the major reaction which takes place during the photolysis of aqueous solutions of amino acids under aerobic conditions (26). 

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