Photooxidation products

Stephanou EG (1992) a,cd-dicarboxylic acid salts and a,co-dicarboxylic acids. Photooxidation products of unsaturated fatty acids, present in marine aerosols and marine sediments. Naturwiss 79 28-131. 

Stephanou EG, N Stratigakis (1993) Oxocarboxylic and a,co-dicarboxylic acids photooxidation products of biogenic unsaturated fatty acids present in urban aerosols. Environ Sci Technol 27 1403-1407. 

Deoxycytidine (dCyd) (14 in Scheme 2) is also an excellent target for one-electron oxidation reactions mediated by triplet excited menadione. On the basis of extensive identification of dCyd photooxidation products, it was concluded that this nucleoside decomposes by competitive hydration and deprotonation reactions of cytosine radical cations with yields of 52% and 40%, respectively [53]. It was also found, on the basis of 180 labeling experiments, that hydration of cytosine radical cations (15) predominantly occurs... 

Dietary modification of human macular pigment density. Invest Ophthalmol Vis Sci. 38, 1795-1801. Jang, Y.P., Matsuda, H., Itagaki, Y., Nakanishi, K., Sparrow, J.R., 2005. Characterization of peroxy-A2E and furan-A2E photooxidation products and detection in human and mouse retinal pigment epithelial cells lipofuscin. J Biol Chem. 280, 39732-39739. 

Initiation by light accelerates oxidation due to the photochemical generation of free radicals, which was noticed by Backstrom [16] and repeated by many others [9,11 — 13], The quantum yield ([Pg.57]

The observed ambient organic aerosol formation rates are also consistent with those estimated by extrapolation of smog-chamber kinetic data. Other heavy unsaturates, such as styrene and indene, are present in the atmosphere and may contribute, in part, to the formation of benzoic acid and homophthalic acid, respectively. Diesel exhaust and industrial emission are possible sources of such heavy unsaturates. Diolefins of C6+ are not present in gasolines and exhaust gases and have not been found in the atmosphere, and their possible role as precursors of the Cs-7 difiinctional acidic compounds is seriously challenged. Lower diolefins are emitted in automobile exhaust. Examination of vapor-pressure data indicates that the bulk of their expected photooxidation products remains in the gas phase, including most of the less volatile C3-4 dicarboxylic acids. 

Photolytic. A photooxidation rate constant of 6 x 10 " cm /molecule-sec at room temperature was reported for the vapor-phase reaction of benzene with OH radicals in air (Atkinson, 1985). The reported rate constant and half-life for the reaction of benzene and OH radicals in the atmosphere are 8.2 x 10 M/sec and 6.8 d, respectively (Mill, 1982). Major photooxidation products in air include nitrobenzene, nitrophenol, phenol, glyoxal, butanedial, formaldehyde, carbon dioxide, and carbon monoxide (Nojima et al., 1975 Finlayson-Pitts and Pitts, 1986). 

Photolytic. Major products reported from the photooxidation of butane with nitrogen oxides under atmospheric conditions were acetaldehyde, formaldehyde, and 2-butanone. Minor products included peroxyacyl nitrates and methyl, ethyl and propyl nitrates, carbon monoxide, and carbon dioxide. Biacetyl, tert-butyl nitrate, ethanol, and acetone were reported as trace products (Altshuller, 1983 Bufalini et al, 1971). The amount of sec-butyl nitrate formed was about twice that of n-butyl nitrate. 2-Butanone was the major photooxidation product with a yield of 37% (Evmorfopoulos and Glavas, 1998). Irradiation of butane in the presence of chlorine yielded carbon monoxide, carbon dioxide, hydroperoxides, peroxyacid, and other carbonyl compounds (Hanst and Gay, 1983). Nitrous acid vapor and butane in a smog chamber were irradiated with UV light. Major oxidation products identified included 2-butanone, acetaldehyde, and butanal. Minor products included peroxyacetyl nitrate, methyl nitrate, and unidentified compounds (Cox et al., 1981). 

In air, formyl chloride is the initial photooxidation product (U.S. EPA, 1985). In the presence of water, formyl chloride hydrolyzes to HCl and carbon monoxide (Morrison and Boyd, 1971). 

Photolytic. Dimethylnitramine, nitrous acid, formaldehyde, V.V-dimethylformamide and carbon monoxide were reported as photooxidation products of dimethylamine with NOx. An additional compound was tentatively identified as tetramethylhydrazine (Tuazon et al., 1978). In the atmosphere, dimethylamine reacts with OH radicals forming formaldehyde and/or amides (Atkinson et al, 1978). The rate constant for the reaction of dimethylamine and ozone in the atmosphere is 2.61 x 10 cmVmolecule-sec at 296 K (Atkinson and Carter, 1984). 

Photolytic. Methyl vinyl ketone and methacrolein were reported as major photooxidation products for the reaction of 2-methyl-l,3-butadiene with OH radicals. Formaldehyde, nitrogen dioxide, nitric oxide, and HO2 were reported as minor products (Lloyd et al, 1983). Synthetic air containing gaseous nitrous acid and exposed to artificial sunlight (X = 300-450 nm) photo-oxidized 2-methyl-1,3-butadiene into formaldehyde, methyl nitrate, peroxyacetal nitrate, and a compound tentatively identified as methyl vinyl ketone (Cox et al, 1980). 

Photolytic. When synthetic air containing gaseous nitrous acid and 4-methyl-2-pentanone was exposed to artificial sunlight k = 300-450 nm), photooxidation products identified were acetone, peroxyacetal nitrate, and methyl nitrate (Cox et al, 1980). In a subsequent experiment, the OH-initiated photooxidation of 4-methyl-2-pentanone in a smog chamber produced acetone (90% yield) and peroxyacetal nitrate (Cox et al, 1981). Irradiation at 3130 A resulted in the formation of acetone, propyldiene, and free radicals (Calvert and Pitts, 1966). 

Photolytic. Photooxidation products reported include 2,2 -dihydroxy-4,4 -dimethylbiphenyl, 2-hydroxy-3,4 -dimethylbiphenyl ether, and 4-methylcatechol (Smith et al., 1978). Anticipated products from the reaction of 4-methylphenol with ozone or OH radicals in the atmosphere are hydroxynitrotoluene and ring cleavage compounds (Cupitt, 1980). Absorbs UV light at a maximum wavelength of 278 nm (Dohnal and Fenclov4, 1995). 

Irradiation of toluene in the presence of chlorine yielded benzyl hydroperoxide, benzaldehyde, peroxybenzoic acid, carbon monoxide, carbon dioxide, and other unidentified products (Hanst and Gay, 1983). The photooxidation of toluene in the presence of nitrogen oxides (NO and NO2) yielded small amounts of formaldehyde and traces of acetaldehyde or other low molecular weight carbonyls (Altshuller et al, 1970). Other photooxidation products not previously mentioned include phenol, phthalaldehydes, and benzoyl alcohol (Altshuller, 1983). A carbon dioxide yield of 8.4% was achieved when toluene adsorbed on silica gel was irradiated with light X >290 nm) for 17 h (Freitag et ah, 1985). 

Photolytic. Reported photooxidation products include phosgene, chlorine, HCl, and carbon dioxide (McNally and Grob, 1984). Acetyl chloride (Christiansen et al, 1972) and trichloroacetaldehyde (U.S. EPA, 1975) have also been reported as photooxldatlon products. 

Photolytic. Irradiation of vinyl chloride in the presence of nitrogen dioxide for 160 min produced formic acid, HCl, carbon monoxide, formaldehyde, ozone, and trace amounts of formyl chloride and nitric acid. In the presence of ozone, however, vinyl chloride photooxidized to carbon monoxide, formaldehyde, formic acid, and small amounts of HCl (Gay et al, 1976). Reported photooxidation products in the troposphere include hydrogen chloride and/or formyl chloride (U.S. EPA, 1985). In the presence of moisture, formyl chloride will decompose to carbon monoxide and HCl (Morrison and Boyd, 1971). Vinyl chloride reacts rapidly with OH radicals in the atmosphere. Based on a reaction rate of 6.6 x lO" cmVmolecule-sec, the estimated half-life for this reaction at 299 K is 1.5 d (Perry et al., 1977). Vinyl chloride reacts also with ozone and NO3 in the gas-phase. Sanhueza et al. (1976) reported a rate constant of 6.5 x 10 cmVmolecule-sec for the reaction with OH radicals in air at 295 K. Atkinson et al. (1988) reported a rate constant of 4.45 X 10cmVmolecule-sec for the reaction with NO3 radicals in air at 298 K. 

Irradiation of ///-xylene isomerizes to p-xylene (Calvert and Pitts, 1966). Glyoxal, methylglyoxal, and biacetyl were produced from the photooxidation of ///-xylene by OH radicals in air at 25 °C (Tuazon et al, 1986a). The photooxidation of ///-xylene in the presence of nitrogen oxides (NO and NO2) yielded small amounts of formaldehyde and a trace of acetaldehyde (Altshuller et al, 1970). ///-Tolualdehyde and nitric acid also were identified as photooxidation products of ///-xylene with nitrogen oxides (Altshuller, 1983). The rate constant for the reaction of ///-xylene and OH radicals at room temperature was 2.36 x 10 " cmVmolecule-sec (Hansen et al., 1975). A rate constant of 1.41 x 10" L/molecule-sec was reported for the reaction of ///-xylene with OH radicals in the gas phase (Darnall et ah, 1976). Similarly, a room temperature rate constant of 2.35 x 10"" cmVmolecule-sec was reported for the vapor-phase reaction of ///-xylene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 2.22 x 10"" cm /molecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). Phousongphouang and Arey (2002)... 

CASRN 1836-75-5 molecular formula C13H7F3N2O5 FW 284.10 Chemical/Physical. When nitrofen as an aqueous suspension was irradiated using UV light (A. = 300 nm), 2,4 -dichloro-4 -aminodiphenyl ether formed as the major products (>80% of total product formation). In addition, 4-nitrophenol and 2,4-dichlorophenol formed as minor products (<10%). In cyclohexanone, the major photooxidation product was aminonitrofen (Ruzo et al., 1980). 

Acher, A.J. and Dunkelblum, E. Identification of sensitized photooxidation products of bromacil in water. /. Agric. Food Chem., 27(6) 1164-1167, 1979. 

Larson RA, Bott TL, Hunt LL, et al. 1979. Photooxidation products of a fuel oil and their antimicrobial activity. Environmental Science and Technology 13(8) 965-969. 

Figure 3 shows the absorption amd MOD spectra recorded under the same conditions during a photolysis of ZnPc(-2)(py). In the upper panel (ABS) are shown the initial absorption spectrum recorded before photolysis (daished line), identified by the intense Q bamd, and the final spectrum recorded at the completion of the photooxidation (solid line). The lower panel shows the MOD spectrum recorded for the photooxidized product, the [ZnPc(-l)(py)] between 300 and 860 nm (solid line), and the UV portion of the MOD spectrum of the unoxidized complex (dashed line) for comparision purposes. There wais still some residual unoxidized ZnPc present when the final spectra were recorded, and this results in the appearamce of... 

The triplet state redox potentials of the MPcL complexes, and the queuitum yields amd the EPR parameters for the photooxidation products of these species. 

Several research groups have focused their attention on the photooxidation of 2 -deoxyguanosine that is used as a model compound for DNA. The major photooxidation products of this nucleoside were identified and classified according to their formation through a radical mechanism (type I) or a singlet oxygen-mediated mechanism (type II). The major type I product was identified as 2,2-diamino-[(2-deoxy-p-D-e/7f/zro-pentofuranosyl)-4-amino]-5(27/)-oxazolone 98 (Fig. 7.16). ... 

Wiesen, E., I. Barnes, and K. H. Becker, Study of the OH-Initiated Degradation of the Aromatic Photooxidation Product 3,4-Dihy-droxy-3-hexene-2,5-dione, Environ. Sci. Technol., 29, 1380-1386... 

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