Triazine photolysis

Triazines biocides, 1, 398 Diels-Alder reactions, 2, 46 in non-silver photography, 1, 383 photolysis azetes from, 7, 283... 

The highly electrophilic 1,3,5-triazinylnitrene generated by photolysis of 2-azido-4,6-dimethoxy-l,3,5-triazine (24) does, however, bring about ring expansion of benzene to l-(4,6-dimethoxy-1,3,5-triazin-2-yl)-1//-azepine (25) in moderate yield.168... 

Atrazine is successively transformed to 2,4,6-trihydroxy-l,3,5-triazine (Pelizzetti et al. 1990) by dealkylation of the alkylamine side chains and hydrolytic displacement of the ring chlorine and amino groups (Figure 1.3). A comparison has been made between direct photolysis and nitrate-mediated hydroxyl radical reactions (Torrents et al. 1997) the rates of the latter were much greater under the conditions of this experiment, and the major difference in the products was the absence of ring hydroxylation with loss of chloride. 

The intervention of an intermediate with the symmetry of a benzocyclopropenone (166, R = Cl) is also demanded by the formation of methyl p-chlorobenzoate in the photolysis of the lithio derivative 173 of the chlorosubstituted 3-p-tolylsulpho-nylamino-benzo-l,2,3-triazin-4-one128) ... 

Thermal decomposition of a doubly labelled azidotriazole gave rise to the open-chain triazine (117) in which the labels were not scrambled. Laser flash photolysis of the triazole leads to (117) within 20 ns with no observable intermediate. Ab initio calculations indicate that a dynamic equilibrium between the open-chain triazine (117) and a cyctic nitrene (118), as originally proposed, is highly disfavoured. 

Photolytlc. The dye-sensitized photodecomposition of ametryn was studied in aqueous, aerated solutions (Rejto et al, 1983). When an aqueous ametryn solution was irradiated in sunlight for several hours, 2-(methylthio)-4-(isopropylamino)-6-amino-5-triazine and 2-(methylthio)-4-(iso-propylamino)-6-acetamido-5-triazine formed in yields of 55 and 2.6%, respectively. Continued irradiation of the solution led to the formation of 2-(methylthio)-4,6-diamino-5-triazine which eventually decomposed to unidentified products (Rejto et al., 1983). The UV (7, = 253.7 nm) photolysis of ametryn in water, methanol, ethanol, n-butanol, and benzene yielded the 2-//analog 4-(ethylamino)-6-isopropylamino-5-triazine. Photodegradation was not observed at wavelengths >300 nm (Pape and Zabik, 1970). 

Photolytic. The reported photolysis half-lives of chlorsulfuron in distilled water, methanol, and natural creek water at 1 >290 nm were 18, 92, and 18 h, respectively. In all cases, 2-chlorobenzenesulfonamide, 2-methoxy-4-methyl-6-amino-l,3,5-triazine, and trace amounts of the tentatively... 

Photolytic. The simulated sunlight (>, >230 nm) photolysis as a thin film on silica gel or sand yielded 6 (l,l-dimethylethyl)-3-(methylthio)-l,2,4-triazin-5-(4/ /)-one and two additional photoproducts. In both of the unnamed photoproducts, the methylthio group in the parent compound is replaced by oxygen and one of the compounds also underwent TV-deamination (Bartl and Korte, 1975). 

When prometryn in aqueous solution was exposed to UV light for 3 h, the herbicide was completely converted to hydroxypropazine. Irradiation of soil suspensions containing prometryn was found to be more resistant to photodecomposition. About 75% of the applied amount was converted to hydroxypropazine after 72 h of exposure (Khan, 1982). The UV (A = 253.7 nm) photolysis of prometryn in water, methanol, ethanol, /i-butanol, and benzene yielded 2-methylthio-4,6-bis(isopropylamino)-s-triazine. At wavelengths >300 nm, photodegradation was not observed (Pape and Zabik, 1970). Khan and Gamble (1983) also studied the UV irradiation (A = 253.7 nm) of prometryn in distilled water and dissolved humic substances. In distilled water, 2-hydroxy-4,6-bis(isopropylamino)-5-triazine and 4,6-bis(isopropylamino)-5-triazine formed as major products. 

The first derivative of 1,2,3-triazine to be prepared, the triphenyl compound (2, R = Ph), was obtained in 1960 by thermolysis of 1,2,3-triphenylcyclopropenyl azide (1, R = Ph)." The physical and spectral (IR and UV) properties of 2 were consistent with the assigned structure, and the presence of three contiguous carbon atoms was demonstrated by hydrolysis experiments, which resulted in formation of 1,2,3-triphenyI-butane-l,3-dione. Photolysis of 2 gave a mixture of nitrogen, benzo-nitriie, and diphenylacetylene. 

Oxidation of l-aminonaphtho[l,8-de]triazine (95) with lead tetraacetate has been shown by trapping experiments to result in formation of 1,8-dehydronaphthalene, again almost certainly via initial formation of the nitrene followed by loss of two molecules of nitrogen. " The same meta aryne is formed during the thermolysis of the lithium salt of l-p-toluenesulfonylaminonaphtho[l,8-de]triazine (119), in a formal oxidation process, while benzocyclopropenone (118) has similarly been generated by photolysis of the lithium salt 120. °... 

Photolysis of l-methylnaphtho[l,8-de]triazine (32, R = Me) also results in extrusion of nitrogen and formation of a diradical intermediate (167). Thus, reaction in cyclohexane as solvent gives, among other products, bicyclohexyl and 1-methylaminonaphthalene, while 8-phenyl-1-methylaminonaphthalene is the only product formed when benzene is used as solvent. Photochemical decomposition of 32, R = Me, in the presence of olefins results in an unusual ring transformation, and with a-methylstyrene, for example, the triazine is converted into the dihydroazaphenalene derivative (168). When vinyl bromide and trans-... 

Azido-4,6-dichloro-133-triazine 35, matrix isolated in argon at 10 K, yields triplet nitrene 36 and the strained cyclic carbodiimide 37 upon photolysis <99CC2113>. 

The general fragmentation pattern of monocyclic 1,2,3-triazines shows peaks for [M+-N2], for an acetylene, and for a nitrile, in accordance with the results of thermolysis and photolysis. The mass spectrum of the parent triazine showed peaks as follows 81 (M+, 47%), 53 (M+-N2, 69%), 27 (HCN,... 

Decomposition of l-methyl-2-pyrrolidinone (67) was studied by vapor-phase photolysis (72JA8281). Irradiation (Hg sensitized) led, in addition to extensive polymer formation, to the following products carbon monoxide (31%), ethene (24%), water (24%), l,3,5-trimethyl-hexahydro-l,3,5-triazine (8%), 1-methylazetidine (6%), 1-methylpyrrole, and methane (<1%). The mechanism of formation of most of these products involves... 

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