1.2.3- Triazine radical substitution

There are no accounts of free-radical substitution reactions of 1,2,3-triazines. 

Free-radical substitution reactions of 1,2,4-triazines have been limited to coupling reactions at the 5-position. These are induced by either potassium in liquid ammonia or by means of a photochemical process shown in Scheme 9 (84MI5). 

In acetonitrile, reduction potentials have been determined for 22 substituted 1,2,4-triazines.347 3,5-Disubstituted and 3,5,6-trisubstituted triazines show reversible behavior, with the formation of the corresponding anion-radicals the anion-radicals from 5-unsubstituted triazines are less stable and react probably by dimerization. 

Oxidation of 1-aminobenzimidazoles with manganese dioxide or lead tetraacetate can give either 1,1 -azobenzimidazoles (735) or 3-substituted benzo-l,2,4-triazines (736). Electrochemical measurements have shown that the first step in this reaction is removal of an electron from a ir-orbital of benzimidazole rather than from the A-amino group. Because the cation radical which is formed must be stabilized by loss of a proton, for (736) to form the 2-substituent must contain an NH or OH group. This is unnecessary for the formation of the azo product (735) which may form via a nitrene intermediate. 

Triazine (e.g., atrazine, simazine) and substituted urea (e.g., diuron, monuron) herbicides bind to the plastoquinone (PQ)-binding site on the D1 protein in the PS II reaction center of the photosynthetic electron transport chain. This blocks the transfer of electrons from the electron donor, QA, to the mobile electron carrier, QB. The resultant inhibition of electron transport has two major consequences (i) a shortage of reduced nicotinamide adenine dinucleotide phosphate (NADP+), which is required for C02 fixation and (ii) the formation of oxygen radicals (H202, OH, etc.), which cause photooxidation of important molecules in the chloroplast (e.g., chlorophylls, unsaturated lipids, etc.). The latter is the major herbicidal consequence of the inhibition of photosynthetic electron transport. 

Successive substitution of carbon by nitrogen lowers the energy of the LUMO. As a consequence, the ease of reduction and the stability of radical anions are increased from benzene to pyridine, diazines, triazines, and tetrazines. 

Halogenated Ketones and Trichloromethyl Triazines It is known that halogenated ketones liberate a Cl radical upon light exposure [45]. Substituted tris-(trichloromethyl)-l,3,5-triazines (10.25) generate a chlorine radical and a carbon-centered radical through the cleavage of a C-Cl bond [46,47] their absorption maxima are located around 400 nm. 

Triazines (XXXII) are a class of symmetrical initiators where multiple fragmentations are brought about by a scission, which on excitation dissociate into three substituted nitriles (XXXIII) (Scheme 631) Specifically, the primary photoproducts are not radicals, but they dissociate into radicals in a secondary thermal step (Scheme 6.38). ... 

Polyguanamine Isopropenyl substituted triazine Styrene, MMA Radical 105... 

TFE undergoes free radical addition reactions typical of other olefins. It readily adds Br, Cl, and I, halogen halides IBr and ICl, and nitrosyl halides such as NOCl and NOBr. Additional reactions of chloro-fluoromethanes and chloromethanes in the presence of catalysts like aluminum chloride have been reported [48]. A variety of other compounds such as alcohols, primary amines and ammonia can be reacted with TFE to prepare tetrafluoroethers (HCF CF OR), difluoroacetamide (HCF CONHR) and substituted triazines. Oxygen can be added to TFE to produce polymeric peroxide or TFE epoxide. In the absence of hydrogen, sodium salts of alcohols will react with TFE to yield trifluorovinylethers (ROCF = CF ), which can be homo- and copolymerized. 

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