“…A similar electron movement, induced by the electron-attracting group, accounts for the shift in the tautomeric equilibrium towards the 3-aryl-tautomer 12 reported previously (21) [5]. A further correlation exists between these results and the protolysis experiments of Matrka and co-workers (31); the basicity of the triazene is affected similarly by changes in electron density at N-3 [6].…”
Treatment of the diazonium salts, X•C6H4N2+, with aqueous methylamine affords good yields of the monomethyltriazenes, X•C6H4•N=N•NHMe, when the substituent is a strongly electron-withdrawing group (X = o-, m-, and p-NO2; o-, m-, and p-CO2R; p-CN and p-COCH3). Preparation of the triazene from the p-bromobenzene diazonium salt was accompanied by formation of a pentaazadiene. Monomethyltriazenes were not obtained when diazonium salts containing other substituents (X = H, p-CH3, o-CF3, p-Cl, p-F, p-NMe2, p-OH, p-OCH3, p-Ph, p-NHCOCH3) were treated with methylamine. In these cases the products were either pentaazadiene, or 1,3-diaryltriazenes or unstable materials. The monomethyltriazenes vary considerably in stability and give rise to a number of different degradation products, which were either diaryltriazenes or 3-alkyl-1,3-diaryltriazenes or simply arylamines. 1(3)-(p-Nitrophenyl)-3(1)-methyltriazene was found to be a moderately effective methylating agent.
“…A similar electron movement, induced by the electron-attracting group, accounts for the shift in the tautomeric equilibrium towards the 3-aryl-tautomer 12 reported previously (21) [5]. A further correlation exists between these results and the protolysis experiments of Matrka and co-workers (31); the basicity of the triazene is affected similarly by changes in electron density at N-3 [6].…”
Treatment of the diazonium salts, X•C6H4N2+, with aqueous methylamine affords good yields of the monomethyltriazenes, X•C6H4•N=N•NHMe, when the substituent is a strongly electron-withdrawing group (X = o-, m-, and p-NO2; o-, m-, and p-CO2R; p-CN and p-COCH3). Preparation of the triazene from the p-bromobenzene diazonium salt was accompanied by formation of a pentaazadiene. Monomethyltriazenes were not obtained when diazonium salts containing other substituents (X = H, p-CH3, o-CF3, p-Cl, p-F, p-NMe2, p-OH, p-OCH3, p-Ph, p-NHCOCH3) were treated with methylamine. In these cases the products were either pentaazadiene, or 1,3-diaryltriazenes or unstable materials. The monomethyltriazenes vary considerably in stability and give rise to a number of different degradation products, which were either diaryltriazenes or 3-alkyl-1,3-diaryltriazenes or simply arylamines. 1(3)-(p-Nitrophenyl)-3(1)-methyltriazene was found to be a moderately effective methylating agent.
“…In all cases, the rate of the reactions follows first-order kinetics, and the corresponding observed rate constants ( k obs ) are found to increase with proton concentration (Table S1) . The acid catalysis is interpreted in terms of an A1 mechanism (eq 1), in accordance with reports in the literature. − The corresponding expression for the observed rate constant is given by eq 2, where K a , k cleavage , and γ H+ represent, respectively, the acid dissociation equilibrium constant for the diazoammonium ion, the first-order rate constant for cleavage of the nitrogen−nitrogen single bond, and the activity coefficient for a proton …”
The thermal cis-to-trans isomerization of some symmetrically p,p'-disubstituted 1,3-diphenyltriazenes has been studied by means of laser-flash photolysis techniques. The geometric isomerization is catalyzed by general acids and general bases as a result of acid/base-promoted 1,3-prototropic rearrangements. Acid catalysis becomes more prominent as the electron-donating character of the para substituent increases, while base catalysis becomes more important as the electron-withdrawing character of the para substituent increases. In addition, the rate ascribed to the interconversion of neutral cis rotamers through hindered rotation around the nitrogen-nitrogen single bond is found to decrease as the electron-withdrawing character of the para substituent increases. Rates of interconversion of neutral cis rotamers are also found to decrease with decreasing solvent polarity, which is indicative of the involvement of a polar transition state. On the other hand, kinetic investigations of the acid-catalyzed decomposition of target triazenes are consistent with an A1 mechanism.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
