Rates of Formation of Some Phenazines by Cyclization of Di- and Monoimines of N-(2-Aminophenyl)-p-benzoquinone

Article abstract of DOI:10.1021/jo00319a027

The spectrophotometrically determined rates for cyclization of N-(2-aminophenyl)-p-benzoquinonediimine and its 5-methyl and 5-chloro derivatives in buffered aqueous media are reported in Table I for the pH range 6-9.The first-order rate equation involves protonated diimine.At higher pH these diimines hydrolyze to the corresponding monoimines which then undergo cyclization.The first order rate expression for cyclization for monoimine 3 (k_L) involves the neutral monoimine and under the conditions used for the reaction is faster than the second-order hydrolysis (k_h) of diimine 1a.Around pH 1 the diimines hydrolyze at the nonterminal imine nitrogen to the corresponding p-benzoquinone monoimine and o-phenylenediamine, which react further.Monoimine 3 undergoes a similar hydrolysis.