Oxidative transformation processes and products of para-phenylenediamine (PPD) and para-toluenediamine (PTD)—a review

Environmental Sciences Europe

Table 3 Oxidation products of PTD

Name, molecular mass (amu), and structural formula	Reaction conditions	Analytical method	Relative analytical reliability^a	References
Semitoluquinone diimine radical cation (STQDIRC) 122.17	Buffer systems^b pH 2, 4, 7, and 10	CVA, Pt electrode, UV–VIS and EPR spectroscopy	+	[47]
• +	ox. ag.: Br₂ acetate buffer pH 4.6	UV–VIS spectroscopy, 466 nm	−	[41]
Toluquinone diimine (TQDI) 120.15	Buffer systems^b pH 2, 4, 7, and 10	CVA, Pt electrode, UV–VIS spectroscopy	−	[47]
2-(4′-Amino-x’-methylphenyl)amino-x’-methyl-PPD 242.32	Buffer systems^b pH 2, 4, 7, and 10	CVA, Pt electrode, UV–VIS and EPR spectroscopy	+	[47]
PTD-Bandrowski’s Base analogue 360.46	Buffer systems^b pH 2, 4, 7, and 10	CVA, Pt electrode, UV–VIS spectroscopy	−	[47]
Triphenylamine derivative 362.48	Buffer systems^b pH 2, 4, 7, and 10	CVA, Pt electrode, UV–VIS spectroscopy	−	[47]

^aFive degrees of relative analytical reliability: ++: two independent high resolution (HR) spectroscopic methods, e.g., MS, NMR, EPR, or combination of one HR method with various others; +: one HR method; ○: one HR method but with interferences; combination of methods with lower resolution or lesser specificity; −: one method with lower resolution/lesser specificity; −−: analysis of reaction mixtures with non-specific or low performance methods
^bBuffer systems: pH 2: hydrogensulfate/sulfate buffer, pH 5: acetate buffer, pH 7: ammonia buffer, pH 10: hydrogencarbonate/carbonate buffer