2-methyl-p-phenylenediamine

Endpoint summary

Description of key information

Aromatic amines are resistant to hydrolysis (Harris, 1990; Solomons, 1980). Even if from the structure of the test item, hydrolysis is not to be expected, disappearance of 2,5-diaminotoluene was observed in a study conducted following OECD 111 guideline and GLP in sterile natural water at two different temperatures in the dark. The disappearance could be related to auto-oxidation processes. The target concentration in the test was 10 mg/L and was below half of the water solubility of the test item. At 25 °C, 2,5-diaminotoluene degraded rapidly representing mean values of 56.8 % after 4 hours and 4.7% of the applied amount after 12 hours of incubation in the dark. At 12 °C, the test item degraded more slowly showing a lag phase for at least 7 hours. After 12 hours, the test item represented 40.8% and 18.5% of the applied dose after 24 hours. The temperatures remained constant throughout the respective incubation periods and no significant variation of pH values was observed in the natural water. The samples also remained sterile throughout the study. 2,5-diaminotoluene degraded rapidly in sterile natural water at 25 °C and 12 °C. At 25 °C, DT50 value was calculated to be 3.63 hours and at 12 °C, estimated to be comprised between 10 and 12 hours. Rapid abiotic degradation in water is confirmed through aquatic toxicity testing in which it was observed a decrease of the measured test item concentrations. A literature review aimed at providing a synopsis of the current state of knowledge of (aut)oxidative reactions of PTD. A few studies were conducted to elucidate the oxidative transformation of PTD.

Most of the detected products are intermediates whose lifetimes are highly variable and regulated by factors widely unknown. The semitoluquinone diimine radical cation (STQDIRC) is firstly formed. The radical has a lifetime of a few hours at neutral pH, but it reacts much faster at low and high pH. Subsequently, the toluquinone diimine (TQDI) is formed which attacks a PTD molecule to yield a dimeric product, not further characterized yet. Trimeric products including a Bandrowski Base (BB)-like structure originate from the reaction of dimeric intermediates with STQDIRC or TQDI.

At environmentally relevant pH, it can be expected that the toluquinone diimine (TQDI) is formed which attacks a PTD molecule to yield a trimeric product.