Registration Dossier
Registration Dossier
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EC number: 231-388-1 | CAS number: 7526-26-3
Endpoint summary
Administrative data
Description of key information
Additional information
Considering the hydrolysis potential, the stability of the test substance was investigated experimentally . The study is reliable (Klimisch 1) in compliance with GLP criteria and can therefore be used for the chemical safety assessment. Besides, stability was determined by the usage of two scientifically accepted calculation / prediction computer tools: EPIWIN (by US-EPA) and the OECD QSAR Toolbox. These predictions are reliable with restrictions (Klimisch 2) and can be used as well for the chemical safety assessment, although no GLP criteria can be applied to the utilisation.
Results for phototransformation:
The computer programs were used to predict the phototransformation behaviour in air of the substance. AOPWIN v1.92 (EPIWIN software) gives an gas-phase reaction constant of 7.36 E-12 cm3/molecules-sec and a half-life of 1.45 days (17.43 hours), assuming a 12- h day with an OH rate constant of 1.5 E6 OH/cm³ (Chemservice S.A., 2011). No ozone reaction as well as no nitrate radical reaction is estimated for the compound. The assumed “Hydrogen Abstraction” gives a value of 0.14 E-12 cm³/molecule-sec, which is equal to the “TOTAL Hydrogen Abstraction” of the compound. The assumed “Addition to Aromatic Rings” resulted in 7.23 E-12 cm³/molecule-sec. All calculations were performed supposing a surrounding temperature of 25 °C.
The prediction with the OECD QSAR Toolbox resulted in an OH rate constant was reported as 5.93E-11 cm³/molecule-sec (0.0000051 cm³/molecule-day) (Chemservice S.A., 2012). This information can only be used as supporting data, since the chemicals in the grouped category of the prediction possessed lower LogPow values than the target one therefore it does not fall into the domain.
No information has to be provided concerning phototransformation in water and soil (not mandatory under REACH).
Results for hydrolysis:
In accordance with GLP compliance, an assessment of hydrolytic stability was carried out using a procedure designed to be compatible with EU Method C.7 Abiotic Degradation, Hydrolysis as a Function of pH of Commission Regulation (EC) No 440/2008 of 30 May 2008 and Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004. At pH 4 the test substance can be regarded as stable at an ambient temperature of 25 °C (half-life greater than 1 year). At pH 7 the estimated half-life at 25 °C amounts 149 days with a hydrolysis rate constant of 1.94 E-4/h. At pH 9 the estimated half-life at 25 °C amounts 33 hours with a hydrolysis rate constant of 2.10 E-2/h. Thus, the higher the pH value (thus the more alkaline the environment), the lower the half-lives for diphenyl methylphosphonate.
Additionally, hydrolysis was predicted by the computer program HYDROWIN v2.00 (EPIWIN software) by US-EPA (Chemservice S.A., 2011).The prediction for the test substance indicated that PHOSPHORUS ESTER was detected as hydrolysable substance class (same class as found in the OECD QSAR Toolbox). The higher the pH value (thus the more alkaline the environment), the lower the half-lives for this type of chemicals.
In conclusion, both the experimental study as well as the prediction by HYDROWIN v.2.00 determine comparable results. The higher the pH value, the lower the half-lives of Diphenyl methylphosphonate.
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