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Environmental fate & pathways

Hydrolysis

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Description of key information

It can be expected that the substance undergoes a slow process of hydrolysis.

Key value for chemical safety assessment

Additional information

The substance is highly insoluble in water. In Annex VIII column 2 of Regulation (EC) No. 1907/2006, it is laid down that the study on hydrolysis does not need to be conducted if the substance is highly insoluble in water.

However, in general organophosphites, such as the described test substance, are known to be hydrolytically unstable [Göghová et al., 1989]. In case of the submission item the hydrolysis of the phosphite group would result in ‘2,4-di-tert-butylphenol’ as metabolite. However, according to Göghová et al., 1989, "a Iow degree of hydrolysis was found for some derivatives in which phenyl was substituted by voluminous groups in positions 2 and 4. " ..."Provided tert-butyl is in position 2 (IV), it is remarkable 'that a significant decrease in the degree of hydrolysis is to be achieved even by introducing methyl (IX), isopropyl (X) or tert-butyl (XI) in position 4." Therefore, due to the steric effects of the tert-butyl grop in both position 2 and 4 the hydrolysis is significantly reduced and the test substance will hydrolyse only slowly.

To quantify the hydrolysis of the test substance a study according to OECD guideline 111 was conducted [Vizon SciTec Inc., 2004]. The test was performed at pH 4.0, 7.0 and 9.0 in sterile buffer solutions at a temperature of 50°C. Due to the extensive adsorption of the test item combined with the low water solubility it was impossible to analyze the hydrolysis.

The producer conducted some internal tests to investigate the stability of products with the test substance under moist storage conditions. The results of this tests indicate that the substance hydrolyses very slowly under such moist storage conditions.

Taking all available information into account it can be concluded, that the substance contains hydrolysable functional phosphite groups. Therefore hydrolysis to ‘2,4-di-tert-butylphenol’ has to be expected. However, based on the physico/chemical properties of the test substance, hydrolysis turned out to be a very slowly process.

 

Göghová, M., Karvas, M., Durmis, J. (1989): Synthesis of the substituted 3,9-bisphenoxy-2,4,8,1O-tetraoxa-3,9-diphosphaspiro[5,5]undecanes and investigation of the effect of substituents on their resistance to hydrolysis. Chem. Papers, 43(3), 421 -432