O,O,O-tris(2(or 4)-C9-10-isoalkylphenyl) phosphorothioate

Hydrolysis

Description of key information

Due to very low water solubility an experimental study was not conducted.  However, the substance has functional groups which could hydrolyse.

According to QSAR calculations the substance hydrolyse faster at high pH values.

As only the dissolved portion of the substance can be hydrolysed, the formation of the hydrolysis is expected to occur only to a minimum extent for poorly soluble substances.   

Additional information

A study could not be conducted because the substance is highly insoluble in water. As the substance is an UVCB, QSAR calculations were performed applying HYDROWIN model for five probable structures in order to provide an estimate on hydrolysis. Table 1 lists calculated Half-Life values in relation to the pH.

Table 1 QSAR calculations on Hydrolytical Half-Life for five different structures of the UVCB substance.

Structure	1	2	3	4	5
pH	Half-Life in days
5	17.6	17.8	14.6	15.6	15.6
6	17.6	17.8	14.6	15.6	15.6
7	17.6	17.7	14.5	15.6	15.6
8	16.9	17.1	13.6	14.8	14.8
9	12.5	12.8	8.5	9.91	9.9
10	3.5	3.6	1.8	2.3	2.3

Overall, it can be assumed that hydrolysis could theoretically take place. However, hydrolysis would be very slow and more likely at higher pH values. Whereas, hydrolysis is further considered to take place more slowly the lower the pH.

Experimental hydrolysis data is available for the similar substance CAS 597 -82 -0, which is also a triphenylphosphorothionate, but whithout alkyl chains. Half-lifes for hydrolyis of the phosphor thioester were determined to be 115 - 24 days at 25 °C and pH 4 -9 (ECHA disseminated data, accessed March 14, 2017). Whereas HYDROWIN calculation estimated 10 -3 days at pH 5 -9. Thus, HYDROWIN calculation can further be considered to rather underestimate Half-Life times for this phosphorus thioester group.