Methyl (R)-2-(4-hydroxyphenoxy)propionate

Hydrolysis

Description of key information

Campbell & Maclean (1993): Under the conditions of this preliminary study, at pH 4 the test material was ca. 10 % hydrolysed after 5 days, at pH 7 the test material was ca. 12 % hydrolysed within 2.4 h and ca. 80 % hydrolysed after 5 days and at pH 9 the test material was completely hydrolysed within 24 hours. Further testing is therefore required at pH 4 and 7.

Campbell & Stagg (1993): The t1/2 values at pH 4 were determined to be 1653.9, 818.7 and 385.0 h at 50, 50 and 70 °C, respectively. The t1/2 values at pH 7 were determined to be 51.3 and 380.3 h at 50 and 30 °C, respectively.

Under the conditions of the study, the rate constants at 25 °C for pH 4 and 7 were obtained by extrapolation and found to be 2.09 x 10^-6 and 6.50 x 10^-4 h^-1, respectively.

Key value for chemical safety assessment

Half-life for hydrolysis:

380.3 h

at the temperature of:

30 °C

Additional information

Campbell & Maclean (1993)

Abiotic degradation testing (hydrolysis as a function of pH) was carried out in accordance with the standardised guidelines OECD 111 and EU Method C.10 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

A preliminary test was carried out at 50 °C and at 3 pH values, namely 4.0 ± 0.1, 7.0 ± 0.1 and 9.0 ± 0.1. For each pH under investigation, ca. 65 mg of test material was accurately weighed into 12 x 50 mL flasks. Buffer was added and after the solid had dissolved, made up to volume. Three flasks for each time and pH were placed in an orbital shaker and shaken at 50 °C. Samples were assayed for test material prior to incubation and thereafter at 2.4 and 24 hours and 5 days at 50 °C.

Under the conditions of this preliminary study, at pH 4 the test material was ca. 10 % hydrolysed after 5 days, at pH 7 the test material was ca. 12 % hydrolysed within 2.4 h and ca. 80 % hydrolysed after 5 days and at pH 9 the test material was completely hydrolysed within 24 hours. Further testing is therefore required at pH 4 and 7.

Campbell & Stagg (1993)

The hydrolysis of the test material was investigated in a study conducted in accordance with the standardised guidelines OECD 111 and EU Method C.10 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

A preliminary test conducted prior to this study indicated that advanced testing was required at pH 4 and pH7, therefore further work was carried out on the test material at pH 4 at 50, 60 and 70 °C and at pH 7 at 30 and 50 °C.

Triplicate samples of test material were prepared by accurately weighing ca. 128 mg of compound into a 100 mL volumetric flask made to volume with buffer and placed in an orbital shaker at 50 °C. Samples were analysed for the test material at various times. A plot of log mean % remaining versus time was constructed. The slope of the linear plot = K/2.303 where K is the rate constant. The half-life of the reaction is given by 0.693/K.

Since first order kinetics were confirmed the procedure was repeated in duplicate at 60 and 70 °C for pH 4 and 30 °C for pH 7. An Arrhenius plot of Ln k versus 1/T was constructed from the data in the advanced tests. Extrapolation of the plot gave an estimate of the rate constant at 25 °C.

The t1/2 values at pH 4 were determined to be 1653.9, 818.7 and 385.0 h at 50, 50 and 70 °C, respectively. The t1/2 values at pH 7 were determined to be 51.3 and 380.3 h at 50 and 30 °C, respectively.

Under the conditions of the study, the rate constants at 25 °C for pH 4 and 7 were obtained by extrapolation and found to be 2.09 x 10^-6 and 6.50 x 10^-4 h^-1, respectively.

Caesar (1991)

The hydrolysis of the test material was investigated in a study conducted in accordance with the EC Official Gazette # L 251/216, C.10 Degradability under GLP conditions. The study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

The experiment was carried out at three pH values: 4.0, 7.0 and 9.0.1 L of the buffer solution was placed in a double-walled (temperature controlled) glass vessel and about 0.5 g of the test material was added with continuous stirring. After the mixture in the test vessel had been allowed to stabilise for about one hour the first sample was taken for analysis. This time corresponds to a residence time of 0 h. Further sampling was then performed at definite time intervals. After extraction of the test solution with chloroform the latter was analysed quantitatively by gas chromatography, using an external standard.

Given that <10 and >50 % hydrolysis occurred at pH 4.0 and 9.0, respectively, no further work was carried out. At pH 7.0, further investigations were conducted at 60 and 70 °C.

Under the conditions of this study, the half-life of the test material at 50 °C was determined to be 2700 hours, 45 hours 5 minutes and 1 hour 25 minutes at pH 4.0. 7.0 and 9.0, respectively. At pH 7.0, the half-life was determined to be 17 hours 49 minutes and 7 hours 15 minutes at 60 and 70 °C, respectively.