Diphenyl carbonate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

6 to 7 samples are taken during the preliminary experiment at pH 4 and 7 and 50°C. At pH 9 only 4 analytical determinations are performed, due to fast degradation at 50°C. In the higher tier experiment 3 and 4 determinations were done at pH 4 and 7 at 30°C, respectively.

Buffers:

pH 4: citric acid/potassium hydroxide/sodium chloride
pH 7: potassium dihydrogen phosphate/Di-sodium hydrogen phosphate
pH 9: borax/hydrochlorid acid

Duration:

7 h

pH:

4

Temp.:

50 °C

Duration:

4.5 h

pH:

7

Temp.:

50 °C

Duration:

0.5 h

pH:

9

Temp.:

50 °C

Transformation products:

yes

No.:

#1

No.:

#2

pH:

4

Temp.:

25 °C

DT50:

61.8 h

Remarks on result:

other: calculated

pH:

4

Temp.:

30 °C

DT50:

40.2 h

pH:

4

Temp.:

50 °C

DT50:

8.2 h

pH:

7

Temp.:

25 °C

DT50:

39.9 h

Remarks on result:

other: calculated

pH:

7

Temp.:

30 °C

DT50:

24.1 h

pH:

7

Temp.:

50 °C

DT50:

3.8 h

pH:

9

Temp.:

50 °C

DT50:

0.2 h

- At pH 9 and 50°C fast degradation was observed. Within ca. 40 minutes the concentration of diphenyl carbonate decreased to less than 7 %. During this time just 4 analytical determinations were possible. Assuming a pseudo-first order reaction a half-life of 0.15 hours at pH 9 was calculated
- At pH 7 and pH 4 degradation was followed at 30 and 50°C

- According to the Arrhenius equation the half-life and the rate constant (first order reaction) at 25°C was calculated.

Conclusions:

Diphenyl carbonate hydrolyses under environmental conditions forming phenol and carbon dioxide. Environmental relevant half-life is 39.9 h at pH 7 and 25 °C.

Executive summary:

The stability of diphenyl carbonate was examined in accordance with the standardised guideline EU Method C.7 under GLP conditions.

The guideline is designed as a tiered approach. Firstly, a preliminary experiment was carried out in different buffer solutions at pH 4, 7 and 9 at 50 °C. Hydrolysis was followed by measuring the increase of the concentration of the hydrolysis product phenol with time, using HPLC. As the results of the preliminary test indicated that less than 50 % of diphenyl carbonate had hydrolysed in 2.4 hours at pH 4 and 7 at 50 °C, further testing was required. Based on the conclusion that degradation is a pseudo-first order reaction, the secondary experiment was carried out only at pH 4 and 7 at 30 °C. No further testing was required at pH 9 since more than 50 % of diphenyl carbonate had hydrolysed in 2.4 hours at 50 °C and pH 9.

Based on the results at 50 and 30 °C an environmentally relevant half-life time was estimated using the Arrhenius equation of a first-order reaction.

Diphenyl carbonate hydrolyses under environmental conditions, forming phenol and carbon dioxide. Environmentally relevant half-life is 39.9 h at pH 7 and 25 °C.

Description of key information

Diphenyl carbonate hydrolyses under environmental conditions forming phenol and carbon dioxide. Environmentally relevant half-life is 39.9 h at pH 7 and 25 °C, EU Method C.7 (Bayer, 2001a).

Key value for chemical safety assessment

Half-life for hydrolysis:

39.9 h

at the temperature of:

25 °C

Additional information

In the key study, the stability of diphenyl carbonate was examined in accordance with the standardised guideline EU Method C.7 under GLP conditions (Bayer, 2001a). The study was awarded a reliability score of 1 in accordance with the criteria for assessing data quality as set forth by Klimisch et al. (1997).

The guideline is designed as a tiered approach. Firstly, a preliminary experiment was carried out in different buffer solutions at pH 4, 7 and 9 at 50 °C. Hydrolysis was followed by measuring the increase of the concentration of the hydrolysis product phenol with time, using HPLC. As the results of the preliminary test indicated that less than 50 % of diphenyl carbonate had hydrolysed in 2.4 hours at pH 4 and 7 at 50 °C, further testing was required. Based on the conclusion that degradation is a pseudo-first order reaction, the secondary experiment was carried out only at pH 4 and 7 at 30 °C. No further testing was required at pH 9 since more than 50 % of diphenyl carbonate had hydrolysed in 2.4 hours at 50 °C and pH 9.

Based on the results at 50 and 30 °C an environmentally relevant half-life time was estimated using the Arrhenius equation of a first-order reaction.

Diphenyl carbonate hydrolyses under environmental conditions, forming phenol and carbon dioxide. Environmentally relevant half-life is 39.9 h at pH 7 and 25 °C.

Further information is available in the form of a supporting study in which the degradation kinetic was determined in accordance with generally accepted scientific principles (Bayer, 2000a). The study was awarded a reliability score of 2 in accordance with the criteria for assessing data quality as set forth by Klimisch et al. (1997).

A saturated solution of diphenyl carbonate in water was stirred at room temperature (23 °C) for 48 h. Following centrifugation, the phases were separated. The concentration of the test material was regularly determined by HPLC.

Diphenyl carbonate hydrolyses in water, forming phenol and carbon dioxide. The half-life is indicated to be 73.5 h at 23 ° C.

Stability of the hydrolysis product phenol was assessed in a European Union Risk Assessment Report(European Chemicals Bureau, 2006). Phenol is hydrolytically stable.