Hexachlorocyclopentadiene

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Justification for type of information:

Although the experiment was not performed in accordance with OECD111, the experiment measures some of the parameters measured by this protocol. The data has been deemed sufficient to include in a European Risk Assessment for the substance.

Principles of method if other than guideline:

Rate of hydrolysis measured at 4 different pH to assess pH influence on hydrolysis. Rate measured by extraction of aliquots with organic solvent to remove the substance from the aqueous solution and quantified using GC.
Once it had been established that pH had no effect on rate of hydrolysis, the reaction at pH 7 was performed at two further temperatures and the activation energy and frequency factor calculated from the results.

GLP compliance:

not specified

Specific details on test material used for the study:

.

Radiolabelling:

no

Analytical monitoring:

yes

Details on sampling:

Aliquots removed at predetermined time intervals

Buffers:

pH 9.76: NaHCO3 (5E-02 M) and Na2CO3 (5E-02 M)
pH 2.88: HCl
pH 5.08: AcoNa / AcOH
pH 6.70: NaH2PO4 / Na2HPO4
pH 7: no buffer used

Details on test conditions:

5mL ampoules filled near capacity, sealed and placed in constant temperature baths for a predetermined time. No comment was made regarding whether the experiment was done in the light or dark.

Number of replicates:

n.a.

Positive controls:

no

Negative controls:

no

Statistical methods:

Rate constants obtained by linear least square analysis of the concentration - time data using integrated form of the first order rate equation.

Preliminary study:

k = 1.5 x 10-6 sec-1 (± 0.6 x 10-6) at 30 °C
No variation between different pH was seen.

Test performance:

Activation energy (Ea) = 20,800 (± 1.6) cal mol-1
Frequency factor (ln(A)) = 21.5 (± 2.7)

Transformation products:

no

Remarks:

Although transformation products were analysed by GC, it was not possible to identify them.

pH:

2.88

Temp.:

30 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 7.64 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Average of two measured results

pH:

5.08

Temp.:

30 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 6.27 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Average of two measured values

pH:

6.7

Temp.:

30 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 3.3 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Average of two measured values

pH:

9.76

Temp.:

30 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 6.27 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Average of two values

pH:

7

Temp.:

40 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 1.71 d

Remarks on result:

other:

Remarks:

Average of two measured value

pH:

7

Temp.:

50 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 0.64 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Average of two measured values

Key result

pH:

7

Temp.:

22 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 0.97 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Value extropolated from the values of activation energy and frequency factor stated in the paper and entered into the Arrhenius equation with the temperature. It does not correlate with the experimental results (i.e. the rate calculated at 22 °C is greater than measured at 40 °C). This is due to the large Standard deviation measured for both the activation energy and frequency factor.

Other kinetic parameters:

Activation energy (Ea) = 20,800 (± 1.6) cal mol-1
Frequency factor (ln(A)) = 21.5 (± 2.7)

Details on results:

The large standard deviation in both values lead to there being a discrepancy between the measured and calculated values. There are a number of typo errors in the paper that meant that assumptions had to be made regarding the reported results.

Validity criteria fulfilled:

not applicable

Executive summary:

Rate constant at 22°C =8.3E-06 s^-1.

Activation energy (Ea) = 20,800 (±1.6) cal mol^-1

Frequency factor (ln(A)) = 21.5 (±2.7)

Reference 2

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Justification for type of information:

Although the experiment was not performed in accordance with OECD111, the experiment measures some of the parameters measured by this protocol. The data has been deemed sufficient to include in a European Risk Assessment for the substance.

Principles of method if other than guideline:

Measurement of residual radiolabelled substance in distilled water at defined timepoints

GLP compliance:

not specified

Radiolabelling:

yes

Analytical monitoring:

yes

Details on sampling:

2 mL aliquots removed at defined timepoints and added to 3 mL distilled water, radioactivity counted.
2 mL sample removed and extracted with petroleum ether to remove unhydrolysed substance. Ether layer analysed by radioactivity counting and gas chromatography.
Aqueous layer extracted with ethyl acetate and both layers analysed by radioactivity counting.

Buffers:

None

Details on test conditions:

14C labelled substance was injected into distilled water (300mL). The flasks were allowed to stand at room temperature for 42 days). Samples were taken at 0, 4, 8, 16, 24 and 42 days. It was not clear whether the samples were stored in the light or in the dark.

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Transformation products:

not specified

Remarks:

Although the hydrolysis products were analysed, it was not possible to identify any of the substances.

Temp.:

22 °C

Hydrolysis rate constant:

ca. 0.002 h-1

DT50:

ca. 4.1 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other:

Remarks:

Average value

Details on results:

The rate of loss from the test solution appeared to be in two stages. The initial loss gave a more rapid hydrolysis rate than the remainder of the experiment. This was believed to be to loss of the substance through evaporation. Therefore the rate measured at the later stages of the experiment were regarded as the true rate of hydrolysis.

In order to compare with other results the hydrolysis rate was converted to s-1 by division by 3600 to give a rate of 6.25E-07 s-1

Validity criteria fulfilled:

not applicable

Executive summary:

 Hydrolysis rate = 2.25 x 10^-3hr^-1at 22 degC = 6.25 x 10^-7s^-1

Time to reach 50 % initial conc. = 4.1 days

Reference 3

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

secondary literature

Justification for type of information:

Although the experiment was not performed in accordance with OECD111, the experiment measures some of the parameters measured by this protocol. The data has been deemed sufficient to include in a European Risk Assessment for the substance.

Principles of method if other than guideline:

Not specified.

GLP compliance:

not specified

Specific details on test material used for the study:

14C - labelled substance used

Radiolabelling:

yes

Analytical monitoring:

not specified

Positive controls:

not specified

Negative controls:

not specified

Transformation products:

not specified

Details on hydrolysis and appearance of transformation product(s):

Hydrolysis products could not be identified.

pH:

3

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 11.4 d

pH:

6

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 11.4 d

Type:

(pseudo-)first order (= half-life)

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 6 d

Type:

(pseudo-)first order (= half-life)

pH:

3

Temp.:

45 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 9.2 d

Type:

(pseudo-)first order (= half-life)

pH:

6

Temp.:

45 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 10.6 d

Type:

(pseudo-)first order (= half-life)

pH:

9

Temp.:

45 °C

Hydrolysis rate constant:

ca. 0 s-1

DT50:

ca. 4.4 d

Type:

(pseudo-)first order (= half-life)

Details on results:

If the assumption that there is no correlation between pH and hydrolysis rate, the average rate of hydrolysis at 25 degC was 8.49E-07 s-1.

Validity criteria fulfilled:

not applicable

Executive summary:

If the assumption that there is no correlation between pH and hydrolysis rate, the average rate of hydrolysis at 25 degC was 8.49E-07 s-1.

Description of key information

None of the studies could be regarded as a key study because of insufficient experimental information and deviation away from the protocol given in the OECD Testing Guideline 111. However, each experiment gave similar results, so the Key value for chemical safety assessment is the average of rate of hydrolysis at 22°C.

Key value for chemical safety assessment

Half-life for hydrolysis:

2.5 d

at the temperature of:

22 °C

Additional information

Hydrolysis rate (k) = 3.26 x 10-6s-1at 22°C.

Activation energy (Ea) = 20,800 (±1.6) cal mol-1

Frequency factor (ln(A)) = 21.5 (±2.7)