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Environmental fate & pathways

Hydrolysis

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Reference
Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Not specified
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
data from handbook or collection of data
Remarks:
Summary of experimental data.
Principles of method if other than guideline:
Hydrolysis study performed under various conditions of pressure and temperature. Limited details reported.
GLP compliance:
not specified
Specific details on test material used for the study:
Molecular weight: 129.91 (Weast 1977)
Melting point: -158°C (Weast 1977)
Boiling point at 760 torr: -29.8°C (Weast 1977)
Vapour pressure at 20°C: 4306 torr (Pearson and McConnell 1975)
Solubility in water at 25°C: 280 mg/l (Pearson and McConnell 1975)
Log octanol/water partition coefficient: 2.16 (Hansch et al. 1975)
Radiolabelling:
not specified
Analytical monitoring:
not specified
Details on sampling:
Not specified
Buffers:
Not specified
Estimation method (if used):
Not specified
Details on test conditions:
Not specified
Number of replicates:
Not specified
Positive controls:
not specified
Negative controls:
not specified
Statistical methods:
Not specified
Transformation products:
not specified
Hydrolysis rate constant:
<
Remarks on result:
other: predicted as stable

The fluorocarbons as a group exhibit a low rate of hydrolysis in comparison to other halogenated compounds, and the rates of hydrolysis are greatly affected by temperature, pressure and the presence of catalytic materials such as metals (Howard et al. 1975). The rate of hydrolysis of dichlorodifluoromethane at 1 atmospheric pressure and 30°C was reported to be not discernable by the analytical technique used in the work cited (Howard et al. 1975), although the compound is known to hydrolyze under more severe conditions such as high pressure, high temperature, presence of high concentrations of metals, or any combination of these (Howard et al. 1975; Hagen and Elphingstone 1974). On the basis that conditions in the aquatic environment typically would more nearly correspond to pure water than to the more severe hydrolytic conditions mentioned above, it is postulated that hydrolysis of dichlorodifluoromethane, if it occurs, would proceed at a negligible rate in comparison to the rate of volatilization and subsequent photodissociation.

Hydrolysis rate of dichlorodifluoromethane in water (grams/liter/year)

 pressure: 1 Atm   

temp.: 86°F / 30°C

 saturation pressure

temp.: 122°F / 50°C

 
 water alone  water with steel  water with steel  1% Na2CO3 solution  10% NaOH solution

 <0.005

0.8 

 10  0.04  40
Validity criteria fulfilled:
not applicable
Conclusions:
Hydrolysis is not predicted for this substance, and as such, abiotic degradation by hydrolysis is predicted to be > 1 year.
Executive summary:

Hydrolysis is not predicted for this substance, and as such, abiotic degradation by hydrolysis is predicted to be > 1 year. Dichlorodifluoromethane introduced into aqueous systems will most likely volatize to the atmosphere. Once in the troposphere, dichlorodifluoromethane remains stable. It eventually diffuses into the stratosphere or is carried back to the earth during the precipitation process. No evidence was found for hydrolysis.

Description of key information

Hydrolysis

Key value for chemical safety assessment

Half-life for hydrolysis:
1 yr
at the temperature of:
20 °C

Additional information

Hydrolysis is too slow to be a significant fate process. < 5mg/litre/year. Half life is considered to be > 1 year.

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