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Hydrolysis

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Endpoint:
hydrolysis
Remarks:
pH 7 only
Type of information:
experimental study
Adequacy of study:
key study
Study period:
no data
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Qualifier:
no guideline followed
Principles of method if other than guideline:
Titration
GLP compliance:
no
Analytical monitoring:
not specified
Transformation products:
yes
pH:
7
Temp.:
25.1 °C
Hydrolysis rate constant:
3 140 s-1
DT50:
0.3 min

Rate constant 105 k1 = 3140 sec -1 at 25 ºC, initially neutral.
At 0 ºC, rate constant was 105 k1 = 348 sec -1

Authors noted rate of hydrolysis of maleic anhydride exceeded all other carboxylic anhydrides evaluated.

Maleic acid was identified as transformation product and is expected to be stable in water since there are no functional groups that would lead to further hydrolysis.

Validity criteria fulfilled:
not specified
Conclusions:
The half-life/DT50 (50% decline time) of maleic anhydride was 0.3 minutes at pH 7 and the major transformation product was maleic acid.
Executive summary:

Hydrolysis of maleic anhydride was studied at pH 7. The experiment was conducted as part of a scientific study on the hydrolysis rate of carboxylic anhydrides. At pH 7 the major transformation product was maleic acid.

The half-life/DT50 (50% decline time) of maleic anhydride was 0.3 minutes at pH 7.

Maleic acid is expected to be stable in water since there are no functional groups that would lead to further hydrolysis.

The study is classified acceptable and satiesfies the guideline requirement for hydrolysis study.

Endpoint:
hydrolysis
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
the study does not need to be conducted because the substance is readily biodegradable

Description of key information

In a study investigating the hydrolysis of maleic anhydride to maleic acid at pH 7 and 25.1°C a half-life/DT50 (50 % decline times) of 0.3 minutes at a hydrolysis rate constant of 3140 sec-1 was determined (Bunton et al. 1963). The major transformation product is maleic acid, for which hydrolysis is not expected to be an important fate path due to the lack of labile functional groups.

Information on hydrolysis of maleic anhydride at pH 4 and 9 is not available. However, in line with REACH Annex VIII, endpoint 9.2.2.1, column 2, no further testing is required as the substance is readily biodegradable.

Key value for chemical safety assessment

Half-life for hydrolysis:
0.3 min
at the temperature of:
25.1 °C

Additional information