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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The test design is considered robust and the results well documented and scientifically acceptable. The test was not performed according to GLPs.
Principles of method if other than guideline:
The hydrolysis of MEKO (at 0.01 M) was examined at pH 4, 7, and 9 and at three different temperatures (20, 35 and 50 °C). Data were collected every day for 5 or 7 days to study the rate of hydrolysis reaction.
GLP compliance:
no
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
The hydrolysis of MEKO (at 0.01 M) was examined at pH 4, 7, and 9 and at three different temperatures (20, 35 and 50 °C). Data were collected every day for 5 or 7 days to study the rate of hydrolysis reaction. The concentration of MEKO and one of its hydrolysis products, methylethylketone, were measured by gas chromatography.
Transformation products:
not specified
No.:
#1
pH:
4
DT50:
< 0.3 min
Type:
not specified
Remarks on result:
other: At this pH, MEKO was hydrolytically unstable regardless of temperature.
pH:
7
Temp.:
50 °C
DT50:
> 7 d
Type:
not specified
pH:
9
Temp.:
50 °C
DT50:
< 14 d
Details on results:
The hydrolysis of MEKO was dependent on pH, but much less dependent of temperature. Detailed results follow:
1) At pH 4, MEKO was hydrolytically unstable, regardless of the temperature (t1/2 < 0.3 minutes).
2) At pH 7, the hydrolysis reaction is much slower; 14% hydrolysis at 20 °C was obtained after 4 days and 44% hydrolysis was obtained at 50 °C after 7 days.
3) At pH 9, no measurable hydrolysis under any of the test conditions was observed. The hydrolysis plateaued at 40-50% by days 4 to 7. The hydrolysis products are methyl ethyl ketone and a hydroxylamine salt.
Conclusions:
The hydrolysis of MEKO was dependent on pH, but much less dependent of temperature. Detailed results follow: 1) At pH 4, MEKO was hydrolytically unstable, regardless of the temperature (t1/2 < 0.3 minutes). 2) At pH 7, the hydrolysis reaction is much slower; 14% hydrolysis at 20 degrees C was obtained after 4 days and 44% hydrolysis was obtained at 50 degrees C after 7 days. 3) At pH 9, no measurable hydrolysis under any of the test conditions was observed.

Description of key information

The hydrolysis of MEKO is strongly pH-dependent. At pH 4, MEKO was hydrolytically unstable, regardless of the temperature (t1/2 < 0.3 min). At pH 7, 14% hydrolysis was obtained at 20 °C. Since from the above results no DT50 could be determined at pH7 in the assessment it is assumed that MEKO is not hydrolysable.

Key value for chemical safety assessment

Additional information

The hydrolysis of MEKO (at 0.01 M) was examined at pH 4, 7, and 9 and at three different temperatures (20, 35 and 50 °C) (Honeywell International, Inc., 1988). Data were collected every day for 5 or 7 days to study the rate of hydrolysis reaction. The hydrolysis of MEKO was dependent on pH, but much less dependent on temperature. At pH 4, MEKO was hydrolytically unstable, regardless of the temperature (t1/2 < 0.3 min). At pH 7, the hydrolysis reaction is much slower; 14% hydrolysis at 20 °C was obtained after 4 days and 44% hydrolysis was obtained at 50 °C after 7 days. At pH 9, no measurable hydrolysis under any of the test conditions was observed.