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Diss Factsheets

Administrative data

Endpoint:
hydrolysis
Type of information:
experimental study
Adequacy of study:
other information
Study period:
August 16 to December 04, 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003
Report date:
2003

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
Isooctyl mercaptoacetate
EC Number:
246-613-9
EC Name:
Isooctyl mercaptoacetate
Cas Number:
25103-09-7
Molecular formula:
C10H20O2S
IUPAC Name:
2-methylheptyl 2-sulfanylacetate
Details on test material:
Identification: Isooctyl thioglycolate (IOTG)
CAS no. 25103-09-7
Source: Bruno Bock Chemische Fabrik GmbH and CoKG
Batch number: 0000002282
Purity: 99.6% (w/w)
Radiolabelling:
no

Results and discussion

Transformation products:
not measured
Dissipation DT50 of parent compoundopen allclose all
pH:
4
Temp.:
25 °C
DT50:
8.7 h
pH:
7
Temp.:
25 °C
DT50:
7.2 h
pH:
9
Temp.:
25 °C
DT50:
13.7 h
pH:
1.2
Temp.:
38 °C
DT50:
6.6 h

Any other information on results incl. tables

During the preliminary test the degradation of IOTG, at each
pH value, indicated an hydrolysis lower than 50% after 2.4
hours and higher than 10% after 3 days. IOTG was considered
as hydrolytically unstable. The hydrolysis rate was then
determined at three different temperatures (50°C,
66°C(twice) and 80°C) for each buffer and one temperature
(37°C) for pH=1,2. The determination was performed to cover
approximately 20-70% hydrolysis.

The results of this test indicated a pseudo-first order
reaction kinetic

The hydrolysis rate constants (Kobs) and half lives (t1/2)
of IOTG at each pH can be tabulated as follows:

Buffer       Temperature  Slope         Kobs      t½ 
(pH)           (deg C)    (h-1)         (h-1)     (h)
1.2               38         -0.0456        0.105          6.6
4.0               50         -0.112                0.258          2.7
4.0               66         -0.180                0.415          1.7
4.0               66         -0.180                0.415          1.7
4.0               80         -0.351                0.807          0.9
7.0               50         -0.137                0.316          2.2
7.0               66         -0.200                0.462          1.5
7.0               66         -0.224                0.517          1.3
7.0               80         -0.428                0.986          0.7
9.0               50         -0.0963        0.222          3.1
9.0               66         -0.236                0.543          1.3
9.0               66         -0.262                0.604          1.1
9.0               80         -0.444                1.02          0.7

The values of the Kobs and t½ at 25°C for each pH were
obtained by extrapolation.

Applicant's summary and conclusion

Conclusions:
Following advanced tests results, IOTG can be considered as
hydrolytically unstable with:
Kobs = -0.0456 h-1 and t½ = 6.6 h at 38°C for pH 1.2,
Kobs = 0.0345 h-1 and t½ = 8.7 h at 25°C for pH 4.0
(estimation),
Kobs = 0.0419 h-1 and t½ = 7.2 h at 25°C for pH 7.0
(estimation),
Kobs = 0.0220 h-1 and t½ = 13.7 h at 25°C for pH 9.0
(estimation).