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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:
guideline study with acceptable restrictions
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 111 (Hydrolysis as a Function of pH)
Deviations:
yes
Remarks:
Only hydrolysis at pH 7.0 was measured and at ambient temperature
Principles of method if other than guideline:
Analytical Bio-Chemistry Laboratories (ABC) Protocol #M-8305
Determination of the hydrolysis of CBS in pH 7.0 buffered deionized water with light excluded at 25°C and identification of hydrolysis products by GC/MS.
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source (i.e. manufacturer or supplier) and lot/batch number of test material: Monsanto Polymer Products Company, lot no. NC06-304
- Purity, including information on contaminants, isomers, etc.: 96%

STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: stored at ambient temperature

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- Treatment of test material prior to testing (e.g. warming, grinding): Primary stock solutions of 1.00 mg/ml in nanograde acetone were produced
- Preliminary purification step (if any): no preliminary purification


OTHER SPECIFICS
- The pH was adjusted to 7.00 ± 0.05 using 0.1 M NaOH/0.1 M KH2PO4.
Radiolabelling:
no
Analytical monitoring:
yes
Details on sampling:
- Sampling intervals for the parent/transformation products: 0.2, 4.4, 8.4 12.1, 16.0 and 25 hours
Buffers:
pH 7.00±0.05 with 0.1 M NaOH/0.1 M KH2PO4
pH was measured with a Corning pH meter using a one-point calibration method.
Duration:
25
pH:
7
Temp.:
25 °C
Initial conc. measured:
0 µg/L
Duration:
16
pH:
7
Temp.:
25 °C
Initial conc. measured:
8.8 µg/L
Duration:
12.1 h
pH:
7
Temp.:
25 °C
Initial conc. measured:
16 µg/L
Duration:
8.4 h
pH:
7
Temp.:
25 °C
Initial conc. measured:
15 µg/L
Duration:
4.4 h
pH:
7
Temp.:
25 °C
Initial conc. measured:
0 µg/L
Remarks:
This measurement was disregarded. Following measurements show linear degradation.
Duration:
0.2 h
pH:
7
Temp.:
25 °C
Initial conc. measured:
26 µg/L
Transformation products:
yes
No.:
#1
Details on hydrolysis and appearance of transformation product(s):
Benzothiazole was identified as sole hydrolysis product. Although Cyclohexylamine was expected as a potential degradation product as a result of stoichiometric hydrolysis, it was not identified by either gas liquid chromatography or GC/MS techniques.
Key result
pH:
7
Temp.:
25 °C
DT50:
12.5 h

The apparent hydrolysis rate is 1µg/hr. The test substance hydrolyzed completely over 24.9 hours.

Conclusions:
An apparent hydrolysis rate of 1µg/hr and a t1/2 of 12.5 hours were determined for CBS in pH 7.0 buffered deionized water with light excluded at 25 °C (Monsanto, 1984). In the same condition, a complete hydrolysis of CBS in 24.9 hours was also observed with the sole hydrolysis product as benzothiazole identified (Monsanto, 1984). However, the expected degradation products as a result of stoichiometric hydrolysis (Cyclohexylamine) was not identified.
Executive summary:

The substance N-cyclohexylbenzothiazole-2-sulphenamide was examined according OECD TG 111. An apparent hydrolysis rate of 1µg/hr and a t1/2 of 12.5 hours were determined for CBS in pH 7.0 buffered deionized water with light excluded at 25 °C (Monsanto, 1984). In the same condition, a complete hydrolysis of CBS in 24.9 hours was also observed with the sole hydrolysis product as benzothiazole identified (Monsanto, 1984). However, the expected degradation products as a result of stoichiometric hydrolysis (Cyclohexylamine) was not identified.

Description of key information

An apparent hydrolysis rate of 1µg/hr and a t1/2 of 12.5 hours were determined for CBS in pH 7.0 buffered deionized water with light excluded at 25 °C (Monsanto, 1984). In the same condition, a complete hydrolysis of CBS in 24.9 hours was also observed with the sole hydrolysis product identified as benzothiazole (Monsanto, 1984). However, the expected degradation product as a result of stoichiometric hydrolysis (i.e. Cyclohexylamine) was not found.


The registrant intends to further investigate the hydrolysis of CBS in due time. It is clearly expected that MBT will be found as the main hydrolysis product.

Key value for chemical safety assessment

Half-life for hydrolysis:
12.5 h
at the temperature of:
25 °C

Additional information

Under oxidative environment of 0.5 M phosphate buffer at pH 6.5, trace amount of MBTS (CAS: 120-78-5) and MBT (CAS: 149-30-4) were also detected (Hansson & Agrup, 1993).