Dimethylbis[(1-oxoneodecyl)oxy]stannane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 September 2017 to 03 November 2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.7 (Degradation: Abiotic Degradation: Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

no

Remarks:

(this is not a toxicological or ecotoxicological test - GLP conditions not required)

Radiolabelling:

not specified

Analytical monitoring:

yes

Details on sampling:

Sample preparation: 370 µL/ 330 µL toluene-d8 (10 mg/mL CrAcAc)

Buffers:

pH 1.2: HCl 0.1 M
pH 4.0: HCl/NaCl/Citric acid
pH 7.0: Na2HPO4/NaH2PO4
pH 9.0: H3BO3/KCl/NaOH

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: 250 mL Erlenmeyer flask with ground in stopper

HIGH pH TESTING (pH 4.0, 7.0, 9.0)
- The test material was used without a co-solvent or a detergent.
- 1 g (2.03 mMol) of the test material was added to 100 mL of the respective buffer solution in a 250 mL Erlenmeyer flask.
- The flask was closed with a stopper and heated in a heating cabinet for 5 days (120 hours) at 50 °C.
- The mixture was stirred by a magnetic stirrer using a 40 x 7 mm stir bar at approx. 100 rpm.
- After the pre-determined reaction time, the solution was allowed to cool down to room temperature; 10 mL of each reaction mixture was taken by a syringe and placed in a headspace glass for TOC analysis. The rest of each reaction mixture was extracted with 20 mL hexane, the phases were separated using a separatory funnel. The organic phase was transferred into a pre-weighed flask and the solvent was removed in a rotary evaporator (< 40°C, 10 mbar). The weight difference was recorded for the mass balance, and the samples were analysed by 119Sn-NMR.

GASTRIC pH TESTING (pH 1.2/ 37 °C)
- The test material was used without a co-solvent or a detergent.
- 1 g (2.03 mMol) of the test material was added to 100 mL of 0.1 M aqueous solution of hydrochloric acid that was preheated to 37 °C in a 250 mL Erlenmeyer flask with ground in stopper.
- The flask was closed with a stopper and heated in a heating cabinet for 4 hours at 37 °C.
- The mixture was stirred by a magnetic stirrer using a 40 x 7 mm stir bar at approximately 100 rpm.
- After the pre-determined exposure time, the solution was allowed to cool down to room temperature; extracted 2 times with 25 mL hexane; the phases were separated using a separatory funnel. The organic phase was transferred into flask, and the solvent was removed in a rotary evaporator (< 40°C, 10 mbar). The sample was analysed by 119Sn-NMR.

Duration:

5 d

pH:

4

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without any solvent

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without any solvent

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without any solvent

Duration:

4 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without any solvent

Number of replicates:

1

Positive controls:

no

Negative controls:

no

Transformation products:

yes

Remarks:

(hydrolysis at pH 1.2)

No.:

#1

% Recovery:

76

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

98

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

78

pH:

9

Temp.:

50 °C

Duration:

5 d

% Recovery:

85

pH:

1.2

Temp.:

37 °C

Duration:

4 h

Key result

pH:

4

Temp.:

50 °C

DT50:

> 1 yr

Key result

pH:

7

Temp.:

50 °C

DT50:

> 1 yr

Details on results:

HYDROLYSIS AT PH 4,7 AND 9
Samples of the test material were added to the respective buffer solutions at 50 °C for 5 days (120 h). At no pH value the 119Sn-NMR spectra of the extracted reaction products showed signs of hydrolysis.
The half-life time of the test material under the conditions of the study is > 1 year for the pH values 4 and 7 and the test material can be considered as hydrolytically stable.
At pH 9 besides the signal for the test material a new broad signal at -200 ppm appeared with an intensity equivalent to 57 Mol% which cannot be attributed unequivocally to a specific tin containing species.
Based on the chemistry the formation of a hydroxide and possible further reaction products can be postulated.

HYDROLYSIS AT PH 1.2
1 g (2.03 mMol) of the test material was added to an excess 0.1 M hydrochloric acid at 37 °C for 4 hours and extracted with hexane after cooling down to room temperature. The 119Sn-NMR spectrum of the organic extract showed no signal between 200 and -500 ppm. A small signal at -523 ppm points to a highly coordinated tin compound or may be just an artefact.
The 1H-NMR spectrum of the hexane extract was identical to the reference spectrum of neodecanoic acid. It can be concluded that under the conditions of the study the neodecanoic acid ligand is hydrolysed from the tin atom and the dimethyltin cation forms a water soluble breakdown product.

ATOMIC ABSORPTION SPECTOMETRY
The aqueous phases of the low pH hydrolysis were analysed after extraction with hexane by AAS and contained 1690 mg/L Sn.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of this study, the test material was hydrolytically stable at pH 7 and 4. At pH 9 57 Mol % of a substance was formed which cannot be unequivocally attributed to a known tin compound. At pH 1.2 the only identifiable breakdown product was the ligand neodecanoic acid.

Executive summary:

The hydrolysis of the test material as a function of pH was investigated in accordance with the standardised guidelines OECD 111 and EU Method C.7.

The stability of the test material was investigated at pH 4, 7 and 9 and pH 1.2 using NMR spectroscopy.

The study showed that the test material is hydrolytically stable at pH 7 and 4. After 5 days of hydrolysis at 50 °C less than 10 % of the test material was hydrolysed (half life at 25 °C > 1 year). At pH 9 / 50 °C / 5 days 57 Mol % of a substance was formed which cannot be unequivocally attributed to a known tin compound. Based on the chemistry the formation of a hydroxide and possible further reaction products can be postulated.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the only identifiable breakdown product was the ligand neodecanoic acid, which was extracted in the hexane phase and identified by 1H-NMR spectroscopy.

The lower recovery of substance in the hexane extract and the content of 1690 mg/L tin remaining in the aqueous phase indicate that the dimethyltin cation remains in a soluble form in water.

Description of key information

Under the conditions of the study, the test material was hydrolytically stable at pH 7 and 4. At pH 9 57 Mol % of a substance was formed which cannot be unequivocally attributed to a known tin compound. At pH 1.2 the only identifiable breakdown product was the ligand neodecanoic acid.

Key value for chemical safety assessment

Half-life for hydrolysis:

1 yr

at the temperature of:

50 °C

Additional information

The hydrolysis of the test material as a function of pH was investigated in accordance with the standardised guidelines OECD 111 and EU Method C.7.

The stability of the test material was investigated at pH 4, 7 and 9 and pH 1.2 using NMR spectroscopy.

The study showed that the test material is hydrolytically stable at pH 7 and 4. After 5 days of hydrolysis at 50 °C less than 10 % of the test material was hydrolysed (half life at 25 °C > 1 year). At pH 9 / 50 °C / 5 days 57 Mol % of a substance was formed which cannot be unequivocally attributed to a known tin compound. Based on the chemistry the formation of a hydroxide and possible further reaction products can be postulated.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the only identifiable breakdown product was the ligand neodecanoic acid, which was extracted in the hexane phase and identified by 1H-NMR spectroscopy.

The lower recovery of substance in the hexane extract and the content of 1690 mg/L tin remaining in the aqueous phase indicate that the dimethyltin cation remains in a soluble form in water.