Dimethylbis(oleoyloxy)stannane

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

experimental study

Adequacy of study:

key study

Study period:

21 September 2016 to 07 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)

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 (1.4 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 (1.4 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 on 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 a solvent.

Duration:

5 d

pH:

7

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Duration:

5 d

pH:

9

Temp.:

50 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Duration:

4 h

pH:

1.2

Temp.:

37 °C

Initial conc. measured:

100 other: %

Remarks:

The test material was used without a solvent.

Number of replicates:

1

Positive controls:

no

Negative controls:

no

Transformation products:

not specified

Remarks:

The oleic acid ligand is hydrolysed from the tin atom and the remaining dimethyltin fragment forms a water soluble breakdown product.

% Recovery:

78

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

20

pH:

7

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: Due to a greasy phase surface, the organic phase was mistakenly disposed of together with the aqueous phase. So this value cannot be considered as meaningful.

% Recovery:

85

pH:

9

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: The values is negatively impacted by a greasy phase surface

Key result

pH:

4

Temp.:

50 °C

DT50:

> 1 yr

Details on results:

HYDROLYSIS AT PH 4,7 AND 9
- At pH 4 the 119Sn-NMR spectra of the extracted reaction products shows no signs of hydrolysis, whereas at pH 7 and to a greater extent at pH 9, new signals in the 119Sn-NMR spectra indicate the breakdown of the substance.
- The half-life time of the test material under the conditions of the study is > 1 year for the pH value 4 the substance can considered as hydrolytically stable.
- At pH 7 and 9 two signals appear at -187 and – 207 ppm in the 119Sn-NMR spectra of the extracted hydrolysate which can be attributed to the formation of a dimeric tetramethyl distannoxane structure. Those structures are formed following a stepwise hydrolysis of initially formed diorganotin hydroxides.

HYDROLYSIS AT PH 1.2
- The 119Sn-NMR spectrum of the organic extract shows no signal between 200 and -800 ppm.
- The 1H-NMR spectrum of the hexane extract is identical with the reference spectrum of oleic acid.
- The recovered mass of 0.79 g corresponds to 100 % of oleic acid (M = 282.46 Da) bound as ligand in the test material.
- It can be concluded that under the conditions of the study the oleic acid ligand is hydrolysed from the tin atom and the remaining dimethyltin fragment forms a water soluble breakdown product.

MASS BALANCE RECOVERY RATES
pH 4: 78 %
pH 7: 20 %
pH 9: 85 %
pH 1.2: 79 %

ATOMIC ABSORPTION SPECTOMETRY
- The aqueous phase of the low pH hydrolysis was analysed after extraction with hexane by AAS and contained 1530 mg/L Sn (92% of Theory).

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of this study, the test material was is hydrolytically stable at pH 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 7 and to a greater extend at pH 9, the test material was found to break down to a dimeric dimethyl distannoxane.
At simulated gastric conditions (0.1 M HCl /pH 1.2 /37°C/ 4 h) the only identifiable breakdown product was the ligand oleic acid, which was extracted in the hexane phase and identified by 1H-NMR spectroscopy. The lower recovery of test material in the hexane extract and the content of 1530 mg/L tin remaining in the aqueous phase indicate that the remaining dimethyltin fragment remains in a soluble form in water.

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.

Under the conditions of this study, the test material was is hydrolytically stable at pH 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 7 and to a greater extend at pH 9, the test material was found to break down to a dimeric dimethyl distannoxane.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37 °C/ 4 h) the only identifiable breakdown product was the ligand oleic acid, which was extracted in the hexane phase and identified by 1H-NMR spectroscopy. The lower recovery of test material in the hexane extract and the content of 1530 mg/L tin remaining in the aqueous phase indicate that the remaining dimethyltin fragment remains in a soluble form in water.

Description of key information

Under the conditions of this study, the test material was is hydrolytically stable at pH 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 7 and to a greater extend at pH 9, the test material was found to break down to a dimeric dimethyl distannoxane.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37°C/ 4 h) the only identifiable breakdown product was the ligand oleic acid, which was extracted in the hexane phase and identified by 1H-NMR spectroscopy. The lower recovery of test material in the hexane extract and the content of 1530 mg/L tin remaining in the aqueous phase indicate that the remaining dimethyltin fragment remains in a soluble form in water.

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 study was awarded a reliability score of 2 in accordance with the criteria set forth by Klimisch et al. (1997).

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

Under the conditions of this study, the test material was is hydrolytically stable at pH 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 7 and to a greater extend at pH 9, the test material was found to break down to a dimeric dimethyl distannoxane.

At simulated gastric conditions (0.1 M HCl /pH 1.2 /37°C/ 4 h) the only identifiable breakdown product was the ligand oleic acid, which was extracted in the hexane phase and identified by 1H-NMR spectroscopy. The lower recovery of test material in the hexane extract and the content of 1530 mg/L tin remaining in the aqueous phase indicate that the remaining dimethyltin fragment remains in a soluble form in water.