Bis[(2-ethyl-1-oxohexyl)oxy]dioctylstannane

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:

(not required as study is not a toxicological/ ecotoxicological study)

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 (1.6 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 (1.6 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 Spectroscopy.

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:

yes

Remarks:

Dimeric teraoctyl distannoxane at pH9 and Dioctyltin chloro 2-ethylhexanoate a monochloroester ot the test material at pH 1.2.

No.:

#1

% Recovery:

95

pH:

4

Temp.:

50 °C

Duration:

5 d

% Recovery:

91

pH:

7

Temp.:

50 °C

Duration:

5 d

% Recovery:

77

pH:

9

Temp.:

50 °C

Duration:

5 d

Remarks on result:

other: After cooling a white waxy solid at room temperature

% Recovery:

97

pH:

1.2

Temp.:

50 °C

Duration:

4 h

Key result

Remarks on result:

hydrolytically stable based on preliminary test

Details on results:

HYDROLYSIS AT PH 4,7 AND 9
- At pH 4 and 7 the 119Sn-NMR spectra were analogous to the unhydrolised substance.
- The pH 9 spectrum of the extracted hydrolysate shows a significant decrease of the product peak at -156 ppm and two sharp peaks (of equal intensity) at -224 and -222 ppm.
- Acyl-substituted teraorganodistannoxanes are reported in literature to be formed as hydrolysis products of dialkyltincarboxylates, following an initial formation of a hydroxide. The reported chemical shifts correlate well with the shifts found in the extract of the hydrolysate.
- So the formation of a dimeric teraoctyl distannoxane is most likely breakdown product of the test material at pH 9.

HYDROLYSIS AT PH 1.2
- The 119Sn-NMR spectrum of the organic extract the substance signal broadens significantly and decrease to 39.5 Mol% in intensity.
- An additional broad peak appears at -34 ppm (52 Mol%).
- This behaviour is similar to the simulated gastric breakdown under the same conditions of DBTL and DOTL.
- The broad signal can be attributed to the formation of dioctyltin chloro 2-ethylhexanoate a monochloroester of the test material.
- The broadening of the signals may point to a intermolecular conjugation of the test material itself or with DOTO. However this is speculative.
- In contrast to the mentioned dioctyltin di laurates here no signals are found which indicate the formation of a dimeric tetraoctyl dichloro distannoxane.
- No DOTC was formed under the conditions of the study

MASS BALANCE RECOVERY RATES
pH 4: 95 %
pH 7: 91 %
pH 9: 77 %
pH 1.2 97 %

ATOMIC ABSORPTION SPECTOMETRY
- The aqueous phase of the low pH hydrolysis has been analysed after extraction with hexane by AAS and contained < 5mg/L Sn. So the formation of an organotin substance better soluble in water than in hexane can be excluded.

Validity criteria fulfilled:

not specified

Conclusions:

Under the conditions of this study, the test material can be considered hydrolytically stable at pH 4 and 7.
After 5 days of hydrolysis at 50 °C at pH 4 and 7 no reaction could be identified based on the 119Sn NMR spectra of the extracted hydrolysates.
At pH 9 under the same conditions the formation of a dimeric teraoctyl distannoxane is the most likely breakdown product.
Under simulated gastric conditions the test material breaks down to its monochloroester. The Formation of DOTC and a dimeric teraoctyl dichloro distannoxane can be excluded. The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.

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 can be considered hydrolytically stable at pH 4 and 7.

After 5 days of hydrolysis at 50 °C at pH 4 and 7 no reaction could be identified based on the 119Sn NMR spectra of the extracted hydrolysates.

At pH 9 under the same conditions the formation of a dimeric teraoctyl distannoxane is the most likely breakdown product

Under simulated gastric conditions the test material breaks down to its monochloroester. The Formation of DOTC and a dimeric teraoctyl dichloro distannoxane can be excluded. The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.

Description of key information

Under the conditions of this study, the test material can be considered hydrolytically stable at pH 4 and 7.

After 5 days of hydrolysis at 50 °C at pH 4 and 7 no reaction could be identified based on the 119Sn NMR spectra of the extracted hydrolysates.

At pH 9 under the same conditions the formation of a dimeric teraoctyl distannoxane is the most likely breakdown product

Under simulated gastric conditions the test material breaks down to its monochloroester. The Formation of DOTC and a dimeric teraoctyl dichloro distannoxane can be excluded. The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.

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 can be considered hydrolytically stable at pH 4 and 7.

After 5 days of hydrolysis at 50 °C at pH 4 and 7 no reaction could be identified based on the 119Sn NMR spectra of the extracted hydrolysates.

At pH 9 under the same conditions the formation of a dimeric teraoctyl distannoxane is the most likely breakdown product

Under simulated gastric conditions the test material breaks down to its monochloroester. The Formation of DOTC and a dimeric teraoctyl dichloro distannoxane can be excluded. The tin content in the aqueous phase of the hydrolysis remained under the detection limit of < 5 mg/L in AAS. Thus the formation of a water soluble organotin species can be excluded.