Bis(2-ethylhexyl) adipate

Hydrolysis

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

hydrolysis

Data waiving:

other justification

Justification for data waiving:

other:

Reference 2

Endpoint:

hydrolysis

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Validated QSAR model. Fragment(s) on this compound are not available from the fragment library. Substitute(s) have been used.

Justification for type of information:

QSAR prediction: migrated from IUCLID 5.6

Principles of method if other than guideline:

Calculation based on HYDROWIN v2.00, Estimation Programs Interface Suite™ for Microsoft® Windows v 4.10. US EPA, United States Environmental Protection Agency, Washington, DC, USA.

GLP compliance:

no

pH:

8

Temp.:

25 °C

DT50:

117.42 d

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Kb half-life; The substance is (not) within the applicability domain of the model.

pH:

7

Temp.:

25 °C

DT50:

> 3.22 yr

Type:

(pseudo-)first order (= half-life)

Remarks on result:

other: Kb half-life; The substance is (not) within the applicability domain of the model.

Other kinetic parameters:

Kb at atom#16: 3.416 E-2 L/mol*sec
Total Kb for pH > 8 at 25 °C : 6.832 E-2 L/mol*sec

Executive summary:

QPRF: HYDROWIN v2.00

1.	Substance	See “Test material identity”
2.	General information
2.1	Date of QPRF	24 Oct. 2013
2.2	QPRF author and contact details	BASF SE, Dept. for Product Safety, Ludwigshafen, Germany
3.	Prediction
3.1	Endpoint (OECD Principle 1)	Endpoint	Aqueous hydrolysis rate
		Dependent variable	Hydrolytic half-life
3.2	Algorithm (OECD Principle 2)	Model or submodel name	WSKOWWIN
		Model version	v. 2.00
		Reference to QMRF	Estimation of Aqueous Hydrolysis Rate Constants using HYDROWIN v2.00 (EPI Suite v4.11) (QMRF)
		Predicted value (model result)	See “Results and discussion”
		Input for prediction	Chemical structure via CAS number or SMILES
		Descriptor values	- SMILES: structure of the compound as SMILES notation Fragment values: - Taft constant (sigma*) - Steric factor (Es) - Hammett constants (sigma-meta and sigma-para)
3.3	Applicability domain (OECD principle 3)	Domains:
		1) Chemical class	An equation for the estimation of the aqueous hydrolytic rate constant is available for the chemical class of the substance.
		2) Fragments (On-Line HYDROWIN User’s Guide, Appendix E)	All fragments were identified.
3.4	The uncertainty of the prediction (OECD principle 4)	According to REACH Guidance Document R.7a, (Nov. 2012), hydrolysis kinetics are usually determined experimentally. The guidance document also lists HYDROWIN as a means to estimate the hydrolytic half-life. The estimation is limited to only a few chemical classes. The model marks uncertainties of the estimate due to substitute values for missing fragments. As yet, the QSAR equations in HYDROWIN have not been rigorously tested with an external validation dataset. Currently, the number of chemicals with evaluated hydrolysis rates is relatively small in number, and the available data have been used to train the QSAR regressions. The training data set for esters has an acceptable size (n = 124). Equations for the other chemical classes were developed on very small databases (n = 7 to 20); therefore the reliability of estimations for members of other chemical classes than esters is low.
3.5	The chemical mechanisms according to the model underpinning the predicted result (OECD principle 5)	Hydrolysis is a common degradation route in the environment, where reaction of a substance with water with a net exchange of the X group with an OH at the reaction centre such that RX + H2O →ROH + HX. Hydrolysis is often dependent upon pH as the reaction is commonly catalysed by hydrogen or hydroxide ions. The model uses the principle of linear free energy relationships (LFER) to estimate the aqueous hydrolysis rate.

References

- US EPA (2012). On-Line HYDROWIN User’s Guide, Appendix E: Fragment Substituent Values Used by HYDROWIN.

- ECHA (2012). REACH Guidance Document R.7a, (Nov. 2012). 381 pp.

Identified fragments for the current substance:

Fragment(s) on this compound are NOT available from the fragment library. Substitute(s) have been used!!! Substitute R1, R2, R3, or R4 fragments are marked with double astericks "**".

 

ESTER: R1-C(=O)-O-R2     ** R1: n-Butyl-

** R2: iso-Butyl-

 

ESTER: R1-C(=O)-O-R2     ** R1: n-Butyl-

** R2: iso-Butyl-

Reference 3

Endpoint:

hydrolysis

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Study period:

14 Oct 1994 - 15 Feb 1995

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Guideline study with acceptable restrictions.

Qualifier:

according to guideline

Guideline:

OECD Guideline 111 (Hydrolysis as a Function of pH)

Deviations:

no

GLP compliance:

not specified

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
PHYSICO-CHEMICAL PROPERTIES
- Vapour pressure: 2.1 * 10E(-02) Pa at 25 °C
- Water solubility: 35 mg/L (at 25 ± 1 °C)

Radiolabelling:

no

Analytical monitoring:

not specified

Details on test conditions:

TEST SYSTEM
- Type, material and volume of test flasks, other equipment used: glass flask with a glass cap

Number of replicates:

2

Positive controls:

no

Negative controls:

no

Preliminary study:

No hydrolysis was observed in pH4 at 50 ± 1 °C after 5 days.

Test performance:

Concentration was 15 mg/L.
Temperature: (pH7) 70 ± 1 °C, 80 ± 1 °C, 90 ± 1 °C
(pH9) 50 ± 1 °C, 60 ± 1 °C, 70 ± 1 °C

Transformation products:

not specified

pH:

7

Temp.:

25 °C

Hydrolysis rate constant:

0 h-1

DT50:

1 850 d

pH:

9

Temp.:

25 °C

Hydrolysis rate constant:

0.004 h-1

DT50:

7.31 d

Description of key information

Hydrolysis is not expected to be a relevant degradation pathway since the substance is readily biodegradable.

Additional information

In accordance with Annex VIII, column 2 (9.2.2.1) of Regulation (EC) No. 1907/2006, the testing for hydrolysis as a function of pH is not required as the substance is readily biodegradable. Furthermore, in accordance with Annex XI, subitem 2. Testing is technically not possible, of Regulation (EC) No. 1907/2006, testing for hydrolysis as a function of pH may be omitted, if the test is technically not possible to conduct. The substance is expected to be very poorly soluble in water (0.0032 mg/L). Thus, the test is technically not possible to conduct since the practical insolubility of the test substance impedes a proper analytics.

Generally, as Bis(2-ethylhexyl) adipate does contain carboxylic ester groups, hydrolysis may be possible to some extent. The stability of the test substance at pH 13.5, the low reactions rate at an increased temperature, and the partly saponification under alcoholic and acidic conditions (11% at pH 2), permits the conclusion, that the hydrolytic degradation of the test substance runs slowly under natural conditions (Brown 1983). QSAR calculations (DT50 [pH 7] > 1 yr; HYDROWIN v2.00) and experimental data for a structurally very similar substance (Dibutyl adipate, DT50 [pH 7] > 1850 d) clearly confirms, that hydrolysis represents a negligible pathway for the environmental fate of the substance in the environment. This assumption of lack of relevance of abiotic degradation is in line with the assessment of substances as defined by the US-EPA "Aliphatic Diester Category" (US-EPA, 2010).