4-hydroxybutyl acrylate

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

- QMRF: see 'Overall remarks, attachments'.
- QPRF: see 'Executive summary'.

Qualifier:

no guideline followed

Principles of method if other than guideline:

Calculation of aqueous hydrolysis rate constant. Software used: SRC HYDROWIN v2.00

GLP compliance:

no

Specific details on test material used for the study:

- SMILES code: O=C(OCCCCO)C=C

Estimation method (if used):

HYDROWIN v2.00 (chemical class: Ester)

pH:

8

Temp.:

25 °C

DT50:

1.061 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.

pH:

7

Temp.:

25 °C

DT50:

10.607 yr

Type:

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

Remarks on result:

other: Kb half-life; The substance is within the applicability domain of the model.

Other kinetic parameters:

Kb hydrolysis at atom #2: 2.071E-002 L/mol*sec
Total Kb for pH > 8 at 25 °C: 2.071E-002 L/mol*sec

Executive summary:

QPRF: HYDROWIN v2.00 

1.	Substance	See “Test material identity”
2.	General information
2.1	Date of QPRF	see "Data source > Reference > Report date"
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	HYDROWIN
		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)	Not 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.7b, (Nov. 2012).69 pp.

Identified fragments for the current substance:

Fragment	Es	sigma*	sigma-meta	sigma-para	Fragment identified by HYDROWIN	Substitute fragment (warning by HYDROWIN)	Name of R group according to HYDROWIN
-CH=CH2	-3.19	0.07	0.08	-0.09	yes	no	R1

Unidentified fragments for the current substance: n-Butyl

Description of key information

The study does not need to be conducted as the substance is readily biodegradable. Supporting QSAR data shows that in contact with water, the substance will hydrolyse slowly (half-life ≥12 hours).

The substance has an estimated half-life in water of ~10.6 years at pH 7 and ~1.1 year at pH 8.

Additional information

QSAR-disclaimer

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met. Furthermore according to Article 25 of the same Regulation testing on vertebrate animals shall be undertaken only as a last resort.

 

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

 

For the assessment of 4-hydroxybutyl acrylate (Q)SAR results were used for hydrolysis. The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be not entirely adequately fulfilled, as unidentified fragments were identified. Nevertheless, the QSAR data provides an indication of the hydrolysis rate.

 

Furthermore, as the substance is readily biodegradable, further experimental studies on hydrolysis are not provided.