Fatty acids, tall-oil, reaction products with linseed oil, maleic anhydride and methanol

Water solubility

Link to relevant study record(s)

Reference

Endpoint:

water solubility

Type of information:

(Q)SAR

Adequacy of study:

weight of evidence

Study period:

2017

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

Estimated data are obtained from a reliable (Q)SAR program developed and validated by the United States Environmental Protection Agency (U.S. EPA). This program is included in the OECD (Q)SAR Toolbox for use in filling REACH data gaps.

Qualifier:

according to guideline

Guideline:

other: validated QSAR

Principles of method if other than guideline:

Reliable (Q)SAR program developed and validated by the U(U.S. EPA and included in the OECD (Q)SAR Toolbox.

GLP compliance:

no

Type of method:

other: validated QSAR

Specific details on test material used for the study:

No test material used for experimental testing.
CAS Number: (null)
SMILES : O=C(OCCCCCC)CCCCCCCC(C(C(=O)(OC))CC(=O)(OC))C=CC=CCC=CCC
CHEM :
MOL FOR: C30 H50 O6
MOL WT : 506.73

Key result

Water solubility:

0 mg/L

Conc. based on:

other: structure (SMILES)

Temp.:

25 °C

pH:

> 4 - <= 7

Details on results:

Water Sol from Kow (WSKOW v1.42) Results:
========================================

Water Sol: 2.032e-006 mg/L

SMILES : O=C(OCCCCCC)CCCCCCCC(C(C(=O)(OC))CC(=O)(OC))C=CC=CCC=CCC
CHEM :
MOL FOR: C30 H50 O6
MOL WT : 506.73
---------------------------------- WSKOW v1.42 Results ------------------------
Log Kow (estimated) : 9.96
Log Kow (experimental): not available from database
Log Kow used by Water solubility estimates: 9.96

Equation Used to Make Water Sol estimate:
Log S (mol/L) = 0.796 - 0.854 log Kow - 0.00728 MW + Correction
(used when Melting Point NOT available)

Correction(s): Value
-------------------- -----
No Applicable Correction Factors

Log Water Solubility (in moles/L) : -11.397
Water Solubility at 25 deg C (mg/L): 2.032e-006

During experimental testing of the UVCB substance ZWA 5496, ambiguous water solubility and log P experimental results were obtained. In the Affolter, 2015 OECD 105 guideline study by the flask method, the water solubility was found to be dependent on the loading rate, and was estimated to be 9.0 - 69.4 mg/L at 20 deg C after a 6 day equilibration period. It was suggested by the authors of the study that the various components of the substance may display varying water solubilities. Potential breakdown of the substance was not addressed.

Structural models were proposed to help clarify this behaviour.  The rationale for using a structural model is based on the demonstrated technical infeasibility of conducting OECD guideline studies on this complex UVCB comprised of esters of linseed oil and tall oil. The flask method was employed and modified to include slow stirring for up to 6 days, without significant resolution of the ambiguities, including continued floculation/surface collection of undissolved material at all concentrations tested.  It is further noted by examining the structure of the substance that it may exhibit surfactant character, which limits the experimental techniques applicable for the measurement of water solubility and partitioning between water and n-octanol. Furthermore, potential ionisation of the species may occur under actual environmental conditions.  

It is possible to select potential analogues which represent a “worst case” for exposure, including a log Kow between 4 and 9 and log Koc > 5, which partitions to pore water and which are within the applicability domains (molecular weight) of the EPI-Suite (OECD QSAR Toolbox) models. In this case, the potential risk to humans and the environment will not be underestimated. It is further noted that the registered substance is essentially used as an intermediate in the polymerization of resins, is fully consumed and has no potential for release to the environment.

 

Several models were considered and their EPI-Suite results were compared, specifically for Kow, Log Kow, Water Solubility (estimate from Log Kow), and Koc (MCI & Kow methods) and Log Koc as shown in the table below.  Three structures were considered:

 

1) a structure based on a succinyl-modified alpha-linolenic acid derived from saponified Linseed oil, which contains an additional free acid moiety:

  

2) the structure in 1) except the free fatty acid has been “esterified” with a hexyl-group to mimic the triglyceride somewhat but also stays in an acceptable molecular weight range for the QSAR module:

  

3) the structure in 2) where the free acid from the succinyl-half ester was also set as a methyl ester to remove issues associated with ionisation of the acid in 2) in the model:

 

 

The results of EPI-Suite modeling are:

 

Structure	Octanol-water partition coefficient (Kow)	Log Kow  (est)	Wat Sol, mg/L	Koc, L/kg	Log Koc
1	2.20E+07	6.343	2.58E-02	8.57E+04	4.933
2	4.68E+09	9.67	1.02E-04	1.66E+05	5.22
3	9.12E+09	9.96	2.03E-06	1.33E+07	7.1251

 

As can be seen in the table, the largest impact was changing the free fatty acid moiety found in 1) by “esterifying” it in 2) to mimic the triglyceride.  Elimination of the acid moiety in the succinyl group in 2) led to a relatively small perturbation as seen in the results for 3).  Structure in 3) was the optimal representation for the purpose of estimating water solubility, partitioning between n-octanol and water, and partitioning between organic carbon and water. 

 

Conclusions:

The estimated water solubility of a representative ester substituting for potentially water soluble components of the UVCB test substance is 2.032E-06 mg/L at 25 deg C.

Description of key information

2.03E-06 mg/L (est.)

Key value for chemical safety assessment

Water solubility:

0 mg/L

at the temperature of:

25 °C

Additional information

Testing of the UVCB test substance for the water solubility endpoint is not technically feasible. The constituents of the complex UVCB test substance are diverse, and unable to be easily modeled. A representative ester was devised which represents a "worst case" for exposure. The behaviour of this representative ester for solubility in water, log Kow and log Koc was examined using EPI-Suite models (v4.11). The water solubility of this idealized analogue is estimated to be 2.032E-006 mg/L, or 0.000002032 mg/L at 25 °C.