Disodium oxybis[methylbenzenesulphonate]

Adsorption / desorption

Description of key information

Ditolylether disulfonic acid disodium salt, isomer mixture is an UVCB substance consisting of positional isomers of two basic structures [sodium salts of disulfonated and trisulfonated ditolylether]. 
Since variations in the positions of the substituents have influence on calculations by the program, the calculations are performed using representative constituents of ditolylether disulfonic acid disodium salt, isomer mixture (two of each basic structure). 
The QSAR determination of the carbon partition coefficient using the model KOCWIN included in the Estimation Program Interface (EPI) Suite v4.1 revealed values of 0.044 to 1.346 L/kg (log Kow method) and 2424 to 82790 L/kg (MCI method) relating to the dissociated and non-dissociated form of representative constituents of ditolylether disulfonic acid disodium salt, isomer mixture, respectively. Estimated pkas are in the range of -1.35 to -0.40, indicating that the ditolylether disulfonic acid disodium salt, isomer mixture exists predominately in its dissociated form at environmentally relevant pH. As Koc values estimated based upon the log Kow method considers the anionic character of ditolylether disulfonic acid disodium salt, isomer mixture the lowest value of 0.044 L/kg is taken into account for further assessment.
 

Key value for chemical safety assessment

Koc at 20 °C:

0.044

Additional information

For ditolylether disulfonic acid disodium salt, isomer mixture no experimental results describing the adsorption properties are available.

Under environmental relevant pHs, ditolylether disulfonic acid disodium salt, isomer mixture exists predominantly in the dissociated form, based upon its pKa values. At pH 5 to 9, ditolylether disulfonic acid disodium salt, isomer mixture will be deprotonated resulting in the corresponding anion. As deprotonated substances in particular generally have a low adsorption potential, adsorption for the dissociated form of ditolylether disulfonic acid disodium salt, isomer mixture is not expected.

Nevertheless, in order to predict the distribution of ditolylether disulfonic acid disodium salt, isomer mixture between the organic phase of soil or sediments and the porewater calculations were performed using different estimation methods which are incorporated in the Estimation Program Interface (EPI) Suite version 4.1.

The organic carbon partition coefficient (Koc) of the substance was predicted using the Estimation Program Interface (EPI) Suite version 4.1.

Ditolylether disulfonic acid disodium salt, isomer mixture is an UVCB substance consisting of positional isomers of two basic structures [sodium salts of disulfonated and trisulfonated ditolylether].

Since variations in the positions of the substituents have influence on calculations by the program, the calculations are performed using representative constituents of ditolylether disulfonic acid disodium salt, isomer mixture (two of each basic structure).

 

The representative constituents are:

A) disodium 3-methyl-4-(3-methyl-4-sulfonato-phenoxy)-benzenesulfonate

B) disodium 2-methyl-4-(3-methyl-4-sulfonato-phenoxy)-benzenesulfonate

C) trisodium 2-methyl-4-(2-methyl-4-sulfonato-phenoxy)-benzene-1,3-disulfonate

D) trisodium 2-methyl-5-(3-methyl-4-sulfonato-phenoxy)-benzene-1,3-disulfonate

 

For estimating Koc, a method based on statistical relationships between Koc and the octanol/water partition coefficient (Kow) was used.

 

The following estimated log Kow values were used for calculation, as ditolylether disulfonic acid disodium salt, isomer mixture exists predominantly in its dissociated from:

Representative constituent A: log Kow = -2.38

Representative constituent B: log Kow = -1.54

Representative constituent C: log Kow = -4.12

Representative constituent D: log Kow = -3.28

 

Koc values in the range of 0.044 to 1.346 L/kg were obtained.

 

Moreover, calculations were performed based upon the molecule structure using the molecular connectivity method yielding Koc values in the range of 2424 to 82790 L/kg (MCI method).

As predictions for a salt cannot be performed by the program, metals (Na) has been removed to allow estimation using the MCI method. Thus, predictions based upon the MCI method, relate to the non-water based parent acids of the representative constituents of ditolylether disulfonic acid disodium salt, isomer mixture in their non-dissociated form.

The results for the representative constituents of ditolylether disulfonic acid disodium salt, isomer mixture fall within the applicability domain described above and the applied estimation rules appear appropriate. Regarding the structures of the representative constituents of ditolylether disulfonic acid disodium salt, isomer mixture the fragment descriptors found by the program are complete.

Therefore the predicted values can be considered reliable yielding a useful result for further assessment.

Due to the fact that the dissociating property of ditolylether disulfonic acid disodium salt, isomer mixture is not incorporated by the estimation program, the lowest Koc value of 0.044 L/kg is taken into account for further assessment, as it considers the anionic character of ditolylether disulfonic acid disodium salt, isomer mixture. The highest estimated Koc of 1.346 L/kg suggest that ditolylether disulfonic acid disodium salt, isomer mixture has a negligible sorption potential to soil and sediment, and a rapid migration potential to groundwater. For all estimations ambient temperature was assumed.