Benzenesulfonic acid and petroleum sulfonic acids, mono- and di-C10-40-(branched and linear)-alkyl derivs., magnesium salts, overbased

Melting point / freezing point

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:

284.219 °C

Additional information

Weight of Evidence according to Annex XI, 1.2 of REACH, an adaptation rule for standard information requirements.

Introduction and background information

The registered substance Benzenesulfonic acid, mono & dialkyl derivs., magnesium salts (CAS: 71786-47-5) is produced, supplied and marketed in the presence of a liquid mineral oil solvent. Removal of this solvent is expected to cause a change in the equilibrium of the chemical structure of the alkaryl benzene sulfonates resulting in a degradation of the chemical structure to a structure that is not representative of the substance being placed on the market in the EU. It is, in consequence, not possible to undertake any study of the registered substance in the absence of the solvent. This is further compounded by the fact that the presence of the mineral oil solvent changes the physical state of the registered substance from solid to liquid and will therefore have a considerable effect on the result of any test conducted on the substance in solvent. It is therefore considered justifiable to omit any study, but the results from QSAR are included to allow for a weight of evidence approach.

In order to provide data on the intrinsic properties of the benzene sulphonic substance itself, in the absence of the mineral oil, data are presented by means of QSAR assessment of the chemical structure of the substance. In order to provide greater reliability of the QSAR data, several structural variation of the UVCB were assessed and a mean value assigned for each endpoint to be representative of the substance as a whole.

 

QSAR assessment

A QSAR assessment using the US EPA On-Line EPI Suite™ v4.1, MPBPWIN (Version 1.43) for the melting point was conducted. MPBPWIN contains a large dataset of 10,051 compounds containing a diverse mix of simple, moderate and very complex structural compounds, taken from the PHYSPROP Database used by the EPI Suite. As the results are derived from a valid QSAR model and contains adequate and reliable documentation it has been assigned a reliability rating of 2. This is assigned due to the fact MPBPWIN has undergone extensive validation and is therefore considered to be a reliable source of information.

For the QSAR assessment of Benzenesulfonic acid, mono & dialkyl derivs., magnesium salts (CAS: 71786-47-5) the following structures were assessed:

Mono alkyl benzene sulphonic acid C20-24

Di alkyl substituted benzene sulphonic acids 2x C10-24 branched

Di alkyl substituted benzene sulphonic acids 2x C10-24 linear

Petroleum sulphonic acids

 

The results of the assessment were as follows:

Substance	Melting Point (°C)
Mono alkyl benzene sulphonic acid C20-24	248.08
Di alkyl substituted benzene sulphonic acids 2x C10-24 branched	289.48
Di alkyl substituted benzene sulphonic acids 2x C10-24 linear	293.54
Petroleum sulphonic acids	305.776
Mean value for the assessed substance:	284.219°C

 

Conclusions

Removal of mineral oil at scale is not possible without degrading the chemical structure of the substance other than by column chromatography at small sample scale for analytical purposes. It was therefore considered acceptable to create a weight of evidence approach based upon Quantitative Structural-Activity Relationship (QSAR). The QSAR model of choice was the EPI Suite v4.1 published by the United States Environmental Protection Agency, which has estimated the melting point to be 284.219°C for Benzenesulfonic acid, mono & dialkyl derivs., magnesium salts (CAS: 71786-47-5).