Registration Dossier

Physical & Chemical properties

Melting point / freezing point

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Description of key information

The registered substance 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.

Key value for chemical safety assessment

Melting / freezing point at 101 325 Pa:
334.45 °C

Additional information

The alkaryl benzene sulfonates are a group of inter-related substances of similar structure typically consisting of a benzene ring with a sulphonic acid which may be present as the free acid or metal substituted salt and one or more long chain alkyl groups that may vary in length and the degree of branching. The alkaryl benzene sulfonates are produced in base oils from petroleum streams and display similar chemistry, characterised typically as relatively high melting glass like substances, in the absence of the mineral oil, extremely low water solubility and very high partition coefficient.

The presence of mineral oil, however, alters the physical appearance from solid to liquid, so it is not technically feasible to conduct a study to measure the melting temperature of the substance. Estimations have, therefore, been undertaken using the EPIWIN Modelling Program. To allow for a weight of evidence approach estimations have been made for all suitable molecular variations in the series alkaryl benzene sulfonates. For the purpose of additional relaibility, the result given above is a mean average melting point value calculated by QSAR across the series of structurally related substances.

To further support this approach a QSAR Prediction Reporting Format (QPRF) is attached to justify the QSAR system as adequate for estimating the value for the purposes of REACH registration