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Physical & Chemical properties

Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The quoted value is an estimate based on an internationally recognised modelling programme
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Qualifier:
according to guideline
Guideline:
other: QSAR Calculation
Principles of method if other than guideline:
Modified Grain Method. Quantitative Structural-Activity Relationship based upon chemical structure devised from the SMILES code drawn from a database of >40,000 chemicals (called PHYSPROP©) that is included in the EPI Suite™ software
GLP compliance:
no
Other quality assurance:
other: ISO 9001
Type of method:
other: QSAR
Key result
Temp.:
25 °C
Vapour pressure:
0 kPa
Conclusions:
The vapour pressure of the substance is considered to be 7.46E-18 kPa at 25C based on a QSAR driven by the EPI Suite v4.0
Executive summary:

Removal of mineral oil is not possible without degrading the chemical struture of the substance. 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 v4.0 published by the United States Environmental Protection Agency, which has estimated the vapour pressure to be 7.46E-18 kPa at 25oC

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 sodium mineral oil 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

Vapour pressure:
0 kPa
at the temperature of:
25 °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 vapour pressure 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