Ethyltriphenylphosphonium acetate

Surface tension

Administrative data

Endpoint:

surface tension

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because surface activity is not a desired property of the material

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING
According to the REACH regulation, Annex VII, endpoint 7.4 surface tension, column two, surface activity, the study does not need to be conducted as surface activity is not a desired property of the material and also not an expected property of the substance.

Surface activity in the context of REACH describes the property of a substance to reduce surface tension of water from above 70 mN/N to below 40-50 mN/N.
For having this surface active property, a molecule/ion has to have an accessible bipolar structure: polar/ionic on one side, non-polar long alkyl chain on the other side. In the mixture with water, a surface active substance is enriched at the surface/interface of the water - the polar/ionic side is directed to water, the non-polar side is directed outside water. Surface active substances are not very well water soluble.
The ETPPAAC substance is ionic. The cation has 3 phenyl and one ethyl group attached to phosphorus - thus the cation has a rigid phenyl and ethyl surface shielding the positively charged phosphorus. The anion, acetate, is too small to have surface active properties. The less polar phenyl groups (compared to phosphorus) and the positively charged phosphorus doesn't lead to surface active properties as the substance is well soluble in water.
A use of the substance as phase-transfer-catalyst is not in contradiction to the statement of having no surface active properties: a phase-transfer-catalyst can transfer polar substance into an apolar solvent whereas a surface active substance can transfer apolar substance into a polar solvent (like water).