Reaction mass of sodium 1-methoxy-1-oxohexadecane-2-sulphonate and sodium methyl 2-sulphooctadecanoate

Dissociation constant

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June 12 - September 21, 2000

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Although the method was not described in detail, the guideline was clearly stated: the test was carried out according to OECD guidelines. Kurume Laboratory is furthermore a well-known and trustworthy, respected laboratory. The signature and name of the author was not present, but this is because the report was an English translation of a Japanese study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Deviations:

not specified

Principles of method if other than guideline:

Conductometric method

GLP compliance:

no

Dissociating properties:

yes

Remarks on result:

not determinable because of methodological limitations

The test material was judged to be a dissociative substance (strong electrolyte) in that its dissociation constant was found to be concentration-dependent and there was a linear relationship between the square root of the concentration and molar conductivity under the above testing conditions. It is thus concluded that the dissociation constant is not measurable.

Conclusions:

The test material was a dissociative substance (strong electrolyte).

Reference 2

Endpoint:

dissociation constant

Type of information:

(Q)SAR

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model, but not (completely) falling into its applicability domain, and documentation / justification is limited

Remarks:

The QSARS were run to have an indication of the behaviour of the substance in the environment. It was not the intention to calculate the precise dissociation constants. The QSARs could not be run on the substance itself. It was run based on the neutralized form.

Qualifier:

no guideline required

GLP compliance:

no

Dissociating properties:

yes

pKa:

-1.03

Remarks on result:

other: estimation by Pallas

pKa:

0.3

Remarks on result:

other: estimation by Sparks

Conclusions:

Although the pKa predictions of C16MES and C18MES are just estimations, they give an indication that the substance will be present in environmental relevant pH ranges (pH 2-10) in the ionized form.

Description of key information

The substance was judged to be a strong electrolyte.

The QSARS were run to have an indication of the behaviour of the substance in the environment. It was not the intention to calculate the precise dissociation constants. The QSARs could not be run on the substance itself. It was run based on the neutralized forms of both components separately.

Additional information

It proved not possible to determine the dissociation constants of the test substance experimentally. As an alternative, the pK_avalues were calculated using the pKalc version 5.0 computer program. Based on the calculation method, it was concluded that both components of the test substance behave similarly with regard to dissociation. Although the pKa predictions of C16MES and C18MES are just estimations, they give an indication that the substance will be present in environmental relevant pH ranges (pH 2-10) in the ionized form.