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Physical & Chemical properties

Dissociation constant

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Administrative data

Endpoint:
dissociation constant
Type of information:
calculation (if not (Q)SAR)
Remarks:
Migrated phrase: estimated by calculation
Adequacy of study:
key study
Study period:
2012 - 2013
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
SPARC v4.6 pKa calculation includes a peer reviewed data base. QSAR method for prediction of physicochemical properties adopted by ECHA Guidance on information requirements and chemical safety assessment Chapter R.7a and validated by U.S. Environmental Protection Agency (see references).

Data source

Referenceopen allclose all

Reference Type:
publication
Title:
Prediction of Chemical Reactivity Parameters and Physical Properties of Organic Compounds from Molecular Structure Using SPARC
Author:
Hilal, S.H., S.W. Karickhoff, and L.A. Carreira
Year:
2003
Bibliographic source:
U.S. Environmental Protection Agency, Athens, GA. Publication No. EPA/600/R-03/030
Reference Type:
publication
Title:
Verification and Validation of the SPARC Model
Author:
Hilal, S.H., S.W. Karickhoff, and L.A. Carreira
Year:
2003
Bibliographic source:
U.S. Environmental Protection Agency, Athens, GA. Publication No. EPA/600/R-03/033

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: QSAR in accordance with ECHA Guidance on information requirements and chemical safety assessment Chapter R.7a
Deviations:
not applicable
GLP compliance:
not specified

Test material

Constituent 1
Reference substance name:
OCCCCCCCCCCCCCCCCCCCC
IUPAC Name:
OCCCCCCCCCCCCCCCCCCCC
Constituent 2
Reference substance name:
O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCC
IUPAC Name:
O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCC
Constituent 3
Reference substance name:
O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCCCC
IUPAC Name:
O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCCCC
Constituent 4
Reference substance name:
O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCC
IUPAC Name:
O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCC
Constituent 5
Reference substance name:
O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCCCC
IUPAC Name:
O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCCCC
Constituent 6
Reference substance name:
O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCC=CCCCCCCCC
IUPAC Name:
O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCC=CCCCCCCCC
Details on test material:
Representative molecules (not dissociated, acid form) for fatty alcohol residues:
1. 1-Eicosanol, CAS Number - CAS 629-96-9, SMILES Code: OCCCCCCCCCCCCCCCCCCCC
Representative molecule (not dissociated, acid form) for alky sulfate components:
2. Eicosanol, 1-(hydrogen sulfate) - CAS 67633-89-0, SMILES Code: O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCC
3. 1-Docosanol, hydrogen sulfate, CAS 30913-03-2, SMILES Code: O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCCCC
Representative molecules (not dissociated, acid form) for alkyl ether sulfate components: Poly(oxy-1,2-ethanediyl), alpha-sulfo-omega-hydroxy-, C16-18 and C18 unsaturated ethers, ammonium salts (selected molecules, not dissociated, acid form):
4. 1-Hexadecanol, ethoxylated, hydrogen sulfate (4 EO), O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCC
5. 1-Octadecanol, ethoxylated, hydrogen sulfate (4 EO), O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCCCC
6. (9Z)-Octadecen-1-ol, ethoxylated, hydrogen sulfate (4 EO), O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCC=CCCCCCCCC

Results and discussion

Dissociating properties:
yes
Dissociation constantopen allclose all
No.:
#1
pKa:
1.07
Temp.:
25 °C
Remarks on result:
other: SMILES: O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCC
No.:
#1
pKa:
1.07
Temp.:
25 °C
Remarks on result:
other: SMILES: O=S(=O)(O)OCCCCCCCCCCCCCCCCCCCCCC
No.:
#1
pKa:
1.06
Temp.:
25 °C
Remarks on result:
other: SMILES: O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCC
No.:
#1
pKa:
1.06
Temp.:
25 °C
Remarks on result:
other: SMILES: O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCCCCCCCCCCC
No.:
#1
pKa:
1.06
Temp.:
25 °C
Remarks on result:
other: SMILES: O=S(=O)(O)OCCOCCOCCOCCOCCCCCCCCC=CCCCCCCCC
No.:
#1
pKa:
15.75
Temp.:
25 °C
Remarks on result:
other: SMILES: OCCCCCCCCCCCCCCCCCCCC

Applicant's summary and conclusion

Conclusions:
UVCB substance consist predominately of alkylsulfates and alkylethersulfates ammonium salts of various carbon chain length and degree of ethoxylation and saturation. Hence a representative set of molecules (not dissociated, acid form) in line with ECHA Guidance on information requirements and chemical safety assessment Chapter R.7a were selected to provide a reasonble input for SPARC QSAR calculations and subsequent regulatory purposes.
The predominant components of this UVCB substance are alkylsulfates, alkylethersulfates as well as low amounts of long chain fatty alcohol residues. Alkylsulfates and alkylethersulfates can be considered as moderately strong acids with pKa values of 1.07 and 1.06.
Consequently no significant acid dissociation between pH 5-9 of alkylsulfates and alkylethersulfates is predicted due to the fact that these substances are already dissociated at lower pH values. For residues long chain fatty alcohols with a calculated pKa of 15.75 no significant acid dissociation between pH 5-9 is predicted.
Executive summary:

Although, acid dissociation is not really a relevant property for this substance (in its ammonium salt, it is actually already dissociated)according to Guidance on information requirements and chemical safety assessment Chapter R.7a: Endpoint specific guidance an estimation of representative individual components’ pKa values is provided.

All alkylsulfates and alkylethersulfates (acid form) can be considered as moderately strong acids.