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Dissociation constant

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

dissociation constant

Type of information:

calculation (if not (Q)SAR)

Adequacy of study:

key study

Study period:

2022

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

accepted calculation method

Justification for type of information:

For more details about the Chemicalize model pKa value calculation methodology, kindly refer to the attachment section of the IUCLID.

Qualifier:

according to guideline

Guideline:

other: ECHA Practical Guide - How to use and report (Q)SARs

Principles of method if other than guideline:

Methodology details about: (a) the prediction of dissociation constant using microconstants were described by Szegezdi et al 2004 (b) the method for calculating the pKa values of small and large molecules were described by Szegezdi et al 2007. For more details, kindly refer to the attachment section of the IUCLID.

GLP compliance:

no

Dissociating properties:

yes

No.:

#1

pKa:

ca. -1.99 - ca. 15.12

Remarks on result:

other: Except for the alcohols remaining constituents can be considered to be 50% dissociated at very low pH values (<2). The alcohols which are present at <20%, are expected to be fully dissociated at environmentally relevant pH (4 to 9).

Remarks:

Therefore, the test substance, which comprises majorly of phosphate esters, is not expected to be dissociated to a significant extent (<1%) at environmentally relevant pH.

Table 1: calculated pKa values for test substance constituents from Chemicalize model

Constituent name	SMILES	pKa value from Chemicalize
hexadecyl dihydrogen phosphate	CCCCCCCCCCCCCCCCOP(O)(O)=O	1.81
octadecyl dihydrogen phosphate	CCCCCCCCCCCCCCCCCCOP(O)(O)=O	1.81
hexadecyl-10 dihydrogen ethoxylated phosphate	CCCCCCCCCCCCCCCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOP(O)(O)=O	1.22
octadecyl-10 dihydrogen ethoxylated phosphate	CCCCCCCCCCCCCCCCCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOP(O)(O)=O	1.22
dihexadecyl hydrogen phosphate	CCCCCCCCCCCCCCCCOP(O)(=O)OCCCCCCCCCCCCCCCC	1.94
bis(octadecyloxy)phosphinic acid	CCCCCCCCCCCCCCCCCCOP(O)(=O)OCCCCCCCCCCCCCCCCCC	1.94
(octadecyloxy)(3,6,9,12,15‐pentaoxahentriacontan‐ 31‐yloxy)phosphinic acid	CCCCCCCCCCCCCCCCCCOP(O)(=O)OCCOCCOCCOCCOCCOCCCCCCCCCCCCCCCC	1.92
di-Ceteareth-10 hydrogen phosphate (diester)	CCCCCCCCCCCCCCCCCCOCCOCCOCCOCCOCCOP(O)(=O)OCCOCCOCCOCCOCCOCCCCCCCCCCC	1.9
hexadecan-1-ol	CCCCCCCCCCCCCCCCO	-1.99
octadecan-1-ol	CCCCCCCCCCCCCCCCCCO	-1.99
C16 ethoxylated alcohol	CCCCCCCCCCCCCCCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOCCO	15.12
C18 ethoxylated alcohol	CCCCCCCCCCCCCCCCCCOCCOCCOCCOCCOCCOCCOCCOCCOCCOCCO	15.12

Conclusions:

The dissociation constant (pKa) value of the test substance was determined by calculating the test substance constituents pKa using the pKa calculator from Chemicalize model of Chemaxon. The pKa values for the test substance constituents were found to be in the range of -1.99 to 15.12

Executive summary:

The dissociation constant (pKa) value of the test substance was determined by calculating the test substance constituents pKa using the pKa calculator from Chemicalize model of Chemaxon. The pKa values for the test substance constituents were calculated to be in the range of -1.99 to 15.12 (Chemaxon, 2022). The alcohols, which are present at <20%, were found to be fully dissociated at all pH values, while the remaining constituents, which are phosphate esters, were found to be 50% dissociated at very low pH values (<2). Therefore, the overall test substance is not expected to be dissociated or significantly ionised (<1%) at environmentally relevant pH.

Reference 2

Endpoint:

dissociation constant

Data waiving:

study technically not feasible

Justification for data waiving:

other:

Reason / purpose for cross-reference:

data waiving: supporting information

Description of key information

The dissociation constant (pKa) value of the test substance was determined by calculating the test substance constituents pKa using the pKa calculator from Chemicalize model of Chemaxon (Chemaxon, 2022).

Additional information

The pKa values for the individual constituents of the test substance were calculated to be in the range of -1.99 to 15.12. The alcohols, which are present at <20%, were found to be fully dissociated at all pH values. The remaining constituents, which are phosphate esters, were found to be 50% dissociated at very low pH values (<2).Therefore, the overall test substance is not expected to be dissociated or significantly ionised (<1%) at environmentally relevant pH.