Zinc bis(dinonylnaphthalenesulphonate)

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

(Q)SAR

Adequacy of study:

key study

Study period:

7 January 2022

Reliability:

2 (reliable with restrictions)

Justification for type of information:

In SPARC, molecular structures are broken into functional units called the reaction center and the perturber in order to estimate pKa in water. The reaction center, C, is the smallest subunit that has the potential to ionize and lose a proton to a solvent. The perturber, P, is the molecular structure appended to the reaction center, C. The pKa of the reaction center is adjusted for the molecule in question using the mechanistic perturbation models. The pKa for a molecule of interest is expressed in terms of the contributions of both P and C.

pKa = (pKa)c + δp(pKa)c

where (pKa)c describes the ionization behavior of the reaction center, and δp(pKa)c is the change in ionization behavior brought about by the perturber structure.

The SPARC pKa calculator was trained on 2500 organic molecules, then validated on 4338 pKa’s (4550 including carbon acid) in water. The calculator was tested for multiple ionization’s up to the 6th (simple organic molecules) and 8th (azo dyes) for molecules with multiple ionization sites. In addition, the pKa models were tested on all the literature values we found for zwitterionic constants (12 data points), the thermodynamic microscopic ionization constants, pki, of molecules with multiple ionization sites (120 measurement data points, the RMS deviation error is 0.5), the corresponding complex speciation as a function of pH and the isoelectric points (29 measurement data points) in water. The diversity and complexity of the molecules used was varied over a wide range in order to develop more robust models during the last few years. Hence, the SPARC pKa models are now very robust and highly tested against almost all the available experimental literature data.

Qualifier:

no guideline available

Principles of method if other than guideline:

In SPARC, molecular structures are broken into functional units called the reaction center and the perturber in order to estimate pKa in water. The reaction center, C, is the smallest subunit that has the potential to ionize and lose a proton to a solvent. The perturber, P, is the molecular structure appended to the reaction center, C. The pKa of the reaction center is adjusted for the molecule in question using the mechanistic perturbation models. The pKa for a molecule of interest is expressed in terms of the contributions of both P and C.

pKa = (pKa)c + δp(pKa)c

where (pKa)c describes the ionization behavior of the reaction center, and δp(pKa)c is the change in ionization behavior brought about by the perturber structure.

The SPARC pKa calculator was trained on 2500 organic molecules, then validated on 4338 pKa’s (4550 including carbon acid) in water. The calculator was tested for multiple ionization’s up to the 6th (simple organic molecules) and 8th (azo dyes) for molecules with multiple ionization sites. In addition, the pKa models were tested on all the literature values we found for zwitterionic constants (12 data points), the thermodynamic microscopic ionization constants, pki, of molecules with multiple ionization sites (120 measurement data points, the RMS deviation error is 0.5), the corresponding complex speciation as a function of pH and the isoelectric points (29 measurement data points) in water. The diversity and complexity of the molecules used was varied over a wide range in order to develop more robust models during the last few years. Hence, the SPARC pKa models are now very robust and highly tested against almost all the available experimental literature data.

GLP compliance:

no

Specific details on test material used for the study:

Zinc bis(dinonylnaphthalenesulphonate) does not have any dissociable proton; therefore a pKa value is not applicable. The corresponding acid, dinonylnaphthalenesulphonic acid, has a pKa of 0.56 as determined by the SPARC QSAR model. The following SMILES notation was used: CC(C)C(Cc1cc2c(cc1)cc(cc2S(=O)(=O)O)C(CC)C(CC)C(C)C)C(C)CC

Dissociating properties:

yes

No.:

#1

pKa:

0.56

Temp.:

20 °C

The pKa of dinonylnaphthalenesulphonic acid was determined to be 0.56.

Conclusions:

The pKa of dinonylnaphthalenesulphonic acid was determined to be 0.56.

Executive summary:

Zinc bis(dinonylnaphthalenesulphonate) does not have any dissociable proton; therefore a pKa value is not applicable. The corresponding acid, dinonylnaphthalenesulphonic acid, has a pKa of 0.56 as determined by the SPARC QSAR model. This QSAR model, developed by the US EPA (SPARC September 2009 release w4.5.1522-s4.5.1522), has been validated and has a high degree of accuracy.

Description of key information

Zinc bis(dinonylnaphthalenesulphonate) does not have any dissociable proton; therefore a pKa value is not applicable. The corresponding acid, dinonylnaphthalenesulphonic acid, has a pKa of 0.56 as determined by the SPARC QSAR model. This QSAR model, developed by the US EPA (SPARC September 2009 release w4.5.1522-s4.5.1522), has been validated and has a high degree of accuracy.

Key value for chemical safety assessment

pKa at 20°C:

0.56