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Physical & Chemical properties

Dissociation constant

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Endpoint:
dissociation constant
Data waiving:
other justification
Justification for data waiving:
other:
Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This value is derived using an accepted calculation method
Principles of method if other than guideline:
Structure-based QSAR property prediction by means of linear free energy relationships and molecular orbital properties.
GLP compliance:
no
Remarks:
QSAR
Dissociating properties:
yes
pKa:
4.59 - 4.8

The value of pKa indicates that in the range of pH usually considered relevant to the human body and environment, i.e. pH 2-9, the fatty and resin acids constituents of the substance will ionised. However, the neutrals constituents will tend not to ionised at the relevant environmental pH. The table below gives pKa values for the acids.

Distilled Tall Oil acid constituents

pKa

LOW BOILING FATTY ACIDS (<C16)

4.75

C16:1 FATTY ACID

4.74

PALMITIC ACID - (C16 SATURATED)

4.75

C17:0 and C17:0 BRANCHED ACIDS

4.75

OLEIC ACID - (cis - C18:1) and isomers

4.74

ELADIC ACID - (trans - C18:1)

4.74

LINOLEIC ACID (c9,c12)  

4.74

CONJ. LINOLEIC ACIDS (18:2)

4.73

PINOLENIC ACID - (C18:3, cis-5,9,12)

4.73

LINOLENIC ACID - (C18:3, c9,c12,c15)

4.74

STEARIC ACID - (C18:0)

4.75

C19:0 ACID

4.75

EICOSANONIC ACID-(C20 SATURATED)

4.75

EICOSENOIC ACID - (C20:1)

4.74

EICOSADIENOIC ACID - (C20:2)

4.74

EICOSATRIENOIC ACID - (C20:3 FA)

4.73

Unknown fatty acids

4.75

ISOPIMARIC ACID

4.80

8,15 ISOPIMARIC ACID/C22 FATTY ACID

4.64

ABIETIC ACID and isomers

4.77

SANDARACOPIMARIC ACID

4.64

DEHYDROABIETIC ACID

4.67

Decarboxylated Rosin acids, MW of 256/258

4.77

NEOABIETIC ACID

4.59

PALUSTRIC ACID/C24 FATTY ACID

4.75

PIMARIC and/or 8,15-PIMARIC ACID

4.64

Conclusions:
Dissociation constant values for the acid constituents of Distilled Tall Oil was obtained using an accepted calculation method. The result is considered to be reliable.

Description of key information

The pKa of the acids ionisable constituents of Distilled Tall Oil is predicted using a reliable freely-available method. 

Key value for chemical safety assessment

Additional information

No measured data for dissociation constant of Distilled Tall Oil were available. The pKa value (normal conditions) was predicted using SPARC.

While the acids constituents (Fatty and Resin acids) group is ionisable, neutrals constituents such as alcohols are extremely weak acids and only dissociate under strongly basic conditions. In the range of pH usually considered relevant to the human body and environment, i.e. pH 2-9, acid constituents will ionise while the neutrals will be non-ionised. There is no need to conduct further testing.