Tall oil

Dissociation constant

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

dissociation constant

Data waiving:

other justification

Justification for data waiving:

other:

Reference 2

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. 

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.