N-[2,5-dichloro-4-(1,1,2,3,3,3-hexafluoropropoxy)-phenyl-aminocarbonyl]-2,6-difluorobenzamide

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

07 Jun 2002 to 22 Jul 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Version / remarks:

12 May 1981

GLP compliance:

yes

Dissociating properties:

yes

No.:

#1

pKa:

10.2

Temp.:

20 °C

From the eight performed titrations the titration with 40 % cosolvent and higher could be evaluated. The absorbance is strongly decreased at lower pH values for titration No. 3 with 30 % co-solvent, this can be attributed to the precipitation of the substance due to the increased level of aqueous titrant. No evaluation is possible with 30 % co-solvent or less.

 

Table 2. Results of five main experiments which could be evaluated

Titration No.	Constent of cosolvent (%)	pKa
4	40	10.26
5	50	10.16
6	60	10.20
7	55	10.14
8	45	10.14
Average ± SD		10.18 ± 0.05

 

Conclusions:

The dissociation constant (pKa) was determined to be 10.2 at at 20 °C (acidic).

Executive summary:

 The dissociation constant of the test substance was determined using spectrophotometric titration according to OECD TG 112 following GLP principles. Due to the relatively low solubility of the test substance in water a determination of the dissociation constant is not possible without the addition of an organic co-solvent. Methanol was used as co-solvent and tested over a range of 10 to 60 %. The dissociation constant (pKa) was determined to be 10.18 ± 00.5 at at 20 °C (acidic).

Description of key information

Dissociation constant: pKa of 10.18 at 20 °C, OECD TG 112, spectrophotometric filtration, Martin 2002

Key value for chemical safety assessment

pKa at 20°C:

10.2