diethyl 1-(2,4-dichlorophenyl)-5-methyl-4,5-dihydro-1H-pyrazole-3,5-dicarboxylate

Dissociation constant

Link to relevant study record(s)

Reference

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22.05.2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7370 (Dissociation constants in water)

GLP compliance:

yes (incl. QA statement)

Remarks:

Hess. Ministerium für Umwelt, Energie, Landwirtschaft und Verbraucherschutz, Mainzer Straße 80, D65189, Wiesbaden

Dissociating properties:

no

Experimental Details

UV/VIS absorbance data were obtained from solutions of constant concentration under three different pH conditions.

A spectrophotometric background correction was done before each experiment using water / acetonitrile 90:10 as the blank solvent. For each of the UV/VIS spectra the test solution was filled into the cuvette with an optical path length of 1 cm. Subsequently the UV/VIS spectrum was recorded.

The UV/VIS spectra were recorded at pH 1.06, pH 5.76 and pH 10.01. The respective data for the extinction indicate no differences in the UV spectra of AE F107892, pure substance at these different pH values. The experiments were carried out at room temperature (21.6 °C to 22.9 °C).

Details of experiment A

Experiment	Volume and concentration of added HCl	Volume and concentration of added NaOH	Resulting pH value
A1	-	-	5.76
A2	10 mL - 1 mol/L	-	1.06
A3	-	1 mL – 0.01 mol/L	10.01

This means that no dissociation equilibrium occurred for AE F107892, pure substance, in the pH range 1 < pH < 10.

This result is equivalent to the conclusion that AE F107892, pure substance, showed no pKa value in the range 1 < pKa < 10.

Due to the lack of stability above pH 9, the UV/VIS spectra of the test item were recorded at pH pH 1.06, pH 5.76 and pH 10.01 at room temperature (approx. 22 °C). The test shows that the test item is sufficiently stable even at pH 10 for the duration of measurement.

The UV/VIS spectra showed neither significant differences in their course nor an isosbestic point. They were almost congruent, taking the UV absorption of the hydrochloric acid into account. No relevant difference was found between the UV/VIS absorption at the examined pH values.

No dissociation constant pKa was found in aqueous solution of Mefenpyr-diethyl (AE F107892), pure substance, in the pH-range of 1 < pH < 10.

Description of key information

The test substance (pure) shows no acidic or basic properties in the range of approximately 1 < pKa < 10 ( OECD Guideline 112).