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Dissociation constant

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Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
GLP compliance:
yes
Specific details on test material used for the study:
The test was performed with 4-chloro-m-cresolate, the conjugate acid of sodium p-chloro-m-cresolate.
99.97 % 4-chloro-3-methylphenol
Dissociating properties:
yes
No.:
#1
pKa:
9.4
Temp.:
20 °C
Remarks on result:
other: +/- 0.1

 Addition of

NaOH (0.1 mol/L)

[mL]

 pH

 [HX]

mmol/L

 [X-]

mmol/L

 lg([HX]/[X-]

 pKa

(result Equ. 2)

 0  5.9  26.144  0    
 5.23  8.33  23.530  2.614  0.95  9.28
 10.46  8.74  20.915  5.229  0.60  9.34
 15.69  9.01  18.301  7.843  0.37  9.38
 20.92  9.22  15.686  10.458  0.18  9.40
 26.15  9.42  13.072  13.072  0  9.42
 31.37  9.62  10.458  15.686  -0.18  9.44
 36.60  9.83  7.843  18.301  -0.37  9.46
 41.83  10.09  5.229  20.915  -0.60  9.49
 47.07  10.46  2.614  23.530  -0.95  9.51
 52.29  11.00  0  26.144    

mean value of the pKa = 9.4

standard deviation s=0.07

Conclusions:
A pKa value of 9.4 at 20 °C was determined for 4-chloro-3-methylphenol (conjugate acid of sodium p-chloro-m-cresolate) during tests according to OECD Guideline 112.
Executive summary:

A pKa value of 9.4 at 20 °C was determined for 4-chloro-3-methylphenol (conjugate acid of sodium p-chloro-m-cresolate) during tests according to OECD Guideline 112.

Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 112 (Dissociation Constants in Water)
GLP compliance:
yes
Remarks:
Ministerium für Umwelt, Raumordnung und landwirtschaft des Landes Nordrhein-Westfalen, Düsseldorf, Germany
Specific details on test material used for the study:
The test was performed with 4-chloro-m-cresolate, the conjugate acid of sodium p-chloro-m-cresolate.
Purity of the test substance: 99.9 % 4-chloro-3-methylphenol
Dissociating properties:
yes
No.:
#1
pKa:
10.3
Remarks on result:
other: no information on temperature given
Conclusions:
A pKa value of 10.3 at ambient temperature was determined for 4-chloro-3-methylphenol (conjugate acid of sodium p-chloro-m-cresolate) during tests according to OECD Guideline 112.
Executive summary:

A pKa value of 10.3 at ambient temperature was determined for 4-chloro-3-methylphenol (conjugate acid of sodium p-chloro-m-cresolate) during tests according to OECD Guideline 112.

Description of key information

pKa (4-chloro-3-methylphenol) = 9.4 at 20 °C

(OECD 112)

Key value for chemical safety assessment

pKa at 20°C:
9.4

Additional information

A pKa value of 9.4 at 20°C was determined for 4-chloro-3-methylphenol (conjugate acid of sodium p-chloro-m-cresolate) during tests according to OECD Guideline 112. A pKa value of 10.3 was determined in a supporting study during tests according to OECD Guideline 112.