m-phenylenebis(methylamine)

Dissociation constant

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2011-11-04

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection 2011-07-19 to 2011-07-21; Date of signature 2011-08-31

Dissociating properties:

yes

No.:

#1

pKa:

9.52

Temp.:

20 °C

No.:

#2

pKa:

8.3

Temp.:

20 °C

- Solution pH for the three titrations is shown in the tables below.

- Data is presented graphically in Figures 4.1, 4.2 and 4.3 (attached).

- Data required for calculation of the two amine functional group dissociation constants is shown in Tables 4.5, 4.6 and 4.7 (attached).

DETERMINATION 1

 

Volume of 0.1 N HCl	pH
0.0	10.09
0.5	9.99
1.0	9.86
1.5	9.74
2.0	9.63
2.5	9.51
3.0	9.38
3.5	9.26
4.0	9.13
4.5	9.01
5.0	8.87
5.5	8.74
6.0	8.58
6.5	8.42
7.0	8.23
7.5	8.01
8.0	7.74
8.5	7.47
9.0	7.10
9.5	5.68
10.0	3.23

 

DETERMINATION 2

 

Volume of 0.1 N HCl	pH
0.0	10.39
0.5	10.19
1.0	10.00
1.5	9.84
2.0	9.70
2.5	9.58
3.0	9.48
3.5	9.36
4.0	9.21
4.5	9.11
5.0	8.98
5.5	8.85
6.0	8.72
6.5	8.57
7.0	8.42
7.5	8.24
8.0	8.02
8.5	7.75
9.0	7.43
9.5	6.41
10.0	3.74

 

DETERMINATION 3

 

Volume of 0.1 N HCl	pH
0.0	10.33
0.5	10.13
1.0	9.98
1.5	9.85
2.0	9.72
2.5	9.60
3.0	9.48
3.5	9.36
4.0	9.26
4.5	9.15
5.0	9.03
5.5	8.92
6.0	8.79
6.5	8.67
7.0	8.53
7.5	8.37
8.0	8.19
8.5	7.98
9.0	7.75
9.5	7.49
10.0	7.08

- The mean dissociation constants determined for the two amine functional groups during the truplicate determination at 20 ºC are shown in the following table:

Determination	Dissociation Constant
	First	Second
1	9.50	8.19
2	9.55	8.35
3	9.50	8.35
Mean	9.52	8.30

- As expected for a polyelectrolyte with closely grouped pKa values, the neutralisation curves do not show clear points of inflection for the dissociation constant for each of the individual amine functional groups.

- End points were masked as the titration of the following group began before that of the previous group was completed.

- Because individual dissociation constants were separated by less than 2.7 units, standard calculation techniques could not be applied and the Noyes method was employed.

- All three determinations resulted in solutions reaching approximately neutral pH on the final addition of acid. This fully supports the presence of two amine functional groups since neutrality was achieved by adding two molar equivalents of acid solution.

Conclusions:

The dissociation constants of the two amine functional groups at 20 ºC were determined by potentiometric titration to be 9.52 and 8.30.

Reference 2

Endpoint:

dissociation constant

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Secondary literature cited in SIDS dossier, experimental data not retained by Japanese Ministry of Economy Trade and Industry

Qualifier:

according to guideline

Guideline:

OECD Guideline 112 (Dissociation Constants in Water)

Deviations:

not specified

GLP compliance:

not specified

Dissociating properties:

yes

No.:

#1

pKa:

9.19

Temp.:

25 °C

Measured results 9.22, 9.18 and 9.16

Conclusions:

The substance contains two groups which can dissociate. Only one pKa value was measured. This may possibly be due to the two pKa values being so close that only one measurement was recorded.

Description of key information

Dissociation constants of the two amine functional groups at 20 ºC were determined by potentiometric titration to be 9.52 and 8.30 (OECD 112)