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Physical & Chemical properties

Dissociation constant

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Endpoint:
dissociation constant
Type of information:
(Q)SAR
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification
Principles of method if other than guideline:
The pKa of the amine group was obtained using the SPARC on-line property calculator.
GLP compliance:
no
Dissociating properties:
yes
No.:
#1
pKa:
7.15
No.:
#2
pKa:
10.09

Results estimated by calculation, no data avaliable for temperature.

Conclusions:
First and second pKa values of 7.15 and 10.09 were determined for the amine groups of the substance using an appropriate predictive method.
Endpoint:
dissociation constant
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Titration method (no further details available)
GLP compliance:
not specified
Dissociating properties:
yes
No.:
#1
pKa:
11.9
Remarks on result:
other: no data on temperature or pH was provided
Conclusions:
A dissociation constant of 11.9 is reported in secondary literature for a silanediol, which is a structural analogue to the hydrolysis product of the submission substance. The original reference was not available for review and no further information is available. The reliability of this result is not assignable.
Endpoint:
dissociation constant
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to additional information field in the endpoint study summary (Dissociation constant).
Reason / purpose:
read-across source
Dissociating properties:
yes
No.:
#1
pKa:
11.9
Remarks on result:
other: Temperature and pH not provided.
Conclusions:
A dissociation constant of 11.9 is reported in secondary literature for a silanediol, which is a structural analogue to the hydrolysis product of the submission substance. The original reference was not available for review and no further information is available. The reliability of this result is not assignable.

Description of key information

N-[3-(dimethoxymethylsilyl)-2-methylpropyl]ethylenediamine (amine groups): First and second pKa's: 7.15 and 10.09
Silanol hydrolysis product (hydroxyl groups): pKa approximately 12, based on read-across from dimethylsilanediol

Key value for chemical safety assessment

pKa at 20°C:
7.15

Additional information

The requirement to test the substance for dissociation constant is waived on the basis that the parent substance hydrolyses rapidly.

For the amine groups of the substance the first and second pKa values 7.15 and 10.09 were obtained using an appropriate calculation method.

There are no reliable measured data for the dissociation constant of hydroxyl protons of the hydrolysis product, N-[3-(dihydroxymethylsilyl)-2-methylpropyl]ethylenediamine. The typical dissociation constants for the hydroxyl protons of silanediols are available from other silanediols. It is appropriate to read-across dissociation constant data for N-[3-(dihydroxymethylsilyl)-2-methylpropyl]ethylenediamine from dimethylsilanediol. This suggests that silanols are not expected to undergo significant dissociation within the range of pH relevant in the environment or in vivo. Dimethylsilanediol has a measured first dissociation constant approximately 12 reported in secondary literature. Additional information is given in a supporting report (PFA, 2013b) attached in Section 13 of the REACH technical dossier.