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Physical & Chemical properties

Dissociation constant

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Description of key information

In the environmentally relevant pH range (ca 4-9) , the substance will occur mainly as the non-ionised form (primary amine NH2), except at very low pH where the NH3+ form may be present (>50% molar if pH < pKa; it is generally assumed that a single species is present at pKa +/- 2 units).

Key value for chemical safety assessment

pKa at 20°C:
4.1

Additional information

Two fully reliable studies, performed according to OECD guideline and under GLP, are available. Results were consistent, with a pKa of 4.0 for the titration study at 20°C, and a pKa of 4.3 for the spectrophotometric study at 25°C. Both are considered of equal value, so the average (4.15) is retained as key data for purpose of CSA. Considering an accuracy of 0.1 unit, and that the reference temperature is 20°C, the result will rounded down to the nearest decimal, i.e. 4.1.