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Environmental fate & pathways

Hydrolysis

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Description of key information

Substance is not hydrolytically stable at pH 7, 9, and 11 at environmental or use-conditions

Key value for chemical safety assessment

Half-life for hydrolysis:
2 d
at the temperature of:
25 °C

Additional information

The structural analogue, Reactive Black 5, was tested for abiotic degradation according to OECD 111. In addition to pH 4, 7, 9 as required by the guideline, the substance was also tested at pH 11 (dyeing conditions) and pH 1.2.

At pH 1.2 and 37°C, there was no abiotic degradation within the 5 days observation period. At pH 4, 7, 9, and 11, the test substance was not stable at 50°C. The degradation at pH 4, 7, and 9 were hence investigated further.

At pH 4, the half-life at 25°C is ca. 5 years; at pH 7, the half-life at 25°C is ca. 2 days; at pH 9, the half-life at 20°C is ca. 50 minutes.

During degradation of the bis-ester, both isoforms of the mono-vinyl form appear temporarily as degradation product. One main degradation product is Reactive Black 5 bis-vinyl as the active dye-form which further hydrolyses to Reactive Black 5-OH.