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Environmental fate & pathways

Phototransformation in air

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Description of key information

The calculated half-life of tetrachlorophthalic anhydride by indirect photodegradation in air was 508 days with an Overall OH rate constant of 3E-14 cm³/molecule-sec. The calculated half-life of the hydrolysis product tetrachlorophthalic acid (CAS 632-58-6) by indirect photodegradation in air was 15 days with an Overall OH rate constant of 1E-12 cm³/molecule-sec.

Key value for chemical safety assessment

Half-life in air:
15 d
Degradation rate constant with OH radicals:
0 cm³ molecule-1 s-1

Additional information

There are no experimental data on the stability of tetrachlorophthalic anhydride and its hydrolysis product tetrachlorophthalic acid (CAS 632-58-6) in the atmosphere available. In the atmosphere a half-life of 508 d for tetrachlorophthalic anhydride is estimated due to reaction with photochemically produced hydroxyl radicals, considering an OH-concentration of 500000 radicals/cm³ as a 24-h average. For the main hydrolysis product, terachlorophthalic acid (CAS 632-58-6), a half-life of 15 d is estimated. The predicted values can be considered reliable yielding useful results for further assessment. The atmospheric half-life of tetrachlorophthalic anhydride is only of theoretical interest, as any decomposition of the substance in water is not considered by the program. Therefore, the atmospheric half-life of 15 days of the hydrolysis product tetrachlorophthalic acid (CAS 632-58-6) is taken into account for further assessment.