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Environmental fate & pathways

Hydrolysis

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Description of key information

In a non guideline study the half-times for the first hydrolysis step of cyanuric chloride were determined to be 
- DT50(pH 2.0, T=298.15 K = 1.2 min
- DT50 (pH 4.0, T=313.15 K)= 1.65 min
- DT50(pH 7.0, T= 298.15 K) = 3.47 min.
Measurements revealed a fast and stepwise hydrolysis of cyanuric chloride. The intermediate and final degradation products of cyanuric chloride were identified as 2,4-dichlor-6-hydroxy-1,3,5-triazine (first intermediate, DT50(pH 7.0, T=298.15 K = 0.52 h = 31.5 min), 2-chlor-4,6-dihydroxy-1,3,5-triazine (also named 6-chloro-1,3,5-triazine-2,4(1H,3H)-dione, sodium salt) (second intermediate, CAS no.: 32998-00-8, DT50 (pH 7.0, T=298.15 K)= 3.98 h =239.0 min ) and cyanuric acid (final degradation product, CAS no: 108 -80-5), respectively.
The rates of hydrolysis rise significantly for all three steps at acidic medium and are slower at basic pH (for T = constant).
The activation energy is idependent from pH and equal for the three hydrolysis steps.

Key value for chemical safety assessment

Half-life for hydrolysis:
3.47 min
at the temperature of:
298.15 K

Additional information

Key study:

Measurements revealed a fast and stepwise hydrolysis of cyanuric chloride. The intermediate and final degradation products of cyanuric chloride were identified as 2,4-dichlor-6-hydroxy-1,3,5-triazine (first intermediate, DT50(pH 7.0, T=298.15 K = 0.52 h = 31.5 min), 2-chlor-4,6-dihydroxy-1,3,5-triazine (also named 6-chloro-1,3,5-triazine-2,4(1H,3H)-dione, sodium salt) (second intermediate, CAS no.: 32998-00-8, DT50 (pH 7.0, T=298.15 K)= 3.98 h =239.0 min ) and cyanuric acid (final degradation product, CAS no: 108 -80-5), respectively.

In this study the half-times for the first hydrolysis step of cyanuric chloride were determined to be

- DT50(pH 2.0, T=298.15 K = 1.2 min

- DT50 (pH 4.0, T=313.15 K)= 1.65 min

- DT50(pH 7.0, T= 298.15 K) = 3.47 min.

The rates of hydrolysis rise significantly for all three steps at acidic medium and are slower at basic pH (for T = constant).

The activation energy is idependent from pH and equal for the three hydrolysis steps.

The half-life (pH 7, 298.15 K) of the first hydrolysis step (decay of cyanuric chloride to first intermediate) was used as value for the key parameter.

Supporting studies:

- The hydrolysis of cyanuric chloride in acid, neutral and alkaline solution was studied. Due to the stepwise process of the hydrolysis of cyanuric chloride, different (intermediate) degradation products have been identified. Furthermore, the rate constants (DT50) of the hydrolysis step in the temperature range 0-25 °C were determined to be in the range 4-50 minutes.

- In a study the hydrolysis of cyanuric chloride was investigated. Cyanuric chloride completely hydrolyzed (1 g/L at 20 ± 2 °C) within 2 hours.

- In an additional study it could be shown that cyanuric chloride hydrolyses fast. This result is in line with the findings reported in the key study.