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Environmental fate & pathways

Hydrolysis

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Description of key information

Calculation with HYDROWIN v2.00 (EPIWIN software by US-EPA): hydrolytically stable compound.  

Key value for chemical safety assessment

Additional information

The hydrolysis potential of the test substance was determined by the computer program HYDROWIN v2.00 (EPIWIN software) by US-EPA (Chemservice S.A., 2012). The program estimates the hydrolysis rate constants for specific organic classes and, furthermore, a chemical´s half-live under typical environmental conditions is also determined. Only esters, carbamates, epoxides, halomethanes (containing 1-3 halogens), specific alkyl halides and phosphorous esters can be estimated, since these are specific organic classes, which are able to undergo hydrolysis. When present, various hydrolysable compound-types will be identified. The prediction for the substanceindicated that ISOCYANATES (-N=C=O) were detected as hydrolysable substance class. Even at low pHs, the hydrolysis half-life will be less than 10 minutes at 25 °C. Isocyanates hydrolyse readily in water to yield carbamic acid, which will decarboxylates to yield CO2 and an amine. The amine reacts further with other isocyanates to produce disubstituted urea. Electron-withdrawing substituents influence the hydrolysis rate, as well as sterical hindrances. According to Ullmann´s Encyclopedia the aliphatic isocyanate rates are as followed: primary > secondary > tertiary. Methyl isocyanate possesses a hydrolysis rate of 9 minutes, phenyl isocyanate of 55 seconds (in water/dioxane solution) at 25 °C (HSDB, 2007).

However, only a minor part of the structure consists of isocyanates. The main structural components are not suspectable for abiotic degradation and therefore, the basic phenolic structure of the compound is considered as hydrolytical stable.