Registration Dossier
Registration Dossier
Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.
The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.
Use of this information is subject to copyright laws and may require the permission of the owner of the information, as described in the ECHA Legal Notice.
EC number: 231-668-3 | CAS number: 7681-52-9
Phototransformation in air
Administrative data
Link to relevant study record(s)
Description of key information
Hypochlorous acid degrades in the atmosphere with a DT50 of 114.6 days (24-hr day), corresponding to 2750 hours. As hypochlorous acid contains no olefinic carbon-carbon double and acetylic triple bonds, it is not supposed to react with ozone.
Key value for chemical safety assessment
- Half-life in air:
- 115 d
Additional information
The photochemical and oxidative decomposition of hypochlorous acid in air was calculated according to Atkinson.
Reaction rate constant kOH= 0.14× 10-12cm3molecule-1sec-1
The DT50for hypochlorous acid was estimated to be 114.6 days (24-hr day), corresponding to 2750 hours, using the reaction rate constant kOH.
As hypochlorous acid contains no olefinic carbon-carbon double and acetylenic triple bonds, it is not supposed to react with ozone.
Atmospheric degradation
At environmental pH values (6.5-8.5) half of the hypochlorite is in the undissociated form of hypochlorous acid and half is dissociated to the hypochlorite anion. Only the hypochlorous acid fraction is volatile, but the amount of hypochlorous acid that could volatilise from water into air is expected to be very low. The calculated half life (Atkinson calculation) for hypochlorous acid in the atmosphere is 2750 hours, but there are indications that the half life is shorter (only a few hours).
Photolysis of hypochlorous acid generates atomic chlorine and hydroxyl radicals OH°:
HOCl + hv => HO° + Cl°
Thus, hypochlorous acid could participate in the atmospheric chlorine reaction routes.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
