Registration Dossier
Registration Dossier
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EC number: 237-430-5 | CAS number: 13780-39-7
Endpoint summary
Administrative data
Description of key information
Additional information
The conduct of a study on hydrolysis of target compound titanium oxychloride is being waived due to technical difficulty of measurement of the expected very short half-life time of titanium oyxchloride in water when reacting to TiO2 and HCl. The short half life of parent compound titanium tetrachloride in aqueous environment of below 0.1 min is based on an expert statement by Fisk (2010). Data taken from three peer reviewed handbooks (weight of evidence) support the view that titanium oxychloride as intermediate of the hydrolysis of parent compound titanium terachloride is very unstable and therefore cannot be isolated in aqueous environment.
Titanium oxychloride is an unstable chemical compound which results from the hydrolysis of titanium tetrachloride.
1. step: TiCl4 + H2O↔TiOCl2 + 2 HCl
2. step: TiOCl2 + H2O↔TiO2 + 2 HCl
Summary reaction: TiCl4 + 2 H2O↔TiO2 + 4 HCl
In water this reaction takes place immediately. The environmental fate of titanium dioxide is likely to be comparable to the naturally occurring mineral rutile, which is inert in the environment like the hydrogen chloride and its dissociation products.
Addition of HCl to the reaction medium, or lack of H2O, leads to a partial hydrolysis only, which results in the formation of titanium oxide chlorides. The Raman spectrum of a yellowish TiCl4 solution in aqueous hydrochloric acid show the occurrence of [TiO2Cl4]4- and [TiOCl5]3- species, as TiOCl2 in aqueous hydrochloric acid reveal the same spectrum.
Unlike parent substance titanium tetrachloride, the atmospheric fate of target substance titanium oxychloride is of no relevance. While titanium tetrachloride is smoking heavily when exposed to the air, there is no relevant evaporation from an aqueous solution containing titanium oxychloride. The molecule only is stabilised in aqueous medium in its hydrated form in equilibrium with hydrochloric acid, thus no atmospheric emissions occur. To a certain extent the evaporation of hydrochloric acid still might be observed.
Studies on direct phototransformation in water are not available but it is assumed the substance and its transformation products are not degraded by direct photolysis due to its spectral properties.
In conclusion both target compound titanium oxychloride as well as parent compound titanium tetrachloride are subject to rapid hydrolysis in contact with water or humidity in air or soil, which leads to transformation into environmentally occurring inorganic inert compounds. The environmental hazard assessment needs to be based on these transformation products.
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