Chlorothalonil

Explosiveness

Link to relevant study record(s)

Reference

Endpoint:

explosive properties of explosives

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because there are no chemical groups present in the molecule which are associated with explosive properties

other:

Description of key information

The study does not need to be conducted because there are no chemical groups present in the molecule which are associated with explosive properties.

Furthermore, according to EEC Method A.14, "Explosive Properties", Part 1.1" tests need not be performed when available thermodynamic information (e.g. heat of formation, heat of decomposition) and/or absence of certain reactive groups in the structural formula establishes beyond reasonable doubt that the substance is incapable of rapid decomposition with evolution of gases or release of heat (i.e., the material does not present a risk of explosion)." Technical test substance, which comprises 98.9 % test substance, is combustible. The measured heat of combustion of test substance in the solid state is -3436.7 kJ/mole or -820.8 kcal/g mole. This can be compared with an estimated -843 kcal/g mole when the products of combustion comprise dilute hydrochloric acid and dilute nitric acids. The molar heat of combustion is about 50 % larger than that of hexachlorobenzene, which is -568 kcal/g mole. A1though combustible, hexachlorobenzene is considered to be non-hazardous with regard to flammability. The test substance should also not be a flammability hazard. Its aromatic nucleus is fully substituted with electron withdrawing groups, a situation which is known to make combustion difficult.  In this dossier it was reported that an unbroken train of technical test substance did not ignite and propagate combustion upon removing the burner flame (see Flammability). This is in agreement with earlier reported work where it was confirmed experimentally that the combustion of technical test substance cannot be sustained outside a high temperature environment. For a reasonable degree of combustion, technical test substance must be placed in a boat inside a quartz tube and the latter heated to 700 °C in a furnace and exposed to a flow of air. The elevated temperature is needed to vaporise test substance / favour the kinetics of its combustion/ and minimise heat losses. It is found that a pool of molten technical test substance can be ignited by an impinging Bunsen burner flame. However, the combustion front is extinguished when the flame is removed. Technical test substance is typically 98.8 % test substance and typically contains 0.55 % M26, 0.30% M27 and 0.35 % M28, M29 and M30 together M30 comprise about half of the mixture of underchlorinated homologs. M26 should have a heat of vaporisation which is within 2 kcal/mole of that of test substance. Its combustion characteristics will, therefore, not differ. The heat of formation and volatility of M27 are intermediate between hexachlorobenzene and test substance. Its combustion will be more difficult than that of test substance. The underchlorinated homologs present will be more combustible to the extent that they contain fewer chlorine atoms and more hydrogen. All impurities listed in the application are planar molecules whose morphology is compatible with test substance. All impurities will be molecularly dispersed in a solid solution and Raoult's law of partial pressures will prevail. At their low concentrations, heat and mass transfer effects will prevent the impurities from exhibiting their combustion tendencies independently. Thus, the combustion characteristics of technical test substance will be sensibly equivalent to those of pure test substance. The above rationale and experimental data show that technical test substance cannot be made to explode in air. Neither test substance nor its impurities have substituents or highly strained bonds which would cause shock sensitivity. The explosion and shock sensitivity tests of EEC Method A.14 will disclose no new information about technical test substance.

Key value for chemical safety assessment

Explosiveness:

non explosive

Justification for classification or non-classification

Based on the available information, classification on explosiveness is not warranted in accordance with EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation No. (EC) 1272/2008.