Molecular modeling as a complement of experimental safety evaluation of products and processes

INERIS is an expert in the risk assessments of industrial substances, products and processes. As a complement to traditional experimental tools for the characterization of hazardous substances and reactions involved in industry, new computational approaches are developed at the Accidental Risk Division based on Molecular Modeling tools to predict hazardous properties and to clarify the chemical mechanisms involved in hazardous reactions like explosive decompositions or chemical incompatibilities. Quantitative Structure-Property Relationships (QSPR) are developed to predict the hazardous physico-chemical properties of compounds based on their only molecular structures. Such models can be used in regulatory context like REACH since they follow validation principles proposed by OECD. They can also be used as screening tools to guide the choice of substances to be involved in chemical processes or in the first steps of development of new chemical compounds at early R&D steps. Indeed, it can allow to identify compounds presented target functional properties and limited hazards, even before synthesis. QSPR models have been already developed for a diversity of properties (notably, flammability, thermal stability and explosivity) and compounds (e.g. nitro compounds, organic peroxides, amines) and examples will be given in this presentation. To characterize the molecular mechanisms involved in hazardous chemical reactions, the density functional theory (DFT) is used. This quantum chemical approach allows the identification and study of all elementary reactions involved in complex reactive processes like ageing, chemical incompatibility or hazardous decompositions. This has been notably applied for the peroxidation of chemical compounds to characterize the complete decomposition mechanism and to identify the best inhibitors and their modes of actions. It also demonstrated its relevance to clarify the detailed mechanisms involved in chemical incompatibilities of ammonium nitrate notably with chlorinated compounds such as the DCCNA, potentially involved in the dramatic accident of Toulouse in 2001