Qualitative approach to instability

The purpose of this section is to enable the reader to identify the potential stability properties of a chemical substance by simply analysing its structural formula. This will be made possible by listing the structural properties of unstable molecules. The reader will see the need to identify two types of structural properties those that bear the hallmarks of an unstable property and those whose presence can increase or alternatively reduce the risk of violent decomposition. Since the latter are the only ones in the molecule, they do not represent any danger for it in terms of stability. But when performing qualitative analysis, one also has to take into account the conditions under which the substance is handled. In addition to the structural properties, the analyst will have to carry out a study on the external risk factors. 

The following are relevant to fragile and incompatible parts of a molecule. 

The presence of weak bonds in a molecule will create instability. The decomposition seat will involve this bond, which will tend to break easily under the influence of a physical cause, sometimes of low intensity. The table below lists the weakest bonds. 

Bond Energy of bond (kJ/mol) Bond Energy of bond (kJ/moO 

Common observation and accident reporte often refer to molecules with these bonds, but especially the first eight in the list. Carbon-metal bonds are to be added to this list, in particular the ones involving transition metals. 

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