Thermal Analysis of Arenediazonium Tetrafluoroborate Salts: Stability and Hazardous Evaluation

Arenediazonium salts represent an important class of aromatic organic compounds widely used as building blocks in academia and industry. Due to the high energy associated with the diazonium group, many of these salts are reported as thermally unstable and/or unsafe to work with. However, most of the tetrafluoroborate arenediazonium salts, are fairly stable to handle at room temperature both in solution and when dry. Nevertheless, some of these salts, especially those containing heteroatoms in the aromatic moiety, present difficulties in their synthesis, and some are indeed highly unstable. To bring some light to this controversial subject, the thermal stability and potential hazards of the 57 most common arenediazonium tetrafluoroborate salts used in our laboratory over the last two decades were evaluated under careful conditions. These results are expected to guide important decisions on the use of arenediazonium tetrafluoroborates in organic synthesis.