First Study of the Thermal and Storage Stability of Arenediazonium Triflates Comparing to 4-Nitrobenzenediazonium Tosylate and Tetrafluoroborate by Calorimetric Methods

Herein, for the first time, using isothermal flow calorimetry and differential scanning calorimetry (DSC)/thermal gravimetric analysis (TGA), we have determined the thermal decomposition energies for the number of solid arenediazonium triflates comparing to 4-nitrobenzene tosylate and 4-nitrobenzentetrafluoroborate. The kinetics of thermal decomposition, activation energies, and half-lives of the studied diazonium salts (DSs) were found. Using gas chromatography–mass spectrometry (MS) and liquid chromatography–MS, we have elucidated the products formed during thermolysis of the investigated DSs. By density functional theory quantum chemical calculations at the B3LYP/aug-cc-pVDZ level of theory, we simulated the thermodynamics of decomposition reactions proceeding via substitution of the diazonium group by corresponding nucleophiles. The method applied predicted the decomposition energies of all the studied compounds fairly precise, except for 2-nitrobenzene diazonium triflate. It has been found that 4-nitrobenzene diazonium triflate has increased storage stability under normal conditions comparing to the corresponding tosylate and tetrafluoroborate. The experimental and theoretical results demonstrated that comparing to DSC/TGA, isothermal flow calorimetry more adequately reflects the energetics of the thermal decomposition of DSs and their storage stability under normal conditions.