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.