Thermal decomposition of aminotetrazoles

Unimolecular Decomposition of 5-Aminotetrazole and its Tautomer 5-Iminotetrazole: New Insight from Isopotential Searching

“…As previously mentioned in the Introduction, Levchik et al 1 found that the imino tautomer, 5-ITZ, initially undergoes thermal decomposition in a sample subjected to thermal treatment. As thermal treatment continues (i.e., temperature is increased), however, an increased proportion of the amino tautomer, 5-ATZ, accumulates and in turn undergoes thermal decomposition.…”

“…1,[12][13][14] The activation barrier predicted for Scheme 1 is approximately 22 kJ/mol lower than the activation barrier predicted for Scheme 2. This result explains why HN 3 and NH 2 CN products are initially detected in thermal decomposition experiments, as opposed to N 2 and CH 3 N 3 SCHEME 4: Relative Energetics (298.15 K) of 1H-5-ATZ Unimolecular Decomposition Pathway Leading to HN 3 and NHCNH Products products (or the secondary decomposition products of CH 3 N 3 ).…”

“…Levchik et al 1 and Lesnikovich et al 14 investigated the thermal decomposition of 5-ATZ, paying close attention to the role of 5-ATZ/5-ITZ tautomerism which had been previously identified in the solid state by vibrational spectroscopy. 15,16 Levchik et al 1 determined that their initial sample of solid 5-ATZ consisted primarily of the imino form, 5-ITZ. However, thermal treatment resulted in an increased proportion of the amino form, 5-ATZ.…”

“…IR spectroscopy and mass spectrometry showed that 5-ITZ thermal decomposition started immediately after melting and resulted in HN 3 and carbodiimide (NHCNH), which likely isomerizes into NH 2 CN. 1,17 Increasing the temperature further led to another thermal decomposition pathway involving 5-ATZ, namely, the formation of N 2 and a metastable CH 3 N 3 product. 1 The apparent activation energies for these two thermal decomposition pathways were estimated to be approximately 200 and 150 kJ/mol, respectively.…”

“…Furthermore, Zhang et al 23 did not investigate the unimolecular decomposition pathway of 5-ATZ leading to the formation of N 2 and a metastable CH 3 N 3 product, which had been previously identified experimentally. 1,10,14 Therefore, a need clearly exists to further investigate the mechanisms and thermodynamics of 5-ATZ and 5-ITZ unimolecular decomposition, using quantum chemical methods.…”