Thermogravimetric analysis, kinetic study, and pyrolysis–GC/MS analysis of 1,1ʹ-azobis-1,2,3-triazole and 4,4ʹ-azobis-1,2,4-triazole

Abstract

BackgroundIn general, the greater the number of directly linked nitrogen atoms in a molecule, the better its energetic performance, while the stability will be accordingly lower. But 1,1ʹ-azobis-1,2,3-triazole (1) and 4,4ʹ-azobis-1,2,4-triazole (2) show remarkable properties, such as high enthalpies of formation, high melting points, and relatively high stabilities. In order to rationalize this unexpected behavior of the two compounds, it is necessary to study their thermal decompositions and pyrolyses. Although a great deal of research has been focused on the synthesis and characterization of energetic materials with 1 and 2 as the backbone, a complete report on their fundamental thermodynamic parameters and thermal decomposition properties has not been published.MethodsThermogravimetric–differential scanning calorimetry were used to obtain the thermal decomposition data of the title compounds. Kissinger and Ozawa–Doyle methods, the two selected non-isothermal methods, are presented for analysis of the solid-state kinetic data. Pyrolysis–gas chromatography/mass spectrometry was used to study the pyrolysis process of the title compounds.ResultsThe DSC curves show that the thermal decompositions of 1 and 2 are at different heating rates involved a single exothermic process. The TG curves provide insight into the total weight losses from the compounds associated with this process. At different pyrolysis temperatures, the compositions and types of the pyrolysis products differ greatly and the pyrolysis reaction at 500 °C is more thorough than 400 °C.ConclusionsApparent activation energies (E) and pre-exponential factors (lnA/s−1) are 291.4 kJ mol−1 and 75.53 for 1; 396.2 kJ mol−1 and 80.98 for 2 (Kissinger). The values of E are 284.5 kJ mol−1 for 1 and 386.1 kJ mol−1 for 2 (Ozawa–Doyle). The critical temperature of thermal explosion (Tb) is evaluated as 187.01 °C for 1 and 282.78 °C for 2. The title compounds were broken into small fragment ions under the pyrolysis conditions, which then might undergo a multitude of collisions and numerous other reactions, resulting in the formation of C2N2 (m/z 52), etc., before being analyzed by the GC/MS system.Electronic supplementary materialThe online version of this article (10.1186/s13065-018-0381-x) contains supplementary material, which is available to authorized users.

Morus alba L. Plant: Bioactive Compounds and Potential as a Functional Food Ingredient

“…However, only simple terpenes were isolated via pyrolysis gas chromatography–mass spectrophotometry (Py/GC/MS), possibly due to terpenes’ lack of a polar group, which makes them more easily volatile compared to alkaloids and phenolics. Further analysis with different pyrolysis temperatures might isolate more compounds from M. alba leaves [ 29 ]. Ultimately, rutin, apigenin, and quercetin were the three highest bioactive constituents among the major phytochemical classes of M. alba leaves ( Table 3 ) [ 30 ].…”

Thermal Stability of Bis-Tetrazole and Bis-Triazole Derivatives with Long Catenated Nitrogen Chains: Quantitative Insights from High-Level Quantum Chemical Calculations

“… a All energy values are given in kcal mol –1 . Experimental data on the decomposition temperatures estimated by the DSC technique ( T dec DSC ), along with the impact sensitivities (IS). b Ref . c Ref . d Ref . e Calculated for a drop mass of 2.5 kg typically used in the experimental setup and a reported value H 50 = 16.6 cm, ref . f Calculated at the W1 level of theory, ref . g Ref . h Ref . I The enthalpy of the azide isomer is lower than that of the bis-tetrazole. The effective rate constants correspond to the N 2 elimination from the azide. j Calculated at the G3 level of theory, ref . k Ref . l This value refers to 1,1′-dimethyl-5,5′-azotetrazole, ref .…”

“…The existing literature data on the kinetics of thermal decomposition of 1 are scarce. Li et al studied the thermolysis of 1 and 4,4′-azobistriazole using thermogravimetry (TG) and DSC. The decomposition of 1 commenced at 176 °C under a moderate heating rate of 5 K min –1 , and the effective Arrhenius parameters of the nonisothermal TG kinetics ( E a = 70 kcal mol –1 and log­(A/s –1 ) = 32.8) were estimated using the Kissinger method.…”

“…The decomposition of 1 commenced at 176 °C under a moderate heating rate of 5 K min –1 , and the effective Arrhenius parameters of the nonisothermal TG kinetics ( E a = 70 kcal mol –1 and log­(A/s –1 ) = 32.8) were estimated using the Kissinger method. The authors also detected the mass spectra of the products of high-temperature pyrolysis of 1 and hypothesized the decomposition mechanism to commence from a radical rupture of the azo-bond followed by the opening and decomposition reactions of radical triazolyl rings.…”

“…Note that the kinetics and mechanism of the decomposition of all aforementioned compounds are not clear yet. Due to their extremely low impact sensitivity, almost no experimental kinetic data for all species (except 1 ) are available. Therefore, quantum chemical calculations are an indispensable tool for the study of the thermal stability of azo-, hydrazo-, and azoxy-bridged heterocyclic compounds containing long nitrogen chains.…”