Kinetic analysis of thermal decomposition in liquid and solid state of 3-nitro and 4-nitro-benzaldehyde-2,4-dinitrophenylhydrazones Jeanina Pandele Cusu • Adina Magdalena Musuc • Dumitru Oancea Received: 29 April 2011 / Accepted: 11 May 2011 / Published online: 29 May 2011 Ó Akade ´miai Kiado ´, Budapest, Hungary 2011 Abstract A kinetic study on the thermal decomposition of 3-nitro and 4-nitro-benzaldehyde-2,4-dinitrophenylhy- drazones was carried out. The isothermal and dynamic differential scanning calorimetric curves were recorded for solids and melts, respectively. The standard isoconver- sional analysis of the obtained curves from both isothermal and nonisothermal analysis suggests an autocatalytic decomposition mechanism. This mechanism is also sup- ported by the temperature dependence of the observed induction periods. Based on the results of the model-free method from nonisothermal regime, the kinetic model was derived and the kinetic parameters were obtained by means of a multivariate nonlinear regression. Keywords Isothermal kinetics  Isoconversional method  Induction period  Multivariate nonlinear regression  Nitro-benzaldehyde-2,4-dinitrophenylhydrazone Introduction When heated at high temperatures, many solid energetic compounds decompose exothermally during or after melt- ing, indicating an increased instability of the liquid state. The literature concerning the thermal stability of various materials offers numerous examples of solids which decompose during or after melting. The kinetic studies of these systems play an important role for the explosion risks assessment. Many of the generally accepted equations for isothermal or nonisothermal kinetics were considered valid for all condensed media—crystals or melts—except those referring only to the specific characteristics of crystals. A large number of published articles dealing with exothermal decomposition after melting are based on the extension to melts of the kinetic equations derived for solids [1–4], although this approach has occasionally been criticized [1, 2]. Solid nitro derivatives have been found to decompose in the liquid phase after their melting, following a complex autocatalytic mechanism. Their exothermal decomposition in solid state is also of practical interest for hazard evalu- ation before melting. Chemical compounds able to decompose autocatalytically are considered more hazard- ous because the decomposition reactions can accelerate even under isothermal conditions during prolonged storage [5, 6]. For the decomposition of nitro compounds, the bond energy of different types of functional groups as well as their position on the aromatic ring determines the thermal stability [7, 8]. The aim of this article is to investigate the thermal behavior of 3-nitro and 4-nitro-benzaldehyde-2,4-dini- trophenylhydrazones which proved to decompose either when the solid sample is kept at constant temperatures, lower than the melting point, or after melting, during a linear heating program, unlike 2-nitro-benzaldehyde-2,4- dinitrophenylhydrazone which is stable in crystalline form [9]. The nitrophenylhydrazines are frequently used in analytical chemistry for identification of carbonyl com- pounds through derivatization to nitrophenylhydrazones, which are often hazardous compounds due to their exo- thermal decomposition at higher temperatures [10–12]. J. Pandele Cusu (&)  D. Oancea Faculty of Chemistry, Department of Physical Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd, 030018 Bucharest, Romania e-mail: jeaninamirea@yahoo.com A. M. Musuc ‘‘Ilie Murgulescu’’ Institute of Physical Chemistry, Romanian Academy, 202 Spl.Independentei, 060021 Bucharest, Romania 123 J Therm Anal Calorim (2012) 109:255–263 DOI 10.1007/s10973-011-1662-y