Thermal stabilities of some benzaldehyde 2,4-dinitrophenylhydrazones Jeanina Pandele Cusu • Adina Magdalena Musuc • Dumitru Oancea Received: 15 February 2011 / Accepted: 9 March 2011 / Published online: 30 March 2011 Ó Akade ´miai Kiado ´, Budapest, Hungary 2011 Abstract The thermal stability of some benzaldehyde 2,4-dinitrophenylhydrazones has been studied using DSC technique. The crystalline solids are thermally stable and start to decompose after melting. Non-isothermal DSC curves, recorded at several heating rates, were used to evaluate the melting properties and the kinetics of thermal decomposition. Both isoconversional and model fitting methods were used for the evaluation of the kinetic parameters. Based on the results of the model free method, a kinetic model was derived and the kinetic parameters were obtained by means of a multivariate non-linear regression. A good agreement between the experimental and fitted data was found. Keywords Benzaldehyde 2,4-dinitrophenylhydrazones  Differential scanning calorimetry  Exothermal decomposition  Multivariate non-linear regression Introduction The derivatives of 2,4-dinitrophenylhydrazone [2,4-DNPH] type have acquired special relevance for the analysis of carbonyl compounds such as aldehydes and ketones [1, 2]. Identification of carbonyls by their 2,4-DNPHs are made by column and thin-layer chromatography. Some 2,4-DNPH derivatives are analyzed by direct Gas–Liquid Chromatography (GLC). An important aspect with regards to the GLC separation of the 2,4-DNPH derivatives lies in their thermal stabilities. As the column temperature required in GLC separation is quite high, artifacts or double peaks occasionally appeared in the chromatograms revealing possible decomposition phenomena [3] of these energetic compounds. Moreover, an increasing interest has been observed during recent years concerning hydrazones due to their coordinative capabilities and physiological activities. The aim of this article is to study the thermal decompo- sition of some benzaldehyde 2,4-dinitrophenylhydrazones in isothermal and non-isothermal regime. The derivatives are obtained from the condensation of 2,4-dinitrophenylhydra- zine with the corresponding carbonyl compounds (benzal- dehyde and its 4-methyl, 4-methoxy and 2 nitro derivatives) as follows (Fig. 1). The conjugation of the benzaldehyde aromatic ring with C=N double bond, as well as the substituent effect, are expected to markedly influence the thermal stabilities of these compounds. The presence of nitro group on the aromatic ring frequently induces thermal instability, a characteristic feature of aromatic derivatives [4–8]. The hazards associated with this instability have been thor- oughly analyzed in many scientific works [9–11]. DNPH is also thermally unstable and decomposes exothermally both in solid and molten state following a multi-step autocata- lytic mechanism [12, 13]. The thermal stability of synthesized and purified hydrazones was investigated by differential scanning cal- orimetry (DSC) under isothermal and non-isothermal conditions. From DSC curves, recorded at several heating rates, several properties such as the melting point, the melting heat, the temperature, and heat of decomposition J. P. Cusu (&)  D. Oancea Department of Physical Chemistry, Faculty of Chemistry, University of Bucharest, 4-12 Regina Elisabeta Blvd, 030018 Bucharest, Romania e-mail: jeaninamirea@yahoo.com A. M. Musuc Romanian Academy, ‘‘Ilie Murgulescu’’ Institute of Physical Chemistry, 202 Spl. Independentei, 060021 Bucharest, Romania 123 J Therm Anal Calorim (2012) 109:123–129 DOI 10.1007/s10973-011-1470-4