Thermal Decomposition of Dinitro-chloro-azido Benzenes: A Comparison of Theoretical and Experimental Results

Abstract

1,2-Dichloro benzene (I) and 1,2,3-trichloro benzene (II) were nitrated under appropriate strong conditions. Nitrated mixtures were reacted with NaN3 in polar solvents. As a result of the nucleophilic substitution, mixtures of nitro-chloro-azido benzene were prepared. After fractional crystallization, two crystalline substances were obtained from the mixtures. These crystalline substances were characterized by infrared (IR), H-1-NMR spectroscopy, mass spectroscopy, and elemental analysis. It was understood that the substance obtained from compound I was 2-chloro-4,6-dinitro azido benzene (III). The crystals of compound III were suitable for single-crystal X-ray diffraction (XRD). The molecular structure of this substance was determined by the mentioned method, XRD. It was revealed that the crystalline substance obtained from compound II was most probably 1,5-dinitro-2,4-diazido-3-chloro benzene (IV). In addition, compounds III and IV were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Compound III turned into 4-nitro-6-chloro phenoxazine (V) at about 120 degrees C with an exothermic reaction. Compound IV completely decomposed at about 150 degrees C with an exothermic reaction similar to that of explosive materials. In addition, theoretical formation enthalpies of compounds III and IV were calculated with Gaussian 09, CBS-4M algorithm. The enthalpies of thermal reactions observed in the TG curves were calculated using the theoretical formation enthalpies. Finally, the theoretical results were compared with the experimental findings obtained from DSC.