Effect of Fluoro Substituents on Polynitroarylenes: Design, Synthesis and Theoretical Studies of Fluorinated Nitrotoluenes

The replacement of traditional polynitroarylenes by their fluorinated derivatives has attracted great attention due to the improvements on detonation performance caused by the fluorine effect. A straightforward synthesis of three novel fluorinated nitrotoluenes with different degrees of nitration was achieved under selected high temperatures. The fluorine exerted remarkable influence on the nitration process through the electron-withdrawing effect and a mechanism of the transformation was proposed according to the experimental results. Thermal decomposition behavior of the fluorinated nitrotoluenes was investigated by differential scanning calorimetry and all the compounds showed ideal low melt points for the melt-cast process. X-ray analysis of the fluorinated derivatives were carried out as well as density functional calculations to establish the electronic density and electrostatic potential on the molecular surface of the optimized structures. The good thermal and detonation properties make the newly developed fluorinated nitrotoluenes possible replacements for trinitrotoluene and dinitrotoluene in the formation of melt-cast energetic materials.