Energetic materials containing fluorine. Design, synthesis and testing of furazan-containing energetic materials bearing a pentafluorosulfanyl group Henry Martinez, Zhaoyun Zheng, William R. Dolbier Jr.* Department of Chemistry, University of Florida, PO Box 117200, Gainesville, FL 32611-7200, United States 1. Introduction Energetic materials can be considered compounds or mixtures of compounds that constitute a source of massive controllable energy. Interest in the design of new materials with higher energy content, better performance, lower cost, less sensitivity to impact and with less danger to synthesize and process has allowed this research area to remain active. Also, continued concerns related to the potential use of chemical and biological weapons (CW/BW) has necessitated the development of new mechanisms of defense [1]. The synthesis of new high energy materials has been focused on use of heterocyclic compounds with high nitrogen content such as tetrazines, furazans, triazoles and tetrazoles due to the relatively positive heats of formation (DH f 8) of these compounds [2]. Recently, the introduction of fluorine into such compounds has resulted in a boost in their performance, mainly due to the increase in their density and their thermal and chemical stability. By definition, an energetic material is a compound or a mixture of compounds that, after an initiation process, undergoes very rapid self-propagating decomposition, producing gases at tremen- dous pressure and with the evolution of a lot of heat. Temperatures ideally can reach up to 6000 K and the pressure up to 40 GP [2]. The performance of an energetic material is mainly evaluated on the basis of the type of products that are formed, the energy that is released, the pressure and speed of detonation, and the thermal and chemical stability of the material. The carbon–oxygen balance (OB) and the density are directly related to a compound’s performance. According to the semi-empirical equations devel- oped by Kamlet and Jacobs, the square of the density is directly proportional to the performance of the compound (Eqs. (1)–(3)) [3]. P ðCJÞ ¼ 15:58r 2 f (1) D ¼ Af 1=2 ð1 þ BrÞ (2) f ¼ NM 1=2 Q 1=2 (3) P is the detonation pressure (GPa), D is the speed of detonation (m/ s), A and B are constants, N is the number of moles of gaseous products of detonation per gram of explosive, M the average molecular weight of the gases, Q is the heat of detonation in calories per gram of explosive and r is density. The higher the density is, the better the performance will be. Although the increase of oxygen balance results in a more sensitive material, it also increases the performance due to the ‘‘complete’’ oxidation of all carbons and hydrogens. Most energetic materials, however, are ‘‘oxygen-deficient’’ [4]. In evaluating new energetic materials, they are generally compared to three of the most important known energetic materials: cyclotrimethylenetrinitramine (RDX), cyclotetra- methylene-tetranitramine (HMX) and trinitrotoluene (TNT). Journal of Fluorine Chemistry 143 (2012) 112–122 A R T I C L E I N F O Article history: Received 16 February 2012 Received in revised form 7 March 2012 Accepted 8 March 2012 Available online 17 March 2012 Keywords: Pentafluorosulfanyl group Furazan Energetic materials Basicity Nucleophilicity A B S T R A C T The advantageous impact of a pentafluorosulfanyl substituent on the properties of furazan-containing energetic materials was demonstrated by the synthesis and study of the energetic properties of ten new compounds. The thermal stability of these compounds was evaluated by DSC and TGA, whereas densities, heats of formation, pressures of detonation and speeds of detonation were obtained computationally. On the basis of these data, it was concluded that the combination of the SF 5 substituent with the furazan ring led to materials of higher density and predicted detonation properties than other known furazans or SF 5 - containing materials. In addition, the synthetic studies provided insight regarding the electron- withdrawing nature of the furazan ring, in particular its effect on the basicity and nucleophilic reactivity of amino furazans. ß 2012 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: wrd@chem.ufl.edu (W.R. Dolbier Jr.). Contents lists available at SciVerse ScienceDirect Journal of Fluorine Chemistry jo ur n al h o mep ag e: www .elsevier .c om /loc ate/f luo r 0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jfluchem.2012.03.010