Methods and strategies to achieve hexanitrohexaazaisowurtzitane (HNIW or CL-20): a comprehensive overview

In recent years, hollow cage-type molecular structures have attracted much scientific attention and have unique properties due to their structure. One of these mentioned compounds and most interesting high energetic molecules developed in recent years is the polycyclic nitramine, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane or (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo dodecane, HNIW or CL-20).CL-20 is a new explosive that is 14~20% more powerful than HMX (tetranitrotetraazacyclooctane). CL-20 has a cage structure in polycyclic nitramine class with interest high density (ρ>2 g/cm3) and heat of formation (∆Hf = 100 kcal/mol). Also, CL-20 has several polymorphs such as α, β, γ, and ε. Its high detonation velocity and pressure make it a suitable candidate for replacing HMX. CL-20 has numerous military and commercial applications. Many reports have been published on the chemical and physicals characteristics of this energetic compound. In recent years, continuous advances in this field have established various methods for synthesizing CL-20.In this review article, various techniques and strategies to achieve CL-20 were studied, comprehensively.