Solubilities of CL‐20 and MDNT in Organic Solvents for Technical Cocrystallization

The 1:1 molar cocrystal of 2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (CL‐20) and 1‐methyl‐3,5‐dinitro‐1,2,4‐triazole (MDNT) is reported to show a detonation velocity 100 m/s faster than β‐ HMX. To establish a scalable synthesis method, the solubility of ε‐ CL‐20 and MDNT was investigated. Solubility data for the educts in three solvents, as well as the cocrystal in ethyl acetate, were recorded using the soil body method in the temperature range 283.1–323.1 K. The results obtained in this study, in combination with data from the literature, revealed points of equal molar solubility in ethyl acetate at 291.3 K and acetone at 249.9 K. Additional investigation of three solvent/anti‐solvent mixtures at 293.1 K delivered a promising molar solubility ratio of 1:0.6 for CL‐20 and MDNT over most of the mixing range for an ethyl acetate/isopropanol mixture. Crystallization from ethyl acetate and ethyl acetate/isopropanol at the given temperatures produces phase‐pure cocrystal samples. A novel solvate crystal structure of CL‐20 with tetramethyl urea was characterized.