WP2750: Development of Solvent-Free Nitration Processes Using Tert-Butyl Nitrite

Objective: The SERDP SEED FY17 Statement of Need sought a solution to the issue of the amount hazardous waste produced during the synthesis of energetic materials. Syntheses of energetic materials through processes that either eliminate waste streams or greatly reduce them to a minimum were required. Investigated processes were required to not be energy-intensive, meaning the reactions should not require high degrees of temperature control. The objective of the proposed work was to develop nitration methods that can be applied to green synthesis and scale-up of energetic materials in such a manner that waste generation and energy expenditure were kept to a minimum. Technical Approach: Mild nitration methods utilizing tert-butyl nitrite at ambient temperature under open air to access directed C-nitro functionalization on aromatic molecules and alkenes were recently reported in the academic literature. To a lesser extent, syntheses of nitramines and nitrate esters using tert-butyl nitrite were also reported in the academic literature. The work reported herein focused on maturing this nitration technology into a process useful for the green chemical scale-up of aromatic/heteroaromatic nitro compounds, nitramines, and nitrate esters. A design of experiments- inspired approach screening various conditions and additives was undertaken to investigate whether processes to conventional nitrate ester, nitroaromatic, and nitramine explosive ingredients was feasible. During the course of this work, it was discovered that very small amounts of nitroglycerin could be synthesized in a reproducible manner, but the major product of the reaction of tert-butyl nitrite with glycerol was glycerol trinitrite. It was also discovered that isomeric mixtures of nitrotoluene and dinitrotoluene could be obtained when toluene was combined with tert-butyl nitrite in the presence of catalyst.