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. 

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. It was found that hexamine could not be nitrolyzed through a truly solventless process in the presence of tert-butyl nitrite and a nitrate salt, but adding a co-solvent did afford small amounts of product which, when analyzed by NMR, exhibited peaks attributable to RDX and HMX.

It was thought that maturing nitration technology utilizing tert-butyl nitrite could provide multiple benefits in the chemical scale-up and production of energetic materials.  If the amount of waste in a process could be reduced through use of mild reactions run neat or with a minimal amount of solvent under pH-neutral conditions, then there would likely be a reduced environmental impact and also significant cost-savings to stakeholders.  With no need to neutralize the waste streams, it was postulated that the saved labor associated with neutralization result in additional cost-savings for stakeholders.  Beyond the scope of process development, the energetics community had a general interest in developing efficient nitration processes that proceed under mild reaction conditions.  Maturing this technology was thought to also be of benefit researchers at the 6.1 level who required more mild nitration conditions to access novel energetic material targets.