Ammonium perchlorate (AP) is widely used as an oxidizer in rocket motors. New alternatives are desired due to multiple environmental driving factors, among which are recently discovered deleterious health effects of environmental perchlorate as well as adverse local effects of hydrogen chloride combustion product from certain applications of AP. The high solubility of perchlorate and its chemical stability in water make its contamination difficult to remediate by conventional water treatment methods. The U.S. Environmental Protection Agency and various states have been proposing stringent cleanup levels for perchlorate, which therefore represents a potential liability for the Department of Defense.
The main objective of this SEED project was to identify alternatives to AP oxidizers used in rocket motors.
This project aimed to meet its objectives by developing a synthetic methodology leading to any example of the chemical class of trinitromethyl ethers—but especially ones that appeared competitive with ammonium perchlorate as an oxidizer in rocket motor applications. Such a methodology is currently unavailable even though these compounds were believed to exist else-where. Certain alternative target compounds were pursued. Other specific variations of trinitro-methyl derivatives were of potential interest, and their pursuit was also a potential alternative objective of this project.
Despite two independent claims in literature of the existence of trinitromethyl ethers, this class of compounds proved not to be established by any precedence, as both claims were discovered to be erroneous. Several attempts to newly prepare examples of this potentially interesting class were unsuccessful, even though it appears to be a fundamentally reasonable chemical linkage.
Although some unprecedented polynitroalkane products, such as nonanitroisobutane, were briefly pursued, they too proved less straightforward than hoped and were abandoned.
One target considered early on, 5,5′-dinitro-2,2′-bis(trinitromethyl)-4,4′-bi-2H-1,2,3-triazole N,N′-dioxide, still appears particularly promising from a standpoint of properties expected to provide superior performance as an oxidizer. However, synthetic strategies that might produce it appeared to be beyond the scope of a SEED project and are likely impractical for a large-scale replacement of AP.
A last target compound pursued, 2,6,8,12-tetranitro-4,10-bis(trinitromethyl)hexaaza-isowurtzitane, still appears conceptually interesting, but synthetic strategies attempted in the course of this SEED project—particularly routes via unknown diacetonyltetraacetylhexaaza-isowurtzitane as a new intermediate—were unsuccessful. This target also remains of interest for pursuit outside the scope of the current project, as it has good oxygen balance and is expected to have good properties as an energetic ingredient (oxidizer or explosive).
A critical issue addressed in this project is the feasibility of preparing certain specific classes of compounds that may be suitable as AP replacement oxidizers. Their isolation and initial characterization would provide enlightenment about general properties of these materials as well as prospects of their suitability as ordnance ingredients. The successful development of this methodology would allow expansion of the scope of pursuit of additional target compounds. A successful replacement oxidizer could revolutionize propellant technology.