Heterocyclic Salt Synthesis and Rational Properties Tailoring (PREPRINT)
Journal article preprint
AIR FORCE RESEARCH LAB EDWARDS AFB CA PROPULSION DIRECTORATE
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Chemical structure determines the inherent properties displayed by a given compound, and these properties, in turn, produce a specific performance behavior. Rationally designing chemical structure to predictably modify compound properties, such that performance behavior can be tailored in a controlled manner, defines the objective of a pertinent synthesis effort. Achieving this objective by introducing structural alterations in a neutral covalent compound offers only one approach for resultant properties modification. Heterocyclic salts significantly enhance the flexibility for achieving properties modification via three strategic approaches 1 compositionally pairing various cation structural classes with a number of anion structural classes, 2 systematically altering the structure of the cation and, 3 systematically altering the structure of the anion. To illustrate this premise, four general synthesis methods to synthesize heterocyclic salts, including several new binary heterocyclium icosahedral closo-borane and closo-carborane salts, first are outlined. Secondly, properties modification approaches of neutral covalent compounds are then compared with those approaches available for various heterocyclic salts. Lastly, a key example, using three unsaturated bridged heterocyclium di-cation salts, demonstrates how rational structure design, and its effect on resultant predictable properties modification, produces tailored performance behavior to reach the thermochemical initiation threshold needed for combustion. This is achieved with predictable properties modifications that increase salt energy content, or that accelerate the reaction kinetics of the thermochemical initiation process.
- Organic Chemistry
- Physical Chemistry
- Rocket Propellants