Accelerated formation of trioximes through confined volume reactors and scale-up using thin film methods

Abstract

Oximes are important functional groups in compounds used for manufacturing, medicinal, and defense applications. Specifically, cyclohexane-1,3,5-trione trioxime is a precursory compound in the synthesis of 1,3,5-trinitrobenzene (TNB). To synthesize oximes faster than traditional bulk reactions, confined-volume techniques can be used. Confined volume systems can drastically accelerate reactions through microreactors such as microdroplets, Leidenfrost droplets, or thin films. Herein, the oximation of phloroglucinol with hydroxylamine to form cyclohexane-1,3,5-trione trioxime was explored. Seven confined volume systems, including three microdroplet setups, Leidenfrost droplets, and three thin film techniques, were compared to evaluate which method was ideal for the acceleration of oxime formation. All of the small-scale confined volume systems accelerated oxime production compared to traditional methods, with thin films having the highest acceleration factor of 2.5 × 10². To scale-up the reaction in thin films, methods based on a rotary evaporator and electrospinner were explored. The electrospinner setup produced product 2.1 × 10² times faster than the bulk reaction, consistent with this method being a paper spray ionization thin film technique. The reaction in the rotary evaporator was 2.3 × 10³ times faster than the bulk reaction. Purified trioxime generated by the scalable rotary evaporator method was analyzed and found to be identical to the traditionally synthesized product. The time to produce trioxime was ∼5 minutes, compared to the legacy synthesis route that requires ∼3 hours.