Oxime functional groups are present in compounds used for manufacturing, medicinal, and defense applications. Due to their prevalent nature, the accelerated formation of product is desirable. Compared to bulk reactions, confined-volume systems have been reported to accelerate reactions due to the lower energy barriers of partially solvated reagents. Confined-volume systems include microdroplets, Leidenfrost droplets, and thin films, however, each technique has unique experimental conditions that can be explored and optimized for each new reaction. Herein, we compared several confined-volume techniques to see which method was ideal for forming trioximes. Microdroplets were created using modified mass spectrometry ionization sources, including easy ambient sonic spray ionization (EASI), electro-sonic spray ionization (ESSI), and nano-electrospray ionization (nESI). Leidenfrost droplets were initially formed with the appropriate reaction mixture and maintained with solvent in a heated Pyrex well (540°C). Thin films were created on a paper surface after depositing the reaction mixture. Acceleration factors were calculated based on signal intensity after a set reaction time compared to bulk reactions. All of the small scale confined systems, including EASI, ESSI, nESI, Leidenfrost, and paper thin films, accelerated the formation of the trioxime product to some degree. The highest acceleration factor was observed using thin films, where the thin film reaction formed product 2.5x102 times faster than the bulk counterpart. A rotary evaporator (rotavap) and an electrospinner were explored as two possible scale-up methods for thin films. For the electrospinner setup, the reaction mixture was continuously sprayed onto a strip of Teslin attached to the rotating collection drum. Thin films on the paper in the electrospinner formed product 2.1x102 times faster than the bulk reaction, similar to the paper spray thin film method. For the rotavap setup, the reaction mixture was added to round-bottom flask and the rotation allows for the thin film formed on the side of the flask to be constantly refreshed with reaction solution. The product formed in the rotavap after five minutes was isolated and compared to the trioxime product formed through traditional organic synthesis (~3 hours). After analytical characterization, the product formed in the rotavap was confirmed to be the trioxime product. The rotavap reaction was 2.3x103 times faster than the bulk.

Scaling-up confined-volume systems for the accelerated formation of trioximes

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