Accelerated d-Fructose Acid-Catalyzed Reactions in Thin Films Formed by Charged Microdroplets Deposition

ABSTRACT: Thin films derived by the deposition of chargedmicrodroplets generated in the ESI source of a mass spectrometeract as highly concentrated reaction vessels in which the finalproducts of an ion−molecule reaction can be isolated by theirprecipitation onto a solid surface under ambient conditions. In thisstudy, the ESI Z-spray source supplied to a Q-TOF Ultima massspectrometer was used to investigate the D -fructose acid-catalyzedreactions by microdroplets deposition onto a stainless-steel targetsurface. High conversion ratios of D -fructose into 5-hydroxyme-thylfuraldehyde (5-HMF), 5-methoxymethylfuraldehyde (5-MMF), and difructrose anhydrides (DFAs) were obtained withHCl and KHSO 4 as metal-free catalysts by using syntheticconditions under which the same products in bulk are not formed.Furthermore, the reaction outcome was found to be highly sensitive to the catalyst and the solvent employed as well as to the ESIsource parameters influencing the thin film formation from microdroplets deposition onto the solid surface.KEYWORDS: microdroplets, thin film, D -fructose, dehydration, methylation, dimerization