To validate our computational predictions, a series of experimental investigations were conducted, which are reported in the following section, which confirm that IEF and partial solvation are not important factors to drive this reaction in microdroplets. Instead, enrichment of reactants in confined volumes driven by fast evaporation becomes predominant. This factor has been identified to be responsible for the acceleration of many reactions in the works of Cooks, Wilson, and Williams. Mass spectrometry experiment. In the bulk phase, the above DA reaction is known to occur in the presence of a heterogeneous catalyst at an elevated temperature. Cyclopentadiene is highly reactive and undergoes a self-DA reaction, forming dicyclopentadiene. Therefore, we used dicyclopentadiene in our microdroplet experiment, which spontaneously undergoes a retro-DA reaction within the droplet to produce cyclopentadiene (vide infra). We separately prepared two solutions by mixing dicyclopentadiene and acrylonitrile, each with 200 µM concentration, in water and acetonitrile for comparison, followed by atomizing those solutions immediately using a home-built sonic spray source in front of a mass spectrometer inlet (Figure ). Unless otherwise stated, the spray source was operated without applying any voltage under a 120-psi nebulizing gas (nitrogen) pressure at a distance of 15 mm from the MS inlet capillary, following a 10 μL/min and 50 μL/min flow rates of water and acetonitrile solutions, respectively, to ensure the recording of ion signals from species at sufficient intensities.