Accelerated Two-Phase Oxidation in Microdroplets Assisted by Light and Heat without the Use of Phase-Transfer Catalysts

Two-phase oxidation of alcohols to corresponding aldehydes could be achieved without any phase-transfer catalyst in microdroplets. Herein, we realized reaction acceleration for two-phase oxidation in microdroplets using diluted oxidants under light and thermal irradiation. Lights of short wavelengths were more desirable to reaction acceleration than lights of long wavelengths. However, yields were dramatically improved by moderate heating but reversely decreased by excess heat owing to crystallization. The yields with 5-fold diluted NaOCl solution under light and thermal irradiation were comparable to those with undiluted NaOCI in the absence of light and heat. The dilution of NaOCI not only improved robustness of the sprayer (no salt deposition at the capillary tip) but also met the requirements of green chemistry.