Microdroplet synthesis of azo compounds with simple microfluidics-based pH control

Daiki Tanaka*, Shunsuke Sawai, Shohei Hattori, Yoshito Nozaki, Dong Hyun Yoon, Hiroyuki Fujita, Tetsushi Sekiguchi, Takashiro Akitsu, Shuichi Shoji

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Conventional solution-phase synthesis of azo compounds is complicated by the need for precise pH and temperature control, high concentrations of pH control reagents, and by-product removal. In this work, we exploited the advantages of microdroplet chemistry to realize the simple and highly efficient synthesis of an azo compound using microfluidics-based pH control. Owing to the small size of microdroplets, heat exchange between a microdroplet and its environment is extremely fast. Furthermore, chemical reactions in microdroplets occur rapidly due to the short diffusion distance and vortex flow. Formation of the azo compound reached completion in less than 3 s at room temperature, compared with 1 h at 0 °C under conventional conditions. pH control was simple, and the pH control reagent concentration could be reduced to less than one-tenth of that used in the conventional method. No by-products were generated, and thus this procedure did not require a recrystallization step. The time course of the chemical reaction was elucidated by observing the growth of azo compound microcrystals in droplets at various locations along the channel corresponding to different mixing times. This journal is

Original languageEnglish
Pages (from-to)38900-38905
Number of pages6
JournalRSC Advances
Issue number64
Publication statusPublished - 2020 Oct 23

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)


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