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- Title
Three-dimensional observations of the electric field distribution of variable frequency microwaves, and scaling-up organic syntheses.
- Authors
Horikoshi, Satoshi; Mura, Haruka; Serpone, Nick
- Abstract
Variable Frequency Microwave (VFM) radiation provides a solution to the inhomogeneity of the electric field in the cavity, which has long led to a decline in the reliability of microwave chemical data and its industrial utilization. Herein, we report in-situ three-dimensional experimental measurements of the electric field's uniform distribution of VFMs within a multimode cavity under high power conditions, and their subsequent comparison to Fixed Frequency Microwaves (FFM) that could only be assessed earlier through theoretical analysis. We also examine the consequences of changes in VFM irradiation conditions and elucidate the threshold at which VFM irradiation might prove beneficial in syntheses. With an ultimate focus on the use of VFM microwave radiation toward industrial applications, we carried out an effective synthesis of 4-methylbyphenyl (4-MBP) in the presence of palladium (the catalyst) supported on activated carbon particulates (Pd/AC), and revisited two principal objectives: (a) the effective suppression of discharge phenomena (formation of hot spots), and (b) synthesis scale-up using a 5-fold increase in sample quantity and a 7.5-fold larger reactor size (diameter) than otherwise used in earlier studies. The variable frequency microwave (VFM) technology is known for its theoretically uniform microwave E-field distribution, although the experimental distribution remains poorly understood. Here, the authors examine the effectiveness of VFM irradiation experimentally by in situ 3D observation of the E-field, and apply VFM to the large scale synthesis of 4-methylbiphenyl via the Suzuki-Miyaura cross-coupling reaction catalyzed by solid Pd supported on activated carbon particulates.
- Subjects
ELECTRIC fields; ELECTRIC field strength; ORGANIC synthesis; MICROWAVE spectroscopy; SUZUKI reaction; ACTIVATED carbon; MICROWAVES
- Publication
Communications Chemistry, 2023, Vol 6, Issue 1, p1
- ISSN
2399-3669
- Publication type
Article
- DOI
10.1038/s42004-023-01062-6