This is a knowledge base on chemical synthesis using laboratory microwave reactors.
Instrument Types / Microwave Reactors
Scientific – so-called dedicated – microwave reactors do not look like kitchen microwave ovens at all. They have been developed especially for chemical laboratories, to serve the individual needs of chemists. Nowadays different microwave reactors are available, depending on the required scale and workflow.
Figure 9: Diagram of the microwave field distri-
Monomode reactors have small compact cavities, in which microwave irradiation is directly focused on the reaction mixture (Figure 9). Consequently, a high microwave field density is provided, resulting in exceedingly fast heating rates.
Monomode reactors are perfect tools for method development and optimization in R&D. They are optionally equipped with autosamplers, providing sequential automation for overnight processing, and with cameras for visualizing the reaction progress.
Multimode reactors for parallel synthesis
Figure 10: Diagram of the microwave field distri-
Multimode reactors have larger cavities, in which the microwave field is distributed in a chaotic manner. In common multimode reactors the waves are reflected from the cavity walls and multiple modes of the electromagnetic waves interact with the cavity load (Figure 10).
Multimode reactors for single-batch scale-up
Figure 11: Diagram of the microwave field distribution in a multimode single-batch reactor (top view)
This special kind of multimode reactor features a circular waveguide, in which various modes of the electromagnetic waves interact with the vessel content at different spots for efficient heating of larger volumes (Figure 11). A single 1 L vessel is positioned in a compact cavity, which provides optimal heating rates for large scales due to the relatively high field density (compared to common multimode microwave ovens as shown in Figure 10).
This kind of multimode reactor is used for single-batch scale-up, if amounts of up to 1 kilogram of reaction product per day are required.