This is a knowledge base on chemical synthesis using laboratory microwave reactors.
Advantages of Microwave Heating
How does microwave heating work? Which solvents can be heated with microwave irradiation? What are the advantages? This crash course introduces you to the most important and interesting topics in microwave synthesis. Learn about the basics and the advantages of this field of chemistry, gather helpful hints and read up on scientific microwave equipment.
Microwave vs. conventional heating
While conventional heating works by means of a heated surface which in turn heats the reaction vessel content (Figure 3, a), microwave irradiation provides energy-efficient internal heating by direct coupling of microwave energy with dipoles and/or ions present in the reaction mixture (Figure 3, b).
This leads to effective, so-called "in-core" heating of the reaction mixture instead of the vessel wall. This direct interaction results in extremely fast heating rates not reproducible with conventional heating.
Figure 3: Simplified temperature distribution in a reaction vessel (a) heated under conventional conditions and (b) heated via microwave irradiation.
What Microwaves provide:
- 1000-fold rate acceleration
- Less by-products
- Higher yields
- Simplified work-up
Scientific microwave reactors vs. kitchen ovens
In the early days of microwave synthesis, household microwave ovens were used in chemical laboratories. Although nowadays dedicated instrumentation is available, there are still chemists who use kitchen microwave ovens for scientific purposes. However, most major scientific journals no longer accept manuscripts wherein domestic ovens have been described as heating sources, since there are serious scientific and safety-related arguments to be made for using dedicated instrumentation.
Using dedicated microwave equipment instead of domestic kitchen microwave ovens has many scientific and practical advantages:
Possibility of convenient solvent superheating
- Higher temperatures
- Considerably reduced overall process times
- Higher yields and purer compounds
Excellent parameter control
- Improved reproducibility
- Great ease of use
Access to automated setups and parallel synthesis
- Improved process efficiency
- Time saved = costs saved
Possibility of stirring
- Improved temperature homogeneity in reaction mixtures
- Increased scientific validity of results
Continuous power output
- Sophisticated reaction control
- Safe and smooth processing
Intuitive user interface (state-of-the-art touchscreen)
- Convenient programming and data management
- Automatic data recording
Safety under high temperature/pressure conditions