1. Using MICROWAVE REACTOR Krystyna R. Brzezinska Materials Research Laboratory

2. Microwave Collective name for electromagnetic irradiation with frequencies in the range of 0.3-300 GHz. To avoid interferences between applications - 2.45 GHz corresponding to wavelength 12.2 cm. temp: 60-250 °C, temp increase: 2-5 °C/sec Power: 0-300 W at 2.45 MHz Pressure: 0-20 bar Pressure: 0-20 bar 20 bar = 290 psi, 250 psi = 17 bar

3. Dipolar oscillationIonic conduction Mechanism of Microwave Heating Molecular Orientation = Molecular Friction = Heat

4. Temp. up to 250 o C and pressure up to 20 bars  Heat much faster than the conventional reaction. Speed Up Chemical Reaction? Vials: 0.2-0.5 ml, 0.5-2 ml, 2-5 ml, 10-20 ml

5. Polar solvents (e.g. DMF, DMSO, ROH etc.)  Heat rapidly.  Same concentration as conventional reaction. Polar solvent with high ionic content (e.g. DMF + K 2 CO 3 etc)  Heat VERY rapidly and may overshoot set temperature. Temp too high! Polar Solvents Dilute reaction mixture. Decrease initial power use: ‘Sample Absorption’ - High or Very High.

6. Less polar solvents (e.g. toluene, dioxane, THF) Less Polar Solvents Concentrate the reaction mixture - speeds workup - lower cost of ‘waste’ solvent removal  Heat poorly Add polar co-solvent Increase ionic concentration

7. 4.5 mL Toluene 4.0 Toluene + 0.5 mL DMF Set temp: 200 °C Solvent polarity Effect of a co-solvent

8. Reaction rate? Arrhenius Equation: K = A e –G/RT Reaction rate ~ doubles for every 10 o C temperature increase

9. Using the 10 o Rule to determine a starting point K = A e –G/RT

10. Prepare Three Vials 160 o C 5 min 140 o C 5 min 180 o C 5 min First Choice

11. Temperatures and pressures measured* with some common organic solvents _______________________________________________________________________________________________ Solvent BPTemp Pressure** (°C)(°C)(bar) _______________________________________________________________________________________________ N,N-Dimethylformamide (DMF) 153250 5 Water 100220 16 Ethanol 7818016 Methanol 6516017 N-Methylpyrrolidinone (NMP) 202220 5 Ammonium hydroxide (28%) -150 19 Dimethylsulfoxide (DMSO) 1892505 Pyridine1152208 1,2-Dimethoxyethane (DME) 85200 6 Dichloromethane 4014015 Acetonitrile 86200 10 o-Dichlorobenzene 190250 2 1,4-Dioxane 101200 4 Acetone 56150 5 Tetrahydrofuran (THF) 65- 67 180 12 Xylene 137-138150 2 1,2-Dichloroethane 831702 Toluene1101704 Diethyl ether351354 *This is a general table with data generated under various reaction conditions. The actual temperature and pressure achieved with a given solvent might differ significantly using different reaction conditions and compositions. Red indicates good microwave absorption, while Blue indicates less good **Volume = 2.5 mL

12. Increase temp. (limit is pressure buil-up in the vial and security max = 250 o C). Extend reaction time. Increase initial power ‘Sample Absorption’ – Normal, High or Very High Increase concentration. Use more polar solvent (water at high temp become less polar). Add polar co-solvent Reaction is not proceeding at all or not going to completion:

13. Lower temperature. Increase initial power ‘Sample Absorption’ – Normal, High or Very High Shorten reaction time. Product is actually formed, but then decomposes rapidly at elevated temperatures. Decrease concentration. Change reagents. Decomposition:

14. Please contact Krystyna (kbrzez@mrl.ucsb.edu)kbrzez@mrl.ucsb.edu -------------------------------------------------------------------------- Login: Faces Scheduling System Group: MRLPOLY User name: kkk@ Password: system will generate for you Account: please send request to Krystyna by E-MAIL ---------------------------------------------------------------------------- Go to: http://microwave.mrl.ucsb.edu/ http://microwave.mrl.ucsb.edu/ Instrument options: status, results, online help, print etc from your office Please clean memory of the Microwave R. Questions?