Procedure for Microwave Option

Preparation Sign in at www.cengage.com/login to answer Pre-Lab Exercises, access videos, and read the MSDSs for the chemicals used or produced in this procedure. Review Sections 2.9, 2.10, and 2.17. 

Apparatus A 10-mL pressure-rated tube with cap. stirbar, apparatus for microwave heating with magnetic stirring and vacuum filtration, ice-water bath. 

Setting Up Equip the 10-mL pressure-rated tube with the stirbar and add 0.40 g of meso-stilbene dibromide, about 0.2 g (two pellets) of solid potassium hydroxide, and 2 mL of methanol. Cap the pressure-rated tube and gently shake it or place it on a magnetic stirrer to facilitate initial mixing of its contents. Place the tube in the cavity of the microwave apparatus. 

Dehydrobromination and Isolation Program the unit to heat the reaction mixture with stirring according to the directions provided by your instructor. Generally, the reaction temperature should be set at 150 C and the power set at a maximum of 25 W with a 1-min ramp time and a 5-min hold time the pressure limit should be set at 275 psi. Allow the mixture to cool to room temperature and remove the tube from the microwave apparatus. Add 5 mL of water and place the tube in an ice-water bath for 5 min. Collect the diphenylacetylene that precipitates by vacuum filtration. Wash the solid with about 2 mL of cold water. Recrystallize the product from a small quantity of 95% ethanol or an ethanol-water mixture. If the solution is allowed to cool slowly undisturbed, you should obtain large, sparlike, colorless crystals. 

Analysis Determine the melting point, weight, and percent yield of the recrystallized product. Test the product for unsaturation using the bromine and Baeyer tests (Secs. 25.8A and B, respectively). Obtain IR and NMR spectra of your starting material and product and compare them with those of authentic samples (Figs. 10.36, 10.37, 11.1, and 11.2). 

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Microwave-assisted digestion procedures are used for total metal analysis in aqueous samples (EPA Method 3015) and for solid or oily samples (EPA Method 3051). These procedures allow for a rapid sample digestion with nitric acid under high pressure and temperature conditions the addition of hydrochloric acid is optional. Samples... 

Combination therapy The use of local-interventional procedures is restricted to a maximum tumour size of 5 cm in diameter. Therefore, a combination of two local techniques is seen as promising. The joint application of PEI and TAB has proved its efficacy for some time. (177) Similarly, there have been reports about the successful use of TACE following laser thermal ablation. (136) Further encouraging options include a combination of TACE and RFTA, TACE with microwave coagulation (149) or TACE with cryotherapy. Using TACE, the size of the HCC can be reduced in some cases, making it possible to carry out subsequent ablation with better results. 

Not aU the available methods extract the mercury species from solid samples (soil, sediment or biological material) with acceptable efficiency. The procedure giving the best recovery for methyl mercury from soil (95 4%) is the distillation method, and from fish tissue it is alkaline digestion using tetramethylammonium hydroxide with focused microwave power (95 to 105%). There is no standardized method to assess the extraction efficiency of a particular method, but several options are described in the subchapter on extraction efficiencies. 

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