Experimental Procedure Place the following in a chemglass microwave reaction ves

Question

Experimental Procedure Place the following in a chemglass microwave reaction vessel containing a stir bar. phenylboronic acid (366 mg); polassium carbonate (1 244 4 b om et phenone (597 ng): 5% palladium (18 ng), TBAB (967mg) and water (60 mL) Seal the read on vessel with a cap, tighten the cap with the torque wrench and then place the vessel into carousel, noting the number where you place your vessel. The carousel is placed in the MARSX microwave and the unit is program to heat the mixture to 160°C over a 5 minutes period and hold for 5 minutes at this temperature. After the reaction is complete and the vessel has cooled to below 50°C, remove the carousel from the microwave and then remove your vessel. Place the vessel in ice bath, then collect the product by vacuum filtration, making sure you scrape solids remaining in the vessel and add to the product. You may rinse the vessel with a small amount of water to get all the solids out of the vessel. Dissolve the collected solid in -20 mL ethyl acetate in 50-ml Erlenmeyer flask and remove the Pd/C by gravity filtration (collect the fltrate in a dry 50-mL Erlenmeyer flask). Transfer the filtrate into separatory funnel and wash with saturated NaCl solution. Separate the organic layer and dry with MgSO4. Filter or decant the mixture into a clean dry 25 mL round bottom flask and remove the ethyl acetate using a Rolavapor. The crystalline product is removed from the flask, weighed and placed in a labeled vial. Calculate the percentage yield and the atom economy Take appropriate physical measurements (mp, IR, H, SC NMR spectra) to ascertain the purity of your compound comparing with lterature data where possible. % Atom Economy # (Mol. wt. of Product/ (Mol wt. of Re ctant s))" 100 Clean-Up nisnose of all waste into the annmnniatelv marked

Explanation / Answer

The given reaction is a coupling between phenylboronic acid and 4-bromoacetophenone with the other reagents either being a solvent (water) or catalysts or oxidants to re-activate the catalysts used.

Limiting reagent is defined as the reactant species with the least no.of moles whose concentration thus affects the overall reaction. Thus the moles of product will be equal to the moles of the limiting reagent as upon its consumption, the reaction ceases to proceed.

From the molar mass of phenylboronic acid (121.93 g/mol) and that of 4-bromoacetophenone (199.047 g/mol) the no.of moles of them are given as 1.244/121.93 = 10.2025mmoles and 0.597/199.047 = 2.9993mmoles. Thus 4-bromoacetophenone is the limiting reagent.

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