Determine the percent yield of triphenylmethanol. Explain the role of iodine in

Question

Determine the percent yield of triphenylmethanol. Explain the role of iodine in the preparation of phenylmagnesium bromide. Why does some magnesium remain unreacted at the end of the preparation of the Grignard reagent? write balanced equations to show what happens to excess magnesium metal after preparation of phenylmagnesium bromide. All glassware must be dried prior to starting this experiment. Glassware can be dried in an oven at 110 degree C for at least 1 hour prior to use. Do not put plastic parts in the oven. Dry a 10-mL round-bottom flask, two 3-mL conical vials, a jacketed condenser, a drying tube, and a Claisen adapter. A heat gun may be used instead to heat glassware. Allow the ware to cool to room temperature. Weigh 192 mg of magnesium turnings and place the turnings and a crystal of iodine in a dry 10-mL round bottom flask containing a spin bar. Immediately cap the flask until ready use. Assemble glassware as pictured. To a dry 3-ml vial, add 0.76 ml. of 2-bromopropane and 1.2 mL of anhydrous diethyl ether a opened can Cap the vial and swirl mix from freshly and add the contents. Draw this solution into a dry syringe a portion of it dropwise through the septum into the 10-mL round-bottom flask containing the magnesium and iodine. cloudiness and bubbles at the surface of the metal indicators that the reaction has

Explanation / Answer

1. Incomplete information.

2. The role of iodine is initiator of the reaction

3. The reason for this is phenyl bromide is destroyed by undergoing a coupling reaction with the Grignard reagent.

4. PhBr + Mg --> PhMgBr

Ph2C=O + PhMgBr --> Ph3COMgBr

Ph3COMgBr + H+ --> Ph3COH + Mg2+ + Br-

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