Grignard arylation Lab Report Example | Topics and Well Written Essays - 750 words

Grignard arylation - Lab Report Example In this reaction, the C=O bond the ketones is attacked by the Grignard reagent to yield an alkoxide ion. The alkoxide ion formed is then protonated by H+ to form alcohol and MgBrOH (McMurry): A 50-mL round-bottomed flask containing 20 mmol of magnesium turnings and a stirbar was flame dried. A rubber stopper was affixed to the flask after it had cooled and then assembled with an addition funnel from the oven before it had cooled. Grease was applied to the glass-to-glass joints to prevent them from freezing as the parts cooled. The addition funnel was charged with a solution of phenyl bromide (20 mmol) in anhydrous ether (15 mL). 1 mL of the solution formed was then added into the flask and stirred until the reaction started. Once the reaction had begun, the rest of the phenyl bromide solution was dripped in over several minutes, at a rate that maintained a gentle reflux. Following the addition, the reaction was allowed to proceed for 20 minutes. During this period, heat was added to maintain the reflux. The Grignard reagent was allowed to cool. A solution of cyclopentanone (13 mmol) in anhydrous ether (10 mL) was added through the addition funnel while stirring. The reaction mixture was worked-up as follows: a sufficient amount of 3M HCl was added to acidify the reaction mixture. The aqueous layer that formed was extracted with CH2Cl2. While swirling, the combined organic layers were washed with 10 mL of 10% aqueous sodium bisulfite and 10 mL of brine. The organic layer was dried and the solvent obtained evaporated over a steambath. The residue obtained was stored in a shell-vial with a well-fitting cap. The workup was repeated by my partner; however, he used 20 mL of 10% aqueous NH4Cl in place of 3M HCl. In the second week of the laboratory session, the evaporation residue was transferred into a flask, after which it was vacuum distilled into a tarred flask. The product obtained was then characterized by