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The Grignard Synthesis II Miniscale Synthesis of Triphenylmethanol from Ethyl Benzoate, Part 2

The Grignard Synthesis II Miniscale Synthesis of Triphenylmethanol from Ethyl Benzoate, Part 2. Organic Chemistry Lab II, Spring 2010 Dr. Milkevitch April 5 & 7, 2010. Today’s Experiment. Complete last week’s experiment Grignard synthesis React the Grignard with an ester Make an alcohol.

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The Grignard Synthesis II Miniscale Synthesis of Triphenylmethanol from Ethyl Benzoate, Part 2

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  1. The Grignard Synthesis IIMiniscale Synthesis of Triphenylmethanol from Ethyl Benzoate, Part 2 Organic Chemistry Lab II, Spring 2010 Dr. Milkevitch April 5 & 7, 2010

  2. Today’s Experiment • Complete last week’s experiment • Grignard synthesis • React the Grignard with an ester • Make an alcohol

  3. Last Week • Prepared the Grignard reagent • Reacted it with ethyl benzoate • In ether • Allowed it to sit until this week • This week: • Workup • Isolation & purification • Characterization

  4. Procedure: Part 2 • Retrieve your RB flask from the hood • Take a look at it • Replace any lost volume with more ether • Remove the stir bar • Pure the reaction mixture into a 50 ml erlenmeyer flask that contains 8 g of ice • Rinse the reaction flask with ~2 ml of ether and add this rinse to the erlenmeyer with the ice • While stirring, carefully add 3M HCl dropwise to the solution • Use a glass stir rod to break up the solid • Continue to add acid until the lower layer is just acidic to litmus • Blue litmus turns red if the solution is acidic • Carefully pour the reaction mixture into your separatory funnel • Leave any unreacted magnesium in the flask

  5. Procedure, con’t • Rinse the flask with 5 ml of diethyl ether • Add this to the separatory funnel • Reaction mixture should separate into 2 layers • Product is in the upper layer (ether layer) • Separate the layers • Into separate erlenmeyer flasks 1)One will have ether layer 2)One will have the water layer • Put the water layer back into the separatory funnel • Extract the water layer with 5 ml of diethyl ether • Allow layers to separate • Drain off the water layer into an erlenmeyer flask • Drain off the ether wash, add it to the original ether wash (#1 above) • Now, put all the ether layers into the separatory funnel • Extract it with 5 ml of DI H2O

  6. Procedure, con’t • Remove the water • Store in a beaker, set aside • Transfer the ether to a clean erlenmeyer flask • Dry over magnesium sulfate ~10 min • Decant or gravity filter the dried solution • Into a pre-weighed 50 ml erlenmeyer flask • Add a stir bar/boiling chip • Evaporate off ether using a hot plate • In the hood • Should get an off-white solid • Mixture of biphenyl and triphenylmethanol • Add 10 ml of petroleum ether • Stir thoroughly • Vacuum filter with a Buchner funnel • Weigh product

  7. Characterization • Do a TLC • Plates are in the oven • Standards are in the hood • Standards: Triphenyl methanol, biphenyl • Spot these • Also spot your compound! • Develop your plate in methylene chloride • Visualize under UV light • Submit a sample for GC analysis • Dissolve a small amount of your compound in methylene chloride • Place in a small vial • Vials are in the hood • Label with your names

  8. Your Report • Formal lab report not required • Complete experiment worksheet

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