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ORGO II Lab Exp 12 Pre Lab
Organic Chemistry Lab II (CHEM201401)
Boston College
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ORGO II Lab Exp 12 PreLab Setting Up the Apparatus for the reaction: (CAUTION: Must use absolutely dry glassware for the reaction)
- Set the clean glassware in a 110 degree oven for 10 minutes or more before assembling the apparatus.
- Set up the apparatus as shown on the diagram on the In-Lab page.
- Mark the separatory funnel with two lines - one at the 9 mL volume and one at the 24 mL volume.
- Insert a calcium chloride drying tube into the top of the condenser to help keep moisture out of the apparatus.
- Allow the set-up to cool to room temp before proceeding with the experiment.
Synthesis of the Grignard reagent from bromobenzene: (CAUTION: Diethyl ether is extremely flammable. Make sure to only use in a fume hood and keep away from fire and heat sources. 1,2-dibromomethane is TOXIC) 1. Set up an ice bath to use to cool the reaction if it becomes too vigorous. 2. Attach a ring clamp to a bar in the fume hood. 3. Weigh 2 grams of magnesium turnings on weighing paper. 4. Place the 2 grams in a 100 mL round bottom flask. 5. Pour the bromobenzene into the separatory funnel first, and fill it up to the first mark at 9 mL. 6. Pour the anhydrous diethyl ether directly from the can (not bottle) into the separatory funnel, and fill it up to the second mark at 24 mL. 7. Swirl to mix the mixture. 8. Immediately stopper the funnel and set it on the Claisen adapter as shown in the figure. 9. Begin running water through the condenser. 10. Remove the stopper from the sep funnel. 11. By opening the stopcock, add the ether and bromobenzene mix to the reaction flask all at once. 12. Close the stopcock and pour the ether from the can into the sep funnel up to the 24 mL mark. a. DO NOT ass it to the reaction flask yet. b. Watch for signs of reaction such as cloudiness or bubbles on the surface of the metal. c. If the reaction does not begin immediately, move the sep funnel to the ring clamp, insert a dry stirring rod into the flask, and scratch the surface of the metal under the liquid. d. Be VERY careful not to punch a hole in the bottom of the flask! 13. Place your hand around the base of the flask to keep it warm. a. If the reaction still has not begun after scratching the metal for several minutes, add one to two frops of 1,2-dibromomethane. b. If the reaction fails to occur, inform your instructor. Make sure that the unreacted products are NOT place in Lab Byproducts Jar as it ca cause an explosive reaction.
- Once you are sure the reaction has occurred, open the stopcock and slowly add the 24 mL of ether. a. DO NOT ADD ETHER until the reaction is bubbling intensely.
- Use the ice bath if the reaction is extremely vigorous, but make sure to not overcool the mixture as the reaction will stop.
- Once the reaction begins, it should boil without external heat.
- When boiling has ended, heat the flask with a VERY low steam bath to gently reflux the mixture for ten minutes.
- Continue with the next section immediately.
Reaction of the Grignard reagent with methy benzoate: 1. Pour the diethyl ether from the can into the sep funnel until the meniscus is about half-way between the two marks (approx. 15 mL). 2. Measure 4 mL (5 grams) of methyl benzoate in a graduated cylinder and add it to the ether in the sep funnel. 3. Open the stopcock very slowly to add this solution dropwise to the reaction mixture. 4. When the addition is complete, swirl the flask until it is at room temperature. 5. Remove the Claisen adapter and sep funnel. 6. Place the condenser with the drying tue directly on the round bottom flask (be sure the connection is tight). 7. Reflux the reaction over low steam for 30 minutes.
Hydrosis of the magnesium alkoxide followed by isolation and purification of the product: 1. Pour 40 mL of 1 M sulfuric acid into a 250 mL Erlenmeyer flask. 2. Add about 25 grams of ice. 3. Pour the reaction mixture into this flask, then use small amounts of sulfuric acid and ether (from bottle not can) to rinse out the round bottom flask. 4. Swirl the flask thoroughly until the hydrolysis is complete (when bubbling has stopped and the solids dissolved). 5. Pour the mixture into a sep funnel (rinse the flask with small amounts of ether). a. More ether may be added if the volume of the organic layer is low. 6. Shake the funnel and vent periodically. 7. Drain and discard the lower aqueous layer. 8. Add more of the 1 M sulfuric acid to the sep funnel to wash the ether layer. 9. Wash the ether layer with saturdated sodium chloride solution. 10. Use approximately ⅓ of the volume of the ether layer in the wash liquid for all the washes in the sep funnel. 11. Pour the ether layer out of the top of the sep funnel into an Erlenmeyer flask. 12. Dry it with about 5 grams of granular anhydrous sodium sulfate. 13. Swirl the flask from time to time for 5 minutes. 14. Filter off the drying agent by gravity filtration through filter paper held in a funnel, and collect filtrate in an Erlenmeyer flask. 15. Rinse the drying agent with a small amount of ether.
ORGO II Lab Exp 12 Pre Lab
Course: Organic Chemistry Lab II (CHEM201401)
University: Boston College
