Experiment 10_ Grignard Reaction with a Ketone_ Triphenylmethanol

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Texas Tech University *

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3306

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Chemistry

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Feb 20, 2024

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November 9.2023. TA: Amin Sk Experiment 10: Grignard Reaction with a Ketone: Triphenylmethanol Purpose: The main purpose is to investigate the reaction of Grignard reagents with ketones to form tertiary alcohols. Reactions and Physical Properties Table: Safety: Diethyl Ether - Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion,of inhalation. Slightly hazardous in case of skin contact (permeator) Benzophenone - Hazardous in case of skin contact (irritant, sensitizer), of eye contact (irritant), of ingestion, of inhalation Procedure: Reaction 1. Rinse a 3 mL conical vial and a Claisen head with acetone.

2. Dry them with paper towel or condensed air. 3. Equip the conical vial containing a magnetic spin vane with the Claisen head protected by calcium chloride drying tube and a septum-cap (see page 265). 4. Ang will dispense 1.5 eq of PhMgCl (0.44 mL) to your reaction vial. 5. Secure the assembly with clamp on a hot plate. 6. Prepare benzophenone solution. 7. To a clean, dry shell vial, add 0.105 g of benzophenone and 0.3 mL of ether. Cap the vial. 8. Draw the benzophenone solution into a syringe (with needle), and then insert the syringe needle through the rubber septum on the Claisen head. 9. To the empty shell vial, place 0.3 mL of ether, cap it and set it aside for step 11. Note: Don’t add benzophenone solution before PhMgCl. 10. Carefully, with stirring, add all the benzophenone solution to the reaction vial over a period of approximately 30 seconds. 11. Draw all the rinse (as indicated in step 8) into a syringe (with needle), and then add all the rinse into the reaction vial through the septum, in a single portion. 12. Stir the reaction mixture for 2-3 minutes and then allow it to cool to room temperature. 13. Remove the reaction vial from the Claisen head.

14. Cap it and place it in a small beaker. Isolation 15. Add 3 drops of ether to the reaction vial. 16. Place the reaction in an ice bath. Hydrolyze the product by carefully, drop-wise adding 5 drops of 3M HCl. 17. Continue the addition until the bottom aqueous phase tests acidic with pH paper. 18. A two-layer reaction mixture forms as the solid gradually dissolves. 19. Remove the spin vane; rinse it with 0.5 mL of ether in a shell vial. 20. Transfer the rinse to the 3 mL conical vial. 21. Cap the 3 mL reaction vial tightly, shake, carefully vent, and allow the layers to separate. 22. Transfer the bottom aqueous layer to a clean 5 mL conical vial. 23. In the 5 mL conical vial, wash the aqueous layer with three 0.5 mL portions of ether. 24. For each portion, cap the vial, shake, vent and allow the layers to separate. 25. After each extraction, transfer the top organic layer to the 3 mL conical vial. 26. In the 3 mL conical vial, extract the combined organic layer with two portions of 0.5 mL of cold water.

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27. Transfer each bottom aqueous layer to a 10 mL Erlenmeyer flask. 28. Dry the combined organic layer in the 3 mL conical vial 29. Evaporate ether away DATA/ OBSERVATION:

• Solution turned dark purple after the addition of benzophenone • Solid residue forms CALCULATIONS/ RESULTS: Shell vial: 4.114 g Shell vial with organic: 4.168 g Weight of product: 0.054 g Theoretical yield: 0.15 g .105 g benzophenone x til mol/ 182.21 g benzophenone) x til mol benzophenone/ 1 mol tripheny|methanol) × ti260.33 g/ 1 mol triphenylmethanol)= Percent yield: ti0.054 g/ 0.15 g) × 100% = 36% Melting point: 140-145 °C CONCLUSION/ DISCUSSION: The primary goal of this experiment is to learn more about how Grignard reagents react with ketones to produce tertiary alcohols. Because we were able to observe the Grignard reagents with ketones reaction occurring, our lab experiment was successful. In this laboratory experiment, we saw that the addition of benzophenone caused the reaction to turn purple. We then had to wait for

the reaction to settle and become solid. We used HCI to dissolve the solid residue after it formed. After completing multiple extractions to get our finished product, we ran an infrared spectrum. Post-Lab Questions

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