What is the percent yield of carvone per gram of caraway seeds? Is the oil you...

   

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What is the percent yield of carvone per gram of caraway seeds? Is the oil you isolated pure? How do you know the answer to this question? Carvone is a member of the terpenoid family of compounds. As you can tell from the drawings below, carvone has one chiral center (and two enantiomers). Interestingly, both enantiomers of carvone can be found in nature. S-Carvone is the major component of the essential oil of caraway seeds; R-carvone is the major component in spearmint. We will isolate the carvone found in caraway seeds today and confirm its identity by using IR and NMR spectroscopy. What other instrument would you want to use to prove that you isolated carvone? (S)-carvone (R)-carvone caraway spearmint Experimental Procedure: 1. Weigh 25 g of fresh seeds and grind them in an electric blender. 2. Put the ground seeds into a 250-mL round-bottomed flask and add 100 mL of water. 3. Set up a steam distillation apparatus as illustrated by your TA and shown in the distillation section of this manual. 4. Use a 100-mL graduated cylinder for the receiver. Be sure that the stopcock is closed before pouring 80 mL of water into the dropping funnel. 5. Boil the mixture vigorously using the heating mantle but be careful not to let any solid material or foam bump over into the condenser. 6. Collect about 80 mL of distillate. During the distillation make periodic additions of 10 mL portions of water from the dropping funnel to maintain the initial liquid level in the distilling flask. 7. Distill the mixture as rapidly as the cooling capacity of the condenser will permit. 8. Pour your distillate into a 125 mL separatory funnel. 9. Add 5 g of sodium chloride and shake the mixture to dissolve the salt. Then add a few pieces of ice to make the solution distinctly cool before adding any dichloromethane. 10. Rinse the graduated cylinder with a small portion (5 mL) of dichloromethane and then add the rinse to the separatory funnel. 11. Repeat this a second time with another 5 mL portion of dichloromethane. 12. Add 50 mL of dichloromethane directly to the separatory funnel. 13. Extract the oil by shaking gently and allow the layers to separate. Place the dichloromethane in a 125 mL Erlenmeyer flask. 14. Repeat the extraction of the aqueous phase with an additional 15 mL dichloromethane. 15. Combine the organic layers. 16. Dry the organic phase by adding the appropriate amount of anhydrous Na2SO4 and allowing the flask to sit for 10 min. 17. Weigh a clean, dry 50 mL Erlenmeyer flask on an analytical balance and transfer half of your dichloromethane solution to the flask by decanting. 18. Add a boiling stone and evaporate the dichloromethane gently on a hot plate in the hood. 19. Transfer the remaining dichloromethane solution to the Erlenmeyer flask once the first half has evaporated and complete the evaporation in the hood. 20. Obtain the mass of the oil and confirm its identity by IR and NMR using dº-DMSO. 21. Your TA will help you obtain the optical activity of a sample of the oil. What is the percent yield of carvone per gram of caraway seeds? Is the oil you isolated pure? How do you know the answer to this question? Carvone is a member of the terpenoid family of compounds. As you can tell from the drawings below, carvone has one chiral center (and two enantiomers). Interestingly, both enantiomers of carvone can be found in nature. S-Carvone is the major component of the essential oil of caraway seeds; R-carvone is the major component in spearmint. We will isolate the carvone found in caraway seeds today and confirm its identity by using IR and NMR spectroscopy. What other instrument would you want to use to prove that you isolated carvone? (S)-carvone (R)-carvone caraway spearmint Experimental Procedure: 1. Weigh 25 g of fresh seeds and grind them in an electric blender. 2. Put the ground seeds into a 250-mL round-bottomed flask and add 100 mL of water. 3. Set up a steam distillation apparatus as illustrated by your TA and shown in the distillation section of this manual. 4. Use a 100-mL graduated cylinder for the receiver. Be sure that the stopcock is closed before pouring 80 mL of water into the dropping funnel. 5. Boil the mixture vigorously using the heating mantle but be careful not to let any solid material or foam bump over into the condenser. 6. Collect about 80 mL of distillate. During the distillation make periodic additions of 10 mL portions of water from the dropping funnel to maintain the initial liquid level in the distilling flask. 7. Distill the mixture as rapidly as the cooling capacity of the condenser will permit. 8. Pour your distillate into a 125 mL separatory funnel. 9. Add 5 g of sodium chloride and shake the mixture to dissolve the salt. Then add a few pieces of ice to make the solution distinctly cool before adding any dichloromethane. 10. Rinse the graduated cylinder with a small portion (5 mL) of dichloromethane and then add the rinse to the separatory funnel. 11. Repeat this a second time with another 5 mL portion of dichloromethane. 12. Add 50 mL of dichloromethane directly to the separatory funnel. 13. Extract the oil by shaking gently and allow the layers to separate. Place the dichloromethane in a 125 mL Erlenmeyer flask. 14. Repeat the extraction of the aqueous phase with an additional 15 mL dichloromethane. 15. Combine the organic layers. 16. Dry the organic phase by adding the appropriate amount of anhydrous Na2SO4 and allowing the flask to sit for 10 min. 17. Weigh a clean, dry 50 mL Erlenmeyer flask on an analytical balance and transfer half of your dichloromethane solution to the flask by decanting. 18. Add a boiling stone and evaporate the dichloromethane gently on a hot plate in the hood. 19. Transfer the remaining dichloromethane solution to the Erlenmeyer flask once the first half has evaporated and complete the evaporation in the hood. 20. Obtain the mass of the oil and confirm its identity by IR and NMR using dº-DMSO. 21. Your TA will help you obtain the optical activity of a sample of the oil.