REACTIONRECRYSTALLIZATION (OPTIONAL)1. Begin assembling your reflux apparatus (i.e. lab jack, stir plate, exten-sion clamp and round-bottom flask of appropriate size).10. Weigh your crude solid to calculate an approximate crude yield. Transfer most of it to a 125 mL erlenmeyer,but keep some aside (~100 mg) for analysis at the end.2. Add para-aminophenol (15.0 mmol), demineralized water ([para-aminophenol] = 0.75 M) and a stirbar to the flask. Set to stir vigorously.11. Recrystallize your solid by boiling in an erlenmeyer in a minimal volume of demineralized water (~8 mL/gramof crude solid) on a hot plate to fully dissolve it. If necessary, slowly add water portion-wise until ahomogeneous solution is obtained.3. Measure the required volume of acetic anhydride (1.30 eq.) in a smallgraduated cylinder. Using a platic pipette, add it to the reaction flask.4. Finish the assembly of the reflux apparatus (i.e. secured water con-denser along with tubing, heating mantle and Variac).12. Cool the homogeneous solution to room temperature for approximately 5 minutes, then transfer to anice-bath for approximately 10 minutes to further precipitate the product. While you are waiting, prepare avacuum-filtration setup and clean your Büchner funnel.5. Bring the reaction to a boil. Once the solid in the flask has completelydissolved, allow the reflux to proceed for an additional 15 minutes.13. Vacuum-filter the recrystallized solid, and wash abundantly with demineralized water. Pump the solid dry forabout a minute using the hand pump.6. Stop the heating: substitute the heating mantle for an ice bath to rapidlycool down the mixture for about 10 minutes and precipitate the product.ANALYSIS14. Prepare a drying-apparatus that uses the water aspirator on the bench. Transfer the Büchner with your solid(crude or recrystallized) to this setup. Dry the solid for approximately 10 minutes. Break the solid clumpsapart every now and then with a spatula to accelerate the drying process.WORK-UP7. While you are waiting for the cooling (step 6) to be over:Perform a TLC analysis on your crude reaction mixture.Assemble a vacuum filtration apparatus in your fumehood.15. Weigh the dried solid so as to calculate a reaction yield for your report.16. Demonstrate the identity and purity of your acetaminophen product (crude and purified, if you were able torecrystallize it) using:TLC: Dissolve a small amount (~10 mg; the tip of a spatula) in a small volume of ethyl acetate (~1-2 mL)in a test tube before spotting on your plate and eluting.Melting point analysis: Pure acetaminophen melts at 169 °C. Pack a small amount (~ 2 mm of height)of solid in a melting point capillary, and record a melting point using the appropriate apparatus. Heatrapidly at first, but slow down when you get near (~20° below) the target melting point to obtain a moreaccurate measurement.8. Copious amounts of solid should now have precipitated from the coldmixture: filter it using your filtration apparatus, and rinse it abundantlywith demineralized water. Pump it dry for about a minute using the handpump.9. Ifyou have sufficient time left (about ~60–75 minutes), proceed to re-crystallize your solid for bonus points. Otherwise, skip to step 14.8)Assuming an initially impure sample of acetaminophen, would you expect its melting pointto change upon a successful recrystallization? If so, how so? Otherwise, why not?

Recrystallization is a process use to purify the impure product by dissolving in appropriate…

RECRYSTAI PTIONAL 1. Begin assembling your reflux apparatus (i.e. lab jack, stir plate, exten- sion clamp and round-bottom flask of appropriate size). 10. Weigh your crude solid to calculate an approximate crude yield. Transfer most of it to a 125 mL erlenmeyer, but keep some aside (~100 mg) for analysis at the end. 2. Add para-aminophenol (15.0 mmol), demineralized water ([para- aminophenol] = 0.75 M) and a stirbar to the flask. Set to stir vigorously. 11. Recrystalllize your solid by boiling in an erlenmeyer in a minimal volume of demineralized water (~8 mL/gram of crude solid) on a hot plate to fully dissolve it. If necessary, slowly add water portion-wise until a homogeneous solution is obtained. 3. Measure the required volume of acetic anhydride (1.30 eq.) in a small graduated cylinder. Using a platic pipette, add it to the reaction flask. 1. Finish the assembly of the reflux apparatus (i.e. secured water con- denser along with tubing, heating mantle and Variac). 12. Cool the homogeneous solution to room temperature for approximately 5 minutes, then transfer to an ice-bath for approximately 10 minutes to further precipitate the product. While you are waiting, prepare a vacuum-filtration setup and clean your Büchner funnel. 5. Bring the reaction to a boil. Once the solid in the flask has completely dissolved, allow the reflux to proceed for an additional 15 minutes. 13. Vacuum-filter the recrystallized solid, and wash abundantly with demineralized water. Pump the solid dry for about a minute using the hand pump. S. Stop the heating: substitute the heating mantle for an ice bath to rapidly cool down the mixture for about 10 minutes and precipitate the producí. ANALYSIS 14. Prepare a drying-apparatus that uses the water aspirator on the bench. Transfer the Büchner with your solid (crude or recrystallized) to this setup. Dry the solid for approximately 10 minutes. Break the solíd clumps apart every now and then with a spatula to accelerate the drying process. WORK-UP . While you are waiting for the cooling (step 6) to be over: Perform a TLC analysis on your crude reaction mixture. Assemble a vacuum filtration apparatus in your fumehood. 15. Weigh the dried solid so as to calculate a reaction yield for your report. 16. Demonstrate the identity and purity of your acetaminophen product (crude and purified, if you were able to recrystallize it) using: TLC: Dissolve a small amount (~10 mg; the tip of a spatula) in a small volume of ethyl acetate (~1-2 mL) in a test tube before spotting on your plate and eluting. Melting point analysis: Pure acetaminophen melts at 169 °C. Pack a small amount (~ 2 mm of height) of solid in a melting point capillary, and record a melting point using the appropriate apparatus. Heat rapidly at first, but slow down when you get near (~20° below) the target melting point to obtain a more accurate measurement. 3. Copious amounts of solid should now have precipitated from the cold mixture: filter it using your filtration apparatus, and rinse it abundantly with demineralized water. Pump it dry for about a minute using the hand pump. you have sufficient time left (abou crystallize your solid for bonus points. Otherwise, skip to step 14. -60–75 minutes), proceed re- 8) Assuming an initially impure sample of acetaminophen, would you expect its melting point to change upon a successful recrystallization? If so, how so? Otherwise, why not?

RECRYSTAI PTIONAL 1. Begin assembling your reflux apparatus (i.e. lab jack, stir plate, exten- sion clamp and round-bottom flask of appropriate size). 10. Weigh your crude solid to calculate an approximate crude yield. Transfer most of it to a 125 mL erlenmeyer, but keep some aside (~100 mg) for analysis at the end. 2. Add para-aminophenol (15.0 mmol), demineralized water ([para- aminophenol] = 0.75 M) and a stirbar to the flask. Set to stir vigorously. 11. Recrystalllize your solid by boiling in an erlenmeyer in a minimal volume of demineralized water (~8 mL/gram of crude solid) on a hot plate to fully dissolve it. If necessary, slowly add water portion-wise until a homogeneous solution is obtained. 3. Measure the required volume of acetic anhydride (1.30 eq.) in a small graduated cylinder. Using a platic pipette, add it to the reaction flask. 1. Finish the assembly of the reflux apparatus (i.e. secured water con- denser along with tubing, heating mantle and Variac). 12. Cool the homogeneous solution to room temperature for approximately 5 minutes, then transfer to an ice-bath for approximately 10 minutes to further precipitate the product. While you are waiting, prepare a vacuum-filtration setup and clean your Büchner funnel. 5. Bring the reaction to a boil. Once the solid in the flask has completely dissolved, allow the reflux to proceed for an additional 15 minutes. 13. Vacuum-filter the recrystallized solid, and wash abundantly with demineralized water. Pump the solid dry for about a minute using the hand pump. S. Stop the heating: substitute the heating mantle for an ice bath to rapidly cool down the mixture for about 10 minutes and precipitate the producí. ANALYSIS 14. Prepare a drying-apparatus that uses the water aspirator on the bench. Transfer the Büchner with your solid (crude or recrystallized) to this setup. Dry the solid for approximately 10 minutes. Break the solíd clumps apart every now and then with a spatula to accelerate the drying process. WORK-UP . While you are waiting for the cooling (step 6) to be over: Perform a TLC analysis on your crude reaction mixture. Assemble a vacuum filtration apparatus in your fumehood. 15. Weigh the dried solid so as to calculate a reaction yield for your report. 16. Demonstrate the identity and purity of your acetaminophen product (crude and purified, if you were able to recrystallize it) using: TLC: Dissolve a small amount (~10 mg; the tip of a spatula) in a small volume of ethyl acetate (~1-2 mL) in a test tube before spotting on your plate and eluting. Melting point analysis: Pure acetaminophen melts at 169 °C. Pack a small amount (~ 2 mm of height) of solid in a melting point capillary, and record a melting point using the appropriate apparatus. Heat rapidly at first, but slow down when you get near (~20° below) the target melting point to obtain a more accurate measurement. 3. Copious amounts of solid should now have precipitated from the cold mixture: filter it using your filtration apparatus, and rinse it abundantly with demineralized water. Pump it dry for about a minute using the hand pump. you have sufficient time left (abou crystallize your solid for bonus points. Otherwise, skip to step 14. -60–75 minutes), proceed re- 8) Assuming an initially impure sample of acetaminophen, would you expect its melting point to change upon a successful recrystallization? If so, how so? Otherwise, why not?

EBK A SMALL SCALE APPROACH TO ORGANIC L

4th Edition

ISBN:9781305446021

Author:Lampman

Publisher:Lampman

Chapter80: Crystallization: Purification Of Solids

Section: Chapter Questions

Problem 4P

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