Tetraphenylcyclopentadienone Synthesis Essay
CHEM 3125 Experiment 4: Multistep synthesis of tetraphenylcyclopentadienone
Overall Synthesis:
CHEMICALS: wk 1: thiamine hydrochloride (1 g/student), 95% ethanol (8 mls/ student), 2M NaOH (5 mls/student), benzaldehyde (4 mls/student) wk 2: 95% ethanol (30 mls/student) wk 3: acetic acid (6 mls/student), ammonium nitrate (1 g/student), 0.1g/ml cupric acetate (1.5 mls/student), dichloromethane (6 mls/ student), 30% acetone in heptanes (3 mls/student), 95% ethanol (20 mls/student) wk 4: 1,3 diphenylacetone (0.5 g/student), triethylene glycol (5 mls/student), 40% benzyltrimethylammonium hydroxide/methanol (0.5 mls/student)
Part A: Thiamine catalyzed condensation benzoin condensation of benzaldehyde
Procedure:
(Week 1)
Dissolve …show more content…
1.0 g of thiamine hydrochloride in 2.0 mL of DI water in a 50-mL RB flask. Add 8 mL of 95% ethanol and a stir bar and begin stirring. Once the mixture is homogeneous, add 5 mL of 2.0 M NaOH dropwise* (plastic or Pasteur pipette) over ~ 2 minutes. Note any color changes during and after the addition of NaOH.
* If fresh benzaldehyde is used, may be able to reduce base. If no product has formed after 1-2 days, add additional NaOH ~1-2 mL.
Once the solution is a pale yellow, add 4.0 mL of benzaldehyde and stir until the mixture is homogeneous.
Cap and store the flask until the next lab period (the reaction requires a few days at room temperature).
(Week 2)
Move the flask to an ice water bath to crystallize the product. Also chill ~10 mL of DI water in the bath. If necessary, use a glass stirring rod to scratch the bottom of the flask to induce crystallization. Once crystallization has started, allow the flask to remain in the cooling bath for 5 minutes. Isolate the crystals by vacuum filtration and rinse the solids with the chilled DI water (2 x ~2 mL).
Allow the product to air dry in the funnel for ~5 minutes and transfer the crystals to a pre-weighed watch glass. Obtain a mass of the moist, crude product and recrystallize from 95% ethanol (~ 8.0 mL for each gram of crude product). After all the solids have dissolved, allow the flask to cool to room temperature. If necessary, scratch the bottom of the flask with a glass stirring rod to induce crystallization. Once crystals have started forming, cool in an ice/water bath for 10 min to complete the process. Isolate the crystals and transfer to a watchglass to dry in your drawer.
Determine the mass and mp of the product and obtain an IR spectrum for your report.
Part B: Copper-catalyzed oxidation of benzoin to benzil
Procedure:
(Week 3)
Add a stir bar, 6.0 mL of acetic acid, 1.0 g of NH4NO3, 2.0 g of benzoin, and 1.5 mL of 0.1 gm/mL Cu(OAc)2 solution to a 50 mL RB flask. Attach a condenser and begin heating the mixture at reflux.
Monitor the progress of the reaction by thin layer chromatography (TLC) at 30 min, 45 min, and 60 min (See pp 221- in Schatz).
Prepare a TLC chamber by cutting a large circle of filter paper in half and placing it in a beaker. Add ~ 6 mL of methylene chloride (or 30% acetone in heptanes-needs to be fresh, otherwise acetone will evaporate) and cover the beaker with a watchglass. For each TLC run, you will need a silica gel plate and two clean capillary tubes for spotting the plate.
Draw a horizontal line near the bottom of each TLC plate (the line must be higher than the level of solvent in the TLC chamber). Draw three dots distributed along the line, (1 = benzoin, 2 = benzoin + reaction mixture, 3 = reaction mixture). Use a capillary tube to draw up a stock solution of benzoin and touch the capillary tube to the plate on the first two dots to spot the plate.
After 30 min at reflux, remove the heating mantle from the RB flask so that the reaction stops boiling. Disconnect the condenser and draw up some of the reaction mixture in a fresh capillary. Reattach the condenser and spot the second and third dots on the plate. Resume heating at reflux and carefully place the plate into the TLC chamber. Place a watch glass on top to prevent evaporation of the methylene …show more content…
chloride.
When the solvent front is close to the top of the plate, remove the TLC plate with tweezers and mark the line of the solvent front with a pencil. View the TLC plate under the UV lamp and circle any spots, noting the relative amounts of benzoin and benzil. Finally, tape the TLC plate into your lab notebook (and/or take a pic with smartphone).
At this point the reaction mixture turns solids upon cooling, might add a few drops of reaction mixture to ethanol and spot that on the plate.
Repeat the TLC procedure above at 45 min. If there is no more benzoin in the reaction mixture, allow the reaction mixture to cool to room temperature. If not, continue heating for another 15 min and run another TLC. Even if there is some starting material left at this point, discontinue heating and allow the reaction mixture to cool to room temperature.
Use a magnetic stick to remove the stirbar and pour the reaction mixture into 40 mL of DI water. Stir vigorously with a glass stirring rod to induce crystallization and break up any lumps of solid that form. Isolate the crystals by vacuum filtration, washing a couple times with ~10-20 mL of DI water. Let the vacuum pull air through the funnel for ~5-10 min to help dry the solids and obtain a mass of the crude benzil. Recrystallize the benzil from 95% ethanol (roughly 8 mL per gram of solid).
After isolating the crystals, allow them to dry on a watchglass for a couple days.
Determine the mass and mp of the recrystallized benzil and obtain an IR spectrum.
Part C: Base-catalyzed aldol condensation of benzil and 1,3-diphenylacetone
(Week 4)
Add 0.50 g of 1,3-diphenylacetone, 0.50 g of benzil and 5 mL of triethylene glycol to a 50 mL round bottom flask. Add a stir bar and heat the mixture at setting 4-5 on heating manual for ~ 10-15 min (will not reflux boiling point too high). The benzil should dissolve during this time. Remove the heating mantle and add ~0.5 mL of a 40% benzyltrimethylammonium hydroxide/methanol solution to the hot reaction with constant stirring.
Allow the reaction to cool to room temperature. As the solution cools dark-colored crystals should appear. Cooling may be accelerated by placing the flask under a stream of cold water (Note: you are NOT adding any water to the inside of the flask). Add 10 mL of cold methanol with stirring and cool the resulting mixture in an ice bath for 5-10 min. Collect the product by vacuum filtration and wash the crystals with a little cold methanol. Allow the crystals to dry on a watchglass for a couple days.
Determine the mass and mp of the
product.
Overall Synthesis:
CHEMICALS: wk 1: thiamine hydrochloride (1 g/student), 95% ethanol (8 mls/ student), 2M NaOH (5 mls/student), benzaldehyde (4 mls/student) wk 2: 95% ethanol (30 mls/student) wk 3: acetic acid (6 mls/student), ammonium nitrate (1 g/student), 0.1g/ml cupric acetate (1.5 mls/student), dichloromethane (6 mls/ student), 30% acetone in heptanes (3 mls/student), 95% ethanol (20 mls/student) wk 4: 1,3 diphenylacetone (0.5 g/student), triethylene glycol (5 mls/student), 40% benzyltrimethylammonium hydroxide/methanol (0.5 mls/student)
Part A: Thiamine catalyzed condensation benzoin condensation of benzaldehyde
Procedure:
(Week 1)
Dissolve …show more content…
1.0 g of thiamine hydrochloride in 2.0 mL of DI water in a 50-mL RB flask. Add 8 mL of 95% ethanol and a stir bar and begin stirring. Once the mixture is homogeneous, add 5 mL of 2.0 M NaOH dropwise* (plastic or Pasteur pipette) over ~ 2 minutes. Note any color changes during and after the addition of NaOH.
* If fresh benzaldehyde is used, may be able to reduce base. If no product has formed after 1-2 days, add additional NaOH ~1-2 mL.
Once the solution is a pale yellow, add 4.0 mL of benzaldehyde and stir until the mixture is homogeneous.
Cap and store the flask until the next lab period (the reaction requires a few days at room temperature).
(Week 2)
Move the flask to an ice water bath to crystallize the product. Also chill ~10 mL of DI water in the bath. If necessary, use a glass stirring rod to scratch the bottom of the flask to induce crystallization. Once crystallization has started, allow the flask to remain in the cooling bath for 5 minutes. Isolate the crystals by vacuum filtration and rinse the solids with the chilled DI water (2 x ~2 mL).
Allow the product to air dry in the funnel for ~5 minutes and transfer the crystals to a pre-weighed watch glass. Obtain a mass of the moist, crude product and recrystallize from 95% ethanol (~ 8.0 mL for each gram of crude product). After all the solids have dissolved, allow the flask to cool to room temperature. If necessary, scratch the bottom of the flask with a glass stirring rod to induce crystallization. Once crystals have started forming, cool in an ice/water bath for 10 min to complete the process. Isolate the crystals and transfer to a watchglass to dry in your drawer.
Determine the mass and mp of the product and obtain an IR spectrum for your report.
Part B: Copper-catalyzed oxidation of benzoin to benzil
Procedure:
(Week 3)
Add a stir bar, 6.0 mL of acetic acid, 1.0 g of NH4NO3, 2.0 g of benzoin, and 1.5 mL of 0.1 gm/mL Cu(OAc)2 solution to a 50 mL RB flask. Attach a condenser and begin heating the mixture at reflux.
Monitor the progress of the reaction by thin layer chromatography (TLC) at 30 min, 45 min, and 60 min (See pp 221- in Schatz).
Prepare a TLC chamber by cutting a large circle of filter paper in half and placing it in a beaker. Add ~ 6 mL of methylene chloride (or 30% acetone in heptanes-needs to be fresh, otherwise acetone will evaporate) and cover the beaker with a watchglass. For each TLC run, you will need a silica gel plate and two clean capillary tubes for spotting the plate.
Draw a horizontal line near the bottom of each TLC plate (the line must be higher than the level of solvent in the TLC chamber). Draw three dots distributed along the line, (1 = benzoin, 2 = benzoin + reaction mixture, 3 = reaction mixture). Use a capillary tube to draw up a stock solution of benzoin and touch the capillary tube to the plate on the first two dots to spot the plate.
After 30 min at reflux, remove the heating mantle from the RB flask so that the reaction stops boiling. Disconnect the condenser and draw up some of the reaction mixture in a fresh capillary. Reattach the condenser and spot the second and third dots on the plate. Resume heating at reflux and carefully place the plate into the TLC chamber. Place a watch glass on top to prevent evaporation of the methylene …show more content…
chloride.
When the solvent front is close to the top of the plate, remove the TLC plate with tweezers and mark the line of the solvent front with a pencil. View the TLC plate under the UV lamp and circle any spots, noting the relative amounts of benzoin and benzil. Finally, tape the TLC plate into your lab notebook (and/or take a pic with smartphone).
At this point the reaction mixture turns solids upon cooling, might add a few drops of reaction mixture to ethanol and spot that on the plate.
Repeat the TLC procedure above at 45 min. If there is no more benzoin in the reaction mixture, allow the reaction mixture to cool to room temperature. If not, continue heating for another 15 min and run another TLC. Even if there is some starting material left at this point, discontinue heating and allow the reaction mixture to cool to room temperature.
Use a magnetic stick to remove the stirbar and pour the reaction mixture into 40 mL of DI water. Stir vigorously with a glass stirring rod to induce crystallization and break up any lumps of solid that form. Isolate the crystals by vacuum filtration, washing a couple times with ~10-20 mL of DI water. Let the vacuum pull air through the funnel for ~5-10 min to help dry the solids and obtain a mass of the crude benzil. Recrystallize the benzil from 95% ethanol (roughly 8 mL per gram of solid).
After isolating the crystals, allow them to dry on a watchglass for a couple days.
Determine the mass and mp of the recrystallized benzil and obtain an IR spectrum.
Part C: Base-catalyzed aldol condensation of benzil and 1,3-diphenylacetone
(Week 4)
Add 0.50 g of 1,3-diphenylacetone, 0.50 g of benzil and 5 mL of triethylene glycol to a 50 mL round bottom flask. Add a stir bar and heat the mixture at setting 4-5 on heating manual for ~ 10-15 min (will not reflux boiling point too high). The benzil should dissolve during this time. Remove the heating mantle and add ~0.5 mL of a 40% benzyltrimethylammonium hydroxide/methanol solution to the hot reaction with constant stirring.
Allow the reaction to cool to room temperature. As the solution cools dark-colored crystals should appear. Cooling may be accelerated by placing the flask under a stream of cold water (Note: you are NOT adding any water to the inside of the flask). Add 10 mL of cold methanol with stirring and cool the resulting mixture in an ice bath for 5-10 min. Collect the product by vacuum filtration and wash the crystals with a little cold methanol. Allow the crystals to dry on a watchglass for a couple days.
Determine the mass and mp of the
product.