Organic Chem

CHM 2012 Experiment 2: Substituted Chalcones1Procedure:
1) Fill a 250 mL beaker ¾ full of tap water. Heat the water to 80-85°C using a
hot plate.
2) Weigh 5 mmol each of the provided aldehyde and ketone. The molecular
weights will be provided.
3) Combine 5 mmol of the aldehyde, 5 mmol of the ketone, and 5 mL of 95%
ethanol in a 25 mL Erlenmeyer flask.
4) Stir the reaction mixture with a glass stir rod until a homogenous solution is
obtained. Add 0.5 mL of ethanol if stirring does not produce a homogenous
solution.
5) Add 0.40-0.50 g of sodium hydroxide to 0.5 mL of warm water in a small test
tube. Stir until dissolved.
6) Add the sodium hydroxide solution to the aldehyde/ketone mixture and swirl
to thoroughly mix the components.
7) Stir the reaction mixture with a glass stir rod until a solid is formed (4-5
minutes).
8) Heat the reaction mixture in your water bath at 80-85°C for 30 minutes with
occasional stirring.
9) Cool the reaction mixture to room temperature. Continue cooling in an ice
bath.
10) Cool the reaction mixture in an ice bath until crystal formation. If no
crystallization is observed in 5 minutes seed the crystals by scratching your
glass stir rod inside the walls of the flask.
11) Add 4-5 mL of water and stir with a glass stir rod until suspension is
achieved. Break down any large chunks with the glass stir rod.
12) Collect this crude product via vacuum filtration. Ask your GSA about this
setup if you have any questions.
13) Keep the vacuum applied and wash the crude product with 5-10 mL of COLD
water.
14) Collect the crude product from the filter, record its mass, and prepare a
melting point sample with this crude product. Transfer the rest to a small
clean Erlenmeyer flask or beaker. Proceed to recrystallize the crude product
with hot 95% ethanol.
15) For recrystallization heat 10-15 mL of 95% ethanol in a 25 mL Erlenmeyer
flask or other small glass beaker.
16) Once the 95% ethanol is hot, add the solvent dropwise to the crude product
containing flask. Swirl to mix the components. After each addition of hot 95%
ethanol add the crude product flask to the hot plate with the solvent to
maintain temperature.
17) Only add the minimum amount of hot 95% ethanol needed to dissolve the
crude product. Adding excess solvent will cause problems recovering the
pure recrystallized product. Ask your GSA if you need help judging this
amount.
18) Once the crude product is dissolved by a minimum amount of hot 95%
ethanol cool the recrystallization mixture to room temperature. Continue
cooling in an ice bath.
19) Perform vacuum filtration to recover the recrystallized product. Collect the
recrystallized product from the filter and record its mass/melting point.
20) Discuss the differences in melting points/masses of crude and recrystallized
products. Obtain the IR/NMR spectra of the recrystallized product from your
GSA.
References:
1) Davidson, T. Synthesis and Reduction of Substituted Chalcones. In
CHM2211L/2200L Organic Chemistry Lab Manual, 2022-2023 ed.; HaydenMcNeil, 2022; pp 89-98.
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