Aldol Condensation - lab report PDF

Preview

Summary

lab report ...

Description

03/28/18 Experiment: Synthesis of 4-methoxychalcone The purpose of this lab experiment is to understand the mechanism of an aldol condensation by synthesizing 4-methoxychalcone. Mechanism

Compound

Boiling point

Melting Point

Amount

weight (g/mol) (g/mL)

°C

°C

used

238.29

NA

NA

73-78

NA

40

1.53

140

12

5 drops

46.08

0.79

78.37

-114

5 mL

Acetophenone

120.16

1.03

201.7

19.7

1 mL

Anisaldehyde

136.16

1.12

248

-1

1 mL

Bromine

159.81

3.10

58.78

-7.25

1 drop

Potassium permanganate

158.03

2.47

NA

240

1 drop

4-methoxychalcone Sodium Hydroxide Ethanol

Structures

Molecular

Density

MSDS 1. 4-methoxychalcone: irritant of skin and eye. 2. Acetophenone: irritant of skin and eye, combustible. 3. Ethanol: irritant of skin and eyes. 4. Anisaldehyde: irritant of skin and eye, may combust at high temperature. 5. Sodium hydroxide: skin and eye irritant, corrosive, may cause burns. 6. Potassium permanganate: skin and eye irritant, corrosive, can cause inflammation. 7. Bromine: corrosive, may cause burns, eye and skin irritant. Procedure 1. Add 1 mL of acetophenone and 1 mL of anisaldehyde to a test tube 2. Add 3 mL of 95% ethanol and stir until dissolved 3. Add 10 drops of the NaOH solution 4. Stir for 20 min 5. Add to an ice bath until crystallization occurs 6. Filter the crude product 7. Recrystallize with 2 mL of EtOH 8. Filter pure product and collect MP and mass 9. Perform a saturation test with a bromine and potassium permanganate solution 10. Obtain NMR from instructor and identify peaks

Calculations

Mass of product: 1.5058 g 1 mol ∏ ¿=1.98 g ∏ ¿ ∏¿ 238.9 g ¿ ¿ ∏ ׿ 1 mol 1 mol aceto 1 mol aceto 1.00 g aceto ׿ × 1.0 mL acetophenone × 1 mL aceto 120.16 g aceto 1mol ∏ ¿=1.96 g ∏ ¿ ∏¿ 238.29 g ¿ ¿ ∏ 1 mol ׿ 1 mol ani 1 mol anis 1.12 g anisa ׿ × 1.00 mL anisaldehyde × 1mL anisa. 136.16 g anis. Percent Yield 1.5058 g × 100=76.83 % 1.96 g

Conclusion/Discussion During this lab experiment, an Aldol condensation was done using acetophenone and anisaldehyde to synthesize 4-methoxychalcone. The crude product was recrystallized to purify it, a melting point was taken and the result was 64-66℃ indicating that there were some impurities left in the final product compares to the literature values of 73-78℃ . The percent yield for this product was 76.83%. In addition, a Br2 and KMnO4 saturation test were conducted. For the bromine test the solution turned colorless indicating an alkene present and the potassium permanganate turned black when originally is supposed to turn brown. This could be due to wrong preparation of potassium permanganate. The NMR of this product was taken. There are 8 different protons in 4-methoxychlacone. Around 7.6 ppm and 8.1 ppm there are the vinyl protons. When drawing two resonance structures one structure is going to make a carbon more electrophilic and the C-O bond more deshielded and does not break conjugation; in the second resonance structure the molecule

breaks conjugation, thus making one proton more downfield than the other one. The more conjugated the system is, the more stable it is. Around 3.8 ppm the most upfield protons come from the methyl group attached to an oxygen....