Lab Report: Aldol Condensation Experiment

Abstract

The purpose of this experiment was to perform an aldol condensation reaction using an unknown aldehyde and an unknown ketone and to identify the products using H NMR spectroscopy and melting point analysis. The product was identified as 2,5-bis(4-methoxybenzylidene)cyclopentanone, which is formed from the reaction between p-Anisaldehyde and cyclopentanone. The melting point of the product was found to be 204-206°C, which closely matched the expected melting range for the synthesized compound.

Introduction

Condensation reactions, also known as dehydration reactions, involve the formation of chemical bonds between molecules, accompanied by the release of water as a byproduct.

Aldol condensation is a specific type of condensation reaction that involves the formation of a carbon-carbon (C-C) bond between the alpha carbon of an aldehyde or ketone and the carbonyl carbon of another aldehyde or ketone. This reaction is distinct from aldol addition reactions, where the alpha carbon of one aldehyde or ketone adds to the carbonyl group of another, resulting in the formation of a beta-hydroxy carbonyl compound, known as an aldol.

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In contrast, aldol condensation reactions proceed by dehydrating the aldol, leading to the formation of an alpha-beta-unsaturated carbonyl compound.

Materials and Methods

The following materials and reagents were used in this experiment:

The experimental procedure was as follows:

Procedure

1. Combine p-Anisaldehyde and cyclopentanone in a round-bottom flask.
2. Add a solution of NaOH to the flask.
3. Attach a reflux condenser to the flask and heat the mixture under reflux conditions.
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4. After the reaction is complete, cool the mixture and extract the product with ethanol.
5. Evaporate the ethanol using a rotary evaporator.
6. Purify the product by recrystallization from diethyl ether.
7. Collect the purified product and determine its melting point.
8. Perform H NMR spectroscopy to analyze the product.

Results

The melting point of the synthesized product was found to be in the range of 204-206°C.

Analysis of the H NMR spectra revealed three distinct regions that corresponded to specific hydrogen atoms in the product:

1. Peak at δ 3.08 (singlet, 4H) representing the four hydrogen atoms of the five-membered ring.
2. Peak at δ 3.85 (singlet, 6H) representing the hydrogen atoms of the two methoxy groups.
3. Peak range from δ 6.95 to 7.56 (multiplet, 10H) representing the hydrogen atoms of the benzene rings and the hydrogen atoms of vinyllic carbons.

Based on the integration of the H NMR spectra, the product was identified as 2,5-bis(4-methoxybenzylidene)cyclopentanone, which is the result of an aldol condensation reaction between p-Anisaldehyde and cyclopentanone.

Discussion

The results of the H NMR analysis provided valuable information about the structure of the synthesized product. The peaks observed in the H NMR spectra were consistent with the expected chemical shifts for the hydrogen atoms in 2,5-bis(4-methoxybenzylidene)cyclopentanone. The singlet at δ 3.08 (4H) confirmed the presence of four hydrogen atoms in the five-membered ring, while the singlet at δ 3.85 (6H) indicated the presence of six hydrogen atoms in the methoxy groups. The multiplet in the range of δ 6.95 to 7.56 (10H) corresponded to the hydrogen atoms in the benzene rings and the vinyllic carbons.

The melting point of the product was determined to be in the range of 204-206°C. This melting point closely matched the expected melting range for 2,5-bis(4-methoxybenzylidene)cyclopentanone, which is approximately 212°C. The close agreement between the observed and expected melting points supports the conclusion that the synthesized product is indeed 2,5-bis(4-methoxybenzylidene)cyclopentanone.

Conclusion

In conclusion, this experiment successfully demonstrated the synthesis of 2,5-bis(4-methoxybenzylidene)cyclopentanone through an aldol condensation reaction between p-Anisaldehyde and cyclopentanone. The product was identified based on H NMR spectroscopy and confirmed by its melting point. The melting range of the synthesized product closely matched the expected range for 2,5-bis(4-methoxybenzylidene)cyclopentanone, providing strong evidence for the accuracy of the identification.

Recommendations

Further studies could involve exploring variations of the aldol condensation reaction with different aldehydes and ketones to investigate the scope of this reaction. Additionally, more advanced analytical techniques, such as mass spectrometry and infrared spectroscopy, could be employed to further characterize the synthesized product and confirm its structure.