Acetanilide Synthesis and Characterization Lab Report

Abstract

The objective of this laboratory experiment was to synthesize acetanilide through the reaction of aniline and acetic anhydride and subsequently characterize the synthesized product. Acetanilide is a commonly used organic compound in various fields, including pharmaceuticals and dyes production. The synthesis involved a nucleophilic substitution reaction, and the purity of the product was assessed through recrystallization, thin-layer chromatography (TLC), melting point determination, and proton nuclear magnetic resonance (HNMR) spectroscopy. The results demonstrated that the synthesized acetanilide was of high purity and closely matched the literature values.

Introduction

Acetanilide, an organic compound with the chemical formula C8H9NO, is a valuable intermediate in the synthesis of various pharmaceuticals, dyes, and perfumes. Understanding its properties and synthesis methods is crucial in organic chemistry. In this experiment, acetanilide was synthesized from aniline (C6H5NH2) and acetic anhydride (C4H6O3) through a nucleophilic substitution reaction. The reaction mechanism involves the nucleophilic attack of aniline on acetic anhydride, resulting in the formation of acetanilide and acetic acid as a side product.

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The synthesized acetanilide was then characterized to assess its purity using several analytical techniques.

Experimental Procedure

The experimental procedure consisted of the following key steps:

1. Weighed 0.182 mL of aniline and placed it into a 4 mL conical vial containing a magnetic spin vane.
2. Added 2 mL of water and stirred the mixture on a magnetic stirrer set at level 9.
3. Added 0.2222 mL of acetic anhydride to the vial and continued stirring for 20 minutes.
4. Cooled the vial in an ice bath for 8 minutes to facilitate crystallization.
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5. Performed vacuum filtration using a Hirsch funnel to isolate the product and washed the vial with ice-cold water to remove impurities.
6. Dried the product for 5 minutes.
7. Weighed the product using weigh paper and subtracted the weight of the weigh paper and the spin vane to obtain the actual product weight.
8. Transferred the product into a flask for recrystallization.
9. Recrystallized the product by making it soluble in hot solvent and insoluble in cold solvent.

Recrystallization Yield

The recrystallization yield was determined to be 44.30%. This relatively low yield may be attributed to product loss during transfer and residual product on the spin vane during crystallization. Despite the yield, it is crucial to note that the purity of the product is of greater significance.

Characterization

Thin-Layer Chromatography (TLC) Analysis

TLC analysis was performed using a solvent system consisting of 20% ethyl acetate in hexanes (hexane/EtOAc). Rf (retention factor) values were calculated for different compounds, including aniline, standard acetanilide, and the synthesized acetanilide:

The TLC analysis results indicated that the Rf value of the synthesized acetanilide closely matched that of the standard acetanilide, suggesting a high level of purity. In contrast, aniline, a starting material, exhibited a higher Rf value, indicating its non-polar nature.

Melting Point Analysis

Melting point analysis was conducted to determine the melting point of the synthesized acetanilide. The observed melting point was 115.1°C, while the literature value for acetanilide is 114.3°C. The slight difference between the observed and literature melting points could be attributed to factors such as pressure in the capillary tube or minor impurities. However, the discrepancy was not significant and did not indicate the presence of substantial impurities.

Proton Nuclear Magnetic Resonance (HNMR) Spectroscopy

HNMR spectra were obtained for acetanilide, aniline, and acetic anhydride. The spectrum for acetanilide displayed three distinct signals:

The chemical shifts observed in the HNMR spectrum of acetanilide closely matched the literature values, confirming the high purity of the synthesized compound. The multiplicity and chemical shifts indicated the presence of specific functional groups within the molecule.

Discussion

The experimental results obtained through TLC analysis, melting point determination, and HNMR spectroscopy consistently supported the conclusion that the synthesized acetanilide was of high purity. The minor differences observed in some values, such as the melting point, could be attributed to experimental factors and did not indicate the presence of substantial impurities in the product.

Conclusion

In conclusion, this laboratory experiment successfully synthesized and characterized acetanilide. The analytical results, including TLC analysis, melting point determination, and HNMR spectroscopy, consistently indicated the high purity of the synthesized acetanilide. Despite the relatively low recrystallization yield, the purity of the product was the primary focus of the experiment. It is essential to minimize product loss during future experiments for improved yields. The experiment provided valuable insights into organic synthesis and characterization techniques.