Nitration of Methyl Benzoate Laboratory Report

Abstract

In this laboratory experiment, the nitration of methyl benzoate was investigated. The study aimed to explore the principles of ortho-, para-, and meta-directing groups in organic chemistry. The reaction involved the introduction of a nitro group onto the methyl benzoate ring, which was primarily directed by the meta-position due to the nature of the substituents present on the aromatic ring. The formation of the active electrophile, the nitronium ion, was crucial for the success of the reaction. The purity of the product was assessed through the determination of its melting point.

The experiment resulted in a 73.5% yield of 3-Nitro Methyl Benzoate, and the obtained melting point closely matched the literature value.

Introduction

Nitration is a fundamental concept in organic chemistry, and understanding the directing effects of substituents on aromatic rings is essential for predicting reaction outcomes. In this experiment, we explored the nitration of methyl benzoate, where the substituent on the aromatic ring played a crucial role in directing the position of nitro group attachment.

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This investigation allowed us to observe the effects of ortho-, para-, and meta-directing groups on the reaction's regioselectivity.

Mechanism of the Reaction

The nitration of methyl benzoate involves several key steps, as outlined below:

1. Reaction between nitric acid and sulfuric acid to produce the nitronium ion, which serves as the electrophile.
2. Attack of the nitronium ion on the aromatic ring, with the electrophile adding to the meta-position.
3. Formation of the arenium ion intermediate.
4. Transfer of a proton from the intermediate to the bisulfate ion, resulting in the formation of methyl 3-nitrobenzoate.
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Experimental Procedure

The experimental procedure for the nitration of methyl benzoate was carried out as per the laboratory instructions. The primary steps involved mixing nitric acid and sulfuric acid to generate the nitronium ion, which subsequently reacted with methyl benzoate to form 3-Nitro Methyl Benzoate. The product's purity was assessed through the determination of its melting point.

Results

The results of the experiment are summarized in the table below:

Discussion

The analysis of the results and the discussion of various aspects of the experiment are presented below:

1. H NMR Spectroscopy: The H NMR spectrum exhibited several peaks. Protons in the aromatic ring appeared in the 7-9 ppm range, with their positions influenced by the directing groups (nitro and ester). Protons closest to these groups exhibited peaks closer to 9 ppm, while the proton furthest from these groups appeared at approximately 7 ppm. Additionally, the singlet proton at 3.8 ppm was attributed to the vibrations of protons on the methyl group of the ester.
2. Melting Point: The obtained experimental melting point of 70°C was close to the literature value of 78°C. The slight deviation from the literature value was likely due to impurities present in the product. Methanol, with its low melting point, may have been left in the product, causing the observed lower melting point. Ensuring thorough drying of the product could have prevented this issue.
3. Percent Yield: The experiment yielded a product with a percent yield of 73.5%. While this is reasonable, it falls short of optimal efficiency. Some of the product may have been left behind in the filtration process or lost in waste, contributing to the lower yield.

Conclusion

The nitration of methyl benzoate provided valuable insights into the principles of directing groups in organic chemistry. Understanding how different substituents direct reactions to specific positions on the aromatic ring is crucial in predicting reaction outcomes. This knowledge has significant applications in the pharmaceutical industry, where specific regioselective reactions are essential for synthesizing various compounds.

The experiment successfully demonstrated the synthesis of 3-Nitro Methyl Benzoate, with the experimental melting point closely matching the literature value. While the percent yield of 73.5% indicates room for improvement, the experiment achieved its objective of illustrating the key steps and concepts involved in the nitration of methyl benzoate.