Nitration of Methyl Benzoate Introduction: Nitration is an example of an electrophile aromatic substitution reaction, where nitro (NO2) group is being substituted for a hydrogen on an aromatic compound. This is achieved by the formation of the nitronium ion by protonation of nitric acid from sulfuric acid. The zirconium ion is a strong electrophile and can react with aromatic compound such as Methyl benzoate to form an arenium ion intermediate. The arenium ion is then depronated to reform the aromatic ring and yield the final product with the newly attached nitro group.
Reaction: ? Table of Physical Contents: ?????? Procedure: Obtain an ice bath. 12 ml of concentrated sulfuric acid was gathered, cooled to 0 degrees Celsius, and put in a 125-ml Erlenmeyer flash. Then 6. 1g of methyl benzoate was added. Then cooled in an ice bath to 0-10 degrees Celsius. A Pasteur pipette was used to add a cooled mixture of 4-mL of concentrated sulfuric acid and 4-mL of concentrated nitric acid. ? Figure 1: How to properly use a Pasteur pipette The mixture was then swirled frequently and maintained a temperature of 5C-15C. Figure 2: Swirling the mixture After all of the nitric acid was added the mixture was then warmed to room temperature. After 15 minutes, it was then poured into a 250-mL. The solid product was isolated by suction filtration using a small Buchner funnel. ? Figure3: Labeled vacuum filtration ? Figure 4: Carefully scraping out the crystals A small amount of sample was saved and weighed. Results: ? Figure 5: NMR of the product ? Discussion/Conclusion: The melting point of the recrystallized product was 73-78 degrees Celsius.
This was very accurate to that of the book. In this experiment, methyl benzoate went through an electrophilic substitution reaction to form Mehyl-m-nitro benzoate, where a NO2 group was added to the methyl benzoate in the meta position. Nitric acid is not a strong enough electrophile to react with the aromatic benzene ring, but the zirconium ion with the positive charge on the nitrogen is a strong electrophile and can react with the double bond of the methyl benzoate. The experiment was an overall success.
The H NMR data successfully confirmed that the experiment was done correctly. Substances Formula Weight g/mol Quantity Moles Used Mole Ratio Boiling Point Melting Point Density g/mL Concentrated Nitric Acid 63. 01 0. 5mL 1. 192 x 10^-2 N/A N/A 121 1. 5027 Concentrated Sulfuric Acid 98. 08 1. 6mL 3. 0 x 10^-2 N/A N/A N/A 1. 841 Ethanol 46. 07 2-3mL N/A N/A N/A N/A N/A Methyl Benzoate 136. 15 0. 55g 4. 039x 10^-3 1 to 1 113-115 N/A N/A Methyl Nitro- Benzoate 181. 13 Product N/A N/A N/A N/A N/A