P Toluidine Synthesis Analysis

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Benzocaine was synthesized from p-toluidine in a four step synthesis. Each intermediate product, including N-acetyl-p-toluidine, p-acetamidobenzoic acid, and p-aminobenzoic acid, was checked for yield, presence, and purity through weighing, taking IR and NMR spectrums, and determining the melting point. Thin Layer Chromatography was used to ensure the completion of the final reaction from p-aminobenzoic acid to benzocaine. The yield of the first step from p-toluidine to N-acetyl-p-toluidine was 91.9%. The yield of the second step from N-acetyl-p-toluidine to p-acetamidobenzoic acid was 49.85% The yield of the third step from p-acetamidobenzoic acid to p-aminobenzoic acid was 32.49%, which was not enough to continue so some product was borrowed …show more content…
It must be synthesized using several, sequential chemical reactions. Benzocaine is useful as a mild topical anesthetic that is the active ingredient in many anesthetic ointments such as Orajel for teething relief and Solarcaine, for sunburn relief. The four step synthesis of benzocaine (ethyl 4-aminobenzoate), 6, in this lab would typically result in overall benzocaine yield of 17.9% from the starting material p-toluidine, 1.
Sharma and associates synthesized benzocaine beginning from vasicine with is found in the leaves of Adhatoda vasica. Specifically, nitro compounds were mixed with vascine in 120°C water for 24 hours and then purified by column chromatography. The final step involved the replacement of an amide with an amine. The result was a 66% yield of benzocaine which is significantly higher than the typical yield of the synthesis of benzocaine from p-toluidine as performed in this experiment.
Ding and Chang-Ze describe the synthesis of benzocaine from p-nitrotoluene using KMnO4 as the oxidizing agent, which is the same as used in this experiment, SnCl4 as the catalyst, which differs from this experiment, and H2 as the reducer, which is the same as used in this experiment. This method resulted in a 70.3% yield under optimal
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The melting point of the product at this step was 145.9-147.1°C, which is slightly below the 150 °C melting point of pure N-acetyl-p-toluidine but much higher than the 43°C melting point of the beginning p-toluidine. The slightly lower melting point could be caused by impurities in the sample. Along with melting point results, the IR spectrum shows a single N–H stretch peak at 1659.31 cm-1 showing the addition of a C=O and shows a peak at 3287.55 cm-1 which suggests an amide while the IR of sample 1 shows N–H stretches at 3416.53 cm-1 and 3334.84 cm-1 which suggests an amine. The 1H NMR shows the addition of an amide by having a peak of three hydrogens at 2.305 ppm that did not exist on the NMR of the

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