A multistep activity procedure was used to synthesize benzocaine via p-toluidine (Scheme 1). In coordination one, p-toluidine was acetylated to produce p-acetotoluidide to protect the amine from oxidation. In coordination two, the methyl substituent on p-acetotoluidide was oxidized to produce p-acetamidobenzoic acid. In step three, p-acetamidobenzoic acid was hydrolyzed to eliminate the guarding group to make p-aminobenzoic acid. In step 4, p-aminobenzoic acid was esterified to produce benzocaine. A burning point selection (Table 1) and 1H NMR spectrographs (Figures 1-4) were acquired for each merchandise to confirm merchandise identity at each step.
The experimental melting selection for each substance was inside one to two examples of the literary works melting level which indicated possible contaminates. This was due to incomplete blow drying and/or mistakes during synthesis.
1H NMR spectra were acquired for each mixture at 300 MHz and were given by Dr . Kim White. The 1H NMR spectrum for each compound was analyzed below (Figures 1-4).
The 1H NMR for p-acetotoluidide (Figure 1) contained five significant signs. Four with the signals had been produced by p-acetotoluidide while the 6th signal (7. 25 Оґ) was manufactured by the 1H NMR solvent, CDCl3. Because of proton exchange due to hydrogen bonding, there were no significant signal made for the hydrogen attached to the amide group. Just for this quality of hydrogen bonding the signal can manifest as wide, at the incorrect chemical shift, or always be absent. In cases like this, the signal produced by the hydrogen attached to the amide group was absent. A directory of the types of hydrogens and their substance shifts intended for p-acetotoluidide was recorded (Table 2).
The 1H NMR for p-acetamidobenzoic acid (Figure 2) contained five significant signa...
... d, normal water (10 mL) was added and the ensuing solution was neutralized to pH 7-8 by adding salt carbonate (1. 51 g, 14. two mmol). The mixture was extracted 2 times with dichloromethane (two twelve mL portions). The combined organic levels were cleaned with water (10 mL) and salt chloride (10 mL). The rest of the organic part was dried up with anhydrous sodium sulfate. The solution was filtered and the remaining solvent was evaporated on a warm plate. Crystallization of benzocaine occurred. The crystals had been recrystallized with methanol and water although heating. The reaction was cooled in an snow bath. The pale discolored precipitate was removed by way of vacuum filtration and dried out under continuous filtration (0. 17 g, 1 . goal mmol). MP = 85-87 Н¦C (literature value 88-90 Н¦C); 1H NMR (300 MHz, CDCl3): Оґ six. 83-7. eighty six (d, 2H), 6. 61-6. 64 (d, 2H), four. 27-4. thirty four (q, 2H), 4. 10 (s, 2H), 1 . 32-1. 37 (t, 3H).