Question

Chemical reaction involve in synthesis of benzocaine from paba

Answer 1

To a 100-mL round bottom flask fitted with a stir bar, add 2.50 g of p-aminobenzoic acid and 20

mL of ethyl alcohol. While stirring, add 2.0 mL of concentrated H2SO4 dropwise. The precipitate

that forms upon the addition of sulfuric acid should dissolve when the solution is heated.

Reflux, with stirring, for 1 hour. If you notice that the white suspension persist, add 1 additional

mL of concentrated H2SO4 dropwise. Cool to room temperature. Neutralize cautiously with

dropwise addition of 10% Na2CO3 until the pH is approximately 8. (Gas evolution will be

vigorous.) Extract with two 10-mL portions of methylene chloride. Wash the combined

methylene chloride layers with two 8-mL portions of water. Dry the methylene chloride

solution over anhydrous sodium sulfate. Gravity filter into a clean Erlenmeyer flask containing a

boiling stone. Evaporate the methylene chloride using the rotary evaporator. Recrystallize the

whitish residue using as a solvent pair, ethyl alcohol and water. Suction filter the product, and

let air dry. Weigh the white crystals and take the melting point. Perform IR spectroscopy and

compare the IR of the p-aminobenzoic acid to that of the product (collect 2 IR spectra: 1 of the

starting material and 1 of the product

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