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Megan Gueli Lab Report 3 Chemistry 216 February 22, 2012 Ester Formation Preparation of Benzocaine Introduction: Benzocaine is a common anesthetic used to numb the body. It works by blocking nerve signals in the body. It became a common anesthetic to replace the use of cocaine, once the addictive properties of cocaine were discovered. It is used to treat many burns, cuts, scrapes, and insect bites. Benzocaine is synthesized by esterification of p- aminobenzoic acid using heat and sulfuric acid as a catalyst. Laboratory techniques, such as reflux, vacuum filtration, and recrystallization are used for the esterification of p- aminobenzoic acid. Simple Reaction Scheme: Experimental: 0.36 g of p-aminobenzioc acid was measured and placed in 3.60 mL of ethanol in a ten mL conical flask. Then a magnetic spin vane was added and the mixture was stirred until the solid acid dissolved. While the solution continued to stir, 0.3 mL of concentrated sulfuric acid was added dropwise, unitl a precipitate was formed. The precipitate was formed from the hydrogen sulfate salt of p-aminobenzioc acid. A water-cooled condenser was then attached, and the mixture was heated to boiling temperature for an hour. After the solution was cooled to room temperature, the solution was transferred to an Erlenmeyer flask containing three mL of water. The precipitate dissolved. 10% sodium carbonate was then added dropwise until the solution was neutralized. The pH was checked using pH paper. The precipitate was collected by vacuum filtration using a Hirsch funnel. Then part of the sample was left to dry overnight. The remaining Benzocaine was recrystallized using water and ethanol. The Benzocaine was dissolved in minimal ethanol, and heated close to the boiling point of ethanol. The mixture continued heat as minimal ethanol, and heated close to the boiling point of ethanol.... View Full Document

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