doc Synthesis of Benzocaine

Synthesis of Benzocaine   Author:L. Phillip Silverman | Size:56.50 K | View:646 | Page:2

Fischer Esterification of p-aminobenzoic acid: Synthesisof BenzocaineAdapted from the Revised Procedure:  Expt. 21.1Multistep Synthesis of Benzocaine Analogshttp://web.uccs.edu/bgaddis/chem338/expt21_1corr.htm    To a 100-mL round bottom flask fitted with a stir bar,add 2.50 g of p-am...  
Fischer Esterification of p-aminobenzoic acid: Synthesisof BenzocaineAdapted from the Revised Procedure:  Expt. 21.1Multistep Synthesis of Benzocaine Analogshttp://web.uccs.edu/bgaddis/chem338/expt21_1corr.htm    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. Whilestirring, add 2.0 mL of concentrated H2SO4 dropwise. The precipitatethat forms upon the addition of sulfuric acid should dissolve when the solutionis heated. Reflux, with stirring, for 1 hour. Cool to room temperature.Neutralize cautiously with dropwise addition of 10% Na2CO3until the pH is approximately 8. (Gas evolution will be vigorous.) Extract withtwo 10-mL portions of methylene chloride. Wash the combined methylene chloridelayers with two 8-mL portions of water. Dry the methylene chloride solutionover anhydrous sodium sulfate. Gravity filter into a clean Erlenmeyer flaskcontaining a boiling stone. Evaporate the methylene chloride using the rotaryevaporator. Recrystallize the whitish residue using as a solvent pair, ethylalcohol and water. Suction filter the product, and let air dry. Weigh the whitecrystals and take the melting point. Perform IR spectroscopy and compare the IRof the p-aminobenzoic acid to that of the product (collect 2 IR spectra:1 of the starting material and 1 of the product). Prelaboratory Questions  Novocaine  1. Refer to the structure of Novocaine. Using p-aminobenzoicacid, propose a mechanism of how Novocaine could be prepared.   2. Which of the two possible amino functional groups inProcaine would be protonated first?Why?  3. What is the purpose of the sulfuric acid for thisreaction? Is the acid consumed during the synthesis?   PostlabQuestions.1. Writeout the mechanism of your reaction. Tell what LeChatlier’s Principle is and howitappliesto this procedure. What is removed to drive the reaction to completion?   2. Why did you wash with aqueous sodium bicarbonate?Explain using balanced chemical equations.  3. The oxygen from which material is incorporated intothe new created ester bond? Where does the oxygen in the product of wateroriginate?BenzocaineThis pagecontains recent news articles, when available, and an overview of Benzocainebut does not offer medical advice. You should contact your physician withregard to any health issues or concerns. Overview: Benzocaine (when available) Pharmacologyand use:Benzocaine is a local anesthetic commonly used as a topical pain reliever. Itis the active ingredient in many over-the-counter analgesic ointments. It isalso indicated for general use as a lubricant and topical anesthetic onintratracheal catheters and pharyngeal and nasal airways to obtund thepharyngeal and tracheal reflexes; on nasogastric and endoscopic tubes; urinarycatheters; laryngoscopes; proctoscopes; sigmoidoscopes and vaginal specula. Forgeneral use as a lubricant and topical anesthetic on esophagus, larynx, mouth,nasal cavity, rectum, respiratory tract or trachea, urinary tract, vagina. Itis also used to suppress gag reflex.Mechanism Of Action: Benzocaine binds to sodium channel and reversibly stabilizes the neuronalmembrane which decreases its permeability to sodium ions. Depolarization of theneuronal membrane is inhibited thereby blocking the initiation and conductionof nerve impulses.Doctors unsure what causes canker sores - 20Apr 2009Liquids or ointments with a numbing ingredient, such as benzocaine (Anbesol,Oragel, Orabase, Zilactin-B, Tanac) help relieve the discomfort of cankerNews-Leader.comFamily Doctor: Chiggers can spoil a day of outdoor fun - ‎Apr9, 2009‎Its active ingredients are precipitated sulfur and benzocaine, which worktogether for quick relief. It can also be used for mosquitoes, fleas,no-see-ums, Canton RepositoryCollingham OAP stashed cocaine in washing machine - ‎Mar31, 2009‎Police also found a 1kg bag of cocaine cutting agent Benzocaine in the tumbledryer at 65-year-old Michael Hunters home in Collingham near Wetherby.Yorkshire Evening Posthttp://www.mongabay.com/health/medications/Benzocaine.html       
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Synthesis of Benzocaine

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