Expmt85 - Expt 85 Esterification - Determination of Keq for...

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Exp’t 85 Esterification - Determination of Keq for the Acid- Catalyzed Esterification of Benzoic Acid with Methanol Adapted by R. Minard and D. Dorisio (Penn State Univ.) from a microscale procedure used by the University of California, Irvine, in its undergraduate labs. The procedure is based on an experiment introduced to the UCI Organic Chemistry Laboratory Program in the early 1970's by Marjorie C. Caserio, Professor of Chemistry. Revised 10/5/00 The purpose of this experiment is to determine Keq for the reaction: COH O COCH 3 O + CH 3 OH H 2 SO 4 + H 2 O Benzoic acid Methyl benzoate This can be accomplished by knowing the exact amounts of reactants and by recovering and weighing unreacted benzoic acid after equilibrium has been reached. COCH 3 O COH O K eq = H 2 O CH 3 OH The success of this experiment depends on quantitative recovery of the benzoic acid. Therefore, care should be taken that no spills occur during the liquid/liquid extraction procedure so that no product or starting material is lost. Prelaboratory Exercises: Prepare a liquid/liquid extraction scheme or flow chart for the separation and isolation of the unreacted benzoic acid from the equilibrium reaction mixture. Write the chemical formulas of the chemicals contained in the centrifuge tube, flask or vial, reaction tube, or test tube at each point in the scheme. Experimental Procedure: Place 0.250 gram benzoic acid, 0.630 mL anhydrous methanol (Hooded Shelf), 2 drops concentrated H 2 SO 4 , and an boiling chip in a reaction tube, use the connector with support rod to attach an air condenser, and cap the top of the condenser tube with a septum. BEFORE YOU START HEATING, pierce the septum with an empty syringe needle and leave it in the septum to prevent possible pressure build-up in the system. IT IS IMPORTANT THAT NO LOSS OF REACTANTS OCCURS DURING REFLUXING. THEREFORE, WATCH YOUR REACTION MIXTURE CAREFULLY AND DO NOT ALLOW THE REFLUXING VAPORS TO RISE ABOVE THE LOWER
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Expmt85 - Expt 85 Esterification - Determination of Keq for...

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