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222_Esterification1_Report (1).doc

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CHEM 222
David Harpp

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Chemistry 222 Fall 2012 1 By: Krishnaa Siva Date: November 8, 2012, Thursday 1:30-5:30 PM Lab Group TA: Mathieu Bedard Fischer Esterification Lab Part 1 1. Objective: 1 mark What is the purpose of this experiment? The objective of this lab is to directly produce the ester, ethyl gallate, by the reaction of a carboxylic acid called gallic acid with ethanol, an alcohol, while using sulfuric acid, as the catalyst. Following the synthesis and isolation of ethyl gallate, characterize the ethyl gallate. In the lab, use TLC (Thin Layer Chromotography), IR Spectroscopy, NMR, and the melting point to verify if it is actually ethyl gallate that is produced. 2. Introduction: 2 marks Brief description of the concept/reaction studied – esterification Fischer esterification is an acid catalyzed process that involves refluxing carboxylic acid with an alcohol. The reflux involves heating the reaction mixture at its boiling temperature and most importantly no compounds are lost when doing this since the condenser catches and returns the escaping vapor (Oxford Dictionaries, 2012). This technique is used to provide that extra energy to the reaction. The Fischer esterification reaction is generally in equilibrium, but this can be modified in various ways. The equilibrium can be shifted and more products can be formed by using excess alcohol or excess carboxylic acid or by removing the water that gets formed. In this reaction it is excess alcohol that is used to drive the reaction towards forming more product. 3. Reaction Equation: 2 marks Include proper structures and data for reactants and products [molar mass, concentration, density, volume, mass, moles, etc – including theoretical yield] Chemistry 222 Fall 2012 2 Molar mass Melting Point Boiling Point Density Volume/ (g/mol) (̊ ) ( ̊C) (g·cm−3) Mass Moles Gallic acid 170.12 250 - 1.7 0.50 g 2.939x10^-3 Ethanol 460.07 -114 78.37 0.789 50 mL 0.08575 Sulfuric Acid (Catalyst) 98.08 10 337 1.84 1 mL 0.01875 theoretical: theoretical: theoretical: 149-153 0.5824 g 2.939x10^(-3) experimental: experimental: experimental: 142-147 447.3 (at 0.04 g 2.018x10^(-4) Ethyl Gallate 198.17 760mmHg) 1.424 Water 18.02 0.9167 0 100 - - 4. Procedure: 2 marks Summary of lab procedure – what YOU did, third person, past tense – be concise! In this part of the lab, ethyl gallate was synthesized , isolated and characterized. To begin with, a sand bath was prepared for the heating step that was to be done soon after. Next, 0.75 g of gallic acid was dissolved in 50 mL of ethanol and approximately 1 mL of H SO in a 102 mL4round bottom flask. The H S2 wa4 added using a pipette. A boiling chip was then added to the flask for stirring purposes. A condenser was then added to the flask and it was refluxed at 100̊C for one hour (it was done on a hot plate). Following that, the TLC of the solution was taken with dichloromethane: methanol (8:2) as the solvent. The plate and some crystals of iodine was placed in a beaker and was covered with a larger beaker until it was possible to see the spots. The reaction mixture was left to cool to room temperature for a while, then ethanol was removed from the solution using a rotovap and this resulted in the formation of a white solid. Water was then added to the solid and then that was transferred to a separatory funnel. 15 mL of diethyl ether was added to the separatory funnel and then it was left a lone for some time (approximately a minute) to allow the organic layer and aqueous layer to separate from each other. Each layer was then collected in a different flask. After, the aqueous layer was put back into the separatory funnel along with another 15 mL of diethyl ether and the aqueous layer was removed. To the organic layer that was already present in the separatory funnel, previously collected organic layer was added along with 15 mL of 10% NaHCO3. The organic layer was washed with 15 mL of 10% NaHCO3 three times in total. The organic layer was separated from the aqueous layer and they were collected in two different flasks. Next, the organic layer was dried with Chemistry 222 Fall 2012 3 sodium sulfate. The solution was then gravity filtrated and the diethyl ether was collected in a 100 mL round bottom flask. Using a rotovap, the diethyl ether was removed. To finish the lab, the melting point and IR of the product was taken. 5. Results: 5 marks a. Table 1: Yield and Physical Properties Purified Ester Yield (g) 0.04 g Yield (%) 6.87 % Appearance White crystalline powder Melting Experimental: 142- 147 ̊C Point Theoretical: 149-153 ̊C b. Figures: TLC, IR and NMR Spectra i. TLC plate – diagram, label spots/solvent front, calculate R vflues ii. IR Spectrum of Ester – attach and label import
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