SC CHEM 333 - Acid Catalyzed Esterification Pre-Lab (7 pages)

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Acid Catalyzed Esterification Pre-Lab



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Organic Chemistry 333L section 03M Laboratory Pre Lab Acid Catalyzed Esterification By Cameron Kahn 29 October 201314 January 2019 TA James Collie Objectives In this lab one will learn to synthesis an ester from an unknown alcohol by means of an acid catalyzed esterification He she will purify the product by means of distillation Finally one will record any data and determine the boiling point Theory In general esters have a low molecular weight and often have a pleasant aroma Because of these factors esters are used in the food industry as artificial flavors and in the perfume industry as fragrances Handy The synthesis of esters is very important to both industries in particular Esters can be prepared through a reaction of carboxylic acid with the presence of an alcohol The acid catalyzed conversion between the carboxylic acid and alcohol to form an ester is called Fischer Esterification Fischer Esterification This reaction can be done in reverse but still be slow This cannot be said about the acetic anhydride ester synthesis During the acid base extraction sodium bicarbonate is used to neutralize the acid Once added the sodium bicarbonate will form carbon dioxide which will in turn cause pressure build up in the apparatus Throughout the esterification he she will need to vent the apparatus often Lastly the use of micro boiling point techniques will determine the boiling point This technique is used when there is only a small amount of liquid left about 2 3 mL of desired product from the reaction 1 Page Mechanism As noted in the Chemistry 333 lab manual written by George Handy Step 1 Step 2 Step 3 2 Page Procedure Start by setting up a 25 mL round bottom flask equipped with a reflux condenser apparatus Handy Lightly grease all glass connections and then sink the round bottom flask into the heating mantle Next he she will add 15 mL of acetic acid 1 5 mL of concentrated sulfuric acid and 2 mL of unknown alcohol to the 25 mL round bottom flask Set the Variac between 70 and 75 and heat until the mixture begins to boil under the reflux Then lower the Variac setting after boiling begins Allow the solution to boil for 1 5 hours Once the time is up allow the flask to cool to room temperature Place the contents from the round bottom flask into a separator funnel that has 12 mL of water Rinse the flask with 12 mL of ether and pour it into the separator funnel Shake thoroughly and discard the lower layer Place 7 mL of water and 7 mL of saturated sodium bicarbonate solution into the separator funnel Shake and discard the lower aqueous layer Then rinse organic layer using 10 mL of saturated sodium chloride solution Handy Transfer remaining layer into an Erlenmeyer flask Add a micro scoop of anhydrous magnesium sulfate and swirl for one minute Let the product settle for 2 3 minutes Transfer the dry supernatant ether solution to a clean 25 mL flask Set up a short path distillation apparatus and heat strongly with a Variac setting of 65 70 Collect the product in a small test tube and determine the boiling point of the purified ester using a micro boiling point Perform a P NMR analysis of final ester to determine the starting alcohol and also an IR analysis To perform a micro boiling point determination on a desired product start by taking a small amount of the sample and pour it into a clean dry test tube Next obtain a small melting point capillary tube and place it into the liquid filled test tube making sure closed side up Now take 3 Page the test tube and rubber band the thermometer to ensure the bottom of your test tube is at the same level as your thermometer bulb Next one will place the entire assembly into an extra large test tube filled with mineral oil so that the entire level of the liquid is below that of the mineral oil bath Handy Using the heating mantle heat the mineral oil bath until it starts to bubble and gas begins to escape from the bottom of the capillary tube The next step after one notices a steady stream of bubbles from the bottom end remove the extra large test tube from the heat source and allow the apparatus to cool While the liquid cools the atmospheric pressure will equal the vapor pressure of the liquid and the liquid will begin to rise up the capillary tube Handy Record your temperature as this will be the boiling point Apparatus Figure 1 Ring Stand Handy 4 Page Figure 2 Suction Funnel Handy Reagent Table Name Structure Molecular Weight g mol Melting Point oC Boiling Point oC Density g mL 60 05 16 6 118 1 05 74 1224 116 34 6 0 706 120 3626 1124 2 66 84 001 801 1413 1 03 98 07 3 290 1 84 C2H4O2 Acetic Acid Diethyl Ether C4H10O MgSO4 Magnesium Sulfate NaHCO3 Sodium Bicarbonate Sulfuric H2SO4 5 Page Acid Sodium Chloride NaCl 58 442 801 1413 2 165 74 12 90 111 1 Propanol 60 11 126 5 97 0 804 Name Molecular Weight g mol Melting Point oC Boiling Point oC Density g mL 60 11 89 5 82 0 785 102 18 52 157 0 814 130 14 15 196 0 827 C4H10O 1 Butanol 0 81 C3H7OH Structure C3H7OH Isopropanol C6H13OH N Hexanol C8H18O 1 Octanol Disposal Dispose of any gloves used during the experiment in the designated container Dispose of all ester synthesized in the organic waste container Organic solvents ether should be disposed of in a different organic waste container than the ester Any broken glass must go in the glass container and one should alert the TA Wash excess aqueous solutions down the drain For other general waste talk to the TA for advice on proper disposal techniques References Ali George Handy and Salman Chemistry 333 334 Laboratory Manual Columbia South Carolina QDE Press 2012 6 Page Fischer EsterificationFischer Speier Esterification Fischer Esterification N p n d Web 27 Oct 2013 7 Page


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