SC CHEM 333 - Acid Catalyzed Esterification Post-Lab (3 pages)

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Acid Catalyzed Esterification Post-Lab



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Organic Chemistry 333L section 03M Laboratory Post Lab Acid Catalyzed Esterification By Cameron Kahn 5 November 2013 TA James Collie Observations The unknown alcohol had a slightly alcoholic odor When the acids acetic and sulfuric were added to the unknown alcohol in the round bottom flask the solution heated up substantially meaning that the reaction was exothermic The solution began to bubble a few minutes later and continued to boil through the hour and a half reflux period The vapors traveled up the column and condensed back into liquid further up Droplets of the liquid were seen sliding back down into the solution After some time during this process the solution turned a slight yellow hue The solution was then transferred to the separatory funnel where water and ether were added Two layers formed but there was barely any noticeable line between the two layers The undesired bottom layers were always removed throughout the process When the sodium bicarbonate was added two distinct layers formed This also occurred when the sodium chloride was added In both steps the stopper could be felt trying to come off the separatory funnel due to the build up of pressure The pressure was caused by the formation of carbon dioxide from the sodium bicarbonate reacting with the acids in the solution Constant venting was needed to decrease the pressure build up from inside the funnel The final product that was recovered after a final distillation had a fruity odor to it Using microboiling point techniques a steady stream of bubbles could be seen coming from the end of the capillary tube and when removed from heat the liquid rose entirely up the capillary tube This process was noted to be capillary action This 1 Page was a similar action that was seen in the TLC experiment where the solution traveled up the adsorbent layer on the TLC paper through capillary action Results Amount of product weight of product and test tube weight of test tube 0 091g 3 788g 3 697g Boiling point measured 92 0oC Boiling point theoretical 102oC Identity of unknown B propyl acetate Conclusions This experiment utilized acid catalyzed esterification This process is better known as Fischer esterification This process allows one to produce an ester from an unknown alcohol In a Fischer esterification the acid catalyst is needed to protonate the carbonyl oxygen and to protonate the OH leaving group Having a strong acid will cause the reaction to speed up The sulfuric acid was needed in the beginning to also speed up the reaction initially The sulfuric acid also provided the ability for the OH leaving group to turn into water more easily which is the reasoning behind why it sped up the reaction initially The esterification using the sulfuric acid as the catalyst made the process reversible and equilibrium is reached with a few hours It is important to note however that with the addition of more alcohol or sulfuric acid the equilibrium is completely dependent on these factors and will shift accordingly Handy After an hour under the reflux process the solution turned from clear to yellow which indicated that the reaction occurred Esterification is an important reaction especially to the food and perfume industries Due to time constraints distillation was not done to completion and therefore caused less product to yield This error did not affect our results beyond the amount of product yielded because the method of microboiling point only needed 2 3mL or less of product to determine a boiling point The measured boiling point was 92oC which was compared to the theoretical of propyl acetate that has a boiling point of 102oC The percent difference of the actual to the suggested theoretical was a mere 10 difference The smell of pears also hinted to propyl acetate as the unknown alcohol Finally the IR analysis done on the product cleared up any doubts The graph showed that there was hardly any impurities including almost no water left in the final product This was the best product yielded out of the entire lab due to the C H stretch at 2950cm 1 and carbonyl stretch that was shifted to the right from the involvement with the ester to about 1680cm 1 The IR supported our hypothesis that unknown B was in fact propyl acetate From the measured boiling point the smell observed and the IR analysis the unknown alcohol B was determined to be propyl acetate IR Analysis 2 Page C H Stretch 2950cm 1 Carbonyl Stretch 1680cm1 References 1 Ali George Handy and Salman Chemistry 333 334 Laboratory Manual Columbia South Carolina QDE Press 2012 2 Fischer EsterificationFischer Speier Esterification Fischer Esterification Organic Chemistry Portal n d Web 04 Nov 2013 3 Page


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