Organic Chemistry Fischer Esterification Lab Report

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San Diego State University

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Complete a lab report for the following Fischer Esterification: The preparation of Methyl Benzoate.

This is submitted with a fully analyzed NMR spectrum. Please also put the following information:
Your name, Compound name, Weight of product in grams, Theoretical and percent yield calculations, Lab section number, Observations (conclusions).  

1. Please show your calculations for obtaining your percent yield. Include the calculations for the theoretical yield as well. Also, if something went wrong during the course of your experiment (i.e you spilled your product, did the work-up wrong, etc.) you can explain it here. Include any modifications made in procedures, changes in colors during reaction or isolation, temperature increases, and report observed melting or boiling points.

2. Analyze your NMR spectra and upload a picture of it on this assignment. In your spectra, you should have the approximate chemical shifts of each peak. You also have to include an explanation matching up the peaks in your NMR spectra to that of the product, methyl benzoate. Explain why you think you got your product and not just starting material. If you have extra peaks in your NMR that do not match up to any proton peaks in your product, explain where they could have come from.  Every peak must be accounted for!Attached are lab Manuel pages as well as results from personal experiment.

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THE PREPARATION OF METHYL BENZOATE: An Example of Fischer Esterification O O OH + CH3 OH excess H+ OCH3 + H2 O Reference: Roberts, Gilbert, Rodewald and Wingrove Chapter 22.A, pages 551-552 and 554-555. Solomons and Fryhle 10th Ed. Chapter 17.7A, pages 797-804. General Concepts The esterification of a carboxylic acid is an equilibrium controlled reaction. In this reaction, we shift the equilibrium to the right by using a large excess of the alcohol. You should be very familiar with the mechanism of this reaction and expect questions on the quiz. The apparatus for reflux is illustrated on the next page. During the work-up, you will first remove the excess methanol. Methanol and sulfuric acid are very soluble in water. Simply washing the solution of methyl benzoate dissolved in chloroform with water removes most all of the methanol and sulfuric acid. You do not need to violently shake the separatory funnel to effect extraction. How do you know which is the aqueous layer and which is the organic one containing your product? You can make a good guess by looking at the density of water versus chloroform (chloroform is denser than water). But the simplest and wisest thing is to check the layers. After you have separated the layers using the separatory funnel, add a drop of water to both fractions. Does the water dissolve, or does it remain as a separate drop that floats or sinks? Think before you dispose of your washes! The wash with 0.6 M NaHCO3 does two things: it removes the last traces of the sulfuric acid and it converts any unreacted benzoic acid to sodium benzoate, which is water soluble. Both of these reactions liberate carbon dioxide, so relieve gas pressure build-up by frequently venting your separatory funnel. Check the pH of the sodium bicarbonate layer until it is basic to litmus. CO2H + soluble in chloroform CO2 - Na + NaHCO3 + CO2 ↑ soluble in water Do you know which litmus paper you need to use (blue or red)? If the bicarbonate layer is not basic, that means there is acid (sulfuric or benzoic acid) still present. Wash the organic layer again with fresh bicarbonate solution until the bicarbonate layer remains basic. Saturated aqueous sodium chloride washes minimize solubility of organic materials in the aqueous washes. Before you distill, you must dry the chloroform solution, otherwise the traces of water will distill over with your methyl benzoate and contaminate the product. If the solution is not dried, droplets of water will be seen in the distilled product with a significant reduction in grade! Dry the chloroform solution using  anhydrous magnesium sulfate. How much is needed? Too much results in loss of product while too little doesn't remove all the water. Before you add the drying agent, note that the solution is turbid (cloudy). Add a half of a spatula of magnesium sulfate and swirl the chloroform solution. Notice how the fluffy MgSO4 cakes-up (hydrates by absorbing water) and quickly settles to the bottom of the Erlenmeyer flask. This may take 30 seconds to occur. The solution is a little less turbid than before. Continue to slowly add more magnesium sulfate while swirling until some of the drying agent remains as a fine powder and is no longer clumping together. The presence of unhydrated MgSO4 indicates that all of the water has been removed. Filter to remove the magnesium sulfate. Isolate the ester by simple distillation. 4 DO IT SAFELY 1. Methanol is very flammable and very hard to see as it burns with an almost invisible blue flame! All ground-glass joints of your apparatus should be well lubricated and tightly mated to prevent leakage of methanol during the reflux. 2. Handle containers of concentrated sulfuric acid with care. Should any of this strong acid come in contact with your skin, flood the affected area immediately with cold water, rinse it with dilute sodium bicarbonate solution and tell your TA. 3. Vent the separatory funnel frequently during the extractions; pressure develops due to the volatility of chloroform and the evolution of carbon dioxide. Experimental Procedure Place a clean stir bar, 41 mmol of benzoic acid and 310 mmol of methanol in a clean 50-mL round-bottomed flask. Carefully pour 1.5 mL of concentrated (18M) sulfuric acid (H2SO4) down the side of the flask. Gently swirl the flask to mix the reagents, attach a reflux condenser as shown in the drawing, and gently reflux Water Out while stirring for 1 hr using a heating mantle. The solid benzoic acid will dissolve as the solution heats. Add 25 mL of water to your 125-mL separatory funnel. Allow the reaction solution to cool enough to handle it easily and transfer it to the separatory funnel containing water. Rinse the round bottomed flask several Clamp Here times using a total of 25 mL of chloroform, CHCl3, combining the chloroform rinsings in the funnel. Shake the funnel thoroughly to facilitate extraction of methyl benzoate into the organic chloroform layer, venting the funnel frequently. Note that the density of chloroform is greater than water and the organic product is in the lower organic layer. Remove the aqueous layer by first draining off the heavier organic layer, then pour out the aqueous Water In portion from the top of the separation funnel, then add the organic layer back to the funnel and wash with a second 15 mL portion of Clamp Here water. After again removing the aqueous layer and adding the organic layer back to the funnel, add 15 mL of 0.6 M aqueous sodium bicarbonate to the funnel (Caution: foaming and gas formation may occur!). Gently shake the mixture, frequently venting the funnel. Separate the layers, keeping your aqueous bicarbonate layer apart from all other aqueous layers, and test the aqueous bicarbonate layer with litmus paper to see whether it is basic. If the layer is not basic, repeat the washing of the organic layer with fresh aqueous bicarbonate, testing each new wash individually until it remains basic. Finally, wash the organic layer with 15 ml of saturated sodium chloride (brine) solution. Dry the organic fraction with anhydrous magnesium sulfate. Dispose of all aqueous washes in the container labeled "Accumulated Aqueous Washes" found in the chemical disposal hood.* Gravity filter the chloroform solution into a 50mL round bottom flask using the glass filter with shark skin or fluted filter paper to remove the magnesium sulfate, and rinse the drying agent and flask once with a minimum amount of chloroform. The drying agent and paper are disposed of in the container labeled "Saturated Magnesium Sulfate & Filter Paper." The product is purified by  simple distillation. Assemble a simple distillation apparatus using a heating mantle and a stir plate. It is important that you do not use a keck clip on the round bottomed flask, since it will melt at temperatures above 150°C. Also remember to grease the glass joints or they will stick and be hard to separate. The collected chloroform is placed in the waste container labeled "Chloroform Accumulation from Distillation". Start collecting the methyl benzoate fraction with a boiling point greater than 190 °C by distilling directly into a weighed clean, dry vial. Determine the yield of the methyl benzoate. Be sure that your product contains no droplets of water or particulate contaminants, and that it is clear and colorless. The residue in the distillation setup, especially the round bottomed flask, will smell strongly. Rinse it with soap and water in your hood and add the wash to the proper waste container.  Observation: 10 mL Methanol 59 Methyl Benzuate 1.5 mL acil sulfuric * Started Refluxing 7 2:55 pm vial weight: 16.81, 16.969 (0.159/5) Content *Stopped Refluxing 3:55pm x 100 = 3%5 zen_Exp1 10.0 8.5 9.0 9.5 FUST 6.5 7.0 7.5 8.0 6.0 5.5 5.0 f1 (ppm) 4.5 M 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 - -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -0.5 0.0 -20 10 -0 -1.0 -10Observation: 10 mL Methanol 59 Methyl Benzoate 1.5 mL acil sulfuric * Started Refluxing 7 2:55 pm vial weight: 16.81, 16.969 (0.159/5) Content *Stopped Refluxing 3:55pm x 100 = 3%5 zen_Exp1 10.0 8.5 9.0 9.5 FUST 6.5 7.0 7.5 8.0 6.0 5.5 5.0 f1 (ppm) 4.5 M 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 - -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -30 -0.5 0.0 -20 10 -0 -1.0 -10
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Please view explanation and answer below.Here you go! I added a small intro and conclusions. It should be good. Let me know if you need anything else

Name
Compound name: Methyl benzoate
Section
Lab Report
Fisher esterification - Synthesis of methyl benzoate
Introduction
The most common synthetic route to obtain ester comes from the interaction between a carboxylic
acid and an alcohol. It is a reversible process known as the Fisher esterification. In this reaction,
the starting materials react to form ester and water and it is usually catalyzed by a strong acid such
as sulfuric or phosphoric acid. The overall mechanism consists in the protonation of the carbonyl
group, followed by the nucleophilic attack of the alcohol to said carbon. Then, a proton transfer
converts the hydroxyl group into water, which leaves the molecule while the carbonyl double bond
is regenerated, leading to the ...


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