Banana oil lab 2 - tripp PDF

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kSeptember 22, 2015

Preparation of Synthetic Banana Oil

McEnaney, K.

Purpose: To find if synthetic banana oil made by Fisher Esterification reaction leaves more than 2% acetic acid at equilibrium Reference: SDS- fishersci.ca Lehman, John W. “Catalyst: The Pearson Custom Library for Chemistry”. 1st Ed. Organic Chemistry Laboratory Manual. 2014. Reaction:

Reagents

M.W

Isopentyl Alcohol

88.15g/mol

Glacial Acetic Acid

60.05g/mol

117C

0.3

17mL

17mL

Sulfuric Acid

98.079g/mol

n/a

0.019

1mL

1mL

Sodium Bicarbonate

84.007g/mol

B.P 130-132C

851C

Moles .150

1.57 60mL

Amount to use

Amount used

13.22g

13.228g

60mL

Magnesium Sulfate

120.366g/mol

Water

18.01g/mol

n/a

100C

n/a

2.77

n/a

n/a

50mL

50mL

Safety Equipment: Gloves, goggles, lab apron, fume hood SDS: Isopentyl alcohol is harmful if inhaled, causes dizziness, and is a eye, skin, and respiratory irritant; glacial acetic acid should not be inhaled and is very flammable; sulfuric acid burns the skin, can cause eye damage, and is a respiratory irritant while being corrosive to metals; water is toxic if inhaled; Magnesium sulfate should not be inhaled or swallowed or in contact with bare skin; sodium bicarbonate can cause serious eye damage and should not be swallowed. Equipment: 2-25mL graduated cylinders 10mL-graduated cylinder Disposable pipettes 100mL round bottom flask Vacuum grease Separatory funnel 2-100mL beaker 250 Erlenmeyer flask Stop cock Filter paper

Simple distillation apparatus Boiling chips Heater Theoretical Yield: 13.02g Procedure: To start the lab, 13.228 grams of isopentyl alcohol was weighed out on analytical balance and then poured into a 100mL round-bottomed flask with a few boiling chips. 17mL of glacial acetic acid and 1mL of sulfuric acid were added into the round bottom flask while being stirred. The mixture was heated and continually stirred for one hour. Once the time was up, the solution was cooled to room temperature and then transferred to a separatory funnel where it was washed with 50mL of water. The bottom aqueous layer was drained, and the top organic layer was kept in the funnel and washed with 5% aqueous sodium bicarbonate. This was repeated twice with the aqueous layer that formed on the bottom drained each time. The organic layer was then drained and dried with two scoops of magnesium sulfate and then put into a gravity filtration. A simple distillation apparatus was set up, and the crude isopentyl acetate was poured into a round bottom flask after it was finished with gravity filtration. The distillation was started, and the temperature at the first drop was recorded. Once the distillation was complete, the distillate was weighed and then 1.5mL of the distillate was poured into a vial that would be kept for gas chromatography. The solution was analyzed in the gas chromatography apparatus where the 1 microliter was placed in the injection over and heated around 300 C. once it was completely vaporized and in gas phase with helium, the more volatile gas quickly went through the AT-FAME column while the less volatile went more slowly. The sample then exited the column and went into the mass spectroscopy apparatus that was coupled with it. Once the sample went into the mass spectroscopy apparatus, the sample immediately went through electron ionization in the ion trap. The ions that were looked at had an m/z range of 40-650. In the mass spectrum data, the ionization and fragmentation pattern was obtained for each 1-second of the scan for the range of m/z. This information would be on the x-axis of the graph, while the total ion count that came from the gas chromatography apparatus would be found on the yaxis. From the gas chromatography and mess spectroscopy data, the peak areas were obtained. From those peaks, the percent yield of isopentyl acetate was found based on the percentage in the distillate. Information regarding the gas chromatography and mass spectroscopy can be found in Table 1.The data compiled into Table 1 can be found in figures 1-4. Apparatus Diagram:

Results: Mass of isopentyl acetate distilled: 11.388g

Mass of isopentyl alcohol needed: 13.222g Percent Yield: 87.5% Boiling Point Ranges for the Distillation: 115C -128C Table 1: Gas Chromatography Data

Isopentyl Acetate Isopentyl Alcohol Acetic Acid

R.T

Peak Area

% Area

Ionization peak

Base Peak

1.653

657364176

97.98%

130.5

43.1

2.056

13129499

1.95%

1.276

169859

.025%

59

43.2

Identificatio n

Molar Mass mol/g 130

GC Peak # 4

88.15

GC Peak # 6

60.0 5

GC Peak #1

 Calculations: Mass of Banana Oil in Graduated Cylinder: 108.312g of beaker – 96.924g of beaker and liquid = 11.388g of Isopentyl acetate Mass in grams of 150mmol isopentyl alcohol: (150mmol isopentyl alcohol) x (1mol/ 1000mmol) x (88.15g isopentyl alcohol/1mol isopentyl alcohol) = 13.222 g of isopentyl alcohol Theoretical Yield: (13.222g isopentyl alcohol) x (1mol isopentyl alcohol/ 88.15g isopentyl alcohol) x (2/3mol isopentyl acetate/1mol isopentyl alcohol) x (130.2 g isopentyl acetate/ 1mol isopentyl acetate) = 13.02g isopentyl acetate Expected Percent Yield: (11.388g isopentyl acetate/ 13.02g isopentyl acetate) x 100% = 87.5% isopentyl acetate Percent Error: (Theoretical-actual)/ actual x 100% [(13.02g – 11.388g)/ 11.388g] x 100% = 14.33% Percent of Isopentyl Acetate: Area under curve of isopentyl acetate x 100% = percent of isopentyl acetate Total area 657364176 x 100% = 97.98% isopentyl acetate (670854112)

Percent of Isopentyl Alcohol Area under curve of isopentyl alcohol x 100% = percent of isopentyl alcohol Total area 13129599 x 100% = 1.95% isopentyl alcohol (670854112) Percent Acetic Acid: Area under curve of acetic acid x 100% = percent of acetic acid Total area 169859 x 100% = .025 % acetic acid (670854112) Discussion/ Conclusion: In conclusion, synthetic banana oil (isopentyl acetate) made via Fisher Esterification can be produced with less than 2% acetic acid. The percent composition of banana oil synthesized was 97.98% while isopentyl alcohol and acetic acid had a percentage of 1.95 % and .025 % respectively. There were some errors that could have occurred that caused an imperfect percent composition of isopentyl acetate such as the intiation and terminations of fractions were not as clear during the experiment, and the second and third fraction may have been switched too late, leaving some of the pure isopentyl acetate in the second fraction when it should have been in the third fraction. Post Lab Questions: 1(a). Acetic Acid Isopentyl Alcohol Isopentyl Acetate Intial 0.3 mol .15 mol 0 mol Change -X -X +X Equilibrium 0.3-X 0.15-X X After completing the ICE table and doing the quadratic formula, the X value I found for the amount of isopentyl acetate that should be present in the reaction mixture at equilibrium was .0732 mol. 2. What gas escaped during the sodium bicarbonate washing? Write balanced equations for the two reactions that took place during this operation. The gas that escaped was CO2 during the bicarbonate washing. The balanced equation is as follows: HC2H3O2 + NaHCO3  C2H3O- + Na+ H2CO3 H2CO3  H2O + CO2 4. Describe and explain how each of the following experimental errors or variations might affect your results. (a) You failed to dry the reaction flask after washing it with water. (b) You forgot to add sulfuric acid. (c) You used twice the amount of acetic acid specified in the procedure. (d) You left out the sodium bicarbonate washing step. (e) Your thermometer bulb was 1cm higher than it should have been. (a): If I failed to dry the reaction after washing it with water, there could still be traces of water left in solution with isopentyl acetate, and if there is water, chances are that some acetic acid and/or sulfuric acid is still mixed with the water, and this can throw off some of the results and compromise the purity of the final product.

(b): Sulfuric acid was used as a catalyst to increase the rate of the equilibrium reaction taking place. Without sulfuric acid, the reaction would take longer, and after the hour was up from heating the solution, the reaction wouldn’t be as complete, leaving more isopentyl alcohol in solution than isopentyl acetate. In result, I wouldn’t have as much product as I want, leaving me with a large amount of error. (c): If I used twice the amount of acetic acid, it doesn’t directly affect my experiment because it is not a limiting reagent, and it is needed for the experiment. It will affect the results, however, if I do not wash the mixture after heating the reaction or dry it because then the extra traces of acetic acid that did not react with still be in solution and that will affect my results and give me more impurities in my final product. (d): Leaving out the washing with sodium bicarbonate will definitely affect my final results. Acetic acid and sulfuric acid are soluble in water, but they are also soluble in the ester that was made during the reaction, so some traces of them will be left in the isopentyl acetate mixture. When the solution is dried, some acetic acid and sulfuric acid will be pulled out, but some will be left in and that will cause a lot of error in the results. (e): If I placed the thermometer bulb 1cm higher than it should have been, it doesn’t affect the reaction directly, but it will affect the results because we were supposed to record the temperature when the distillation began and when it ended to give us a range. If our range is off, then some of our results are slightly skewed. The way this would cause the temperature to be off was that the gas would have to travel farther to reach the thermometer, and by that time, some of the gas will have cooled since it was passing the condenser. Again, this will throw off some of my results if I did that....