Question

weight of cylinder 10.48g

weight of cylinder with of isopentyl alcohol 14.55g

weight of collecting flask 56.77 g

weight of collecting flask with product 60.42g

I need help getting theoretical yield and % yield.

Experiment 12 Isopentyl Acetate (Banana Oil) 93 Rasmussen, P. W. Qualitative Analysis by Gas Chromatography-G.C. versus the Nose in Formu- lation of Artificial Fruit Flavors." Journal of Chemical Education, 61 (January 1984): 62. Shreve, R. N., and Brink, J. Chemical Process Industries, 4th ed. New York: McGraw- Hill, 1977. Welsh, F. W., and Williams, R. E. "Lipase Mediated Production of Flavor and Fragrance Esters from Fusel Oil." Journal of Food Science, 54 (November/December 1989): 1565. EXPERIMENT 1 2 Isopentyl Acetate (Banana Oil) Esterification Heating under reflux Separatory funnel Extraction Simple distillation In this experiment, you will prepare an ester, isopentyl acetate. This ester is often re- ferred to as banana oil, because it has the familiar odor of this fruit. CH3 н" CH2-C-OH +CH-CH-CH2- CH OH Acetic acid Isopentyl alcohol (ехсess) CH3 O CH3-C-O-CH2 CH2-CH-CH3 + H20 Isopentyl acetate bran Isopentyl acetate is prepared by the direct esterification of acetic acid with isopentyl alcohol. Because the equilibrium does not favor the formation of the ester, it must be shifted to the right, in favor of the product, by using an excess of one of the starting materials. Ace- tic acid is used in excess because it is less expensive than isopentyl alcohol and more eas- ily removed from the reaction mixture. In the isolation procedure, much of the excess acetic acid and the remaining isopentyl alcohol are removed by extraction with sodium bicarbonate and water. After drying with anhydrous sodium sulfate, the ester is purified by distillation. The purity of the liquid prod- uct is analyzed by determining the infrared spectrum. n-0r Vu ost Required Reading Techniques 5 and 6 Review: Reaction Methods Technique 7 Technique 12 New: Extractions, Separations, and Drying Agents Procedure Apparatus. Assemble a reflux apparatus, using a 25-mL round-bottom flask and a water-cooled condenser (refer to Technique 7, Fig. 7.6, p. 628). Use a heating mantle to heat. In order to control vapors, place a drying tube packed with calcium chloride on top of the condenser. Reaction Mixture. Weigh (tare) an empty 10-mL graduated cylinder and re- cord its weight. Place approximately 5.0 mL of isopentyl alcohol in the graduated cylinder and reweigh it to determine the weight of alcohol. Disconnect the round bottom flask from the reflux apparatus and transfer the alcohol into it. Do not clean or wash the graduated cylinder. Using the same graduated cylinder, measure approxi- mately 7.0 mL of glacial acetic acid (MW = 60.1, d = 1.06 g/mL) and add it to the al- cohol already in the flask. Using a calibrated Pasteur pipet, add 1 mL of concentrated sulfuric acid, mixing immediately (swirl), to the reaction mixture contained in the flask. Add a corundum boiling stone and reconnect the flask. Do not use a calcium carbon- ate (marble) boiling stone because it will dissolve in the acidic medium. Reflux. Start water circulating in the condenser and bring the mixture to a boil. Continue heating under reflux for 60-75 minutes. Then disconnect or remove the heat- ing source and allow the mixture to cool to room temperature. Extractions. Disassemble the apparatus and transfer the reaction mixture to a separatory funnel (125-m L) placed in a ring that is attached to a ring stand. Be sure that the stopcock is closed and, usina a funnel, pour the mixture into the top of the separatory funnel. Also be careful to avoid transferring the boiling stone, or you will need to remove it after the transfer. Add 10 mL of water, stopper the funnel, and mix the phases by careful shaking and venting (Technique 12, Section 12.4, and Fig. 12.6, pp. 704 and 705). Allow the phases to separate and then unstopper the funnel and drain the lower aqueous layer through the stopcock into a beaker or other suitable container. Next, extract the organic laver with 5 mL of 5% aqueous sodium bicarbon- ate just time with 5 mL of saturated aqueous sodium chloride. as you did previously with water. Extract the organic layer once again, this 250IT2 U0 Drying. Transfer the crude ester to a clean, dry 25-mL Erlenmeyer flask and add approximately 1.0 g of anhydrous granular sodium sulfate. Cork the mixture and al- low it to stand for 10-15 minutes while you prepare the apparatus for distillation. If the mixture does not appear dry (the drying agent clumps and does not "flow," the solution is cloudy, clean, dry or drops of water are obvious), transfer the ester to a new 25-mL Erlenmeyer flask and add a new 0.5-g portion of anhydrous sodium sulfate to complete the drying. 20BTVOSO Distillation. Assemble a distillation apparatus using your smallest round- bottom flask to distill from (Technique 14, Fig. 14.1, p. 734). Use a heating mantle to heat. Preweigh (tare) and use another small round-bottom flask, or an Erlenmeyer 7.1e 96 Introduction to Basic Part One flask, to collect the product. Immerse the collection flask in a beaker of ice to ensure condensation and to reduce odors. You should look up the boiling point of your ex- pected product in a handbook so you will know what to expect. Continue distillation drops of liquid remain in the distilling flask. Record the observed noD until only one or two boiling point range in your notebook. Yield Determination. Weigh the product and calculate the percentage yield of the ester. At the option of your instructor, determine the boiling point using the methods described in Technique 13, Sections 13.2 and 13.3, pages 724 and 727. )Spectroscopy. At your instructor's option, obtain an infrared spectrum using salt plates (Technique 25, Section 25.2, p. 875). Compare your spectrum with the one re- produced in the text. Interpret the spectrum and include it in your report to the in- structor. You may also be required to determine and interpret the proton and carbon- 13 NMR spectra (Technique 26, Part A, pp. 911-916, and Technique 27, Section 27.1, p. 947). Submit your sample in a properly labeled vial with your report. one of b

Answer 1

Mass of isopentyl alcohol = 14.55-10.48 = 4.07 g

Mass of product collected = 60.42-56.77 = 3.65 g

1 mole isopentyl alcohol give 1 mole product

88.148 g isopentyl alcohol give 130.19 g product.

4.07 g isopentyl alcohol give 130.19×4.07/88.148 g product

= 6.01 g product

Theoretical yield = 6.01 g

% yield = 3.65×100/6.01 = 60.73%