Homework answers / question archive / Northampton Community Collage Esterification: Isopentyl Acetate (Oil of Banana) REACTION: last Quest mass s H+ fr, NMR, H2O + + OH OH Isoamyl alcohol acetic acid Isoamyl acetate THEORY Esters are fragrant substances found in many plants, and also in animal tissues

Northampton Community Collage Esterification: Isopentyl Acetate (Oil of Banana) REACTION: last Quest mass s H+ fr, NMR, H2O + + OH OH Isoamyl alcohol acetic acid Isoamyl acetate THEORY Esters are fragrant substances found in many plants, and also in animal tissues

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Northampton Community Collage Esterification: Isopentyl Acetate (Oil of Banana) REACTION: last Quest mass s H+ fr, NMR, H2O + + OH OH Isoamyl alcohol acetic acid Isoamyl acetate THEORY Esters are fragrant substances found in many plants, and also in animal tissues. They impart many of the customary fragrances and flavors associated with fruits, and the lower molecular weight esters are also useful as solvents in paints, lacquers, etc. Esters are commonly made by reacting a carboxylic acid with an alcohol using a trace of acid catalyst in a dry apparatus, yielding an ester and water. The reaction equilibrium is best shifted to the right, favoring product formation, if the water is removed as it forms, or the product is removes as it forms, in accordance with LaChatelier's Principle. In some cases, as in this synthesis, the equilibrium is sufficiently far to the right that the product forms easily without removal of any reaction component during the heating process. Isoamyl acetate is a colorless liquid with the odor of banana, and is a component of banana oil. It has a strong odor and has a "heady” effect, so the product should be kept covered and cold as much as possible during the procedures. PROCEDURE: Set up a typical reflux apparatus with vertical-mounted water-cooled condenser using a 100-mL round bottom tapered flask. Add 17.6g (22mL; 0.2 mol) isoamyl alcohol (density = 0.81), followed by 30 mL (0.5 mol) of glacial acetic acid (density = 1.01). Carefully add 4.0 mL of concentrated sulfuric acid, and swirl the contents of the flask to mix the reagents. Add a boiling chip or two, grease the joints, mount the condenser, and heat the mixture gently using a heating mantle. Allow the reaction to reflux for 1 hour, then cool the mixture in a cool water bath. Pour the mixture slowly into about 100 mL of water in a 400-mL beaker, and then transfer the entire mixture to a large (250-mL) separatory funnel. Determine which layer is the organic (ester) layer. Separate the layers, and return the crude ester layer to the separatory funnel. Wash it with about 30 mL of 10 % aqueous sodium bicarbonate solution. Sodium bicarbonate will produce high pressure be sure to vent often. Swirl gently, venting off pressure periodically. (There will be a pressure build-up, so keep a finger over the glass stopper during the wash process). Separate the layers again, and wash the ester with water (about 30 mL), swirl vigorously for a few minutes. Questions: 1. Another way to make esters is to react an alcohol with an acid chloride, which resembles a carboxylic acid except the OH group is replaced by a Cl in the structure. Write an equation showing the preparation of Isopentyl acetate using isoamyl alcohol and the acid chloride of acetic acid. The process evolves HCl, and no H catalyst is needed. 2. Give equations, showing structures, giving the esters formed in the following cases: (a) cyclohexanol and pentanoic acid (b) excess butanol and butanedioic acid (HOOC-CH2CH2-COOH) 3. In process 2 (b) above, assume you use 7.4 grams of butanol and 11.8 grams of the butanedioic acid. Calculate the theoretical yield of ester which could result using these amounts. esc ? 12 Separate the layers again, and transfer the ester to a dry Erlenmeyer flask, and dry it for 30 minutes over about 3 grams of anhydrous magnesium sulfate. Decant into an amber storage bottle and store until next week. Carefully pour your product into a 50-ml taper round-bottom flask, add a boiling chip, and distill the product, collecting material over the range 137 - 142 deg C. Run an IR on your product and attach the IR to your lab. Product Data: Theoretical mass (g) Calculation for theoretical mass: Wt of product (g). percent yield Calculation for % yield: esc 11 ? " Lab Report: Isopentyl Acetate Name Section Locker No. Equation for main reaction (balanced): Table of Reagents (actual reactants and catalysts only; no solvents) Compound Density Vol. (mL) % conc. Weight (g) Mol. Wt. Mols. (liquids) isoamyl alcohol .81 22mL 17.6 g 88.15g •2 acetic acid 1.01 30 ml 60.05 ml .5 . ---- Product Mols. Isoamyl acetate Density Vol. (mL) Weight collected (g) Mol. Wt. (liquids 46 ML 21.45g 130.19 bottle= 63.478 both = 84.92g almol Summary of Procedure (one paragraph)