Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil)

1. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) Resources Pavia: p. 84 – 91; 686 – 688; 693 – 697 Lab Website: http://classweb.gmu.edu/chemlab Schornick: http://classweb.gmu.edu/ jschorni/chem318

2. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) • Overview • Synthesis – Acid (H2SO4) catalyzed Fischer Esterification reaction of a Carboxylic Acid (Acetic Acid) with the Hydroxyl group of an Alcohol (Isopentyl [Amyl] Alcohol) This is a Condensation reaction where the molecules become joined through the intermolecular elimination of water • Refluxing - Reagents will be Refluxed for about 60 minutes. • Liquid/Liquid Extraction - The product will be washed several times with Water, Sodium Bicarbonate, Sodium Chloride • Dry Sample • Refractive Index (with temperature correction) • Infrared Spectrum

3. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) • The Laboratory Report: • Synthesis Experiment • Mass, Moles, Molar Ratio, Limiting Reagent, Theoretical Yield • Procedures • Title – Concise: Simple Distillation, Dry Sample, IR Spectrum, etc. • Materials & Equipment (2 Columns in list (bullet) form) Note: include all reagents & principal equipment used, including details of distillation setup • Description: • Use list (bullet) form • Concise, but complete description • Use your own words – Don’t copy book!!

4. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) • The Laboratory Report: (Con’t) • Results – Neat, logically designed template to present results • Summary – experimental results, including Theoretical Yield results, in paragraph form • Analysis & Conclusions • Limiting reagent • Discuss reaction mechanism in the context of your experimental results • Verification of product

5. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil)

6. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) ReagentsProduct Acetic Acid Isopentyl (amyl) Acetate Mol Wgt - 60.05 g/mole Mol Wgt - 130.19 g/mole Density - 1.049 g/mL Density - 0.876 Boiling Point - 117.9oC Boiling Pnt - 142oC % Acid - 100% Ref. Index - 1.4040 Isopentyl (amyl) Alcohol Mol Wgt - 88.15 g/mole Density - 0.809 g/mL Boiling Point - 130.0oC Sulfuric Acid Mol Wgt - 98.08 g/mole Density - 1.84 g/mL % Acid - 96.5 % Molarity - 36 moles/Liter

7. Synthesis of Isopentyl (Amyl) Acetate Ester (Banana Oil) • Heating Under Reflux • The reaction mixture is heated in a “reflux apparatus” consisting of a 25 or 50 mL round bottom flask attached to a vertical water-cooled condenser set in a heating mantle. Liquid/Liquid Extraction

8. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Elements of the Experiment • Equilibrium • Reaction equilibrium does not favor formation of the ester • Therefore, an excess of one of the reagents (Acetic Acid – Cheap!!!) is used to force the equilibrium to product side, i.e., to the right

9. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Elements of the Experiment (Con’t) • Liquid/Liquid Extraction • The reaction mixture is mixed with Distilled Water and placed in a separatory funnel where the phases separate into two layers – Aqueous (higher density) layer on bottom and the Organic layer on top. Separate the Aqueous phase into a waste beaker • Extract Organic phase twice with 5% Sodium Bicarbonate to remove excess acid. Discard Aqueous phase into waste beaker • Extract Organic phase twice with Saturated Sodium Chloride to remove excess water. Discard Aqueous phase into waster beaker

10. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Elements of the Experiment (Con’t) • Dry Product – Dry crude ester (organic layer) with Anhydrous Sodium Sulfate (less than 1 gram) • Purification – Simple Distillation (if so instructed) • Mass of Product • Percent (%) Yield • Refractive Index corrected for temperature • Infrared (IR) Spectrum

11. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure • Measure out ~10 mL of Glacial Acetic Acid to the nearest 0.1 mL and compute the mass from the volume and density • Weigh the Isopentyl Alcohol in the vial to the nearest 0.001 g • Mix the reagents in a Beaker, swirling gently to ensure complete solution • If necessary, heat gently to help dissolution of reactants • Carefully add 1.0 mL concentrated Sulfuric Acid to the mixture mixing (swirling) quickly

12. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure (Con’t) • Set up a “Reflux” Apparatus using 50 mL round bottom flask • Add a “Corundum” or “Teflon” (not calcium carbonate) boiling chip and heat the mixture under “Gentle” reflux for 50 – 60 minutes • Cool the mixture to Room Temperature • Liquid/Liquid Extraction • Pretest the Separatory Funnel to ensure that the stopper and the stopcock assembly do not leak • Add about 50 mL distilled water to the funnel • Shake vigorously for about 10 seconds • Adjust stopper or stopcock as necessary and repeat

13. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure • Liquid/Liquid Extraction (con’t) • Transfer the reaction mixture to the Separatory Funnel using a short neck stem funnel • Note: Do not transfer boiling chip to funnel • Rinse reaction vessel with 10 mL Distilled Water and add to mixture in separatory funnel • Mix phases by shaking and venting • Remove the lower aqueous layer and put it aside for later disposal

14. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure (Con’t) • Liquid/Liquid Extraction (Con’t) • Extract the upper organic layer again with 10 mL aqueous Sodium Bicarbonate to remove excess Acid Note: The reaction between the residual acid and Sodium Bicarbonate produces CO2 gas and could be under considerable pressure in the separatory funnel. Hold the stopper firmly, invert the funnel, and release the stopcock very slowly so the venting of the gas is controlled

15. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure (Con’t) • Liquid/Liquid Extreaction (Con’t) • Remove the lower aqueous layer and add to previous waste aqueous solution • Repeat the NaHCO3 extraction a second time • Perform a third extraction of the upper organic layer in the Separatory Funnel with 10 mL of saturated Sodium Chloride to remove excess water • Remove the lower aqueous layer and add to previous waste aqueous solution

16. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure (Con’t) • Liquid/Liquid Extraction (Con’t) • Repeat the Sodium Chloride extraction a second time • Transfer the organic layer containing the crude ester to a small, clean, Erlenmeyer flask • Instructor will add 1.0 g of Anhydrous Sodium Sulfate Note: If mixture does not appear to dry (drying agent will clump), add a little more Sodium Sulfate

17. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure (Con’t) • Allow the mixture to settle • Decant the dried sample into a pre-weighed 100 mL beaker, leaving all solid material in the flask • Reweigh the beaker and determine the mass of product • Determine percentage yield • Measure the Refractive Index and correct for temperature • Obtain the IR Spectrum

18. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Purification of Product • If so instructed, purify and determine the boiling point of the sample using Simple Distillation (Boiling Point of Isopentyl Acetate is 142oC) • Transfer purified product to small Erlenmeyer flask • Add ~ 1 g Anhydrous Sodium Sulfate • Pre-weigh a small, clean 100 mL beaker • Decant the dried / purified sample into the pre-weighed beaker, leaving all solid material in the flask • Weigh the beak and calculate the mass of the product by difference • Compute % yield • Determine Refractive Index corrected for temperature

19. Synthesis of Isopentyl (Amyl) Acetate Ester(Banana Oil) • Procedure (Con’t)