synthesis of isopentyl (amyl) acetate ester (banana oil)

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

04/21/23 1

Resources

Pavia: p. 84 – 91; 686 – 688; 693 – 697

Lab Website: http://classweb.gmu.edu/chemlab

Schornick: http://classweb.gmu.edu/ jschorni/chem318


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 Spectrum04/21/23 2


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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) formConcise, but complete descriptionUse your own words – Don’t copy book!!


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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


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Reagents ProductAcetic Acid Isopentyl (amyl) Acetate

Mol Wgt - 60.05 g/mole Mol Wgt - 130.19 g/moleDensity - 1.049 g/mL Density - 0.876Boiling Point - 117.9oC Boiling Pnt - 142oC% Acid - 100% Ref. Index - 1.4040

Isopentyl (amyl) AlcoholMol Wgt - 88.15 g/mole Density - 0.809 g/mLBoiling Point - 130.0oC

Sulfuric AcidMol Wgt - 98.08 g/moleDensity - 1.84 g/mL% Acid - 96.5 %Molarity - 36 moles/Liter


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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

Synthesis of Isopentyl (Amyl) Acetate Ester

(Banana Oil)

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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


(Banana Oil)

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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


(Banana Oil)

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Elements of the Experiment (Con’t)

Dry Product– Dry crude ester (organic layer) with Anhydrous Sodium Sulfate (less than 1 gram)

Mass of Product

Percent (%) Yield

Refractive Index corrected for temperature

Infrared (IR) Spectrum


(Banana Oil)

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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


(Banana Oil)

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Procedure (Con’t) Set up a “Reflux” Apparatus using a 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 Drain water from funnel


(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 disposal04/21/23 13


(Banana Oil)

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Procedure (Con’t)

Liquid/Liquid Extraction (Con’t)

Extract the upper organic layer with 10 mL aqueous Sodium Bicarbonate (NaHCO3) to remove excess Acid.

Note: The reaction between any 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


(Banana Oil)

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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


(Banana Oil)

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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


(Banana Oil)

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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

synthesis of isopentyl (amyl) acetate ester (banana oil)

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