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11 Dec 2019

Synthesis of Isoamyl Acetate

Acetic acid + isoamyl alcohol ----> isoamyl acetate + water

Sulfuric acid was used as the catalyst

1) a. Assuming that the reaction had gone to completion after the 20 minutes of refluxing, what compound(s) besides the desired product, isoamyl acetate, would be in the reaction flask?

b. Explain, using balanced chemical equations wherever possible and incorporating structural formulae, how you removed each of these compounds (answer to question 1a.) from the reaction mixture during the isolation/purification of the product, isoamyl acetate.

2) If this reaction between the acetic acid and isoamyl alcohol could only obtain a maximum yield of 67% of the desired ester, if you needed to produce 45 grams of isoamyl acetate, what are the minimum weights of both the acetic acid and isoamyl alcohol that you would need to measure out for this experiment? Show calculations.

3) Using structural formulae, give balanced equations to illustrate how you could synthesize the following esters, using the same type of reaction that was utilized in this experiment:

(i) Phenyl cyclopropylmethanoate

(ii) 2-pentyl propanoate

(iii) benzyl butanoate

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How to create a table of reagents with the information given. Ester of choice is isoamyl acetate

7. SYNTHISIS OF FRUITY ESTERS USING THE FISCHER ESTERIFICATION REACTION H2504 (cat) soamyl alel acetic acie H-S04 (cat) n-butanolaccid H2504 (cat) the chemistry of fragrances, chemical equilibria Experimental techniqees: Microscale reflux, NMR, microscale aqueous extraction Adapted from: Palleros, P. K etal "Microscale Organic Laboratory". p. 480. Befone he lab period pick one of the esters drawn ahove. If you work in a team, try to coordinate this with your teammate befosehand. If you don't do this in time for the lab, then just worry about it when you get to lab, and then copy(and double-check) the rclevant dataãquestions 3a and 3b) for the ester you decide to make with your partner 2. Prepare your pre-experiment notcbook entry (lowchart, table of reagents with physical constamts, etc) 3. Answer the following questions: For only the ester you are making, please draw a dctailed clectron-pushing mechanism to show the formation of compound. There are many sesources available to you on the web, etc) fr the mechamism of the Fischer esterification reaction a. b. You will start with 500 mg of one of your starting alcohel(whichever one you will be using to gencrate your product). While the acohols are liquids, we will measure them by mass directly on the balance, no by volume (ie. the density of the alcohol will not be used: pretend the alcohol is a solid). Acetic acid (or propionic acid) will be mcasured by volume. Delermine the volume of acetic acid (or propionic acid) to add that will correspond to 40 molar equivalents based on mmols of starting c. Considering that the reaction produces water in the mechanism (question a), what reagents could be added to the reaction mixture to enhance coeversion to product? (Think of a specific Reaction Inlo 10 ml RBF, add the aleohol you chose (500 mg), acetie acid or peopionie acid (alulated quantity, by pluringe, and cone, sulfuric acid (3äº ops, no more). Do not spill conc, sulfuric acid on yourself! 2. Altach (screw on) a microscale condenser (with rubber O-ring seall) to the RBF, and flow water through You can the bottom of the condenser. Be very careful when tuming the water on to avoid a waler spill then directly clamp the condenser and have the RBF suspended it into the sand bath Heat the reaction mixture in a sand bath to a gentle boil (roughly-130-140â, but it varies for each experiment) for 45 min, and them allow the mixture to cool to necarly ambient temperature 3. Workup and purification Transfer the reaction mixture by pipette from the RBF to a 4 ml conical vial 5. Rinse the residual reaction misture from the RBF to the cotical vial using 2 ml 5% NaHCO/19% NaCl 6. Cap the tube and invert it several times to mix the layers. Vent the tube as necessary, Allow the layers 7. Wash the product with additional 5% NaHCO,19% NaCI

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rosedeer521

Preparation of acetyl salicyclic acid (Aspirin) post-lab questions

1.)At the end of the reaction, you were asked to add ice-cold water to the reaction mixture. What do you think is the reason for this? Explain with chemical equations.

2.)How would the % yield of aspirin be changed if the final rinse of the solid product on the filter paper was done with warm water instead of ice-cold water?

3.)If you run a thin-layer chromatography for a mixture containing salicylic acid and aspirin using a 1:1 solvent mixture of ethyl acetate and hexane, which compound do you think would have more R_f value. Explain why? Bring in the structural features in your explanation.

summary Procedure of lab we did:

- Place approximately 0.300 g of salicylic acid in a tared empty 5 mL conical reaction vial. Record the actual weight of salicylic acid used. Using automatic pipet, add 0.8 mL of acetic anhydride (acetic anhydride vapors are very irritating-handle it carefully, in the hood). Add 2-3 drops of concentrated sulfuric acid using a dropper.

-Clamp the assembly so that the vial is partially submerged in the hot water. Turn on the magnetic stirrer. Once the water bath starts boiling, start timing the reaction. When the mixture has been allowed to react at 100 oC (the temperature of boiling water) for 15 minutes, you can consider the reaction to be complete. During the heating time, take about 20 mL of deionized water in a flask and chill it in an ice-water bath.

- After the reaction has gone on for 15 minutes, add very cautiously, drop by drop, 1 mL of deionized water to the reaction vial. At this point you should have a solution in your reaction vial. Remove the reaction vial form the hot water bath, add another 1-2 mL of DI water and let it stand at room temperature for few minutes. Then, detach the air condenser carefully and remove spin vane with forceps. Place the vial in a beaker and cool down to RT. During this time, the aspirin may begin crystallizing. If not, scratch the walls of the vial with a glass rod. Then, cool the vial in an ice-water bath.

- When the vial appears full of crystals, add about 3-4 mL of ice-cold DI water. Filter the aspirin using vacuum filtration (use Hirsch funnel). Leave the filtration setup in place for few minutes-this will draw air through the sample and will help dry aspirin.

Recrystallization of Aspirin:

- Transfer the rest of the crude aspirin to a 25 mL Erlenmeyer flask and do recrystallization using ethanol.

Purity of Aspirin:

- Using the melting point apparatus, determine the melting point of your crude aspirin and the recrystallized aspirin.

- To do FeCl3 test, get 4 test tubes. Place 1 mL of ethanol and 2 drops of 1% FeCl3 solution in each test tube. Add few crystals of salicylic acid to one test tube. Add few crystals of your crude aspirin product to the second test tube. In the thirst test tube, place a few crystals of your recrystallized aspirin. The fourth test tube will be your âblankâ. Shake each of the test tubes and record your observations.

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