Title: Turning up the Heat: Preparation of Isopentyl Acetate Using a Microwave Reactor with Gas Chromatographic Analysis
1. Purpose: In a short paragraph, give the purpose of the experiment (up to 2 pts). Include brief discussion of the mechanism. Proper English and punctuation is required. (pre-lab)
. With the combination of a carboxylic acid and 3-methyl-1-butanol, a reaction will occur between the carboxylic acid and alcohol that will result in the loss of water is going to be the main process in synthesizing the required ester group. The purpose of this experiment is to create an ester group by Fischer Esterification. To achieve equilibrium, the scientist performs and addition and subtraction of reactants using. microwave energy and Dowex-50 as the catalyst for the reaction. The use of microwave allows for a more accurate and efficient result in a short period of time, while monitoring the reaction to determine if the reaction has gone to completion and measure the purity of the resulting product.
2. Balanced equation: (up to 2 points) (pre-lab)
e.g.
There are several free structure drawing programs available e.g. acdlabs.com. If you don’t have a drawing program, hand draw the structures.
3. Reagents (up to 4 points) (pre-lab)
Name M.W. Density (if applicable) Amount (grams or mL) Moles Hazards/Precautions
Glacial acetic acid 60.052g/mol 1.05g/mL 4.0mL 0.070 mol Causes severe skin burns and eye damage. Wash your hands when finishing the lab.
3-methyl-1-butanol 88.148g/mol 0.809g/mL 2.5mL 0.023 mol Causes respiratory, skin and eye irritation. Highly flammable. Avoid inhaling the fumes. Wear PPE.
Dowex-50 432 g/mol solid so not applicable 0.3g Not applicable (catalyst) Can causes severe eye damage. Handle with care and wear PPE.
Anhydrous sodium sulfate 142.0g/mol 2.68 g/mL spatula portions (enough) Drying agent so not applicable Causes skin and eye irritation. harmful when ingested or swallowed. Wear PPE when and dispose properly.
Silica gel 60.08g/mol Not applicable (solid) 0.4g It causes respiratory, skin, and eye irritation. Handle with care.
Diethyl ether 74.12 g/mol 0.713 g/mL 10mL extremely flammable and causes eye and skin irritation. Handle with care. Wear PPE.
Sodium bicarbonate 84.007 g/mol 1.1g/mL 20mL Can cause respiratory tract, eye, and skin irritation
N.B. For solvents (like methanol) or drying agents (e.g. sodium sulfate), you don’t need to calculate the moles.
4. Procedure, Observations and Data
Procedure Observations and Lab Data
Pre-lab: A summary of the procedure done with bullet points) (2 points)
Glacial acetic acid (4.0 mL, 70 mmol), 3-methyl-1-butanol (2.5 mL, 23 mmol), Dowex-50 (0.3 g) and silica gel (0.4 g) are added to a microwave vessel together with a stir bar.
The vessel is fitted with a vessel top and disk. Make sure to tighten the top with a torque wrench
Place in a microwave carousel and heated. Ramping up to 130 Celsius over 6 minutes and maintaining 130 Celsius for 12 minutes.
Let it cool sufficiently without removing from the carousel..
While the microwave is running, set up the Mini-GC and run the reaction standards (acetic acid, 3-Methyl-1-butanol and a known sample of isopentyl acetate) and launch Logger-Pro. Tap the Collect arrow (u) and input the following parameters: Start Temperature 40°C, Hold Time 1 min, Ramp Rate 5°C/min, Final Temperature 70°C, Hold Time 6 min, Total Length 13 min, and Pressure 15 kPa.
When ready for an injection, the LED will turn green. While the GC is warming up, clean the syringe with methanol as demonstrated by your instructor.
Do not pull the syringe plunger out past the 0.5 µL.
When the LED turns green, fill the syringe with 0.2 µL of one of the standards. Insert the needle through the septum on the Mini-GC.
Simultaneously press the syringe plunger and “Collect” on the computer.
When the run is complete, analyze the chromatogram.
Click on “Peak Integration” from the Analyze Menu. Select the peak by starting from the left side of the peak and dragging across the graph.
Record the peak area with the retention time. Repeat with the other standanrds.
Remove 0.2 µL of the crude reaction mixture with the GC syringe and inject it into the mini-GC.
Decant the remaining liquid into a separatory funnel and dilute with 8 mL of ether, being careful to leave any solids.
Gently rinse the reaction vessel with 2 mL of ether. Be careful not to disturb the solid and transfer it to the separatory funnel.
Carefully wash the ether sequentially with saturated sodium bicarbonate two times (10 mL X 2) and water (10 mL
Pour the ether layer into a clean Erlenmeyer flask and dry with sodium sulfate.
Decant the ether off the sodium sulfate into a preweighed flask and evaporate it as directed by your instructor.
Obtain the weight of product and determine your percent yield.
Inject a 0.2 µL sample of your isopentyl acetate into the Mini-GC and analyze your results.
Leave enough space for recording actual procedures. (in-lab) (4 points)
Record any color changes, exothermic or endothermic reactions, gas generation, etc.; tare weights for flasks, etc. (4 points)
5. Calculations: Show each calculation for moles of reagents and for theoretical and actual yield. (up to 4 points). Include these calculations at the end of this section and fill in the box with the number:
The limiting reagent is
The theoretical yield is
Show your calculations here (post-lab)
6. Results and conclusions (post-lab). (4 points)
7. Reflection (post-lab). (4 points)
Finish your writing and calculations, and upload pictures the whole report to the Blackboard within two days.