Chemistry 3112, Spring 1999. Experiment 10. The Diels-Alder Reaction: Synthesis of 9,10-Dihydroanthracene-9,10-endo-a,b-succinic Anhydride

Name ___________________________ Date _________________ TA ___________________

Read Solomons, Organic Chemistry, 6th ed., pp 520-524; and lab text pp 191-197.

Pre-Lab

1. Write out the chemical equation for the Diels-Alder reaction of anthracene with maleic anhydride showing structures of the reactants and the product.

 

 

 

 

 

 

 

 

 

2. Fill in the table of reactants and solvents. Calculate molecular weights and mmol of each reactant.

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Compound MW mp or bp, oC mg mmol

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Maleic Anhydride mp 54-56

Anthracene mp 216-218

Xylenes (mixture) bp 137-144

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3. Which reagent is limiting? ____________________________

4. Calculate the theoretical yield in mg and mmol. Show your work.

 

 

 

 

 

Procedure

Trade a clean, dry test tube for a test tube containing 40 mg of maleic anhydride.

1. Weigh and place 80 mg of anthracene and 40 mg of maleic anhydride in a 3.0 mL conical vial containing a boiling stone, and equipped with an air condenser protected by a drying tube. Your TA will show you how to construct a drying tube from a short glass dropper by rolling calcium chloride pellets into the dropper and inserting a piece of cotton at the top to keep them from rolling out. Add 1.0 mL of xylene to the solid mixture using an automatic delivery pipet.

2. Set up a reflux apparatus using a heat transfer block and the small hot plate. Reflux the mixture for 60 minutes. Allow the mixture to cool to room temperature, and then place it in an ice bath for 10 minutes.

3. Collect the crystals by vacuum filtration using a Hirsch funnel. Be sure to scrape out solid product that may stick to the inner walls of the condenser. Wash the filtered solid with two small (<0.5 mL) portions of cold ethyl acetate under suction.

4. Have your TA verify that you isolated the product, weigh it, and calculate the % yield. Turn in the sample in a small clean vial labeled with your name, the name of the product, and the weight. The mp of pure product is 262-264 oC. You will not measure it because many of the thermometers in the lab go to only 250 oC.

5. Interpret completely the spectra of the product. Write the structure on each spectrum. Assign all NMR peaks and IR bands at >1500 cm-1.

Observations

Record any unusual observations. Could anything be done to improve your % yield if you were to repeat the experiment?

 

 

 

 

 

Results:

Limiting reagent: ___________________________ _______________mmol

Diels-Alder product isolated: _______________mg; _______________mmol; TA___________

% Yield: _______________%

Post-lab

1. Why does the initial yellow color of the reaction mixture fade during the reaction?

 

 

2. The following information comes from the 1998-1999 Aldrich Chemical Co. catalog.

isomer,purity (least pure available) bp, oC quantity cost, $

ortho-xylene, 97% 143-145 1L 14.55

meta-xylene, 98% 138-139 1L 20.70

para-xylene, 99% 138 1L 17.45

xylenes, isomers plus ethylbenzene 137-144 1L 12.85

4L 32.05

18L 86.50

Why do the separate isomeric xylenes cost more than the mixture of xylenes?

 

 

3. Calculate the cost per L of xylene in 4L and 18L containers.

 

 

4. Why does the cost per unit volume decrease with increasing amount purchased?

 

 

5. What are the IR frequencies of the carbonyl stretching vibration(s) of the starting maleic anhydride and the Diels-Alder product? Explain why they differ.