Diels-Alder Rxn Lab: 1. What was the purpose of using a “solvent-pair” for the r

Question

Diels-Alder Rxn Lab: 1. What was the purpose of using a “solvent-pair” for the reaction of cyclopentadiene with maleic anhydride?
2. Why is it important to collect cyclopentadiene from fractional distillation in an ice-cold receiver?
3. Determine the number of moles of each reactant. What was the limiting reactant in the experiment? Calculate the theoretical yield.
4. Which of the two reactants was used in excess? Why was it used in excess knowing that the molar ratio of the reactants for the reaction is 1:1?
5. Dicyclopentadiene can also undergo the Diels-Alder reaction with cyclopentadiene. What is (are) the structure(s) of the product(s)?

Explanation / Answer

1. The solvent pair used is ethyl acetate and ligroin. Ethyl acetate, being polar is used to dissolve maleic anhydride, while ligroin and cyclopentadiene, would keep the overall reaction mixture as non-polar in order to ensure that the reaction is complete.

2. Cyclopentadiene is unstable at room temperature, so it is collected in ice cold water after fractional distillation.

3. Moles of maleic anhydride = 0.200 g x 1 mol/ 98.06 g = 0.00204 mol

Moles of cyclopentadiene = 0.200mL x 0.80g/mL * 1 mol/66.1 g = 0.00242 mol

Amount of product cis-norbornene-endo-5,6,dicarboxylic anhydride (C9H8O3) formed will depend on moles of maleic anhydride, limiting reactant.

Moles of C9H8O3 formed =  0.00204 mol maleic anhydride x 1 mol C9H8O3/1 mol maleic anhydride =0.00204 mol

Mass of C9H8O3 = 0.00204 mol x 164.16 g C9H8O3 / 1 mol C9H8O3 = 0.335 g C9H8O3

4. Cyclopentadiene was used in excess. Inorder to limit the formation of the product one of the reactant was used in excess.

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