Diels-Alder Lab

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Diels-Alder Reaction
Heather Jost
Lab Partner: Jasmina Salcinovic
CHEM2642L
Luise Strange de Soria
Georgia Perimeter College
September 29, 2004

Diels-Alder Reaction
Resources:
Mayo, Pike, Trumper, Strange de Soria. Microscale Organic Laboratory. New York: John Wiley and Sons, 2002.

Strange de Soria, Luise. “Student Survival Guide”.
http://www.gpc.edu/~lstrange/2642lab/survivalguide/grignard2.pdf. 2004.

Purpose:
The purpose of these experiments is to create two different cyclic products using Diels-Alder reactions.
Summary of the Theory behind the Diels-Alder Reaction:
A Diels-Alder reaction creates two new C-C bonds and up to four stereocenters in a single step. By mixing and matching different dienes and dienophiles (diene lovers) a large amount of different products can be produced. A ‘good’ dienophile will have an electron withdrawing substituent group which makes for a quicker reaction, if the diene possesses electron donating groups. Diels-Alder reactions are not exothermic and the equilibrium constant is dependant upon temperature. Increasing the temperature will increase the rate of reaction but will reduce the amount of product that was created. It is therefore imperative that the lowest temperature deemed possible be used to maximize the amount of product formed throughout the experiment.

The Diels-Alder reaction is a cycloaddition reaction which means it forms rings in the product. This type of reaction is known as a pericyclic reaction because the bonds form around the circle. Compounds in the cyclic form are restricted to cis conformations and therefore react faster because it cannot rotate out of cis into a trans conformation that won’t react. Compounds with a trans conformation won’t react because a cyclic product must be formed from the Diels-Alder reaction and that cannot occur with a trans reagent.

Experiment 14 Mechanism:

Experiment 15 Mechanism:

Reaction Analysis:
Experiment 14:
Balanced Chemical Equation:
C4H6 + C4H2O3 → C7H8O3

Theoretical yield:
1)Take the amount of maleic anhydride, convert it to mg and divide it by the molecular weight •0.45g x 1000 = 450mg
450mg ÷ 98.06g/mol = 4.59m/mol
2)Take the value found in step 1 and multiply it by the molecular weight of the product •4.59m/mol x 152g/mol = 698mg theoretical yield
Potential side products:
Sulfur dioxide
Experiment 15:
Balanced Chemical Equation:
C14H10 + C4H2O3 → C18H12O3

Theoretical yield:
3)Take the amount of maleic anhydride, convert it to mg and divide it by the molecular weight •0.2g x 1000 = 200mg
200mg ÷ 98.06g/mol = 2.04m/mol
4)Take the value found in step 1 and multiply it by the molecular weight of the product •2.04m/mol x 276g/mol = 563mg theoretical yield
Potential side products:
No side products
Procedure:
Experiment 14
Put 0.85g of 3-sulfolene, 0.45g of maleic anhydride, 2mL of Xylenes, and a stir bar into a round bottom flask. Use aluminum foil to insulate between the flask and the bottom of the reflux condenser and be sure to attach a drying tube with anhydrous calcium chloride. Heat the solution between 150 – 155oC, once at this temperature; keep it there for 20 minutes and avoid overheating. Then allow the mixture to cool to room temperature. Transfer contents to a 25mL Erlenmeyer flask and add 3mL of toluene (if the crystals do not dissolve then the contents may be heated). Add about 3mL of petroleum ether until slight cloudiness continues then heat the flask until the solution is clear. Crystals should form as the solution cools to room temperature, then you may put on an ice bath to complete crystallization. (Using vacuum filtration) Wash the product with approx. 5mL of cold petroleum ether and allow the product to completely dry over the next week (so an accurate weight and melting point may be obtained).

Experiment 15
Put 0.4g of anthracene, 0.2g of maleic anhydride, 5mL of...
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