Experiment 5: Diels-Alder Reaction: Maleic Anhydride with Anthracene PDF

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Jessica Milligan K00423355 CHEM 3125-101 28 September 2020

Experiment 5: Diels-Alder Reaction: Maleic Anhydride with Anthracene

Purpose The purpose of this lab is to run a Diels-Alder reaction by using Anthracene and maleic anhydride to form a cyclohexane ring. A Diels-Alder reaction is reaction between a diene and a dienophile to from a cyclohexane ring. In this specific experiment, the anthracene is the diene and the maleic anhydride is the dienophile. Abstract A Diels-Alder reaction is reaction between a diene and a dienophile to from a cyclohexane ring. Additionally, a Diel-Alder reaction id a formal 4Π+2 Π cycloaddition reaction. The diene (4Π component) is usually electron rich and the dienophile (2Π component) is usually electron poor. The dienophile contains a conjugated electron withdrawing group (EWG).

Atom mapping technique is the mapping between the atoms in the reactant molecules and the atoms in the product molecules. The blue arrows indicate a characteristic electron flow, which occur in a concerted fashion for this type of reaction. Two single σ bonds are generated and one new Π is formed. Overall, there is net formation of two σ bonds and loss of two Π bonds. Therefore, there is a favorable enthalpy of this reaction and is an exothermic process.

The middle ring of anthracene is the active diene component because it is most electron rich and because the product still maintains two aromatic rings. There are no possible regioisomers because the dienophile (maleic anhydride in this experiment) is symmetrical, so no byproducts should be generated. MSDS  Anthracene o Chemical Formula: C14H10 o State: Solid o Molecular Weight: 178.23 g/mol Health: 2 o Boiling Point: 340°C Fire: 1 Reactivity: 1

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o Melting Point: 215-218°C o Density: 1.25 g/cm3 o Hazards: Anthracene may cause eye irritation to the eyes. If ingested, it may cause irritation to the gastrointestinal tract. If inhaled, it may cause respiratory tract irritation. If exposed to skin, it may cause irritation. Maleic anhydride o Chemical Formula: C4H2O3 o State: Soild o Molecular Weight: 98.06 g/mol Health: 3 o Boiling Point: 395.6℃ Fire: 1 o Melting Point: 127℃ Reactivity: 1 o Density: 1.48 g/cm3 o Hazards: Maleic anhydride may cause severe irritation and eye burns if exposed to the eyes. If ingested, it may cause gastrointestinal tract burns. If inhaled, it may cause chemical burns to respiratory tract and asthmatic attacks. If exposed to skin, it may cause skin burns. Xylene o Chemical Formula: C8H10 o State: Liquid o Molecular Weight: 106.16 g/mol Health: 2 o Boiling Point: 139℃ Fire: 3 o Melting Point: -47 ℃ Reactivity: 0 o Density: .864g/mL o Hazards: Xylene may cause eye irritation. If ingested, it may cause gastrointestinal irritation and central nervous system depression. If inhaled, it may call CNS depression. If exposed to skin, it may cause skin irritation.

Procedure 1. Weight anthracene (0.2g) and maleic anhydride (0.11g) 2. Place weighted reagents in 50ml round bottom reaction flask and add 6mL of xylene 3. Assemble a reflux apparatus

4. Heat anthracene and maleic anhydride at reflux for 30 minutes over sand bath, the reaction should be mostly complete after 15 minutes if you get the reaction temperature to above 210℃ 5. Cool reaction mixture in an ice bath 6. Use vacuum filtration to collect crude product

7. Weigh the crude product 8. Recrystallize from xylenes 9. Use vacuum filtration to collect purified product 10. Dry the purified product on watch glass and get percent yield 11. Take a melting point of crude and purified product

Data

Compound Maleric anhydride Anthracene Diels-Alder Adduct

Physical Properties of Compounds in Diels-Alder Reaction Molecular Melting Point Boiling Point Weight (g/mol) 98.06 g/mol 54-56℃ 200℃ 178.23 g/mol 276.29 g/mol

216-218℃ 262-264℃

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Density N/A N/A -

Weight and Moles of Anthracene and Maleric anhydride Weight of Moles of Weight of Maleric Moles of Maleric Anthracene (g) Anthracene (mol) anhydride (g) anhydride (mol) 0.21g .0012 mol 0.11g .0011mol Weight and Melting Point of Crude and Pure Products Compound Weight (g) Melting Point (℃) Crude Product .157g Pure Product .073g 260-261℃ Notes/Observations Anthracene appears as brown powered while maleic anhydride is a white powder. The reflux apparatus is greased to prevent vapors from escaping. When turning on water to the reflux apparatus, it is done slowly to ensure the hoses don’t pop off which can happen if the pressure of the water is too high. DI water is added to the filter paper of the vacuum filtration to create a suction to filter the solid. Additional cold xylene was added to collect the rest of white solid stuck inside the round-bottom flask. The melting point ended up higher than the literature value since it was calibrated. Calculations Moles of Anthracene 0.21 g Anthracene x

1 mole Anthracene = .0012 mol Anthracene 178.23 g

Moles of Maleic anhydride 0. 11 g Maleic anhydride x

1 mole Maleic anhydride = .0011 mol Maleic anhydride 98.06 g

Theoretical Yield .0011 mol Maleic anhydride x

1 mole Diels−Alder Adduct x 276.29 g Diels−Alder Adduct = . 1 mol Maleic anhydride

3099g Percent Yield Actual = x 100% Theoretical .073 g = x 100% .3099 g = 23.55%

Conclusion The purpose of this lab was to run a Diels-Alder reaction by using Anthracene and maleic anhydride to form a cyclohexane ring. The anthracene weighted .21g which yield .0012 moles while the maleic weighted .11g to yield .0011 moles. The crude product, after being dried, weight .157g and the pure product after recrystallization weighted .073g and had a melting point of 260-261℃ . The theoretical yield was calculated to be .3099g which yielded a percent yield of 23.55%. The percent yield most likely correlates to error in the experiment. The amount of crude product filtrated was extremely small and could be the cause of such low percent yield, giving it more time to solidify might increase the outcome. Since the recrystallization process was not shown, error could have occurred there. Pre and Post-Lab Questions Pre-Lab Exercises 1. Draw the Endo or Exo product that forms from the following Diels-Alder reaction between acrylonitrile and 1-methoxy-1,3-butadiene.

2. Draw the Endo or Exo product that forms from the following Diels-Alder reaction between acrylonitrile and 2-methoxy-1,3-butadiene....