Homework answers / question archive / Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 Title: Diels-Alder Reaction: Identification of an Unknown Diene in Eucalyptus Oil 1

Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 Title: Diels-Alder Reaction: Identification of an Unknown Diene in Eucalyptus Oil 1

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Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 Title: Diels-Alder Reaction: Identification of an Unknown Diene in Eucalyptus Oil 1. Abstract and Purpose: (2 point). The Diels-Alder reaction is a very useful organic synthesis reaction of complex molecules. This reaction includes two reactants which are a conjugated s-cis diene and a substituted alkene called a dienophile. The diene is electron-rich while the dienophile is electron-poor. The product is a cyclohexene ring with defined regio- and stereochemistry. For this reaction to happen, the three pi-bonds of the diene and dienophile are replaced by two new sigma-bongs and one pi-bond. The Diels-Alder reaction is ran in an organic solvent such as toluene or ether and usually requires heat for completion. This reaction was discovered in 1928 by Otto Diels and Kurt Alder in which they won the 1950 Noble Prize in Chemistry. Many have used or smelled the eucalyptus sent that is quite popular. The eucalyptus oil is a natural material that is obtained from the leaf of the eucalyptus plant by distillation. This oil has been stated to have antibacterial activity, decongestant activity, and stimulant effects on the immune system. However, this oil is actually a mixture of many different chemical components. One of these components is a diene as which stated above is a reactant of a Diels-Alder reaction. The purpose of this experiment is to assume that the structure of the diene in eucalyptus oil is unknown and that it is believed to be either ?-phellandrene or ?terpinene. The goal is to identify the unknown diene by reacting eucalyptus oil with a dienophile, maleic anhydride, in a Diels-Alder reaction. The spectral properties from an NMR and IR as well as the melting point of the resulting Diels-Alder adduct with the Diels-Alder adducts formed from the known dienes will be compared. It is important to Name: Exp # 5 and 6 Date: 3/1/2021 Lab Partner: n/a remember that the dienes in this case are locked in the s-cis conformation and the dienophile is doubly activated by the two carbonyl groups of the anhydride. 2. Balanced equation: (2 point) Basic Equation for Diels-Alder Reaction Specific Equations for Experiment 3. Reagent Table (Add more rows when needed) (3 points) Name M.W. (g/mol) Density* (g/mL) M.P.* (°C) B.P.* (°C) Amount (grams or mL) Moles Hazards/Precautions Name: Exp # 5 and 6 Date: 3/1/2021 Lab Partner: n/a ?-Terpinene 136.23 0.837 n/a 173-175 0.817 g 6 mmol Flammable liquids, Acute oral toxicity, Skin irritation, Eye irritation, Specific target organ toxicity, Acute aquatic hazard, Chronic aquatic hazard ?-Phellandrene 136.23 0.85 n/a 171.5 0.817 g 6 mmol Flammable liquids, Acute oral toxicity, Skin irritation, Eye irritation, Respiratory sensitization, Specific target organ toxicity Petroleum Ether 86.18 0.63 < -30 30 5 mL n/a Maleic Anhydride 98.06 1.48 52-54 200 0.39 g 4 mmol Acute oral toxicity, Skin corrosion, Serious eye damage, Respiratory sensitization, Skin sensitization, Specific target organ toxicity, Acute aquatic hazard Isopropyl Alcohol 60.10 0.785 -89.5 82 n/a n/a Flammable liquids, Eye irritation, Specific target organ toxicity Eucalyptus Oil 154.25 0.909 n/a 175 2 mL n/a Flammable liquids Diethyl Ether 74.12 0.71 -116 34.6 5 mL n/a Flammable liquids, Acute oral toxicity, Specific target organ toxicity Flammable liquids, Skin irritation, Reproductive toxicity, Specific target organ toxicity, Aspiration hazard, Acute aquatic hazard, Chronic aquatic hazard Name: Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 3. Calculations: Shown each calculation for moles of reagents, limiting reagent, theoretical yield and percent yield. (4 points) Molecular Mass of product: ?-Phellandrene + Maleic Anhydride = 136.23 g/mol + 98.06 g/mol = 234.39 g/mol Calculating moles of reagents: 6 mmol ?-Phellandrene (0.001 mol / 1 mmol) = 0.006 mol ?-Phellandrene 6 mmol ?-Terpinene (0.001 mol / 1 mmol) = 0.006 mol ?-Terpinene 4 mmol Maleic Anhydride (0.001 mol / 1 mmol) = 0.004 mol Maleic Anhydride Determining limiting reagent: 0.006 mol ?-Phellandrene (1 mol / 1 mol) = 0.006 mol product 0.006 mol ?-Terpinene (1 mol / 1 mol) = 0.006 mol product 0.004 mol Maleic Anhydride (1 mol / 1 mol) = 0.004 product The limiting reagent is Maleic Anhydride. Calculating theoretical yield: 0.004 mol Maleic Anhydride (1 mol product / 1 mol Maleic Anhydride)(234.32 g product / 1 mol product) = 0.937 g product The theoretical yield is 0.937 g. Name: Exp # 5 and 6 Date: 3/1/2021 Lab Partner: n/a The actual yield is 0.29 g. Calculating Percent yield: (actual yield/theoretical yield) × 100% = (0.29 g/0.937 g) × 100% = 30.95 % Reaction percent yield is 30.95%. 5. Procedure, Observations and Data Procedure (4 point) Observations and Lab Data (4 point) Name: Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 A summary of the procedure done with bullet points) Report all observations and all data that you collect in the (2 points) lab here • Combine maleic anhydride (4mmol), your assigned diene (6.0 mmol), and 5 mL of anhydrous diethyl ether into a tared 25 mL round bottom flask. For eucalyptus oil, use 2 mL of the oil. Add 3 boiling stones. • Caution: Diethyl ether is highly flammable! Maleic anhydride is corrosive and toxic. • Attach a condenser to the round bottom flask. Be sure the connection is tight. • Gently reflux the mixture over low steam for 45 minutes. • While it is warm, transfer the reaction mixture to a small beaker, cover with a watch glass, and let cool to room temperature. • Cool it further on ice before colleting the crystals by vacuum filtration. Wash the crystals with 5 mL of cold petroleum. • Recrystallize the Diels-Alder product from isopropanol. Add hot isopropanol until the material has dissolved. It may remain slightly cloudy. Cool to room temperature to form crystals. • N/A Name: Lab Partner: n/a • Exp # 5 and 6 Date: 3/1/2021 Complete the crystallization by placing the flask on ice. If crystals do not form, scratch the bottom of the flask with a glass rod and place in ice. • Isolate the pure material using the Hirsch funnel. Use some ice-cold isopropanol to rinse all the crystals into the funnel. Air dry on the funnel for 5 minutes by pulling air through the solid using the vacuum. Transfer the material to a watch glass and dry in the oven at 75?C. • Important! Alcohol can cause the product to undergo solvolysis, so it is important that you avoid prolonged boiling during recrystallization. • Weigh the solid after drying and obtain a melting point and infrared spectrum. • In addition, perform a mixed melting point in the following manner: half the teams who used eucalyptus oil will exchange about 25 mg of their product for about 25 mg of product from each team in the ?-phellandrene group. The other half of the eucalyptus oil Name: Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 teams will exchange with the ?-terpinene group. • Combine the product you obtained from the other group with an equal amount of your product and grind them together until they are mixed well. • Perform a melting point on the mixed material. If the two substances are identical, there will be no change in the melting point. If they are different substances, the melting point will be depressed. • If you do not have a high field NMR available to assess your sample, your instructor will provide the NMR spectra of the two known Diels-Alder adducts and the unknown from eucalyptus oil. Using your data and the data generated by the other two teams in your group, determine the unknown diene in eucalyptus oil. Name: Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 6. Conclusions and discussions (4 points) In this experiment, a Diels-Alder reaction was conducted to determine the diene in eucalyptus oil. The dienes in this case are locked in the s-cis conformation and the dienophile is doubly activated by the two carbonyl groups of the anhydride. The reaction consisted of alpha-phellandrene and maleic anhydride in which it produced white needleshaped crystals. The actual yield was 0.29 g and the percent yield was 30.95%. This could have been due to multiple aspects of the experiment including the techniques used in the laboratory. To determine what diene is present in the eucalyptus oil, the melting point was taken as well as an IR spectrum and an NMR spectrum in order to compare the results. The melting point of the product was 121.4-123.375?C. However, this will not help determine the diene in eucalyptus oil because there was no melting point provided for ?Phellandrene or ?-Terpinene. When comparing the IR spectrum of the Diels-Alder Adduct of ?-Phellandrene and maleic anhydride and the Diels-Alder Adduct of ?Terpinene and maleic anhydride, it is concluded to not be useful. This is because both IR spectrums show the same functional group at a peak of ? 1775-1780. Lastly, based on the NMR spectrum, eucalyptus oil consists of ?-Phellandrene as its diene. When looking at the NMR spectrum, there is only one set of a doublet around 5 ppm. Therefore, this indicates the one double bond proton in ?-Phellandrene unlike ?-Terpinene that would have shown two sets of doublets due to it having two double bond protons. In conclusion, eucalyptus oil is quite popular and is a mixture of many different chemical components. From this experiment, the component as the diene in the Diels- Name: Lab Partner: n/a Exp # 5 and 6 Date: 3/1/2021 Alder reaction of eucalyptus oil was determined to be ?-Phellandrene. As stated above, the NMR spectrum of the product was the most useful in obtaining this conclusion.