Diels Alder Reaction

Diels Alder Reaction The purpose of this lab experiment is to understand the Diels Alder reaction with a cis diene and a dienophile. Mechanism Compound Molecular weight (g/mol) Density (g/mL) Boiling point °C Melting Point °C Amount used Toluene 92.1 0.87 110.6 -95.0 5 mL Maleic anhydride 98.06 1.48 202 52.8 0.4 g E, E-2,4- 98.14 0.83 94 30.5 0.4 g 196.2 NA NA 156-159 NA hexadien-1-ol l cis1,3,3a,4,5,7aHexahydro-5methyl-3-oxo-4isobenzofurancarboxylic acid Structures 1. E,E- 2,4- hexadien-1-ol 2. Maleic anhydride 3. Toluene 4. l cis-1,3,3a,4,5,7a-Hexahydro-5-methyl-3-oxo-4-isobenzofuran-carboxylic acid MSDS Toluene: flammable, irritant of skin and eyes, may cause dizziness or drowsiness. Maleic Anhydride: causes severe skin and eye damage, damages respiratory problems. E,E- 2,4- hexadien-1-ol: May cause irritation if in contact with skin, eyes, or is ingested. l cis-1,3,3a,4,5,7a-Hexahydro-5-methyl-3-oxo-4-isobenzofuran-carboxylic acid: flammable, corrosive, irritant of skin and eyes. Toxic. Procedure 1. Weigh approximately 0.4 g of maleic anhydride and 0.4 g of E,E-2,4-hexadien-1-ol into a 25 mL round bottom flack and attach a condenser. Weigh out the diene first then match the mass of the maleic anhydride. 2. Add approximately 5 mL of toluene and a stir bar. 3. Place water bath on a hot plate. 4. Heat the mixture until it refluxes and continue for an additional 15 minutes. 5. Remove the 25 mL round bottom flask from the hot plate and allow to cool to room temperature. 6. Then cool it in an ice bath for 10 minutes to ensure complete crystallization. You may have to scratch the bottom of the beaker with your glass stirring rod to initiate crystallization. 7. Use vacuum filtration to collect the product (Büchner funnel). 8. Rinse the beaker with several portions of COLD toluene. Use these rinses to wash your product. 9. Allow the product to air dry for several minutes. 10. Determine the melting point of your product. If it does not have a fairly sharp melting point, recrystallize it from toluene. 11. Determine your yield and do MP (lit 156 – 159°C). Calculations Mass of final product: 0.084g Theoretical Yield 0.4003 g maleic anhydride× 0.4003 g diene× 1 mol product 196.20 g 1 mol maleic anhydride =0.8009 × × 98.06 g 1 mol maleic anhydride 1 mol product 1 mol 1 mol of product 196.20 g =0.8002 g × × 1 mol of product 98. 145 g 1 mol Percent Yield 0.084 g × 100=10.5 % 0.8002 g Conclusion/Discussion During this lab experiment a Diels Alder reaction was completed using cis diene, (E,E2,4-hexadien-1-ol) and a dienophile maleic anhydride to form 1-cis-1,3,3a,4,5,7a-hexahydro-5methyl-3-oxo-4-isobenzofuran-carboxylic acid. The reaction was set to reflux and at completion crystals were collected and then recrystallized twice. Originally, the product should’ve have a white color but instead it was a combination of yellow and white, which can be due to impurities in the reaction. A melting point was taken after the product was recrystallized reflecting 149°C which again reflects impurities and possibly some residual toluene since the melting point for this product is around 156°C. The percent yield for this product was 10.5%. NMR was taken for this product; at 1 ppm there is a peak indicating the protons on methyl group HB. HA is around 12.5 ppm indicating a hydrogen from the OH from the carboxylic acid because it is attached to an oxygen is going to be more downfield. Vinyl hydrogens HC and HC’ are around 5.90 ppm; HC’ is going to be more downfield because is closer to the oxygen atom. In addition, it shows in the NMR some impurities along with the solvent. HF is slighty more downfield than HE because of the neighboring oxygen to it. For the IR, lactone shows around 1763 cm-, the carboxylic acid ~1728 cm-, the vinyl ~1680 cm-, the methyl ~2850-3000 cm-.