The Diels-Alder reaction is the most famous example of a pericyclic reaction, i.

Question

The Diels-Alder reaction is the most famous example of a pericyclic reaction, i.e. a reaction that involves neither a nucleophile or an electrophile. Discovery of this novel type of reactivity led to a Nobel Prize for Otto Diels and Kurt Alder in 1950. This reaction is controlled by favorable overlap of pi orbitals between a conjugated 1, 3 diene and an olefin (called the dienophile, because it likes dienes). Since then, a vast number of different types of pericyclic reactions have been discovered (as you will discover in Chem 12C). In this experiment, you will perform a combination of a Diels-Alder cycloaddition and a "cheletropic cycloreversion". A cheletropic reaction is a subclass of the Diels-Alder reaction whereby both new bonds are made to the same atom. As you are aware from class, pericyclic reactions are reversible, so the cycloreversion reaction merely means that we will perform the reverse of a cycloaddition. The compound sulfolene is a diene surrogate, i.e. it can form 1, 3-butadiene upon heating by expelling gas molecule. You will perform the combination process and analysis the two mechanisms present in the reaction. Prelab Questions The Material Safety Data Sheets (MSDS) for all the chemicals involved in this lab are on iLearn. Read these and answer the following questions: Which chemical is the most dangerous in this lab? Explain why you chose your answer for part a), and the safety precautions you will take when handling this material. Fill in the reaction table below. Make sure you correctly calculate the molar amounts of your reactive materials. Based on your answers to Q2, which is the limiting reagent in this reaction? Calculate the Theoretical Yield of your product, i.e. the mass you would expect to recover, assuming 100% conversion to product.

Explanation / Answer

118.15 g/mol

Calculation Name Formula Mol Eq MW mmol amount 3-sulfolene C4H6O2S 1

118.15 g/mol

1.25/118.15 = 10.54mmol 1.25g Maleic anhydride C4H2O3 1 98.06 g/mol 0.750/98.06 = 7.648 mmol 750 mg Xylenes C8H10 0.5 ml Toluene C6H5-CH3 7 ml Product (4-cyclohexene-cis-1,2-dicarboxylic anhydride) C8H8O3 1 152.1399 7.65mmol 1.164

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