The Diels-Alder reaction is a [4+2] cycloaddition between a diene and a dienophile to form a cyclic product. 1. Identify the diene and dienophiles in your experiment. Please draw the structures. 2. What is a [4+2] cycloaddition? (Be sure to say what the 4 and 2 denote) 9.7. Diels-Alder reactions: butadiene and maleic anhydride 9.7.1. Goal To perform a Diels-Alder cycloaddition between a diene and an alkene to produoe a highly functionilized cyclohexene derivative. 9.7.2. Background The Diels-Alder is one of the most remarkable chemical reactions discovered in the 20th century. The authors of this reaction won the Nobel Prize in 1950. It is a powerful tool to build 6 -membered rings and has been used for the synthesis of many complex molecules. A cycloaddition [4+2], it is usually performed at moderate or high temperatures and even under pressure. This reaction is stereospecific with respect to both the diene and dienophile. In this experiment, two examples of Diels-Alder reactions are described, in the first case the diene is prepared in situ from 3-sulfolene, and in the second case a functionalized diene A) Cycloaddition [4+2] between the maleic anhydride and butn-1,3-diene: In a 100ml round-bottom flask, place 10g of 3 -sulfolene (buta-1,3-diene keep the mixture refluxed for 45min wher. Next, add 10ml of x ylene and attached at the end of the condenser with magnetic stirring. A gas trap is because the reaction releases SO2. Cool the rolution containing 5%NaOH, of toluene and activated carbon to discolor the solution to r.t. and add 50ml To the filtrate, add 2530ml of hexane, and hentution. Filter by gravity. solution to r.t. and then place it in an ice bath. to 80C. First cool the formed (see refs. [1,2] ). B) Cycloaddition [4+2] between maleic anhydride and E,E-2,4-hexadien-1-ol: Reflux a mixture of 0.40g of maleic anhydride and 0.40g of E,E-2,4-hexadienwill start to appear on the walls of the solution cool slowly to r.t.; a solid tation of the product, chill in an ice bath for 10 . To ensure a complete precipidry. It can be recrystallized from toluene for 10min. Vacuum filter and air see refs. [1,2]). Table 9.7: Physico-chemical properties of the reacente wwad a For brevity, only GHS icons are indicated. The information offered in the Material Safety Data Sheet (MSDS) should be consulted