In this laboratory, we will study the classic reaction between anthracene and ma

Question

In this laboratory, we will study the classic reaction between anthracene and maleic anhydride described in Eaton's now famous paper. We do not want to wait 4,800 hours in the lab for the reaction to go to completion, but instead of using AlCl, to speed up the reaction, we will be using a high-boiling solvent, namely xylene. This is somewhat safer than using AICl,, which reacts violently with water even when only small amounts are present. We will then use 'H NMR spectroscopy (not reported in Eaton's paper as it w not yet widely available in 1960) to analyze the product and determine if the middle ring of the anthracene molecule is indeed the one that has reacted with the dienophile. as Prior to the lab, you will need to calculate the amount of maleic anhydride needed to react with 1.0g of anthracene. You will not be allowed to start the experiment without this calculation in your notebook. Experimental Procedure Spot the starting materials on TLC plate, labeling them appropriately. We will be using 1.0g of anthracene, and an equimolar amount of maleic anhydride. Prior to th will need to calculate the amount of maleic anhydride needed. Set up a reflux ap consisting of a heating mantle, 100mL round bottom flask, and a reflux condenser. Put approximately 30mL of xylene into the round-bottom flask, 3-4 boiling chips, then add the anthracene and maleic anhydride. Attach a drying tube filled with drierite to the top of the condenser, but make sure that the outlet of the tube is not closed - otherwise you would be heating a closed system which would result in an explosion! Connect the hoses for cooling water to the reflux condenser. Reflux the mixture for one hour, then let it cool down and remove the condenser. Place the reaction flask on an ice bath to precipitate the product. Vacuum filter the solid and wash the solid several times with 10mL portions of pentane. Air dry the product by keeping it on the filtration apparatus for approximately 10 minutes. Weigh the crude product to calculate the yield. Spot the product on the same TLC plate and develop it in TLC chamber using methylene chloride as an eluting solvent. Analyze your TLC and check if you need to recrystallize the product. If you indeed need to do that, then use methylene chloride.

Explanation / Answer

Reaction of anthracene with maleic anhydride

This is a typical diels-alder reaction. Anthracene acts as a diene and maleic anhydride acts as an dienophile. The two reactant reacts in a 1:1 molar ratio

moles of anthracene taken = 1.0 g/178.23 g/mol = 0.0056 mol

moles maleic anhydride needed = 0.0056 mol

mass maleic anhydride required = 0.0056 mol x 98.06 g/mol = 0.55 g

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