I need help to find out why we use a reflux condenser, vacuum filtration in the Diels-Alder Reaction In this laboratory, we will study the classic reaction between anthracene and maleicanhydride described in Eaton's now famous paper. We do not want to wait 4,800 hoursthein the lab for the reaction to go to completion, but instead of using AICI, to speed upreaction, we will be using a high-boiling solvent, namely xylene. This is somewhat saferthan using AlCl,, which reacts violently with water even when only small amounts arepresent. We will then use 'H NMR spectroscopy (not reported in Eaton's paper as it wasnot yet widely available in 1960) to analyze the product and determine if the middle ringof the anthracene molecule is indeed the one that has reacted with the dienophile.Prior to the lab, you will need to calculate the amount of maleic anhydride needed toreact with 1.0g of anthracene. You will not be allowed to start the experiment withoutthis calculation in your notebook.Experimental ProcedureSpot the starting materials on TLC plate, labeling them appropriately. We will be using1.0g of anthracene, and an equimolar amount of maleic anhydride. Prior to the lab, youwill need to calculate the amount of maleic anhydride needed. Set up a reflux apparatusconsisting of a heating mantle, 100mL round bottom flask, and a reflux condenser. Putapproximately 30mL of xylene into the round-bottom flask, 3-4 boiling chips, then addthe anthracene and maleic anhydride. Attach a drying tube filled with drierite to the topof the condenser, but make sure that the outlet of the tube is not closed – otherwise youwould be heating a closed system which would result in an explosion! Connect the hosesfor cooling water to the reflux condenser. Reflux the mixture for one hour, then let itcool down and remove the condenser.Place the reaction flask on an ice bath to precipitate the product. Vacuum filter the solidand wash the solid several times with 10mL portions of pentane. Air dry the product bykeeping it on the filtration apparatus for approximately 10 minutes. Weigh the crudeproduct to calculate the yield. Spot the product on the same TLC plate and develop it inTLC chamber using methylene chloride as an eluting solvent. Analyze your TLC andcheck if you need to recrystallize the product. If you indeed need to do that, then usemethylene chloride.Waste disposal:Organic filtrates should be placed in the organic waste container.'H NMR AnalysisAnalyze the 'H NMR spectra of both of your starting compounds. Compare these spectrawith that obtained for your product. Try to assign all peaks in all three spectra. Inparticular, try to answer the following questions:1. In the spectrum of anthracene, which signal belongs to the protons on themiddle ring? Why? Is that signal still present in the spectrum of the product?2. In the spectrum of the product, which signals correspond to the protonsattached to the carbons where the new sigma bonds have been formed? Diels-Alder Reaction Between Anthracene and Maleic AnhydrideAICI3 or heatAnthraceneMaleic AnhyrdideDiels-Alder AdductBackground. The Diels-Alder reaction is one of the most useful reactions in all oforganic chemistry. Usually, an electron-rich diene is reacted with an electron-poordienophile resulting in the formation of a new six-membered ring. There are no ionic orradical intermediates in this reaction. Instead, bond-breaking and bond-making occurs atthe same time; the reaction is said to be concerted. Electrons flow from the HighestOccupied Molecular Orbital (HOMO) of either reactant to the Lowest UnoccupiedMolecular Orbital (LUMO) of the other reactant. The smaller the energy gap betweenthe HOMO and LUMO, the less energy is needed to move the electrons from the HOMOto the LUMO, and the faster is the reaction. In fact, the role of electron-withdrawingsubstituents on the dienophile is to lower the energy of the LUMO, thus decreasing theHOMO-LUMO energy gap, and making the Diels-Alder reaction kinetically feasible.Benzene and related aromatic compounds do not undergo Diels-Alder reactions.However, anthracene, which consists of three fused benzene rings, does undergo Diels-Alder reactions, although the kinetic barrier is quite high. One of the reasons for the highkinetic barrier is the fact that as a result of the pi-bond of one of the anthracene ringsreacting, this ring will no longer be aromatic. It has been estimated that at room-temperature, it would take 4,800 hours to react anthracene with the excellent dienophile(low-lying LUMO) maleic anhydride! There are two ways of accelerating such slowDiels-Alder reactions:One possibility is to simply reflux the solution in a solvent with a high boiling point.This is in fact what we will be doing in our laboratory experiment.Another method that has become very important was first discovered by Prof. Eaton (thenat Harvard) and coworkers.' A Lewis acid such as AlCl, is added to the reaction mixture.It forms a complex with the dienophile making it much more electron-deficient andlowering the energy of its LUMO, thereby lowering the overall activation energy neededfor the reaction. The first Lewis-acid catalyzed Diels-Alder reaction studied was in factthe reaction of anthracene with maleic anhydride. Eaton reported that addition of one totwo equivalents of AlCl, led to a complete reaction within minutes at room-temperatureinstead of the 4,800 hours needed without the catalyst. Since then, many different Lewis-acid catalysts have been used to accelerate Diels-Alder reactions. Much research is stillbeing undertaken with chiral Lewis acids as this may lead to the selective formation ofonly one stereoisomer.?

In a polycyclic aromatic hydrocarbon, the aromatic rings that are made up of only carbon and…

Answered: I need help to find out why we use a…

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter1: Chemical Foundations

Section: Chapter Questions

Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...