Discuss how one would differentiate between the starting material and product. A

Question

Discuss how one would differentiate between the starting material and product. Answer all of the questions please! 1) TLC 2) MS 3) IR 4) NMR Diels-Alder Cycloaddition In this experiment furan and maleic anhydride react to form a bicyclic Diels-Alder adduct. The bicyclic product can have either endo or exo stereochemistry furan maleic anhydride endo product exo product In Diels-Alder reactions the endo product forms faster- it has a lower energy transition state due to favorable pi orbital overlap. If the endo product forms the reaction is sald to be under kinetic control. Exo products are generally more stable than endo products because they are less sterically hindered. if the exo product forms the reaction is said to be under thermodynamic control After forming and purifying the Diels-Alder product, you will take the melting point and determine if kinetic or the thermodynamic product was formed. The melting point of the endo product is 81 C and the melting point of the exo product is 114 2 Procedure Put 1.20 g of maleic anhydride and 10 mL of ether in 50 mL Erlenmeyer flask. Heat the mixture in a warm (not boiling) water bath until all the anhydride has dissolved under a fume hood. Stir with a glass stirring rod if needed. Add more ether to replace any that evaporates. (Caution- Ether has a low boiling point and a tendency to quickly boil over when heated to excess. As soon as bubbles form, remove the flask from the water bath). When the solution has cooled to room temperature, add 1.00 mL of feran. Stopper the flask and cover the seal with paraffin to prevent evaporation. / Etherhas a low biling poi t stoppering a warm flask will generate pressure and could lead to an explosion caution Allow the flask to stand in the designated test tube rack for several days at room temperature. Lyclopenladiun Collect the solid product with vacuum filtration. Recrystallize part of your product by dissolving it in a minimum amount Collect crystals by vacuum filtration and rinse the of acetone and adding hexanes dropwise until precipitate forms. crystals with cold hexanes Determine the percent yield by weighing the crude crystals before you recrystallize part of your product. The product tends to decompose near its melting point, therefore, get a rough estimate of the melting point by heating one sample at a rapid rate, then retake the measurement at a slower rate, inserting a second sample when the melting point apparatus has reached the approximate melting point. Determine if your product is endo or exo and propose an Chemicals: furan, maleic anhydride, diethyl ether, hexanes, acetone

Explanation / Answer

TLC

If we run TLC after reaction we should have observed new polar spot with less Rf value than starting material, it is the product. From the starting material spots we will come to know whether reaction has done full conversion or not.

MS

Mass spectrometry will give a mass corressponds to the product which confirms the formation of product. But it will reveal the completion of the reaction.

IR

IR spectrum is not useful in this conversion since no IR active functional groups are either disappeard or appeared.

NMR

After checking TLC, new spot can be isolated and shoud be taken NMR reveal the formation of product. In NMR 2 aliphatic carbons should present which are present in the starting materials.

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