Question

This is from an organic chemistry diels-alder lab using anthracene, maleic anhydride and xylenes. Can anyone tell me the correct answers to all of these? For question 3 I need a method to remove xylene and a method to remove acetone. Thank you!

CHM 20L Organic ll Lab Discussion and conclusion Provide responses to each of the following questions." Attach the 'H NMR spectrum for your product to respond to the following (on the spectrum, where appropriate) 1. Use the 'H NMR spectrum from your submitted sample to determine the identity of your product. Following the format employed for Determination of an unknown by NMR, assign all peaks on your product spectrum, including the chemical shif, splitting patterns, coupling constants, and rounded integral value for each peak. You may wish to compare to the other available spectra (in the "Common Spectra' folder) to support your argument. Number the protons in the spectrum as in the figure below. Attach copies of all supporting spectra to your report. 2. If there are any impurities present in your 'H NMR spectrum, identify their source(s). A list of common impurities, such as solvents, can be found in your MNova instruction packet. would fall backin COP Corator *2 3. For any impurities found in your NMR sample, suggest at least one method that could be used to remove each impurity. To remove the myrene impurity, you could continue to refinx for inger Than 30 minutes. The H2O impurity can be removed by adding a drying agent. 4. The expected product appears to have a high level of symmetry, yet there are differences in chemical shift between hydrogens 3 and 5, and 4 and 6. Explain the origin of the difference in chemical shift. 5 The difference in chemical shift is due to protons (5) 3+ 4 being more deshielded while protons steare more shielded. why more deshielded? 5. Based on the solubility of this product in water, water would appear to be a good candidate for a recrystallization solvent for this procedure. Explain why water is actually a poor choice for recrystallizing 10 this anhydride. 10. The courbonyl groups can undergo Th moleophilic substitution reactions in water which would change the product molecule. Dets. Alter Reaction

Answer 1

Diels Alder reaction of antracene and maleic anhydride which gives the adduct is as shown below. anthracene maleic anhydride 1. The theoretical NMR of the product is shown below 14 7.31 019 2131 7.19 731 7.31 7.19 Estimation quality is indicated by color: good, medium, rough PPM From the NMR given in the problem, the peaks for the hydrogens 3 & 5 are little shielded than the protons of 4 & 6. So in the problem, 7.22-7.20 belongs to 3 & 5, 7.40-7.33 belongs to the protons 4 & 6. For the protons 1 signal is at 3.53 and for the bridged protons 2 signal is at 4.83. 2. In the problem, the HNMR looks clean with slight solvent impurity. It looks like the solvent impurity might be acetone. 3. In the problem, there is less chance of xylene impurity until and unless you use that as solvent in the reaction. In case xylene is present then the compound has to be dried using high vacuum. And acetone impurity also removed using high vacuum (of course it's not the last choice, if you keep it above 30 degree in room temp it will evaporate). 4. Only the structure looks with high symmetry but it's not. One phenyl ring in exo and another with endo symmetry. That's the reason there is difference. Also 3 proton is more de- shielded than 4 protons. As it is near to electron withdrawing group.