Question

The following ¹H NMR spectra represent the composition of the products submitted by two groups of students after completing the Diels Alder reaction between cyclopentadiene and maleic anhydride.

a Which product looks purer? ( 1 point)

b What impurities appear to be present in the other sample? ( 1 point )

C What purification technique involving a “solvent pair” might be used to purify the impure product? Briefly explain how you would carry out such a purification (experimental procedure). ( 1 point )

Answer 1

The reaction is as follows: cyclopenta-1,3-diene furan-2,5-dione (3aR,4R,7S,7aS)-hexahydro-4,7-methanoisobenzofuran-1,3-dione (a) First spectra looks pure. Since it do not have any additional impurity (b) From second NMR, it seems that maleic anhydride is present as impurities. (c) Here column chromatography can be used to purity of the product. Solvent pair: Ethylacetate + Hexane Experimental analvsis Packed the column with 100-200 much of silica gel and run the mobile phase of solvent ethylacetate and hexane. Increase the polarity of solvent after monitoring the TLC