King Fischer

This year we performed the Fischer esterification synthesis of a series of ethyl cycloalkane carboxylates. The starting carboxylic acids were cyclopropane, cyclobutane, cyclopentane, and cyclohexane carboxylic acid. A couple of the carboxylic acids had a distinctive butyric acid type odor: ugh! We used sulfuric acid an excess of ethanol to complete the reaction. The products were recovered with liquid-liquid separation with methyl tert-butyl ether or hexane as the organic phase to add some volume to the water immiscible esters. The recovery of ethyl cyclopropane carboxylate was rather low. Most likely this was due to partial solubility of ethyl cyclopropane carboxylate in water. The products were all liquid so a refractive index was taken. All the esters had a vaguely fruity odor which is common for simple esters. An IR was performed on all samples. It was possible to distinguish between the four esters in IR by the shape and pattern of their C-H stretching bands.  In the NMR it is interesting to compare the chemical shifts and dddd multiplicities of the methine (methanetriyl?) hydrogen: cyclopropane (1.45 ppm), cyclobutane (2.85 ppm), cyclopentane (2.55 ppm), cyclohexane (2.09 ppm).



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