Reaction of Dimedone and Benzaldehyde: A Discovery-Based Lab for Second-Semester Organic Chemistry

摘要

A simple, two-step synthesis of 9-phenylxanthene-1,8-dione from dimedone and benzaldehyde was developed for second-semester undergraduate organic chemistry. Both reactions afford crystalline solids in excellent yield by simply precipitating the product from solution. Reaction times are very short, and no specialized equipment, reagents, or purification techniques are needed. Multiple spectroscopic methods (IR and H-1, C-13, and DEPT NMR) are employed to solve the structures of the intermediate and final product, which are unknown to students. The products are not ones students would initially predict, but rather are derived from careful analysis of the spectroscopic data in conjunction with logical mechanistic steps. H-1 NMR peaks are well resolved, even at low field. Students have responded favorably over the five years this experiment has been used as a culminating experience in organic chemistry lab.