There is a lack of pictorial evidence of the outcome of most reactions in core organic chemistry. This places visual learners at a disadvantage. Photographic evidence is presented for the preparation of 2,3,4,5-tetraphenylcyclopentadienone via the crossed aldol reaction of dibenzyl ketone with benzil. Then the 2,3,4,5-tetraphenylcyclopentadienone was used as a trap for benzyne, which was generated in situ from anthranilic acid and isopentyl nitrite. The effluent carbon dioxide was confirmed by the formation of a milky precipitate with limewater and decolorization of blue basic thymolphthalein. The carbon monoxide byproduct was confirmed by reaction with an iron(II) porphyrin. Finally, the interaction of picric acid with the 1,2,3,4-tetraphenylnaphthalene was compared with the reaction with naphthalene. In addition to supplying students with evidence for the benzyne intermediate, students also learn about the binding of carbon monoxide with porphyrins which is critical to the toxicity of carbon monoxide.

Aesthetically appealing benzyne trapping reaction via mixed aldol and Diels-Alder reactions

244th National Meeting (2012)

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