The chemistry of Obermayer test for indican in urine
Abstract
The purpose of this article is to provide the reaction mechanism of the process occurring during the Obermayer colour test for indican in urine. This test differs from cognate tests because no chemical oxidant is used in order to oxidise 3-hydroxy-indol to indigo blue, but exclusively fuming hydrochloric acid is employed. From this fact it is deduced the intervention of aerial oxygen. The approach to the chemistry of this test is based on the chemical deportment of reagent and substrate, in union with cogent reasons (Theoretical Organic Chemistry). The proposed intermediates show a parallelism with those suggested in alkaline medium during the obtention of indigo blue from natural source. However, the formation of indigo red (indirubin) in acidic medium goes through different intermediates and the reaction mechanism is given here for the first time.
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