The chemistry of the Wender’s test for Dulcin

Abstract

The reaction route of Wender’s test for Dulcin, p-phenetolecarbamide, is disclosed in this article. The many steps in this interesting oxido-degradation process are fully commented and the electron flow is given. Wender used fuming nitric acid as reagent. A violent reaction takes place; however, the test is safe due to the minute quantity employed of this sweetener. Further addition of phenol solution and sulphuric acid gives a blood-red colour. The reactions that occur are as follows: nitration of the ureido group, nitrous acid removal, nitrate formation, elimination of nitrous acid, nitroso group formation, separation of nitric acid and carbon monoxide, free radical degradation to p-benzoquinone imine, hydrolysis, and formation of red phenoquinone, the colour observed in the test.