The effect of benzene ring substituents on the mechanism of Duquenois Levine (DL) test for cannabinoid detection

Carlos Rubiano, Jeffrey St Fir

Abstract

Tetrahydrocannabinol is detected by the presumptive Duquenois-Levine Test (DL), a chemical spot test based on the aldol condensation reaction. However, the chemistry and mechanism of the reaction is not fully understood. In the present study several substituted benzene compounds were tested to better comprehend the mechanism of the reaction.Compounds containing different substituents on the benzene ring gave differential results when tested with the Duquenois-Levine reagents. While activating substituents containing a lone pair of electrons resulted in a positive color change, the presence of substituents with no lone pair resulted in no change in color. These studies suggest that the activating groups contribute to the conjugation of the resultant chromophore product resulting in a color change. These studies provide a better understanding of the mechanism of the presumptive cannabinoid color test.