Degradation of immediate precursors of fentanyl and fentalogs

Abstract

Remediation of clandestine laboratory and processing operations for fentanyl and its analogs (i.e., fentalogs) may involve application of oxidants, most commonly household hypochlorite bleach, to chemically degrade the fentanyl to enable disposition of the site. While the chemical degradation of fentanyl has been reported, the degradation of immediate precursors has not been. Chemical degradation of fentanyl and fentalogs can cause these immediate precursors to reform. The immediate precursors of fentanyl investigated here are norfentanyl and 4-ANNP, which are controlled substances, along with norcarfentanil, precursor for carfentanil and remifentanil. The 4-ANNP was degraded within minutes in chlorine bleach, somewhat faster than fentanyl itself, whereas norfentanyl and norcarfentanil showed apparent degradation half lives up to days. Also, degradation rates were reduced in the presence of common diluents, like cutting agents, with apparent half-lives of several weeks for fully dissolved solutions. When the fentalog was added as a powder, globules were observed which could indefinitely prevent contact between the chlorine and the contents of the globules, prolonging persistence unless the globules are mechanically or otherwise broken. Because of shared structural characteristics among fentalogs, such as presence of reactive nitrogen groups, the results of this study may be applicable to a wide array of fentalogs. This study may also help inform remediation and waste management strategies to provide not only effective remediation of contamination, but also reduce the possibility that wastes of controlled substances are handled inappropriately, e.g., leading to continued personnel exposure and/or reprocessing of controlled substances.

Keywords: Bleach; Degradation; Fentalog; Fentanyl; Precursor.

Fig. 1.

Oxidation of 4-ANPP, fentanyl, and related compounds for the starting concentrations shown with 10% bleach. The controls contain no bleach. The solid lines are intended to guide the eye and not to imply a functional form.

Fig. 2.

Percent norfentanyl calculated for several concentrations of bleach when no diluents are present. The dotted lines represent best fits to an exponential function corresponding to an apparent first order reaction.

Scheme 1.

Possible pathways of immediate precursors to fentanyl and remifentanil. 4-ANPP forms fentanyl, and norfentanyl is both precursor and degradation product of fentanyl. Norcarfentanil is a degradation product of remifentanil. Remifentanil acid is formed by ester hydrolysis and potentially degrades to norcarfentanil.