Glossary entry (descriptive, non-procedural): In forensic-chemistry reference texts, fentanyl is classified as an anilidopiperidine. Such glossaries name N-phenethyl-4-piperidone (NPP) and 4-ANPP as the characteristic precursors associated with this compound class, alongside an acylating agent such as propionyl chloride and the aromatic amine aniline. The same references discuss reductive amination and acylation as named reaction types, the piperidine ring system, and the phenethyl substituent, purely as nomenclature.

Encyclopedic entries also list generic laboratory associations: dichloromethane as a common solvent, triethylamine as a base, liquid-liquid extraction during workup, and hydrochloride salt forms of the final product. Purification is noted via recrystallization and column chromatography, with fume hood ventilation as a safety norm and HPLC used to assess purity. Pharmacology summaries describe its potency in the microgram range. Physical-property tables record values such as 70 degrees celsius and 1 atm. No quantities, ratios, ordered steps, or settings are given; this entry is definitional only.
