Fentanyl

Athanor · official

C₂₂H₂₈N₂O · 336.5 g/mol

IUPAC name: N-phenyl-N-[1-(2-phenylethyl)piperidin-4-yl]propanamide

Also called Duragesic, Sublimaze, opioid

Drugs Rings

Open in Athanor

Drawn from its SMILES with RDKit

DangerFatal if swallowed · Fatal in contact with skin · May cause an allergic skin reaction · Fatal if inhaled · May cause allergy or asthma symptoms or breathing difficulties if inhaled · Suspected of damaging fertility or the unborn child · May cause harm to breast-fed children · May cause long lasting harmful effects to aquatic life

Names and identifiers

IUPAC name: N-phenyl-N-[1-(2-phenylethyl)piperidin-4-yl]propanamide
Synonyms: Duragesic, Sublimaze, opioid
+ 37 more
Phentanyl, Fentanil, Fentanest, Sublimase, Fentanylum, Durogesic, Fentanila, Matrifen, Duragesic-100, Duragesic-12, Duragesic-25, Duragesic-50, Duragesic-75, Fentanyl-12, Fentanyl-25, Fentanyl-50, Fentanyl-75, Recuvyra, N-(1-Phenethylpiperidin-4-yl)-N-phenylpropionamide, Subsys, Fentanyl-100, PecFent, Fentanyl CII, effentora, 1-Phenethyl-4-N-propionylanilinopiperidine, Fendrop, Durogesic d-trans, N-(1-Phenethyl-4-piperidyl)propionanilide, N-Phenethyl-4-(N-propionylanilino)piperidine, 1-Phenethyl-4-(N-phenylpropionamido)piperidine, N-phenyl-N-[1-(2-phenylethyl)piperidin-4-yl]propanamide, N-(1-Phenethyl-4-piperidinyl)-N-phenylpropionamide, Fentanilo, Rapinyl, DTXSID9023049, R 4263, Fentanyl Transdermal System
Molecular formula: C₂₂H₂₈N₂O
Empirical formula: C₂₂H₂₈N₂O
Molecular weight: 336.5 g/mol
Exact mass: 336.22016
CAS number: 437-38-7
PubChem CID: 3345
Canonical SMILES: CCC(=O)N(C1CCN(CC1)CCC2=CC=CC=C2)C3=CC=CC=C3
Isomeric SMILES: CCC(=O)N(C1CCN(CC1)CCC2=CC=CC=C2)C3=CC=CC=C3
InChI: InChI=1S/C22H28N2O/c1-2-22(25)24(20-11-7-4-8-12-20)21-14-17-23(18-15-21)16-13-19-9-5-3-6-10-19/h3-12,21H,2,13-18H2,1H3
InChIKey: PJMPHNIQZUBGLI-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Crystals or crystalline powder.[1]
Solubility in water: In water, 200 mg/L at 25 °C[2]
log P: log Kow = 4.05[2]
pKa: pKa = 7.3[2]
2 values
Only one source reports it.
Value As written Source
–shown pKa = 7.3 [2] Hazardous Substances Data Bank (HSDB)cites Boleda MR et al; Chemosphere 84: 1601-7 (2011)
– pKa: 8.3 /Fentanyl citrate/ [2] Hazardous Substances Data Bank (HSDB)cites Osol, A. and J.E. Hoover, et al. (eds.). Remington's Pharmaceutical Sciences. 15th ed. Easton, Pennsylvania: Mack Publishing Co., 1975., p. 1044
Vapor pressure: 4.43 × 10⁻⁹ mmHg at 25 °C (estrapolated)[2]

Value	As written	Source
–shown	pKa = 7.3	[2] Hazardous Substances Data Bank (HSDB)cites Boleda MR et al; Chemosphere 84: 1601-7 (2011)
–	pKa: 8.3 /Fentanyl citrate/	[2] Hazardous Substances Data Bank (HSDB)cites Osol, A. and J.E. Hoover, et al. (eds.). Remington's Pharmaceutical Sciences. 15th ed. Easton, Pennsylvania: Mack Publishing Co., 1975., p. 1044

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 25
Rings: 3
Aromatic rings: 2
Fraction sp³ carbons (Fsp3): 0.41
H-bond donors: 0
H-bond acceptors: 2
Rotatable bonds: 6
TPSA (Å²): 23.6
Formal charge: 0
XLogP3: 4 PubChem
Complexity: 391 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C78.53%
H8.39%
N8.33%
O4.75%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 4.14 Crippen (Wildman and Crippen 1999)
log S (water solubility): -4.49 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 1.98 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 336.48
log P ≤ 5 (Crippen): 4.14
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 2

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Most widely reported: 77 company reports to ECHA. Source [3].

Acute toxicity
Harmful or irritant
Health hazard

H300Fatal if swallowed (98.7% of reports)
H310Fatal in contact with skin (44.2% of reports)
H317May cause an allergic skin reaction (15.6% of reports)
H330Fatal if inhaled (48.1% of reports)
H334May cause allergy or asthma symptoms or breathing difficulties if inhaled (15.6% of reports)
H361Suspected of damaging fertility or the unborn child (15.6% of reports)
H362May cause harm to breast-fed children (13% of reports)
H413May cause long lasting harmful effects to aquatic life (11.7% of reports)

Precautionary statements: P203, P233, P260, P261, P262, P263, P264, P270, P271, P272, P273, P280, P284, P301+P316, P302+P352, P304+P340, P316, P318, P320, P321, P330, P333+P317, P342+P316, P361+P364, P362+P364, P403, P403+P233, P405, P501

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]The National Institute for Occupational Safety and Health (NIOSH) · Public domain (US CDC) · via PubChem · retrieved 2026-10-14
[2]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[3]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[4]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[5]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[6]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[7]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
[8]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.