Methadone (C21H27NO): structure, properties and hazards

Names and identifiers

IUPAC name: 6-(dimethylamino)-4,4-diphenylheptan-3-one
Synonyms: Dolophine, Methadose, opioid
+ 38 more
dl-Methadone, Diaminon, Phenadone, Dolophin, Heptadone, Ketalgin, Methadon, Adanon, Amidone, Algovetin, Heptanon, Physeptone, Racemic methadone, (+-)-Methadone, Methadonum, Metadona, Metasedin, 6-(dimethylamino)-4,4-diphenylheptan-3-one, Eptadone, Methadona, 3-Heptanone, 6-(dimethylamino)-4,4-diphenyl-, 6-Dimethylamino-4,4-diphenyl-3-heptanone, Methadonum [Latin], Polamivet, UC6VBE7V1Z, K 174, 6-(Dimethylamino)-4,4-diphenyl-3-heptanone, CHEBI:6807, IDS-NM-002, DTXSID7023273, CHEBI:167309, 3-14-00-00279 (Beilstein Handbook Reference), Methadonum (Latin), Phymet, RefChem:6010, DTXCID003273, 200-996-9, Depridol
Molecular formula: C₂₁H₂₇NO
Empirical formula: C₂₁H₂₇NO
Molecular weight: 309.4 g/mol
Exact mass: 309.20926
CAS number: 76-99-3
PubChem CID: 4095
Canonical SMILES: CCC(=O)C(CC(C)N(C)C)(C1=CC=CC=C1)C2=CC=CC=C2
Isomeric SMILES: CCC(=O)C(CC(C)N(C)C)(C1=CC=CC=C1)C2=CC=CC=C2
InChI: InChI=1S/C21H27NO/c1-5-20(23)21(16-17(2)22(3)4,18-12-8-6-9-13-18)19-14-10-7-11-15-19/h6-15,17H,5,16H2,1-4H3
InChIKey: USSIQXCVUWKGNF-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Melting point: Reported, but no value passed the checks.
The 2 values and why
no odor. MP: 232-235 °C. Soluble in water, alcohol, and chloroform (could not be read; source [1])
practically insoluble in ether and glycerol. pH (1% aqueous solution): 4.5-6.5 /Methadone hydrochloride/ (could not be read; source [1])
Solubility in water: Solubility: 1 g in 13 mL water; 8 mL alcohol, 3 mL chloroform; practically insol ublein ether and glycerin. Colorless crystals or a white, crystalline powder (methadone hydrochloride)[1]
log P: log Kow = 3.93[1]
pKa: pKa = 8.94 (conjugate acid)[1]

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: 23
Rings: 2
Aromatic rings: 2
Fraction sp³ carbons (Fsp3): 0.38
H-bond donors: 0
H-bond acceptors: 2
Rotatable bonds: 7
TPSA (Å²): 20.3
Formal charge: 0
XLogP3: 3.9 PubChem
Complexity: 346 PubChem
Stereocenters: 0 defined, 1 undefinedCIP: C7: undefined
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

C81.51%
H8.79%
N4.53%
O5.17%

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: 4.29 Crippen (Wildman and Crippen 1999)
log S (water solubility): -4.39 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 2.71 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 309.45
log P ≤ 5 (Crippen): 4.29
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: 3 company reports to ECHA. Source [2].

Acute toxicity
Harmful or irritant

H300Fatal if swallowed
H336May cause drowsiness or dizziness
H412Harmful to aquatic life with long lasting effects

Precautionary statements: P261, P264, P270, P271, P273, P301+P316, P304+P340, P319, P321, P330, P403+P233, P405, P501

View all classifications (2)

[2] European Chemicals Agency (ECHA) · 3 reports · DangerH300, H336, H412
[1] Hazardous Substances Data Bank (HSDB) · DangerH300

Storage

Methadone hydrochloride preparations should be stored in tight, light-resistant containers. Methadone hydrochloride oral concentrate and oral solution should be stored at 15-30 °C; the tablets and injection should be stored at a controlled room temperature of 25 °C, but may be exposed to temperatures ranging from 15-30 °C.[1]
Keep container tightly closed in a dry and well-ventilated place. Light sensitive. Keep in a dry place. (methadone hydrochloride)[1]

Incompatibilities

Incompatible materials: Alkalis, Oxidizing agents, iodides, mercury salts, saccharin sodium, Amaranth, Bordeaux B. (methadone hydrochloride)[1]

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]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[2]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[3]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[4]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[5]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[6]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
[7]MassBank Europe · Linked only · 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.