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Melatonin

Athanor · official

C13H16N2O2 · 232.28 g/mol

IUPAC name: N-[2-(5-methoxy-1H-indol-3-yl)ethyl]acetamide

Also called N-acetyl-5-methoxytryptamine, Circadin

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The structure of Melatonin
Drawn from its SMILES with RDKit

Names and identifiers

IUPAC name
N-[2-(5-methoxy-1H-indol-3-yl)ethyl]acetamide
Synonyms
N-acetyl-5-methoxytryptamine, Circadin, Melatonine
+ 36 more

N-Acetyl-5-methoxytryptamine, N-[2-(5-Methoxy-1H-indol-3-yl)ethyl]acetamide, 5-Methoxy-N-acetyltryptamine, Melatol, N-(2-(5-Methoxy-1H-indol-3-yl)ethyl)acetamide, Melovine, Melapure, Acetamide, N-[2-(5-methoxy-1H-indol-3-yl)ethyl]-, N-[2-(5-methoxyindol-3-yl)ethyl]acetamide, DTXSID1022421, N-acetyl-5-methoxy-tryptamine, N-(2-(5-Methoxyindol-3-yl)ethyl)acetamide, NSC 113928, Acetamide, N-(2-(5-methoxyindol-3-yl)ethyl)-, JL5DK93RCL, Acetamide, N-(2-(5-methoxy-1H-indol-3-yl)ethyl)-, NSC-56423, 5-methoxy n-acetyl-tryptamine, NSC-113928, J5.258B, BCI-049, NSC113928, Acetamide, N-[2-(5-methoxyindol-3-yl)ethyl]-, DTXCID002421, CHEBI:16796, NSC56423, N-[2-(5-Methoxy-1H-indol-3-yl)ethyl)acetamide, somease, Heidadouppi, Melaxen, Travelag, Vytalonin, Icenia, Vespro, General nutrit, Natures bounty

Molecular formula
C13H16N2O2
Empirical formula
C13H16N2O2
Molecular weight
232.28 g/mol
Exact mass
232.12118
CAS number
73-31-4
PubChem CID
896
Canonical SMILES
CC(=O)NCCC1=CNC2=C1C=C(C=C2)OC
Isomeric SMILES
CC(=O)NCCC1=CNC2=C1C=C(C=C2)OC
InChI
InChI=1S/C13H16N2O2/c1-9(16)14-6-5-10-8-15-13-4-3-11(17-2)7-12(10)13/h3-4,7-8,15H,5-6H2,1-2H3,(H,14,16)
InChIKey
DRLFMBDRBRZALE-UHFFFAOYSA-N
Molfile

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

Physical properties

Appearance
White-cream to yellowish crystalline powder[1]
Solubility in water
In water, 2 g/L at 20 °C; 5 g/L at 50 °C[1]
log P
log Kow = 1.18 at 28 °C[1]
pKa
Reported, but no value passed the checks.
The value and why
  • Melatonin has pKa of 16.51 and -0.69 and is uncharged in the entire pH-range (could not be read; source [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
17
Rings
2
Aromatic rings
2
Fraction sp³ carbons (Fsp3)
0.31
H-bond donors
2
H-bond acceptors
2
Rotatable bonds
4
TPSA (Ų)
54.1
Formal charge
0
XLogP3
0.8 PubChem
Complexity
270 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

  • C67.22%
  • H6.94%
  • N12.06%
  • O13.78%

Isotope pattern

100%232.12115%233.1241.5%234.127235.129

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
1.86 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-2.58 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
1.91 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 232.28
  • log P ≤ 5 (Crippen): 1.86
  • H-bond donors ≤ 5: 2
  • 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

This chemical does not meet GHS hazard criteria for 96.5% (139 of 144) of all reports.[2]

Safety data sheets on the supplier’s page: INTERBIOSCREEN, BenchChem, Achemtek.

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

Data last updated 2026-10-14.