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Thyroxine

Athanor · official

C15H11I4NO4 · 776.87 g/mol

IUPAC name: (2S)-2-amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]propanoic acid

Also called T4, levothyroxine, Synthroid, thyroid hormone

DrugsAmino acids
Open in Athanor
The structure of Thyroxine
Drawn from its SMILES with RDKit
Harmful or irritantHealth hazardDangerHarmful if swallowed · Suspected of damaging fertility or the unborn child · Causes damage to organs through prolonged or repeated exposure

Names and identifiers

IUPAC name
(2S)-2-amino-3-[4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl]propanoic acid
Synonyms
T4, levothyroxine, Synthroid
+ 38 more

thyroid hormone, thyroxin, L Thyroxin beta, L Thyrox, L Thyroxine Roche, L Thyroxin Henning, Levothyroxin Delalande, RefChem:5946, L-3,5,5'-tetraiodothyronine, 2-amino-3-(4-(4-hydroxy-3,5-diiodophenoxy)-3,5-diiodophenyl)propanoic acid, Tyrosine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-, L-thyroxine, Tetraiodothyronine, Thyreoideum, Thyroxinal, Levothyroxin, Thyratabs, Thyrax, Thyroxine iodine, (-)-Thyroxine, 3,3',5,5'-Tetraiodo-L-thyronine, O-(4-hydroxy-3,5-diiodophenyl)-3,5-diiodo-L-tyrosine, L-Thyroxin, 3,5,3',5'-Tetraiodo-L-thyronine, L-T4, Thyroxine (l), DL-Thyroxin, Thyroxine (VAN), Laevothyroxinum, Levothyroxinum (acid), Laevothyroxinum (acid), 3,5,3',5'-Tetraiodothyronine, Thryroxine, l-, t4, Thyroxine, L-, L-3,5,3',5'-Tetraiodothyronine, MFCD00002595, Forthyron (TN)

Molecular formula
C15H11I4NO4
Empirical formula
C15H11I4NO4
Molecular weight
776.87 g/mol
Exact mass
776.68670
CAS number
51-48-9
PubChem CID
5819
Canonical SMILES
C1=C(C=C(C(=C1I)OC2=CC(=C(C(=C2)I)O)I)I)CC(C(=O)O)N
Isomeric SMILES
C1=C(C=C(C(=C1I)OC2=CC(=C(C(=C2)I)O)I)I)C[C@@H](C(=O)O)N
InChI
InChI=1S/C15H11I4NO4/c16-8-4-7(5-9(17)13(8)21)24-14-10(18)1-6(2-11(14)19)3-12(20)15(22)23/h1-2,4-5,12,21H,3,20H2,(H,22,23)/t12-/m0/s1
InChIKey
XUIIKFGFIJCVMT-LBPRGKRZSA-N
Molfile

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

Calculated

Heavy atoms
24
Rings
2
Aromatic rings
2
Fraction sp³ carbons (Fsp3)
0.13
H-bond donors
3
H-bond acceptors
4 computed here · PubChem 5
Rotatable bonds
5
TPSA (Ų)
92.8
Formal charge
0
XLogP3
2.4 PubChem
Complexity
420 PubChem
Stereocenters
1 definedCIP: C2: S
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

  • C23.19%
  • H1.43%
  • I65.34%
  • N1.80%
  • O8.24%

Isotope pattern

100%776.68717%777.6902.2%778.692779.695

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
4.56 Crippen (Wildman and Crippen 1999)
log S (water solubility)
-7.57 ESOL (Delaney 2004), log mol/L
Synthetic accessibility
3.37 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

  • Molecular weight ≤ 500: 776.87
  • log P ≤ 5 (Crippen): 4.56
  • H-bond donors ≤ 5: 3
  • H-bond acceptors ≤ 10: 4

Breaks 1 of the 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: 25 company reports to ECHA. Source [2].

  • Harmful or irritant
  • Health hazard
  • H302Harmful if swallowed (56% of reports)
  • H361Suspected of damaging fertility or the unborn child (28% of reports)
  • H372Causes damage to organs through prolonged or repeated exposure (32% of reports)

Precautionary statements: P203, P260, P264, P270, P280, P301+P317, P318, P319, P330, P405, P501

View all classifications (2)
  • [2] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 8% (2 of 25) of reports.
  • [2] European Chemicals Agency (ECHA) · 25 reports · DangerH302, H361, H372

Storage

  • Store at 25 °C (77 °F); excursions permitted to 15 deg -30 °C (59 deg - 86 °F).[1]
  • Keep container tightly closed in a dry and well-ventilated place.[1]

Incompatibilities

  • Incompatible materials: Strong oxidizing agents, Strong bases[1]

Safety data sheets on the supplier’s page: Sigma-Aldrich, AbMole Bioscience, Glixx Labs Inc.

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]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
  4. [4]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
  5. [5]SpectraBase · Linked only · 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. [8]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
  9. ·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
  10. ·Literature on PubChem

Data last updated 2026-10-14.