Pyrimethamine (C12H13ClN4): structure, properties and hazards

Names and identifiers

IUPAC name: 5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diamine
Synonyms: Daraprim, antimalarial, antifolate
+ 37 more
Chloridine, 5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diamine, Chloridin, Diaminopyritamin, Ethylpyrimidine, Pirimecidan, Pirimetamin, Pirimetamina, Chloridyn, Darachlor, Erbaprelina, Khloridin, Tindurin, Malocid, Primethamine, Pyrimethamin, 5-(4-CHLOROPHENYL)-6-ETHYL-2,4-PYRIMIDINEDIAMINE, Pyrimethaminum, 2,4-Pyrimidinediamine, 5-(4-chlorophenyl)-6-ethyl-, Pyremethamine, 2,4-Diamino-5-(p-chlorophenyl)-6-ethylpyrimidine, RP 4753, 2,4-Diamino-5-(4-chlorophenyl)-6-ethylpyrimidine, TCMDC-125860, NCI-C01683, 2,4-Diamino-5-chlorophenyl-6-ethylpyrimidine, BW 50-63, 5-(4'-Chlorophenyl)-2,4-diamino-6-ethylpyrimidine, NSC-3061, GNF-Pf-5586, DTXSID9021217, WR 2978, 5-(4-Chlorophenyl)-6-ethyl-2,4-diaminopyrimidine, Z3614QOX8W, 4753 R.P., NSC 3061, WR-2978
Molecular formula: C₁₂H₁₃ClN₄
Empirical formula: C₁₂H₁₃ClN₄
Molecular weight: 248.71 g/mol
Exact mass: 248.08287
CAS number: 58-14-0
PubChem CID: 4993
Canonical SMILES: CCC1=C(C(=NC(=N1)N)N)C2=CC=C(C=C2)Cl
Isomeric SMILES: CCC1=C(C(=NC(=N1)N)N)C2=CC=C(C=C2)Cl
InChI: InChI=1S/C12H13ClN4/c1-2-9-10(11(14)17-12(15)16-9)7-3-5-8(13)6-4-7/h3-6H,2H2,1H3,(H4,14,15,16,17)
InChIKey: WKSAUQYGYAYLPV-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: White scored tablets contains 25 mg pyrimethamine (daraprim)[2]
2 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Pyrimethamine is an odorless white crystalline powder. Tasteless. An antimalarial drug. [1] CAMEO Chemicals
–shown White scored tablets contains 25 mg pyrimethamine /Daraprim/ [2] Hazardous Substances Data Bank (HSDB)cites US Natl Inst Health; DailyMed. Current Medical Information. Daraprim. Available from, as of June 20, 2012: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=31681
Melting point: 233 to 234 °C (451 to 453 °F) (capillary) (NTP, 1992)[1]
Solubility in water: In water, 10 mg/L (temperature not specified)[2]
2 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– less than 0.1 mg/mL at 70 °F (NTP, 1992) [1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
–shown In water, 10 mg/L (temperature not specified) [2] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan, Jain, P. Handbook of Aqueous Solubility Data Second Edition. CRC Press, Boca Raton, FL 2010, p. 877
log P: log Kow = 2.69[2]
pKa: pKa = 7.34 at 20 °C (conjugate acid)[2]

Value	As written	Source
–	Pyrimethamine is an odorless white crystalline powder. Tasteless. An antimalarial drug.	[1] CAMEO Chemicals
–shown	White scored tablets contains 25 mg pyrimethamine /Daraprim/	[2] Hazardous Substances Data Bank (HSDB)cites US Natl Inst Health; DailyMed. Current Medical Information. Daraprim. Available from, as of June 20, 2012: https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?id=31681

Value	As written	Source
–	less than 0.1 mg/mL at 70 °F (NTP, 1992)	[1] CAMEO Chemicalscites National Toxicology Program, Institute of Environmental Health Sciences, National Institutes of Health (NTP). 1992. National Toxicology Program Chemical Repository Database. Research Triangle Park, North Carolina.
–shown	In water, 10 mg/L (temperature not specified)	[2] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan, Jain, P. Handbook of Aqueous Solubility Data Second Edition. CRC Press, Boca Raton, FL 2010, p. 877

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): 0.17
H-bond donors: 2
H-bond acceptors: 4
Rotatable bonds: 2
TPSA (Å²): 77.8
Formal charge: 0
XLogP3: 2.7 PubChem
Complexity: 243 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

C57.95%
H5.27%
Cl14.25%
N22.53%

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: 2.52 Crippen (Wildman and Crippen 1999)
log S (water solubility): -3.36 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 2.12 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 248.72
log P ≤ 5 (Crippen): 2.52
H-bond donors ≤ 5: 2
H-bond acceptors ≤ 10: 4

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

Warning

Most widely reported: 133 company reports to ECHA. Source [3].

Harmful or irritant

H302Harmful if swallowed (99.2% of reports)

Precautionary statements: P264, P270, P301+P317, P330, P501

First aid

Eyes: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. Immediately transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop. Skin: Immediately flood affected skin with water while removing and isolating all contaminated clothing.[1]

Storage

Store at 15 deg to 25 °C (59 deg to 77 °F) in a dry place and protect from light.[2]

Safety data sheets on the supplier’s page: BOC Sciences, Cooke Chemical Co., Ltd, AiFChem, an XtalPi Company.

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]CAMEO Chemicals · Public domain (NOAA) · 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]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[6]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[7]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[8]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
[9]RRUFF Project · 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.