Diphenhydramine (C17H21NO): structure, properties and hazards

Names and identifiers

IUPAC name: 2-benzhydryloxy-N,N-dimethylethanamine
Synonyms: Benadryl, antihistamine, Nytol
+ 38 more
Benzhydramine, Alledryl, Probedryl, Dihidral, Antistominum, Benzhydraminum, Benzhydroamina, Diphantine, Baramine, Dermodrin, Desentol, Dibondrin, Histaxin, Benylan, Difenhidramina, Difenidramina, Restamin, Rigidyl, Diphenylhydramine, Diphenhydraminum, Ethanamine, 2-(diphenylmethoxy)-N,N-dimethyl-, O-Benzhydryldimethylaminoethanol, 2-(Benzhydryloxy)-N,N-dimethylethylamine, FAR 90X2, PM 255, 2-(Diphenylmethoxy)-N,N-dimethylethylamine, alpha-(2-Dimethylaminoethoxy)diphenylmethane, 2-benzhydryloxy-N,N-dimethylethanamine, beta-Dimethylaminoethanol diphenylmethyl ether, [2-(diphenylmethoxy)ethyl]dimethylamine, N-(2-(Diphenylmethoxy)ethyl)-N,N-dimethylamine, beta-Dimethylaminoethylbenzhydrylether, Dimedrolum, Diphenhdyra, N-(Benzhydryloksy-etylo)dwumetyloamina, Benzantin, beta-dimethylaminoethyl benzhydryl ether, DTXSID4022949
Molecular formula: C₁₇H₂₁NO
Empirical formula: C₁₇H₂₁NO
Molecular weight: 255.35 g/mol
Exact mass: 255.16231
CAS number: 58-73-1
PubChem CID: 3100
Canonical SMILES: CN(C)CCOC(C1=CC=CC=C1)C2=CC=CC=C2
Isomeric SMILES: CN(C)CCOC(C1=CC=CC=C1)C2=CC=CC=C2
InChI: InChI=1S/C17H21NO/c1-18(2)13-14-19-17(15-9-5-3-6-10-15)16-11-7-4-8-12-16/h3-12,17H,13-14H2,1-2H3
InChIKey: ZZVUWRFHKOJYTH-UHFFFAOYSA-N
Molfile

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

Physical properties

Solubility in water: In water, 3.06 × 10³ mg/L at 37 °C[1]
log P: log Kow = 3.27[1]
pKa: pKa = 8.98[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: 19
Rings: 2
Aromatic rings: 2
Fraction sp³ carbons (Fsp3): 0.29
H-bond donors: 0
H-bond acceptors: 2
Rotatable bonds: 6
TPSA (Å²): 12.5
Formal charge: 0
XLogP3: 3.3 PubChem
Complexity: 211 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

C79.96%
H8.29%
N5.49%
O6.27%

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: 3.35 Crippen (Wildman and Crippen 1999)
log S (water solubility): -3.61 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 1.82 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 255.36
log P ≤ 5 (Crippen): 3.35
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

Warning

Most widely reported: 6 company reports to ECHA. Source [2].

Harmful or irritant

H302Harmful if swallowed
H315Causes skin irritation (66.7% of reports)
H319Causes serious eye irritation (66.7% of reports)

Precautionary statements: P264, P264+P265, P270, P280, P301+P317, P302+P352, P305+P351+P338, P321, P330, P332+P317, P337+P317, P362+P364, P501

Storage

Keep container tightly closed in a dry and well-ventilated place. (diphenhydramine hydrochloride)[1]

Safety data sheets on the supplier’s page: Shenghe Chemical, AA BLOCKS, MolCore.

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.