Phenolphthalein
Athanor · official
C20H14O4 · 318.3 g/mol
IUPAC name: 3,3-bis(4-hydroxyphenyl)-2-benzofuran-1-one
Also called pH indicator, Ex-Lax, 3,3-bis(4-hydroxyphenyl)phthalide
DangerSuspected of causing genetic defects · May cause cancerNames and identifiers
- IUPAC name
- 3,3-bis(4-hydroxyphenyl)-2-benzofuran-1-one
- Synonyms
- pH indicator, Ex-Lax, 3,3-bis(4-hydroxyphenyl)phthalide
+ 38 more
Phthalimetten, Euchessina, Phenolax, Phthalin, Espotabs, Purgophen, Koprol, Laxogen, Trilax, Purga, Spulmako-lax, Chocolax, Purgen, Dihydroxyphthalophenone, Phenolphtaleine, Correctol, Medilax, Colax, Laxin, 3,3-Bis(4-hydroxyphenyl)phthalide, FemiLax, 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone, Fenolftalein, Fenolftaleina, 3,3-bis(4-hydroxyphenyl)-2-benzofuran-1-one, 1(3H)-Isobenzofuranone, 3,3-bis(4-hydroxyphenyl)-, 3,3-Bis(p-hydroxyphenyl)phthalide, NCI-C55798, Phenolphthaleinum, DTXSID0021125, alpha-Di(p-hydroxyphenyl)phthalide, 3,3-bis(4-hydroxyphenyl)-1,3-dihydro-2-benzofuran-1-one, 6QK969R2IF, NSC-10464, DTXCID901125, CHEBI:34914, NSC10464, Laxettes
- Molecular formula
- C20H14O4
- Empirical formula
- C10H7O2
- Molecular weight
- 318.3 g/mol
- Exact mass
- 318.08921
- CAS number
- 77-09-8
- PubChem CID
- 4764
- Canonical SMILES
- C1=CC=C2C(=C1)C(=O)OC2(C3=CC=C(C=C3)O)C4=CC=C(C=C4)O
- Isomeric SMILES
- C1=CC=C2C(=C1)C(=O)OC2(C3=CC=C(C=C3)O)C4=CC=C(C=C4)O
- InChI
- InChI=1S/C20H14O4/c21-15-9-5-13(6-10-15)20(14-7-11-16(22)12-8-14)18-4-2-1-3-17(18)19(23)24-20/h1-12,21-22H
- InChIKey
- KJFMBFZCATUALV-UHFFFAOYSA-N
- Molfile
Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.
Physical properties
- Appearance
- Pale yellow powder[2]
3 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source – Phenolphthalein appears as white or yellowish-white to pale orange fine crystalline powder. Odorless. Aqueous solution is acidic. Colorless to pH 8.5; pink to deep-red above pH 9. Colorless in presence of large amounts of alkali. Tasteless. (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. – White rhombic needles [2] Hazardous Substances Data Bank (HSDB)cites Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V4 3297 –shown Pale yellow powder [2] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J., Sr (Ed.). Hawley's Condensed Chemical Dictionary. 12th ed. New York, NY: Van Nostrand Rheinhold Co., 1993, p. 895 - Odor
- ODORLESS[2]
- Melting point
- 262.5 °C[2]
2 values
Sources disagree; from Hazardous Substances Data Bank (HSDB), the most authoritative.
Value As written Source 258 to 262 °C 496 to 504 °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. 262.5 °Cshown 262.5 °C [2] Hazardous Substances Data Bank (HSDB)cites Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V4 3297 - Density
- 1.277 @ 32 °C[2]
3 values
3 of 3 sources agree on it (most common value).
Value As written Source – 1.299 at 77 °F (NTP, 1992) - Denser than water [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 1.277 @ 32 °C [2] Hazardous Substances Data Bank (HSDB)cites Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V4 3297 – 1.299 @25 °C [3] PAC Chemical Database, U.S. Department of Energy - Solubility in water
- In water, 400 mg/L @ room temperature[2]
3 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source – less than 1 mg/mL at 66 °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. – Insoluble in benzene and petroleum ether; slightly soluble in carbon disulfide; soluble in ethyl ether, chloroform, and toluene; very soluble in ethanol, acetone, and pyrene. [2] Hazardous Substances Data Bank (HSDB)cites Lide, D.R., G.W.A. Milne (eds.). Handbook of Data on Organic Compounds. Volume I. 3rd ed. CRC Press, Inc. Boca Raton ,FL. 1994., p. V4 3297 –shown In water, 400 mg/L @ room temperature [2] Hazardous Substances Data Bank (HSDB)cites Yalkowsky, S.H., He, Yan., Handbook of Aqueous Solubility Data: An Extensive Compilation of Aqueous Solubility Data for Organic Compounds Extracted from the AQUASOL dATAbASE. CRC Press LLC, Boca Raton, FL. 2003., p. 1151 - log P
- log Kow = 2.41[2]
- Vapor pressure
- 6.7 × 10⁻¹³ mmHg @ 25 °C (estimated)[2]
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
- 24
- Rings
- 4
- Aromatic rings
- 3
- Fraction sp³ carbons (Fsp3)
- 0.05
- H-bond donors
- 2
- H-bond acceptors
- 4
- Rotatable bonds
- 2
- TPSA (Ų)
- 66.8
- Formal charge
- 0
- XLogP3
- 3.6 PubChem
- Complexity
- 438 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
- C75.46%
- H4.43%
- O20.10%
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
- 3.56 Crippen (Wildman and Crippen 1999)
- log S (water solubility)
- -4.48 ESOL (Delaney 2004), log mol/L
- Synthetic accessibility
- 2.3 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)
Drug-likeness: Lipinski’s rule of five
- Molecular weight ≤ 500: 318.33
- log P ≤ 5 (Crippen): 3.56
- 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
Danger
Harmonized EU classification (CLP Annex VI). Source [4].
- Health hazard
- H341Suspected of causing genetic defects
- H350May cause cancer
Precautionary statements: P203, P280, P318, P405, P501
View all classifications (3)
- [4] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH341, H350
- [5] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 0.2% (2 of 1181) of reports.
- [5] European Chemicals Agency (ECHA) · 1,181 reports · DangerH341, H350, H361
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
- Precautions FOR "carcinogens": Storage site should be as close as practical to lab in which carcinogens are to be used, so that only small quantities required for ... Expt need to be carried. Carcinogens should be kept in only one section of cupboard, an explosion-proof refrigerator or freezer (depending on chemicophysical properties ...) that bears appropriate label. An inventory ... Should be kept, showing quantity of carcinogen & date it was acquired ... Facilities for dispensing ... Should be contiguous to storage area. (chemical Carcinogens)[2]
Safety data sheets on the supplier’s page: RR Scientific, Hunan Huateng Pharmaceutical Co., Ltd., Thermo Fisher Scientific.
Always read the supplier’s safety data sheet before working with it.
Spectra
- NMRHazardous Substances Data Bank (HSDB) · NMRShiftDB
- 1H NMRHuman Metabolome Database (HMDB) (JEOL · 90 MHz · DMSO-d6)
- 13C NMRHuman Metabolome Database (HMDB) (NEVA · 15.09 MHz · DMSO-d6) · SpectraBase
- GC-MSNIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center · NIST Mass Spectrometry Data Center · SpectraBase
- MS-MSHuman Metabolome Database (HMDB) (Negative) · Human Metabolome Database (HMDB) (Negative) · Human Metabolome Database (HMDB) (Positive) · Human Metabolome Database (HMDB) (Positive) · Human Metabolome Database (HMDB) (Negative) · Human Metabolome Database (HMDB) (Negative)
- LC-MSMassBank Europe (Q Exactive Orbitrap (Thermo Scientific) · LC-ESI-QFT · NEGATIVE) · MassBank Europe (Q Exactive Orbitrap (Thermo Scientific) · LC-ESI-QFT · NEGATIVE) · MassBank Europe (Q Exactive Orbitrap (Thermo Scientific) · LC-ESI-QFT · NEGATIVE) · MassBank Europe (Q Exactive Orbitrap (Thermo Scientific) · LC-ESI-QFT · NEGATIVE) · MassBank Europe (Q Exactive Orbitrap (Thermo Scientific) · LC-ESI-QFT · NEGATIVE) · MassBank Europe (Q Exactive Orbitrap (Thermo Scientific) · LC-ESI-QFT · NEGATIVE)
- Other MSHazardous Substances Data Bank (HSDB)
- UVHazardous Substances Data Bank (HSDB)
- IRHazardous Substances Data Bank (HSDB)
- FTIRSpectraBase (Bruker IFS 85 · KBr-Pellet)
- ATR-IRSpectraBase (Bio-Rad FTS · ATR-Neat (DuraSamplIR II))
- RamanSpectraBase (Thermo Nicolet FT-Raman 960 · FT-Raman)
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]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
- [4]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
- [5]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
- [6]NMRShiftDB · Linked only · via PubChem · retrieved 2026-10-14
- [7]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
- [8]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
- [9]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
- [10]MassBank Europe · Linked only · via PubChem · retrieved 2026-10-14
- [11]MassBank of North America (MoNA) · CC BY 4.0 · 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.