Phenolphthalein

This article is about Phenolphthalein. For other related dyes in the phthalein family, see Phthalein dye.
Phenolphthalein
Names
Preferred IUPAC name
3,3-Bis(4-hydroxyphenyl)-2-benzofuran-1(3H)-one
Other names
3,3-Bis(4-hydroxyphenyl)isobenzofuran-1(3H)-one
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.914 Edit this at Wikidata
KEGG
UNII
  • 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 checkY
    Key: KJFMBFZCATUALV-UHFFFAOYSA-N checkY
  • InChI=1/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
    Key: KJFMBFZCATUALV-UHFFFAOYAH
  • O=C1OC(C2=C1C=CC=C2)(C3=CC=C(C=C3)O[H])C4=CC=C(C=C4)O[H]
Properties
C20H14O4
Molar mass 318.328 g·mol−1
Appearance White powder
Density 1.277 g/cm3 (32 °C (90 °F))
Melting point 258–263 °C (496–505 °F; 531–536 K)[1]
400 mg/l
Solubility in other solvents Insoluble in benzene and hexane; very soluble in ethanol and ether; slightly soluble in DMSO
UV-vis (λmax) 552 nm (1st)
374 nm (2nd)[1]
Pharmacology
A06AB04 (WHO)
Hazards
GHS labelling:
GHS08: Health hazard[1]
Danger
H341, H350, H361[1]
P201, P281, P308+P313[1]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
3
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Phenolphthalein (/fɛˈnɒl(f)θəliːn/[citation needed] feh-NOL(F)-thə-leen) is a chemical compound with the formula C20H14O4 and is often written as "HIn", "HPh", "phph" or simply "Ph" in shorthand notation. Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions. It belongs to the class of dyes known as phthalein dyes.

Phenolphthalein is slightly soluble in water and usually is dissolved in alcohols in experiments. It is a weak acid, which can lose H+ ions in solution. The nonionized phenolphthalein molecule is colorless and the double deprotonated phenolphthalein ion is fuchsia. Further proton loss in higher pH occurs slowly and leads to a colorless form. Phenolphthalein ion in concentrated sulfuric acid is orange red due to sulfonation.[2]

  1. ^ a b c d e "Phenolphthalein". Archived from the original on 8 November 2015. Retrieved 7 October 2014.
  2. ^ Cite error: The named reference Tamura1996 was invoked but never defined (see the help page).