Phenolphthalein
Title: Phenolphthalein
CAS Registry Number: 77-09-8
CAS Name: 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone
Additional Names: 3,3-bis(p-hydroxyphenyl)phthalide; a-(p-hydroxyphenyl)-a-(4-oxo-2,5-cyclohexadien-1-ylidine)-o-toluic acid; white phenolphthalein
Molecular Formula: C20H14O4
Molecular Weight: 318.32
Percent Composition: C 75.46%, H 4.43%, O 20.10%
Literature References: Prepn: A. Baeyer, Ber. 4, 658 (1871); idem, Ann. 202, 36 (1880); M. Hubacher, US 2192485 (1940 to Ex Lax). Reactions at various pH values: G. Wittke, J. Chem. Educ. 60, 239 (1983). Polarographic analysis in aqueous soln: M. M. Ellaithy et al., Farmaco Ed. Prat. 41, 326 (1986). Subchronic toxicity studies: D. D. Dietz et al., Fundam. Appl. Toxicol. 18, 48 (1992). Toxicology and carcinogenicity studies: NTP Technical Report 465 (PB97-3390) 348 pp. Comprehensive description of properties, clinical and laboratory uses: F. J. Al-Shammary et al., Anal. Profiles Drug Subs. 20, 627-664 (1991).
Properties: White or yellowish white minute, triclinic crystals, often twinned. mp 258-262°. d 1.299. Sol in 95% alcohol and ether, slightly sol in chloroform. One gram dissolves in 12 ml alcohol, in ~100 ml ether. Almost insol in water. Sol in dil solns of alkali hydroxides and hot solns of alkali carbonates forming a red soln. pKa (25°C): 9.7. uv max (methanol): 205, 229, 276 nm (e 27261.147, 14692.144, 2006.369). Log P (octanol/pH 7.4): 2.4. Shows color change from colorless in acid range to purple at pH 8-9.
Melting point: mp 258-262°
pKa: pKa (25°C): 9.7
Log P: Log P (octanol/pH 7.4): 2.4
Absorption maximum: uv max (methanol): 205, 229, 276 nm (e 27261.147, 14692.144, 2006.369)
Density: d 1.299
 
Derivative Type: Yellow Phenolphthalein
CAS Registry Number: 8053-05-2
Literature References: Produced in the mfg process prior to final purification of white phenolphthalein. Contains yellow bodies which impart characteristic color. Review of chemistry and use as a laxative: M. H. Hubacher, S. Doernberg, J. Am. Pharm. Assoc. Sci. Ed. 37, 261 (1948).
Properties: d420 1.290-1.296. mp 255-260°. One gram dissolves in 12 ml alcohol, in 102 ml ether. Solns show a slight greenish fluorescence.
Melting point: mp 255-260°
Density: d420 1.290-1.296
 
CAUTION: Phenolphthalein is reasonably anticipated to be a human carcinogen: Report on Carcinogens, Eleventh Edition (PB2005-104914, 2004) p III-214.
Use: A 1% alcoholic soln as an indicator in titrations of mineral and organic acids and most alkalies.
Therap-Cat: Cathartic.
Therap-Cat-Vet: Has been used as a laxative.
Keywords: Laxative/Cathartic.

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