Thymolphthalein

Thymolphthalein
Names
	IUPAC name 3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1-one
Identifiers
CAS Number	125-20-2 ;
3D model (JSmol)	Interactive image;
ChEMBL	ChEMBL587849 ;
ChemSpider	29054 ;
ECHA InfoCard	100.004.300
EC Number	204-729-7;
PubChem CID	31316;
CompTox Dashboard (EPA)	DTXSID2051633 ;
	InChI InChI=1S/C28H30O4/c1-15(2)20-13-23(17(5)11-25(20)29)28(22-10-8-7-9-19(22)27(31)32-28)24-14-21(16(3)4)26(30)12-18(24)6/h7-16,29-30H,1-6H3 Key: LDKDGDIWEUUXSH-UHFFFAOYSA-N ; InChI=1/C28H30O4/c1-15(2)20-13-23(17(5)11-25(20)29)28(22-10-8-7-9-19(22)27(31)32-28)24-14-21(16(3)4)26(30)12-18(24)6/h7-16,29-30H,1-6H3 Key: LDKDGDIWEUUXSH-UHFFFAOYAV;
	SMILES O=C1OC(c2ccccc12)(c3cc(c(O)cc3C)C(C)C)c4cc(c(O)cc4C)C(C)C;
Properties
Chemical formula	C28H30O4
Molar mass	430.544 g·mol−1
Appearance	White powder
Melting point	248 to 252 °C (478 to 486 °F; 521 to 525 K) (decomposes)
Hazards
NFPA 704 (fire diamond)	1 0 0
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Thymolphthalein is an acid-base (pH) indicator. Its transition range is around pH 9.3-10.5. Below this pH, it is colorless; above, it is blue. The molar extinction coefficient for the blue thymolphthalein dianion is 38000 M⁻¹cm⁻¹ at 595 nm.^[1]

Thymolphthalein (pH indicator)
below pH 9.3		above pH 10.5
9.3	⇌	10.5

Preparation

Thymolphthalein can be synthesized from thymol and phthalic anhydride by Friedel-Crafts alkylation:

References

^ Hahn HH; Cheuk SF; Elfenbein S; Wood WB (April 1970). "Studies on the Pathogenesis of Fever: Xix. Localization of Pyrogen in Granulocytes" (PDF). J. Exp. Med. 131 (4): 701–9. doi:10.1084/jem.131.4.701. PMC 2138774. PMID 5430784.

[1] Hahn HH; Cheuk SF; Elfenbein S; Wood WB (April 1970). "Studies on the Pathogenesis of Fever: Xix. Localization of Pyrogen in Granulocytes" (PDF). J. Exp. Med. 131 (4): 701–9. doi:10.1084/jem.131.4.701. PMC 2138774. PMID 5430784.

[1]