Thymolphthalein

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Thymolphthalein

IUPAC name 3,3-bis(4-hydroxy-2-methyl-5-propan-2-ylphenyl)-2-benzofuran-1-one
Identifiers
CAS number	125-20-2^N
PubChem	31316
ChemSpider	29054^Y
EC number	204-729-7
ChEMBL	CHEMBL587849^Y
Jmol-3D images	Image 1
SMILES O=C1OC(c2ccccc12)(c3cc(c(O)cc3C)C(C)C)c4cc(c(O)cc4C)C(C)C
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^Y Key: LDKDGDIWEUUXSH-UHFFFAOYSA-N^Y 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
Properties
Molecular formula	C₂₈H₃₀O₄
Molar mass	430.54 g mol⁻¹
Appearance	White powder
Melting point	248 - 252 °C (decomp.)
Hazards
R-phrases	4, 10
S-phrases	S22 S24/25
NFPA 704	0 1 0
N (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Thymolphthalein is an acid-base (pH) indicator. Its transition range is at approximately pH 9.3-10.5. Below this pH, it is colorless; above this pH, 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 via 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". J. Exp. Med. 131 (4): 701–9. doi:10.1084/jem.131.4.701. PMC 2138774. PMID 5430784.

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