Thymol blue

Thymol blue
IUPAC name 4-[9-(4-hydroxy-2-methyl-5-propan- 2-yl-phenyl)-7,7-dioxo-8-oxa- 7λ6-thiabicyclo[4.3.0]nona-1,3,5-trien-9-yl]- 5-methyl-2-propan-2-yl-phenol
Other names α-hydroxy-α,α-bis(5-hydroxycarvacryl)- o-toluenesulfonic acid γ-sultone; thymolsulfonephthalein
Identifiers
CAS number	76-61-9 Y
PubChem	65565
ChemSpider	59008 Y
Jmol-3D images	Image 1
SMILES O=S2(=O)OC(c1ccccc12)(c3cc(c(O)cc3C)C(C)C)c4cc(c(O)cc4C)C(C)C
InChI InChI=1S/C27H30O5S/c1-15(2)19-13-22(17(5)11-24(19)28)27(21-9-7-8-10-26(21)33(30,31)32-27)23-14-20(16(3)4)25(29)12-18(23)6/h7-16,28-29H,1-6H3 Y Key: PRZSXZWFJHEZBJ-UHFFFAOYSA-N Y InChI=1/C27H30O5S/c1-15(2)19-13-22(17(5)11-24(19)28)27(21-9-7-8-10-26(21)33(30,31)32-27)23-14-20(16(3)4)25(29)12-18(23)6/h7-16,28-29H,1-6H3 Key: PRZSXZWFJHEZBJ-UHFFFAOYAE
Properties
Molecular formula	C27H30O5S
Molar mass	466.59 g mol−1
Appearance	Brownish-green crystal powder
Solubility in water	Insoluble
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Thymol blue (thymolsulphonephthalein) is a brownish-green or reddish-brown crystalline powder that is used as a pH indicator. It is insoluble in water but soluble in alcohol and dilute alkali solutions. It transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6.

Structures of thymol blue at different pH

Color of thymol blue solution at different acid-base conditions: left: acidic, middle: neutral, right: alkaline

Bibliography

• Merck. "Thymol Blue." The Merck Index. 14th ed. 2006. Accessed via web on 2007-02-25.

External links

• PubChem entry