Thymol blue

Thymol blue
Names


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^N
ChemSpider	59008^Y
Jmol interactive 3D	Image
PubChem	65565
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
SMILES O=S2(=O)OC(c1ccccc12)(c3cc(c(O)cc3C)C(C)C)c4cc(c(O)cc4C)C(C)C
Properties
Chemical formula	C₂₇H₃₀O₅S
Molar mass	466.59 g·mol⁻¹
Appearance	Brownish-green crystal powder
Melting point	221–224 °C (430–435 °F; 494–497 K) decomposes^[1]
Solubility in water	Insoluble
UV-vis (λ_max)	594 nm (1st) 376 nm (2nd)^[1]
Hazards
Main hazards	Harmful
EU classification (DSD)	Xn N
NFPA 704	1 1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is ^YN ?)
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.

Thymol blue (pH indicator)
below pH 8.0		above pH 9.6
8.0	⇌	9.6

Thymol blue (pH indicator)
below pH 1.2		above pH 2.8
1.2	⇌	2.8

It transitions from red to yellow at pH 1.2–2.8 and from yellow to blue at pH 8.0–9.6. It is usually a component of Universal indicator.

Structures

Thymol blue has different structures at different pH.

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

Safety

It may cause irritation. Its toxicological properties have not been fully investigated.

Bibliography

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

References

1 2 Thymol Blue

External links

Wikimedia Commons has media related to Thymol blue.

PubChem entry

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