Thymol blue

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Thymol blue
Thymolblau skeletal.png
Thymol Blue crystals.jpg
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
76-61-9 N
ChemSpider 59008 YesY
Jmol-3D images Image
PubChem 65565
Properties
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]
Insoluble
UV-vismax) 594 nm (1st)
376 nm (2nd)[1]
Hazards
Main hazards Harmful
EU classification Harmful XnDangerous for the Environment (Nature) N
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity (yellow): no hazard code Special hazards (white): no codeNFPA 704 four-colored diamond
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N verify (what isYesY/N?)
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[edit]

Thymol blue has different structures at different pH.

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

Safety[edit]

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

Bibliography[edit]

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

References[edit]

External links[edit]