Chlorophenol red
Chemical compound
From Wikipedia, the free encyclopedia
Chlorophenol red is an indicator dye that changes color from yellow to violet in the pH range 5.4 to 6.8.[2] The pH of a substance is determined by taking the negative logarithm of the Hydronium ion concentration and the indictor changes color due to the dissociation of H+ ions.[3] The lambda max is at 572 nm.[4]
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| Names | |
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| Preferred IUPAC name
3,3-Bis(3-chloro-4-hydroxyphenyl)-2,1λ6-benzoxathiole-1,1(3H)-dione | |
| Other names
3′,3′-Dichlorophenolsulfonaphthalein | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.022.382 |
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PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C19H12Cl2O5S | |
| Molar mass | 423.26 g·mol−1 |
| Melting point | 261 °C (502 °F; 534 K)[1] |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Chlorophenol red (pH indicator) | ||
| below pH 5.4 | above pH 6.8 | |
| 5.4 | ⇌ | 6.8 |
Properties and uses
The dissociation mechanism of chlorophenol red is similar to that of phenolphthalein meaning it can be used as a color indicator. The dissociation of hydroxyl and hydrogen atoms creates the dissociate scheme of chlorophenol red to change color from yellow to red.[5] The pH properties of chlorophenol red are used to selectively determine the amount of chlorine dioxide in drinking water. Chlorophenol red selectively reacts with 0.1–1.9 mg/L chlorine dioxide at pH 7.[6] The electrochemical properties of Chlorophenol red allows it to be a chromogenic label and can undergo oxidation creating several phenolic intermediates. The bacterial hydrolysis of a chlorophenol red labelled substrate produces chlorine retaining intermediates on electrodes.[7]