Chlorophenol red

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]

Chlorophenol red

Names
Preferred IUPAC name 3,3-Bis(3-chloro-4-hydroxyphenyl)-2,1λ6-benzoxathiole-1,1(3H)-dione
Other names 3′,3′-Dichlorophenolsulfonaphthalein
Identifiers
CAS Number	4430-20-0 Y
3D model (JSmol)	Interactive image
ChemSpider	19293 N
ECHA InfoCard	100.022.382
EC Number	224-619-2
PubChem CID	20486
UNII	P3S5KH33EA Y
CompTox Dashboard (EPA)	DTXSID4063450
InChI InChI=1S/C19H12Cl2O5S/c20-14-9-11(5-7-16(14)22)19(12-6-8-17(23)15(21)10-12)13-3-1-2-4-18(13)27(24,25)26-19/h1-10,22-23H N Key: WWAABJGNHFGXSJ-UHFFFAOYSA-N N InChI=1/C19H12Cl2O5S/c20-14-9-11(5-7-16(14)22)19(12-6-8-17(23)15(21)10-12)13-3-1-2-4-18(13)27(24,25)26-19/h1-10,22-23H Key: WWAABJGNHFGXSJ-UHFFFAOYAK
SMILES C1=CC=C2C(=C1)C(OS2(=O)=O)(C3=CC(=C(C=C3)O)Cl)C4=CC(=C(C=C4)O)Cl
Properties
Chemical formula	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). N verify (what is YN ?) Infobox references

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]