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
Skeletal formula of chlorophenol red in cyclic form
Ball-and-stick model of the chlorophenol red molecule in cyclic form
Names
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)
ChemSpider
ECHA InfoCard 100.022.382
EC Number
  • 224-619-2
UNII
  • 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
  • C1=CC=C2C(=C1)C(OS2(=O)=O)(C3=CC(=C(C=C3)O)Cl)C4=CC(=C(C=C4)O)Cl
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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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]

References
  1. Haynes, p. 3.116
  2. Haynes, p. 8.88
  3. "pH Indicators". Chemistry LibreTexts. 2013-10-02. Retrieved 2021-03-14.
  4. "Chlorophenol Red".
  5. Hanai, Toshihiko (2016). "Quantitative Evaluation of Dissociation Mechanisms in Phenolphthalein and the Related Compounds". Journal of Computer Chemistry. 15: 13–21.
  6. Sweetin, Deborah L.; Sullivan, Elizabeth; Gordon, Gilbert (1996-01-01). "The use of chlorophenol red for the selective determination of chlorine dioxide in drinking water". Talanta. 43 (1): 103–108. doi:10.1016/0039-9140(95)01721-6. PMID 18966469.
  7. Casimero, Charnete; Bigham, Teri; McGlynn, Ruairi J.; Dooley, James S. G.; Ternan, Nigel G.; Snelling, William J.; Critchley, Megan E.; Zinkel, Cameron L.; Smith, Robert B.; Sabogal-Paz, Lyda P.; Davis, James (2019-12-01). "Electroanalytical properties of chlorophenol red at disposable carbon electrodes: Implications for Escherichia coli detection". Bioelectrochemistry. 130: 107321. doi:10.1016/j.bioelechem.2019.06.006. PMID 31306878.

Cited sources
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