Xylenol orange

Xylenol orange
Names
	Preferred IUPAC name 2,2′,2′′,2′′′-{(1,1-Dioxo-2,1λ6-benzoxathiole-3,3(1H)-diyl)bis[(6-hydroxy-5-methyl-3,1-phenylene)methylenenitrilo]}tetraacetic acid
	Other names XO
Identifiers
CAS Number	1611-35-4 ; 3618-43-7 (tetrasodium salt) ;
3D model (JSmol)	Interactive image;
ChemSpider	65838 ;
ECHA InfoCard	100.015.049
EC Number	216-553-8;
PubChem CID	73041;
UNII	S2VDY878QD ; 0549U815B1 (tetrasodium salt) ;
CompTox Dashboard (EPA)	DTXSID1061819 ;
	InChI InChI=1S/C31H32N2O13S/c1-17-7-21(9-19(29(17)42)11-32(13-25(34)35)14-26(36)37)31(23-5-3-4-6-24(23)47(44,45)46-31)22-8-18(2)30(43)20(10-22)12-33(15-27(38)39)16-28(40)41/h3-10,42-43H,11-16H2,1-2H3,(H,34,35)(H,36,37)(H,38,39)(H,40,41) Key: ORZHVTYKPFFVMG-UHFFFAOYSA-N ;
	SMILES O=C(O)CN(CC(=O)O)Cc1c(O)c(cc(c1)C3(OS(=O)(=O)c2ccccc23)c4cc(c(O)c(c4)CN(CC(=O)O)CC(=O)O)C)C;
Properties
Chemical formula	C31H32N2O13S
Molar mass	672.66 g·mol−1
Melting point	195 °C (383 °F; 468 K)
Solubility in water	200 mg/mL
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 1 2
Flash point	> 93 °C (199 °F; 366 K)
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Xylenol orange is an organic reagent, most commonly used as a tetrasodium salt as an indicator for metal titrations. When used for metal titrations, it will appear red in the titrand and become yellow once it reaches its endpoint. Historically, commercial preparations of it have been notoriously impure,^[2] sometimes consisting of as little as 20% xylenol orange, and containing large amounts of semi-xylenol orange and iminodiacetic acid. Purities as high as 90% are now available.

It is fluorescent, and has excitation maximums of 440 & 570 nm and an emission maximum of 610 nm.^[3]

References

^ Li, Zhong-Guang (2019-01-01), Khan, M. Iqbal R.; Reddy, Palakolanu Sudhakar; Ferrante, Antonio; Khan, Nafees A. (eds.), "Chapter 5 - Measurement of Signaling Molecules Calcium Ion, Reactive Sulfur Species, Reactive Carbonyl Species, Reactive Nitrogen Species, and Reactive Oxygen Species in Plants", Plant Signaling Molecules, Woodhead Publishing, pp. 83–103, ISBN 978-0-12-816451-8, retrieved 2023-11-11{{citation}}: CS1 maint: deprecated archival service (link) CS1 maint: work parameter with ISBN (link)
^ Gay, Craig; Collins, James; Gebicki, Janusz M. (1999), "Determination of Iron in Solutions with the Ferric–Xylenol Orange Complex", Analytical Biochemistry, 273 (2): 143–148, doi:10.1006/abio.1999.4207, PMID 10469483
^ "Fluorescence - Fluorochrome Data Tables". Molecular Expressions Microscopy Primer: Specialized Microscopy Techniques. 2018-09-11. Retrieved 2020-01-30.

[1] Li, Zhong-Guang (2019-01-01), Khan, M. Iqbal R.; Reddy, Palakolanu Sudhakar; Ferrante, Antonio; Khan, Nafees A. (eds.), "Chapter 5 - Measurement of Signaling Molecules Calcium Ion, Reactive Sulfur Species, Reactive Carbonyl Species, Reactive Nitrogen Species, and Reactive Oxygen Species in Plants", Plant Signaling Molecules, Woodhead Publishing, pp. 83–103, ISBN 978-0-12-816451-8, retrieved 2023-11-11{{citation}}: CS1 maint: deprecated archival service (link) CS1 maint: work parameter with ISBN (link)

[2] Gay, Craig; Collins, James; Gebicki, Janusz M. (1999), "Determination of Iron in Solutions with the Ferric–Xylenol Orange Complex", Analytical Biochemistry, 273 (2): 143–148, doi:10.1006/abio.1999.4207, PMID 10469483

[Molecular_Expressions_Microscopy_Primer:_Specialized_Microscopy_Techniques_2018-3] "Fluorescence - Fluorochrome Data Tables". Molecular Expressions Microscopy Primer: Specialized Microscopy Techniques. 2018-09-11. Retrieved 2020-01-30.

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