Acid orange 5

Acid orange 5
Names
Preferred IUPAC name
Sodium 4-[(E)-(4-anilinophenyl)diazenyl]benzene-1-sulfonate
Other names
Fast yellow; Tropaeolin OO
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.008.248 Edit this at Wikidata
UNII
  • InChI=1S/C18H15N3O3S.Na/c22-25(23,24)18-12-10-17(11-13-18)21-20-16-8-6-15(7-9-16)19-14-4-2-1-3-5-14;/h1-13,19H,(H,22,23,24);/q;+1/p-1/b21-20+;
    Key: MLVYOYVMOZFHIU-ANVLNOONSA-M
  • InChI=1/C18H15N3O3S.Na/c22-25(23,24)18-12-10-17(11-13-18)21-20-16-8-6-15(7-9-16)19-14-4-2-1-3-5-14;/h1-13,19H,(H,22,23,24);/q;+1/p-1/b21-20+;
    Key: MLVYOYVMOZFHIU-LGLICYIRBD
  • c1ccc(cc1)Nc2ccc(cc2)/N=N/c3ccc(cc3)S(=O)(=O)[O-].[Na+]
Properties
C18H14N3NaO3S
Molar mass 375.38 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Tropaeolin OO (pH indicator)
below pH 1.4 above pH 3.2
1.4 ⇌ 3.2

Acid orange 5 is a compound with formula Na(C6H5NHC6H4N=NC6H4SO3). It is an azo dye. It is also used as a pH indicator; it is red in pH under 1.4, orange-yellow in pH over 3.2.[1]

Preparation

Acid orange 5 may be prepared by diazotization of sulfanilic acid, followed by reaction with diphenylamine:

HO3SC6H4N+2 + (C6H5)2NH → HO3SC6H4N=NC6H4N(H)C6H5 + H+

References

  1. ^ Beilstein 16 II 171.


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