page_title: Azo violet
section_title: Reactivity
hierarchical_section_title: Azo violet / Reactivity
caption_attribution_description: English: Tautomerization of Azo Violet
context_page_description: Azo violet is an azo compound with the chemical formula C₁₂H₉N₃O₄. It is used commercially as a violet dye and experimentally as a pH indicator, appearing yellow below pH 11, and violet above pH 13. It also turns deep blue in the presence of magnesium salt in a slightly alkaline, or basic, environment. Azo violet may also be used to test for the presence of ammonium ions. The color of ammonium chloride or ammonium hydroxide solution will vary depending upon the concentration of azo violet used.
context_section_description: The chemical character of azo violet may be attributed to its azo group (-N=N-), six-membered rings, and hydroxyl side groups. Due to steric repulsions, azo violet is most stable in the trans-configuration, but isomerization of azo dyes by irradiation is not uncommon. The para-position tautomerization of azo violet provides mechanical insight into the behavior of the compound in an acidic environment, and thus its use as a basic pH indicator.
  The predicted ¹H-NMR of pure azo violet shows the hydroxyl protons as the most deshielded and acidic protons. The participation of these hydroxyl groups' electron-donation to the conjugated π system likewise influences azo violet's λₘₐₓ and pKₐ value.
caption: Tautomerization of Azo Violet
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