What do you call a colored complex that includes a benzene ring and a chromophore and is not considered a dye?

• A. Chromagen
• B. Dye
• C. Chromophore
• D. Auxochrome

Answer: (A)

Chromagen refers to a substance that is not itself a dye but can form a dye after undergoing a chemical change, such as oxidation or coupling during staining. It often contains an aromatic system, like a benzene ring, linked to a chromophore that has the potential to absorb visible light and develop color once activated. In histology, the dye is the colored product that actually stains, while the chromagen is the precursor that becomes that dye. The other terms describe parts or end products: a chromophore is the color-bearing portion of a molecule, an auxochrome is a group that shifts or intensifies color but isn’t the color itself, and a dye is the final colored staining compound. Therefore, the colored complex that includes a benzene ring and a chromophore but isn’t yet a dye fits the concept of a chromagen.