Solved previous year question from the OPSC OAS/OCS 2024 Preliminary Examination (General Studies), with the official answer key and a detailed explanation.
Question
Which of the followings is not a dye
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Answer & Explanation
Correct answer: (D) Anthranilic acid
Correct Answer: (D) — Anthranilic Acid
Anthranilic Acid — Not a Dye
Anthranilic acid (2-aminobenzoic acid) is an aromatic amine compound that serves as a precursor or intermediate in the synthesis of dyes, pharmaceuticals, and perfumes. It is not itself a dye as it lacks the necessary chromophore-auxochrome combination required to impart color to substrates. It is primarily used in the manufacture of indigo dye and saccharin, but remains a raw chemical intermediate, not a functional dye.
| Note: Alizarin is a natural red dye originally extracted from the madder plant and later synthesized from anthracene. It is one of the oldest known dyes, used extensively in textile dyeing, and belongs to the anthraquinone class of dyes. Fluorescein is a synthetic fluorescent dye widely used in biological research, medical diagnostics, and water tracing applications due to its intense yellow-green fluorescence. Phenolphthalein, though commonly known as a pH indicator, is structurally a dye belonging to the triarylmethane dye family and exhibits color change properties characteristic of dyes.### Key DistinctionA dye must possess a chromophore (color-bearing group) and an auxochrome (color-intensifying group) to bind with substrates. Anthranilic acid lacks this functional combination and acts only as a chemical building block, not a finished dye — making it the correct answer. |
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