Definition
Hydroxyquinol, also known as 1,2,4‑benzenetriol, is an aromatic organic compound with the molecular formula C₆H₆O₃. It belongs to the class of phenolic compounds and is one of three structural isomers of benzenetriol.
Overview
Hydroxyquinol is a white to off‑white crystalline solid that is soluble in water and polar organic solvents. It is employed as an intermediate in the synthesis of dyes, pharmaceuticals, and polymer additives, and it serves as a corrosion inhibitor and antioxidant in certain industrial formulations. The compound can be produced by the hydrolysis of nitro‑substituted precursors or by selective oxidation of phenolic substrates.
Etymology / Origin
The name “hydroxyquinol” combines “hydroxy,” referring to the presence of hydroxyl (–OH) groups, with “quinol,” an older term historically used for hydroquinone (1,4‑dihydroxybenzene) and related phenolic quinones. The designation reflects its structural relationship to quinone derivatives, although hydroxyquinol itself is a fully reduced, non‑quinone phenol.
Characteristics
| Property | Data |
|---|---|
| Chemical formula | C₆H₆O₃ |
| Molar mass | 110.11 g·mol⁻¹ |
| Structural formula | ![1,2,4‑benzenetriol] – OH groups at the 1, 2, and 4 positions of a benzene ring |
| Physical state | Crystalline solid |
| Melting point | 171–173 °C |
| Boiling point | Decomposes before boiling; no reliable boiling point |
| Solubility | Soluble in water (≈20 g L⁻¹ at 25 °C) and in alcoholic solvents |
| Density | Approximately 1.34 g cm⁻³ (at 20 °C) |
| Acidity | Phenolic – pKₐ values around 9–10 for the hydroxyl groups |
| Reactivity | Undergoes typical phenolic reactions: esterification, ether formation, oxidation to quinones, and electrophilic aromatic substitution |
Related Topics
- Benzenetriols – The three isomeric trihydroxybenzenes: 1,2,3‑, 1,2,4‑, and 1,3,5‑benzenetriol.
- Catechol (1,2‑dihydroxybenzene) – A dihydroxybenzene isomer used as a building block in polymer chemistry.
- Resorcinol (1,3‑dihydroxybenzene) – Another dihydroxybenzene employed in dyes and pharmaceuticals.
- Hydroquinone (1,4‑dihydroxybenzene) – A widely used antioxidant and skin‑lightening agent.
- Quinones – Oxidized derivatives of phenols that play critical roles in biological redox processes.
- Phenolic antioxidants – A class of compounds that protect materials from oxidative degradation, of which hydroxyquinol is a member.
Note: The data presented reflects commonly accepted chemical information from standard reference works and peer‑reviewed literature.