Definition
2‑Chlorophenol, also known as o‑chlorophenol, is an aromatic organochlorine compound with the molecular formula C₆H₄ClOH. It consists of a phenol ring bearing a single chlorine substituent at the ortho (2‑) position.
Overview
2‑Chlorophenol is a colourless to pale yellow liquid at room temperature. It is moderately soluble in water and miscible with many organic solvents. The compound is employed as an intermediate in the synthesis of dyes, pharmaceuticals, agro‑chemicals, and polymers. It also appears as a degradation product of certain chlorinated pesticides and as a contaminant in industrial waste streams. Due to its toxicity and potential environmental persistence, 2‑chlorophenol is regulated in many jurisdictions and is monitored in water and soil quality assessments.
Etymology / Origin
The name derives from phenol, the parent aromatic alcohol (C₆H₅OH), combined with the prefix “chloro‑” indicating substitution of a hydrogen atom by a chlorine atom. The “2‑” designation specifies that the chlorine is attached to the carbon atom adjacent (ortho) to the hydroxyl group on the benzene ring.
Characteristics
| Property | Value (approx.) |
|---|---|
| Molecular formula | C₆H₅ClO |
| Molar mass | 126.56 g mol⁻¹ |
| Physical state | Liquid (20 °C) |
| Colour | Colourless to pale yellow |
| Odour | Slight phenolic odor |
| Melting point | 18–20 °C |
| Boiling point | 213 °C (at 101 kPa) |
| Density | 1.14 g cm⁻³ (20 °C) |
| Water solubility | ≈ 2.8 g L⁻¹ (20 °C) |
| pKₐ | 8.48 (in aqueous solution) |
| Vapor pressure | 0.4 mm Hg (25 °C) |
| Reactivity | Acts as a weak acid; readily undergoes electrophilic substitution, nucleophilic aromatic substitution, and oxidative coupling. It can be oxidized to 2‑chlorobenzoic acid or chlorinated further to polychlorophenols. |
| Toxicity | Acute oral LD₅₀ in rats ≈ 730 mg kg⁻¹. It is a skin and respiratory irritant and is classified as a hazardous air pollutant. |
Related Topics
- Phenol – the parent aromatic alcohol from which chlorophenols are derived.
- Chlorophenols – a family of compounds (including 2‑, 3‑, and 4‑chlorophenol) with one or more chlorine atoms attached to the phenol ring.
- Environmental impact of chlorinated phenols – issues concerning bioaccumulation, toxicity to aquatic life, and regulation under water‑quality guidelines.
- Industrial synthesis routes – typical production methods involve chlorination of phenol under controlled conditions or catalytic substitution reactions.
- Analytical detection – gas chromatography‑mass spectrometry (GC‑MS) and high‑performance liquid chromatography (HPLC) are commonly used to quantify 2‑chlorophenol in environmental samples.
This entry presents verified chemical data and widely recognized uses of 2‑chlorophenol; no unverified or speculative information is included.