Phenol
Properties
| State | Solid at room temperature (low melting point, often liquid) |
| Color | White crystalline solid (turns pink to red on oxidation) |
| Solubility | Moderately soluble in water (8.3 g/100 mL at 20 °C) |
| Melting Point | 40.5 °C |
| Boiling Point | 181.7 °C |
About Phenol
Phenol is the simplest aromatic alcohol — a hydroxyl group hung directly off a benzene ring — and it behaves nothing like ethanol or any other aliphatic alcohol you've handled. Its pKa of 9.95 makes it roughly a million times more acidic than cyclohexanol because the phenoxide anion delocalizes that negative charge into the ortho and para ring positions. That single resonance trick is why phenol dissolves in NaOH solution but cyclohexanol doesn't, and it's the diagnostic test every sophomore organic student runs in lab. Joseph Lister sprayed dilute phenol over surgical fields in the 1860s and dropped post-operative mortality from around 45% to under 15% — the founding moment of antiseptic surgery before anyone understood germ theory mechanistically. Today phenol is made on a 10-million-tonne scale by the cumene hydroperoxide process, which co-produces acetone in a roughly 0.6:1 ratio. The biggest end use is bisphenol A for polycarbonate (eyeglass lenses, water bottles) and epoxy resins, followed by phenol-formaldehyde resins (Bakelite, the original 1907 synthetic plastic) and caprolactam for nylon-6.
Where you'll encounter it
If you've ever used Chloraseptic throat spray, you've sprayed dilute phenol on your tonsils — the 1.4% solution is still FDA-approved as a topical anesthetic almost 160 years after Lister. In an organic teaching lab, phenol shows up in two places students remember: the FeCl3 test, where a single drop turns a phenol solution intense purple from the iron-phenoxide complex (and the same drop does nothing to ethanol), and the bromine water test, where 2,4,6-tribromophenol crashes out of solution as a white precipitate the instant Br2 hits the ring. Process chemists also know phenol melts at 40.5 °C, which means a winter shipment can arrive as a frozen block and a summer one as a syrupy, pink-tinged liquid (it darkens as traces oxidize to quinones).
Common Uses
- Cumene-process feedstock for bisphenol A and polycarbonate plastic production
- Phenol-formaldehyde (Bakelite) resin manufacture for plywood adhesives and circuit boards
- Caprolactam intermediate in nylon-6 fiber and engineering-resin synthesis
- Active ingredient in Chloraseptic throat spray and similar topical anesthetics
- Synthesis of aspirin (via Kolbe-Schmitt salicylic acid route) and acetaminophen
Safety Information
Highly toxic by all routes — phenol penetrates intact skin readily and causes systemic toxicity, including cardiac arrhythmias and renal failure, after surprisingly small dermal exposures. OSHA PEL is 5 ppm (19 mg/m³) TWA with a skin notation; ACGIH TLV is the same. GHS H301/H311/H331 (toxic if swallowed, in contact with skin, or inhaled), H314 (causes severe skin burns), H341 (suspected mutagen). PEG-400 wash is the standard first aid for skin contact rather than water alone. Use under fume hood with nitrile-over-butyl gloves; nitrile alone is permeated within minutes by molten phenol.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.