Phenol (CAS 108-95-2) is an important industrial chemical that has been known under several names since its discovery in the 19th century. The most common alternative name is carbolic acid, but phenol is also called hydroxybenzene, benzenol or phenic acid. This article explains the nomenclature, physical and chemical properties, principal industrial applications, and the safety measures required when handling this versatile but hazardous substance.
What Is Another Name for Phenol?
The most widely used synonym for phenol is carbolic acid. This name dates back to the early days of antiseptic surgery, when phenol was used as a disinfectant. In systematic chemical nomenclature, phenol is named hydroxybenzene or benzenol, reflecting its structure: a benzene ring (C6H5) carrying a hydroxyl group (-OH). The molecular formula is C6H6O and the molecular weight is 94.11 g/mol. The term carbolic acid is still encountered in historical literature and in some industrial and medical contexts, but modern safety data sheets and regulations generally use the name phenol together with its CAS number 108-95-2.
Physical and Chemical Properties
| Property | Typical Value |
|---|---|
| Molecular formula | C6H6O |
| Molecular weight | 94.11 g/mol |
| Appearance | Colorless to light pink crystalline solid, or liquid when molten |
| Melting point | About 40.5 °C |
| Boiling point | About 181.7 °C |
| Density (20 °C) | About 1.07 g/cm3 |
| Solubility in water | About 8 g per 100 mL at room temperature |
| Odor | Characteristic sweet, tarry odor |
Phenol is a weak acid. It is more acidic than aliphatic alcohols because the hydroxyl group is attached directly to the aromatic ring, which stabilizes the phenoxide anion. It is soluble in most organic solvents, partially soluble in water, and highly reactive toward electrophilic substitution reactions.
Main Industrial Uses of Phenol
Phenol is a core raw material for the chemical industry. Its principal applications include the following:
Resins: Phenol reacts with formaldehyde to produce phenolic resins, which are used in adhesives, molding compounds, laminates and insulation materials. It is also a raw material for epoxy resins.
Bisphenol A: Phenol and acetone are combined to produce bisphenol A (BPA), the key intermediate for polycarbonate plastics and epoxy resins.
Caprolactam and nylon: Phenol participates in the synthesis of caprolactam, which is polymerized into nylon fibers and engineering plastics.
Salicylic acid and pharmaceuticals: Phenol is converted to salicylic acid, which is used to make aspirin and other pharmaceuticals, as well as dyes and textile auxiliaries.
Disinfectants and antiseptics: Phenol and its derivatives such as cresols are used in disinfectants, antiseptics and preservatives.
Pesticides: Phenol serves as an intermediate in the production of herbicides, insecticides and fungicides.
Solvent and extraction: In petroleum refining, phenol is used as a solvent and additive for lubricating oil refining and extraction processes.
Health Hazards and Safety Considerations
Phenol is a toxic and corrosive substance. It causes severe burns to skin and eyes, and it is readily absorbed through intact skin, which can lead to systemic poisoning affecting the nervous system, liver and kidneys. Inhalation of vapors irritates the respiratory tract. In transport regulations, solid phenol is assigned UN 1671, a Class 6.1 toxic substance with corrosive properties, while molten phenol is assigned UN 2312. Because of these hazards, phenol must only be handled with appropriate personal protective equipment: chemical-resistant gloves and boots, protective clothing, a face shield or goggles, and respiratory protection where vapors may be present.
Storage and Handling Guidelines
Phenol should be stored in a cool, dry, well-ventilated area, away from heat, open flames and incompatible materials such as strong oxidizers. Solid phenol should be kept in tightly sealed containers to prevent moisture uptake and contamination. When stored as a liquid, it must be kept molten or handled with heated transfer systems, since it solidifies below about 40 °C. Storage areas should be equipped with spill containment and fire-fighting equipment. In case of skin contact, contaminated clothing must be removed immediately and the skin rinsed with large amounts of water or polyethylene glycol, followed by prompt medical evaluation.
Frequently Asked Questions
What is another name for phenol? Phenol is commonly known as carbolic acid. Its systematic names include hydroxybenzene and benzenol, and the CAS number is 108-95-2.
Is carbolic acid the same as phenol? Yes. Carbolic acid is the historical name for phenol, which was used as an antiseptic in the 19th century. The two terms refer to the same compound.
What is phenol mainly used for? Phenol is mainly used to produce phenolic and epoxy resins, bisphenol A, caprolactam for nylon, salicylic acid for pharmaceuticals, disinfectants, pesticides and industrial solvents.
Is phenol dangerous? Yes. Phenol is corrosive and toxic. It causes severe burns, is absorbed through the skin, and can cause systemic poisoning, so it requires strict safety management.
What UN number is assigned to solid phenol? Solid phenol is assigned UN 1671 as a Class 6.1 toxic substance with corrosive properties, and molten phenol is assigned UN 2312.
How should phenol be stored? Store in a cool, dry, well-ventilated area in sealed containers, away from oxidizers and ignition sources, with spill containment and appropriate personal protective equipment available.
