Acetic Acid (CH₃COOH) is one of the simplest and most widely used carboxylic acids. Also known as vinegar essence or ethanoic acid, it is the main component of edible vinegar, responsible for its sour taste. At room temperature, acetic acid appears as a colorless liquid with a sharp, pungent odor. Due to its unique physical and chemical properties, acetic acid has broad applications across many industries.

Structure of Acetic Acid

The molecular structure of acetic acid consists of a methyl group (−CH₃) and a carboxyl group (−COOH), connected by a carbon–carbon bond.
The carboxyl group is responsible for the acidic properties of the compound because it can release a proton (H⁺) in aqueous solutions.

Physical and Chemical Properties of Acetic Acid

Property	Description
Physical state	Colorless liquid at room temperature
Melting point	16.6°C – Below this temperature, it solidifies into crystalline form known as glacial acetic acid
Boiling point	118–119°C at 1 atm
Odor	Sharp, pungent, vinegar-like (irritating at high concentrations)
Solubility	Completely miscible with water, alcohols, ethers, and most polar organic solvents
Acidity (pKa)	≈ 4.76 – weak acid, partially ionized in aqueous solution
Corrosiveness	Corrosive at high concentrations; may cause chemical burns to skin and eyes
Flammability	Flammable; vapors can form explosive mixtures with air
Density	~1.049 g/cm³ at 25°C

Applications of Acetic Acid

Acetic acid is a versatile reagent and solvent, playing a vital role in many industrial and laboratory processes.

1. Chemical Industry

Vinyl Acetate Monomer (VAM) production: Used to manufacture adhesives, resins, and polymers.
Synthesis of acetate esters such as:
- Ethyl acetate: solvent in nail polish remover, paints, and adhesives.
- Butyl acetate: solvent in inks and coatings.
Purified Terephthalic Acid (PTA) synthesis: key precursor for PET plastics and polyester fibers.

2. Pharmaceutical Industry

Intermediate in the synthesis of drugs, antibiotics, and biological compounds.

3. Textile Industry

Acts as a pH regulator and color fixative in dyeing and printing processes.

4. Food Industry

Functions as an acidity regulator and preservative (food additive code E260).
Primary component of vinegar and flavoring agent in sauces, pickles, and canned foods.

5. Rubber and Plastics Industry

Used as a catalyst or reaction modifier in polymerization processes.

6. Other Uses

Manufacture of pesticides and herbicides.
As an industrial solvent for resins, paints, and oils.

Advantages of Acetic Acid

✅ Abundant and readily available: One of the most commonly produced organic acids in the world.
✅ Chemically versatile: Participates in esterification, polymerization, oxidation, and reduction reactions.
✅ Preservative capability: Its acidity inhibits microbial growth.
✅ Mild, controllable acidity: Suitable for sensitive formulations.
✅ Biodegradable: Rapidly decomposes in nature to CO₂ and H₂O.

Disadvantages of Acetic Acid

⚠️ Corrosive: Highly concentrated forms can cause severe skin, eye, and respiratory burns.
⚠️ Pungent odor: Inhalation of concentrated vapors may cause coughing and irritation.
⚠️ Flammable: Vapors form explosive mixtures with air; must be stored away from open flames.
⚠️ High freezing point: Easily solidifies in cold climates.
⚠️ Toxic by inhalation at high concentrations: May cause lung damage.

Safety and Handling Information

Parameter	Details
Chemical formula	CH₃COOH
CAS Number	64-19-7
IUPAC Name	Ethanoic Acid
Appearance	Clear, colorless liquid with pungent vinegar-like odor
Hazard Classification	Corrosive, Flammable, Respiratory Irritant
GHS Classification	Flammable (Cat. 3) / Corrosive (Cat. 1A) / Acute Toxicity (Cat. 4)

Health and Safety Hazards

Type of Exposure	Potential Effects
Skin contact	Chemical burns, redness, severe irritation
Eye contact	Corneal damage, potential blindness
Inhalation	Respiratory irritation, coughing, headache, shortness of breath
Ingestion	Severe throat and gastrointestinal burns; toxic or fatal in large doses
Reactivity	Reacts violently with strong bases, peroxides, and oxidizing agents

Personal Protective Equipment (PPE)

Equipment	Recommended Type
Gloves	Acid-resistant nitrile or PVC gloves
Eye protection	Laboratory safety goggles with side shields
Respiratory protection	Filter mask (organic vapor cartridge for high vapor levels)
Protective clothing	PVC or PE-coated lab coat/apron
Ventilation	Mandatory in enclosed areas – use exhaust fans or fume hoods

Storage and Handling Conditions

Parameter	Recommended Condition
Storage temperature	10–30°C, away from heat and direct sunlight
Container material	Acid-resistant steel tanks or heavy-duty HDPE containers
Avoid contact with	Strong bases, reactive metals, peroxides, oxidizers
Flammability	Yes – flash point ≈ 39°C
Firefighting media	Alcohol-resistant foam, CO₂, or dry chemical powder
Safety labeling	Corrosive, Flammable, Respiratory Warning (GHS/CLP compliant)