Ethanol (Ethyl Alcohol) (C₂H₅OH) — Properties, Uses & Safety

Overview

Ethanol (C2H5OH), also known as ethyl alcohol or grain alcohol, is a simple two-carbon alcohol with a molar mass of 46.07 g/mol. It is a colorless, volatile, flammable liquid with a characteristic odor and a burning taste. Ethanol is miscible with water in all proportions due to its hydroxyl (-OH) group, which forms hydrogen bonds with water molecules, while its short hydrocarbon chain keeps it small enough to dissolve readily. This dual nature — a polar hydroxyl group attached to a nonpolar ethyl group — makes ethanol an excellent solvent for both polar and nonpolar substances. Ethanol is produced naturally through the fermentation of sugars by yeast (C6H12O6 → 2 C2H5OH + 2 CO2), a process humans have exploited for thousands of years to make beer, wine, and spirits. Industrially, ethanol is also produced by the catalytic hydration of ethylene (C2H4 + H2O → C2H5OH), connecting it to petrochemistry. In everyday life, ethanol serves as the active ingredient in alcoholic beverages, a widely used disinfectant and antiseptic (typically at 70% concentration), a common laboratory solvent, and a renewable fuel additive (E10 and E85 gasoline blends). Ethanol burns cleanly in air (C2H5OH + 3 O2 → 2 CO2 + 3 H2O), producing carbon dioxide and water, which makes it attractive as a biofuel. Safety considerations for ethanol include its flammability (flash point 13 °C), its classification as a central nervous system depressant when consumed, and its potential for addiction. GHS hazard codes typically include flammable liquid and vapor warnings. For chemistry students, ethanol is a gateway to understanding functional groups in organic chemistry, particularly the alcohol (-OH) group. It illustrates key concepts including fermentation as a biochemical reaction, combustion stoichiometry, hydrogen bonding and solubility, distillation and separation techniques, and the relationship between molecular structure and physical properties. Ethanol's presence in everyday products from hand sanitizer to fuel makes it one of the most relatable organic compounds in the chemistry curriculum.

IUPAC Name

ethanol

CAS Number

64-17-5

PubChem CID

702

Molecular Formula

C₂H₅OH

Molar Mass

46.07 g/mol

State at STP

liquid

Appearance

Colorless liquid with characteristic odor

Physical Properties

Melting Point

-114.1 °C

Boiling Point

78.37 °C

Density

0.789 g/cm³

Specific Heat

2.44 J/(g·K)

ΔH°f

-277 kJ/mol

ΔG°f

-174.8 kJ/mol

S°

160.7 J/(mol·K)

Composition

Bonding

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