Ethanol is a simple alcohol with the chemical formula C₂H₆O, made of two carbon atoms, six hydrogen atoms, and one oxygen atom. It is the type of alcohol found in beer, wine, and spirits, but it also serves as a fuel additive, industrial solvent, and antiseptic. At room temperature, ethanol is a clear, colorless liquid that boils at 78.2 °C (173 °F) and mixes easily with water.
Chemical Properties
Ethanol’s molecular structure is often written as CH₃CH₂OH, which highlights the hydroxyl group (an oxygen bonded to a hydrogen) at one end of the molecule. That hydroxyl group is what makes ethanol miscible with water and gives it its characteristic ability to dissolve both water-based and oil-based substances. This dual nature is why ethanol works so well as a solvent in everything from perfumes to pharmaceuticals.
One quirk of ethanol is that mixing it with water produces less volume than you’d expect. Combine one volume of ethanol with one volume of water and you get about 1.92 volumes of mixture, not two. The molecules essentially tuck into each other’s empty spaces. Ethanol is also highly flammable, with a flash point of just 13 °C (55 °F), meaning it can ignite at temperatures well below room temperature.
How Ethanol Is Made
The oldest and most common method is fermentation. Yeast, particularly the species Saccharomyces cerevisiae (baker’s yeast), consumes simple sugars and produces ethanol and carbon dioxide as waste products. This is the same basic process behind brewing beer and making wine, scaled up massively for industrial purposes.
The starting material can vary widely. Sugarcane and sugar beets provide sugars that yeast can ferment directly. Starchy crops like corn, wheat, and cassava need an extra step: enzymes first break the starch down into fermentable sugars. Newer production methods use cellulosic biomass, the tough fibrous material in wood chips, agricultural waste, and grasses, though converting cellulose into fermentable sugars is more technically challenging. S. cerevisiae dominates commercial production because it tolerates high concentrations of ethanol without dying off, letting fermentation continue until the alcohol content is relatively high.
What Happens When You Drink It
Ethanol is a central nervous system depressant, meaning it slows down signaling between nerve cells. Even at low blood alcohol concentrations, around 0.02%, you can experience mood changes, slight relaxation, and a mild loss of judgment. As concentration rises, the effects deepen: coordination suffers, reaction time slows, speech slurs, and at high enough levels, breathing and heart rate can become dangerously depressed.
Your body treats ethanol as a toxin and begins breaking it down almost immediately, primarily in the liver. The first enzyme in the process, alcohol dehydrogenase, converts ethanol into acetaldehyde, a highly reactive and toxic compound classified as a known carcinogen. Acetaldehyde is responsible for many of the unpleasant effects of drinking, including facial flushing and nausea. A second enzyme, aldehyde dehydrogenase, then converts acetaldehyde into acetate, a much less harmful substance. Acetate is eventually broken down into water and carbon dioxide in tissues throughout the body. The speed of this process is limited, which is why drinking faster than your liver can keep up leads to rising blood alcohol levels.
Some people, particularly those of East Asian descent, carry genetic variants that make their aldehyde dehydrogenase less effective. Acetaldehyde lingers longer in their system, causing intense flushing, nausea, and rapid heartbeat after even small amounts of alcohol.
Cancer and Long-Term Health Risks
The International Agency for Research on Cancer has classified ethanol in alcoholic beverages as a Group 1 carcinogen, its highest category, since 1987. Both ethanol itself and the acetaldehyde produced during metabolism are considered carcinogenic to humans. The cancers linked to alcohol consumption include cancers of the mouth, throat, voice box, esophagus, liver, colon, rectum, and female breast.
The scale of this risk is significant. In 2020, an estimated 741,300 new cancer cases worldwide, about 4.1% of all new cancers, were attributable to alcohol consumption. Men accounted for a disproportionate share, with 6.1% of male cancers linked to alcohol compared to 2.0% in women. These risks exist on a dose-response curve: more alcohol over time means higher risk, with no established “safe” threshold for cancer prevention.
Uses Beyond Drinking
Ethanol’s versatility as a solvent and its ability to kill bacteria and viruses make it valuable across many industries. In pharmaceuticals, it serves as a carrier in liquid drug formulations and as the active ingredient in hand sanitizers and mouthwashes. In cosmetics and personal care, ethanol appears in hair sprays, lotions, and soaps, where it helps other ingredients dissolve evenly and evaporate quickly on application.
As a fuel, ethanol is blended with gasoline in many countries. In the United States, most gasoline contains up to 10% ethanol, which reduces certain tailpipe emissions. Brazil has long used sugarcane-derived ethanol as a major transportation fuel, with some vehicles running on blends as high as 85% ethanol.
Ethanol also serves as a laboratory solvent, a feedstock for producing other chemicals like ethylene, and a preservative in biological specimens. Its range of applications is one reason global production runs into tens of billions of gallons per year.
Denatured vs. Pure Ethanol
Because ethanol is taxed as a beverage alcohol in most countries, industrial ethanol is typically “denatured,” meaning small amounts of chemicals are added to make it undrinkable. A common formulation includes about 5% methanol along with smaller amounts of ethyl acetate, hydrocarbons, and methyl isobutyl ketone. These additives make the ethanol taste terrible and potentially dangerous to consume, which allows it to be sold without the steep taxes applied to drinking alcohol. Denatured ethanol is sometimes called industrial methylated spirit.
Pharmaceutical and food-grade ethanol, by contrast, must meet strict purity standards set by organizations like the US Pharmacopeia and is subject to oversight from the FDA and the Alcohol and Tobacco Tax and Trade Bureau. The production process for these grades is more tightly controlled to ensure no harmful contaminants end up in products people will ingest or apply to their skin.