Alcohol is any organic compound in which the hydroxyl group, OH, is affixed to a carbon atom of an alkyl or substituted alkyl group. Alcohols can be classified as monohydric, dihydric, or trihydric. Methanol and ethanol, for example, are monohydric alcohols. Alcohols can be categorized into three groups—primary, secondary, and tertiary—according to the number of carbon atoms that are bound to the C-OH group’s carbon atom.
Common alcohols are methyl alcohol, or methanol (wood alcohol, CH3OH), known as the simplest alcohol; ethanol (ethyl alcohol, C2H6O), a primary alcohol; isopropyl alcohol (rubbing alcohol, C3H7OH), a simple secondary alcohol; and tert-Butanol (butanol, C4H9OH), a simple tertiary alcohol. Alcohols are neither alkaline nor acid, but they are described by their chemical reactions with acids—the formation of esters.
Alcohol appears in various products, ranging from fuels, industrial chemicals, disinfectants, and solvents—but most familiar are alcoholic beverages. Ethanol—also known as pure alcohol, grain alcohol, or drinking alcohol—is a psychoactive drug that appears in the form of a colorless, volatile, flammable liquid with a pungent odor.
The word alcohol derives from Medieval Latin, Old Spanish, and the word kohl from the Arabic word al-kuhul. Kohl is a finely powdered antimony sulfide, a powder used as an eye cosmetic. In its original use, alcohol once denoted a “fine powder.” Medieval alchemists later adapted the word to represent the essences obtained by distillation, now known as the liquid substance derived from fermentation and distillation.
The use of ethanol can be traced as far back as the Neolithic period. Its application and usages have been present throughout history—such as its use as an alcoholic beverage in civilizations going back 9,000 years, its distillation characteristics as discovered during the Islamic Renaissance, and its chemical compound classification and energy resources as identified during the Industrial Revolution.
Ethanol content in alcoholic beverages can vary depending on its combination with the foodstuffs from which the beverage is made, such as fruits or fruit juices (wine and ciders), sugarcane juice, cereal grains, meads from honey, starches, herbs, spices, molasses, or potatoes. Fermentation is caused by the action of yeast on these sugary products, by which fermented beverages are produced.
Alternative forms of fermentation include freeze distillation methods. Common distilled beverages include brandy, gin, rum, vodka, and whiskey, which are produced by fermentation and distillation. The more thoroughly distilled a liquid is from the fermented material, the more tasteless the distilled liquid becomes. Alcoholic proof units (or percentages) are measured by the amount of ethanol present in the beverage.
When ingested, ethanol becomes metabolized by the body as the carbohydrate nutrient acetyl (a process similar to glucose metabolism), which can be used for biosynthesis or as energy in the citric acid cycle. This stimulates the production of insulin, resulting in low levels of blood sugar, which causes irritability and potential for death in diabetics.
Ethanol is a depressant that affects the body’s central nervous system. It serves as an agonist to the GABA receptors and causes notable action to take place in the brain system. The level of intoxication is classified at 0.08% blood-alcohol content, most noticeably causing slurred speech and delayed reflexes, but can also produce such side effects as dizziness, disorientation, vomiting, or unconsciousness.
Heavier drinkers develop higher tolerances to alcohol’s effects as the brain and body adjust to accept the constant presence of alcohol in the system. Over-consumption of alcohol can result in alcohol poisoning. Habitual drinkers can experience serious health risks and chronic illnesses such as heart disease, dementia, and several types of cancers. A fatal amount of alcohol in the system measures 0.45% blood-alcohol content which, in normal health, can have lethal effects. Alcohol can be addictive if used regularly, resulting in the chronic disorder known as alcoholism.
See also history of alcohol use