Alcohol is most familiar as an ingredient of alcoholic drinks, but drinkable alcohol is only one of many different kinds. Drinking alcohol is properly known as ethyl alcohol or ethanol, and it can be fatal in large doses. Small amounts of other alcohols can cause brain damage and death.
Industrial alcohol is used as a solvent and in the manufacture of acetic acid, ether, chloroform, plastics such as polyethylene (polythene), and the tetraethyl lead added to gasoline as an antiknock compound—though this additive is gradually being banned in many countries, including the United States, because it is poisonous.
Methyl alcohol, or methanol (wood alcohol, so called because it was originally made from the destructive distillation of wood), is used as a solvent in the manufacture of formaldehyde and in antifreeze. It is also used in methylated spirit, which is ethanol made undrinkable by adding about 9 percent methanol and very small amounts of benzene, pyridine, and dye, which by their taste, smell and color, considerably reduce the danger of accidental poisoning. Methanol may also be used in in antifreeze and is also useful as an alternative to gasoline-producing low pollution emissions and a high octane rating.
Ethanediol, or ethylene glycol (sometimes referred to simply as glycol), is also used in antifreeze to make various plastics and synthetic resins, such as polyurethane, and many modern adhesives. Glycerol (also known as glycerine) is used to make other plastics, explosives (nitroglycerine), cosmetics, inks, and antifreeze. It is a by-product in soap making.
Structure of alcohols
When one or more of the hydrogen atoms in a hydrocarbon is replaced by the hydroxyl group, –OH, the result is an alcohol. Ethane, C2H6, for example, becomes ethanol, C2H5OH. Hence the names for alcohols: methanol, ethanol, propanol, butanol, and so on, corresponding to the related hydrocarbon gases, methane, ethane, propane, and butane. These alcohols, which contain a single hydroxyl group, range from volatile liquids to waxy solids. Those with 12 or more carbon atoms are solid, while those with fewer than 12 carbon atoms are liquid.
Isomerism
Structurally, from propanol onward, the alcohols show isomerism—that is, there is more than one position where the –OH group can go, although the overall number of carbon, hydrogen, and oxygen atoms remains the same. This structural difference can give molecules different characteristics, that is, the molecules undergo different types of chemical reactions. For example, primary alcohols (where the –OH group is attached to the end of a carbon chain) can be oxidized to aldehydes and to carboxylic acids, while secondary alcohols are oxidized to ketones. In secondary alcohols, such as isopropyl alcohol or propan-2-ol, the hydroxyl group is attached to a carbon atom that is in the middle of a carbon chain. A tertiary alcohol has a hydroxyl group attached to a carbon that is bonded to three other carbons. Alcohols with more than one hydroxyl group are known as polyols. Both ethanediol and glycerol belong to this class. These alcohols usually have a syrupy consistency.
