Functional group of an alcohol molecule. The carbon atom is attached to other carbon or hydrogen atoms.


Generally, the word alcohol usually refers to ethanol, also known as grain alcohol or (older) spirits of wine. Ethanol is a very strong smelling, colorless, volatile liquid formed by the fermentation of sugars. It also often refers to any beverage that contains ethanol (see alcoholic beverage). It is the most widely used depressant in the world, and has been for thousands of years. This sense underlies the term alcoholism (addiction to alcohol).



Some simple alcohols and their sources

Methanol and ethanol

The simplest and most commonly used alcohols are methanol (common name methyl alcohol), with the formula CH3OH, and ethanol (ethyl alcohol), with the formula CH3CH2OH. Methanol was formerly obtained by the distillation of wood and called "wood alcohol." It is now a cheap commodity, produced by the reaction of carbon monoxide and hydrogen under high pressure.

In common usage, "alcohol" often refers to ethanol or "grain alcohol." Methylated spirits ("Meths"), also called "surgical spirits" or "denatured alcohol," is a form of ethanol rendered undrinkable by the addition of methanol. Aside from its primary use in alcoholic beverages, ethanol is also used as a highly controlled industrial solvent and raw material.

Two other alcohols that are relatively widely used (though not as much as methanol and ethanol) are propanol and butanol. Like ethanol, they are produced by fermentation processes. (However, the fermenting agent is the bacterium Clostridium acetobutylicum, which feeds on cellulose, not sugars like the Saccharomyces yeast that produces ethanol.)


The word "alcohol" almost certainly comes from the Arabic language (the "al-" prefix being the Arabic definite article); however, the precise origin is unclear. The Persian physician and scientist Rhazes (ca. 865 – 925) discovered this substance, but because he wanted his book to be published in most of the then-known world, he used the Arabic language instead of Persian (although he made copies in Persian). The word was introduced into Europe, together with the art of distillation and the substance itself, around the twelfth century by various European authors who translated and popularized the discoveries of Islamic and Persian alchemists.[1]

A popular theory, found in many dictionaries, is that it comes from الكحل al-kuḥl, originally the name of very finely powdered antimony sulfide Sb2S3 used as an antiseptic and eyeliner. The powder is prepared by sublimation of the natural mineral stibnite in a closed vessel. According to this theory, the meaning of alkuhul would have been first extended to distilled substances in general, and then narrowed to ethanol. This conjectured etymology has been circulating in England since at least 1672 (Oxford English Dictionary).

However, this derivation is suspicious because the current Arabic name for alcohol, الكحول al-kuḥūl

, does not derive from al-kuḥl

. The Qur'an, in verse 37:47, uses the word الغول al-ġawl

—properly meaning "spirit" or "demon"—with the sense "the thing that gives the wine its headiness." The word al-ġawl

is also the origin of the English word "ghoul," and the name of the star Algol. This derivation would, of course, be consistent with the use of "spirit" or "spirit of wine" as synonymous of "alcohol" in most Western languages.

According to the second theory, the popular etymology and the spelling "alcohol" would not be due to generalization of the meaning of al-kuḥl, but rather to Western alchemists and authors confusing the two words al-kuḥl and al-ghawl, which have indeed been transliterated in many different and overlapping ways.


Common names for alcohols usually start with the name of the corresponding alkyl group followed by the word "alcohol." Examples are methyl alcohol, ethyl alcohol, and tert-butyl alcohol. Propyl alcohol would be called n-propyl alcohol, if the hydroxyl group is bonded to the first carbon atom on the propane chain; or isopropyl alcohol, if the hydroxyl group is bonded to the second carbon atom on the propane chain. Isopropyl alcohol is also occasionally called sec-propyl alcohol.

In the systematic nomenclature recommended by the International Union of Pure and Applied Chemistry (IUPAC), the name of the alcohol begins with the name of the corresponding alkane chain, but the terminal "e" is replaced by "ol." Examples are "methanol" (for methyl alcohol) and "ethanol" (for ethyl alcohol). When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the "ol." Examples are propan-1-ol (for n-propyl alcohol or CH3CH2CH2OH) and propan-2-ol (for isopropyl alcohol, CH3CH(OH)CH3).

Sometimes, the position number is written before the IUPAC name: 1-propanol and 2-propanol. If a higher priority group is present (such as an aldehyde, ketone or carboxylic acid), then it is necessary to use the prefix "hydroxy." An example is 1-hydroxy-2-propanone (CH3COCH2OH).

Some examples of simple alcohols and how to name them:

Examples of alcohols & their names

Three classes of alcohols

Alcohols may be subdivided into three major classes: 'primary' (1°), 'secondary' (2°) and 'tertiary' (3°), based upon the number of carbon atoms attached to the carbon in the C-OH group. Methanol is the simplest 'primary' alcohol. The simplest secondary alcohol is isopropyl alcohol (propan-2-ol). A simple tertiary alcohol is tert-butyl alcohol (2-methylpropan-2-ol), consisting of a propane chain with methyl and hydroxyl groups both attached to the middle (#2) carbon.

Carbohydrates and phenols

Carbohydrates (sugars) and sugar alcohols are an important class of compounds containing multiple alcohol functional groups and may be called polyols. For example, sucrose (common sugar) contains eight hydroxyl groups per molecule and sorbitol has six. Most of the attributes of these polyols—such as nomenclature, occurrence, use, and toxicity—sufficiently differ from simple aliphatic alcohols to require separate treatment.

The phenols, named after the parent compound phenol, also have a hydroxyl group, but it is attached to an aromatic ring (usually benzene), not an aliphatic chain. As a result, their properties are very different and they are treated separately.

Physical and chemical properties





Acidity & basicity of methanol




Alcohol is often used as an automotive fuel. Ethanol and methanol can be made to burn more cleanly than gasoline or diesel. Alcohol was once used as an antifreeze in automobile radiators. To add to an internal combustion engine's performance, methanol may be injected into turbocharged and supercharged engines. This cools the air intake charge, providing a denser air charge.

Scientific, medical, and industrial





The LD50 of ethanol in rats is 11,300 mg/kg.[2] This ratio would correspond to an 80kg (176.4lb) man drinking 65 shots of 80 proof alcohol, although the LD50 does not necessarily translate directly to humans. A more accurate but less precise figure would estimate the LD50 of the same 80kg (176.4lb) at about 15.5 shots of 80 proof alcohol.[3]



Preparation of alcohols

Many alcohols can be created by fermentation of fruits or grains with yeast, but only ethanol is commercially produced this way—chiefly for fuel and drink. Other alcohols are generally produced by synthetic routes from natural gas, petroleum, or coal feed stocks; for example, via acid catalyzed hydration of alkenes. For more details see Preparation of alcohols.


Several methods exist for the preparation of alcohols in the laboratory.

  • Aldehydes or ketones are reduced with sodium borohydride or lithium aluminium hydride (after an acidic workup). Another reduction by aluminumisopropylates is the Meerwein-Ponndorf-Verley reduction.
  • Alkenes engage in an acid catalysed hydration reaction using concentrated sulfuric acid as a catalyst which gives usually secondary or tertiary alcohols.
  • Grignard reagents react with carbonyl groups to secondary and tertiary alcohols
  • Noyori asymmetric hydrogenation is the asymmetric reduction of β-keto-esters


Preparation of a secondary alcohol


Industrially alcohols are produced in several ways:

  • By fermentation using glucose produced from sugar from the hydrolysis of starch, in the presence of yeast and temperature of less than 37°C to produce ethanol. For instance the conversion of invertase to glucose and fructose or the conversion of glucose to zymase and ethanol.
  • By direct hydration using ethane or other alkenes from cracking of fractions of distilled crude oil. Uses a catalyst of phosphoric acid under high temperature and pressure of 50-120.
  • Methanol is produced from water gas: It is manufactured from synthesis gas, where carbon monoxide and two equivalents of hydrogen gas are combined to produce methanol using a copper, zinc oxide and aluminum oxide catalyst at 250°C and a pressure of 50-100 atm.

Reactions of alcohols



2 R-OH + 2 NaH → 2 R-O-Na+ + H2
2 R-OH + 2Na → 2R-ONa + H2






Nucleophilic substitution

The OH group is not a good leaving group in nucleophilic substitution reactions, so neutral alcohols do not react in such reactions. However if the oxygen is first protonated to give R−OH2+, the leaving group (water) is much more stable, and nucleophilic substitution can take place. For instance, tertiary alcohols react with hydrochloric acid to produce tertiary alkyl halides, where the hydroxyl group is replaced by a chlorine atom. If primary or secondary alcohols are to be reacted with hydrochloric acid, an activator such as zinc chloride is needed. Alternatively the conversion may be performed directly using thionyl chloride.[1]

Some simple conversions of alcohols to alkyl chlorides


3 R-OH + PBr3 → 3 RBr + H3PO3



















  • Chromium-based reagents, such as Collins reagent (CrO3·Py2), PDC or PCC.
  • Activated DMSO, resulting from reaction of DMSO with electrophiles, such as oxalyl chloride (Swern oxidation), a carbodiimide (Pfitzner-Moffatt oxidation) or the complex SO3·Py (Parikh-Doering oxidation).
  • Hypervalent iodine compounds, such as Dess-Martin periodinane or 2-Iodoxybenzoic acid.
  • Catalytic TPAP in presence of excess of NMO (Ley oxidation).
  • Catalytic TEMPO in presence of excess bleach (NaOCl) (Anelli’s oxidation).
Oxidation of alcohols to aldehydes and ketones




  • Potassium permanganate (KMnO4).
  • Jones oxidation.
  • PDC in DMF.
  • Heyns oxidation.
  • Ruthenium tetroxide (RuO4).
  • TEMPO.
Oxidation of primary alcohols to carboxylic acids


Oxidative breakage of carbon-carbon bond in 1,2-diols

See also


  1. Philippus Aureolus Paracelsus, [1] The Free Encyclopedia by Farlex. Retrieved September 10, 2007.
  2. Robert S. Gable, 2003. Comparison of acute lethal toxicity of commonly abused psychoactive substances. Retrieved September 10, 2007.
  3. John Brick, 2003. Alcohol Overdose. Rutgers Center of Alcohol Studies. Retrieved September 10, 2007.


  • McMurry, John. 2004. Organic Chemistry. 6th ed. Belmont, CA: Brooks/Cole. ISBN 0534420052
  • Morrison, Robert T., and Robert N. Boyd. 1992. Organic Chemistry. 6th ed. Englewood Cliffs, NJ: Prentice Hall. ISBN 0136436692
  • Solomons, T. W. Graham, and Craig B. Fryhle, 2004. Organic Chemistry. 8th ed. Hoboken, NJ: John Wiley. ISBN 0471417998.



