AskDefine | Define alcohols

User Contributed Dictionary

English

Noun

alcohols
  1. Plural of alcohol

French

Noun

alcohols
  1. Plural of alcohol

Extensive Definition

In chemistry, an alcohol is any organic compound in which a hydroxyl group (-OH) is bound to a carbon atom of an alkyl or substituted alkyl group. The general formula for a simple acyclic alcohol is CnH2n+1OH.
The word alcohol was introduced into the English language circa 1543 from the , "al-ġuḥl". In layman's terms, it usually refers to ethanol, also known as grain alcohol or (older) spirits of wine, or to any alcoholic beverage. Ethanol is a colorless, volatile liquid with a mild odor which can be obtained by the fermentation of sugars. (Industrially, it is more commonly obtained by ethylene hydration—the reaction of ethylene with water in the presence of phosphoric acid.) Ethanol 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).
Other alcohols are usually described with a clarifying adjective, as in isopropyl alcohol (propan-2-ol) or wood alcohol (methyl alcohol, or methanol). The suffix -ol appears in the "official" IUPAC chemical name of all alcohols.
There are three major subsets of alcohols: primary (1°), secondary (2°) and tertiary (3°), based upon the number of carbon atoms the C-OH group's carbon (shown in red) is bonded to. Ethanol is a simple 'primary' alcohol. The simplest secondary alcohol is isopropyl alcohol (propan-2-ol), and a simple tertiary alcohol is tert-butyl alcohol (2-methylpropan-2-ol).
The phenols with parent compound phenol have a hydroxyl group (attached to a benzene ring) just like alcohols, but differ sufficiently in properties as to warrant a separate treatment.
Carbohydrates (sugars) and sugar alcohols are an important class of compounds containing multiple alcohol functional groups. For example, sucrose (common sugar) contains eight hydroxyl groups per molecule and sorbitol has six. Most of the attributes of these polyols, from nomenclature, to occurrence, use and toxicity, are sufficiently different from simple aliphatic alcohols as to require a separate treatment.

Simple alcohols

The simplest and most commonly used alcohols are methanol and ethanol. Methanol was formerly obtained by the distillation of wood and called "wood alcohol." It is now a cheap commodity, the chemical product of carbon monoxide reacting with hydrogen under high pressure. Methanol is intoxicating but not directly poisonous. It is toxic by its breakdown (toxication) by the enzyme alcohol dehydrogenase in the liver by forming formic acid and formaldehyde which cause permanent blindness by destruction of the optic nerve.
Apart from its familiar role in alcoholic beverages, ethanol is also used as a highly controlled industrial solvent and raw material. To avoid the high taxes on ethanol for consumption, additives are added to make it unpalatable (such as denatonium benzoate—"Bitrex") or poisonous (such as methanol). Ethanol in this form is known generally as denatured alcohol; when methanol is used, it may be referred to as methylated spirits ("Meths") or "surgical spirits".
Two other alcohols whose uses are relatively widespread (though not so much as those of methanol and ethanol) are propanol and butanol. Like ethanol, they can be produced by fermentation processes. (However, the fermenting agent is a bacterium, Clostridium acetobutylicum, that feeds on cellulose, not sugars like the Saccharomyces yeast that produces ethanol.)

Nomenclature

Systematic names

In the IUPAC system, the name of the alkane chain loses the terminal "e" and adds "ol", e.g. "methanol" and "ethanol". When necessary, the position of the hydroxyl group is indicated by a number between the alkane name and the "ol": propan-1-ol for CH3CH2CH2OH, propan-2-ol for 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",
Other alcohols are substantially more poisonous than ethanol, partly because they take much longer to be metabolized, and often their metabolism produces even more toxic substances. Methanol, or wood alcohol, for instance, is oxidized by alcohol dehydrogenase enzymes in the liver to the poisonous formaldehyde, which can cause blindness or death.
An effective treatment to prevent formaldehyde toxicity after methanol ingestion is to administer ethanol. Alcohol dehydrogenase has a higher affinity for ethanol, thus preventing methanol from binding and acting as a substrate. Any remaining methanol will then have time to be excreted through the kidneys. Remaining formaldehyde will be converted to formic acid and excreted.

References

Bibliography

  • The World in So Many Words
alcohols in Arabic: كحول
alcohols in Asturian: Alcohol
alcohols in Belarusian (Tarashkevitsa): Сьпірт
alcohols in Bosnian: Alkohol
alcohols in Bulgarian: Алкохол
alcohols in Catalan: Alcohol
alcohols in Czech: Alkoholy
alcohols in Welsh: Alcohol
alcohols in Danish: Alkohol (stofklasse)
alcohols in German: Alkohole
alcohols in Estonian: Alkoholid
alcohols in Spanish: Alcohol
alcohols in Esperanto: Alkoholo
alcohols in Persian: الکل
alcohols in Faroese: Alkohol
alcohols in French: Alcool (chimie)
alcohols in Scottish Gaelic: Alcol
alcohols in Galician: Alcohol
alcohols in Korean: 알코올
alcohols in Croatian: Alkoholi
alcohols in Ido: Alkoholo
alcohols in Indonesian: Alkohol
alcohols in Icelandic: Alkóhól
alcohols in Italian: Alcoli
alcohols in Hebrew: כוהל
alcohols in Javanese: Alkohol
alcohols in Kurdish: Alkol
alcohols in Latin: Alcohol
alcohols in Latvian: Spirti
alcohols in Lithuanian: Alkoholis
alcohols in Hungarian: Alkoholok
alcohols in Macedonian: Алкохол
alcohols in Malayalam: ചാരായം (രസതന്ത്രം)
alcohols in Malay (macrolanguage): Alkohol
alcohols in Dutch: Alcohol (stofklasse)
alcohols in Japanese: アルコール
alcohols in Norwegian: Alkoholer
alcohols in Norwegian Nynorsk: Alkohol
alcohols in Occitan (post 1500): Alcòl
alcohols in Polish: Alkohole
alcohols in Portuguese: Álcool
alcohols in Romanian: Alcooli
alcohols in Russian: Спирты
alcohols in Sicilian: Alcool
alcohols in Simple English: Alcohol
alcohols in Slovak: Alkohol (hydroxyderivát)
alcohols in Slovenian: Alkohol
alcohols in Serbian: Алкохол
alcohols in Sundanese: Alkohol
alcohols in Finnish: Alkoholi
alcohols in Swedish: Alkoholer
alcohols in Thai: แอลกอฮอล์
alcohols in Vietnamese: Rượu (hoá học)
alcohols in Cheyenne: Manestôtse
alcohols in Turkish: Alkol
alcohols in Ukrainian: Спирти
alcohols in Vlaams: Alcool
alcohols in Yiddish: אלקאהאל
alcohols in Chinese: 醇
Privacy Policy, About Us, Terms and Conditions, Contact Us
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2
Material from Wikipedia, Wiktionary, Dict
Valid HTML 4.01 Strict, Valid CSS Level 2.1