Alcohol oxidation

Alcohol oxidation
Mechanism of oxidation of primary alcohols to carboxylic acids via aldehydes and aldehyde hydrates

Alcohol oxidation is an important organic reaction. Primary alcohols (R-CH2-OH) can be oxidized either to aldehydes (R-CHO) or to carboxylic acids (R-CO2H), while the oxidation of secondary alcohols (R1R2CH-OH) normally terminates at the ketone (R1R2C=O) stage. Tertiary alcohols (R1R2R3C-OH) are resistant to oxidation [1].

The direct oxidation of primary alcohols to carboxylic acids normally proceeds via the corresponding aldehyde, which is transformed via an aldehyde hydrate (R-CH(OH)2) by reaction with water before it can be further oxidized to the carboxylic acid.

Often it is possible to interrupt the oxidation of a primary alcohol at the aldehyde level by performing the reaction in absence of water, so that no aldehyde hydrate can be formed.

Contents

Oxidation to aldehydes

Oxidation of alcohols to aldehydes and ketones

Reagents useful for the transformation of primary alcohols to aldehydes are normally also suitable for the oxidation of secondary alcohols to ketones. These include:

Allylic and benzylic alcohols can be oxidized in presence of other alcohols using certain selective oxidants such as manganese dioxide (MnO2).

Oxidation to ketones

Reagents useful for the oxidation of secondary alcohols to ketones, but normally inefficient for oxidation of primary alcohols to aldehydes, include chromium trioxide (CrO3) in a mixture of sulfuric acid and acetone (Jones oxidation) and certain ketones, such as cyclohexanone, in the presence of aluminium isopropoxide (Oppenauer oxidation). Another method is oxoammonium-catalyzed oxidation.

Oxidation to carboxylic acids

Oxidation of primary alcohols to carboxylic acids

The direct oxidation of primary alcohols to carboxylic acids can be carried out using:

Diol oxidation

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

Alcohols possessing two hydroxy groups located on adjacent carbons —that is, 1,2-diols— suffer oxidative breakage at a carbon-carbon bond with some oxidants such as sodium periodate (NaIO4) or lead tetraacetate (Pb(OAc)4), resulting in generation of two carbonyl groups. The reaction is also known as glycol cleavage.

References

  1. ^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7 

Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Alcohol — This article is about the generic chemistry term. For the kind of alcohol found in alcoholic beverages, see Ethanol. For beverages containing alcohol, see Alcoholic beverage. For other uses, see Alcohol (disambiguation) …   Wikipedia

  • Alcohol dehydrogenase — Crystallographic structure of the homodimer of human ADH5.[1] Identifiers …   Wikipedia

  • Oxidation with chromium(VI)-amine complexes — involves the conversion of alcohols to carbonyl compounds or more highly oxidized products through the action of chromium(VI) oxide amine adducts and salts. Representative members of this family of reagents include Collins reagent, pyridinium… …   Wikipedia

  • alcohol — /al keuh hawl , hol /, n. 1. Also called ethyl alcohol, grain alcohol, ethanol, fermentation alcohol. a colorless, limpid, volatile, flammable, water miscible liquid, C2H5OH, having an etherlike odor and pungent, burning taste, the intoxicating… …   Universalium

  • Oxidation of primary alcohols to carboxylic acids — The oxidation of primary alcohols to carboxylic acids is an important oxidation reaction in organic chemistry. When a primary alcohol is converted to a carboxylic acid, the terminal carbon atom increases its oxidation state by four. Oxidants able …   Wikipedia

  • Oxidation of secondary alcohols to ketones — The oxidation of secondary alcohols to ketones is an important oxidation reaction in organic chemistry. When a secondary alcohol is oxidised, it is converted to a ketone. The hydrogen from the hydroxyl group is lost along with the hydrogen bonded …   Wikipedia

  • alcohol consumption — Introduction  the drinking of beverages containing ethyl alcohol. alcoholic beverages are consumed largely for their physiological and psychological effects, but they are often consumed within specific social contexts and may even be a part of… …   Universalium

  • alcohol dehydrogenase — An oxidoreductase that reversibly converts an alcohol to an aldehyde (or ketone) with NAD+ as the H acceptor. For example, ethanol + NAD+ ⇄ acetaldehyde + NADH. SEE ALSO: a. (acceptor) …   Medical dictionary

  • alcohol dehydrogenase (NADP+) — al·co·hol de·hy·dro·gen·ase (NADP+) (alґkə hol de hiґdro jən ās) [EC 1.1.1.2] an enzyme of the oxidoreductase class that catalyzes the reversible oxidation of primary (or secondary) alcohols to aldehydes (or ketones), using NADP+… …   Medical dictionary

  • alcohol dehydrogenase (NAD(P)+) — al·co·hol de·hy·dro·gen·ase (NAD(P)+) (alґkə hol de hiґdro jən ās) [EC 1.1.1.71] an enzyme of the oxidoreductase class that catalyzes the reversible oxidation of primary or secondary alcohols to aldehydes or ketones respectively,… …   Medical dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”