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Information about Dehydration Reaction

This article is about chemical reactions resulting in the loss of water from a molecule. For the removal of water from solvents and reagents, see desiccation.
In chemistry, a dehydration reaction is usually defined as a chemical reaction that involves the loss of water from the reacting molecule. Dehydration reactions are a subset of elimination reactions. Because the hydroxyl group (-OH) is a poor leaving group, having an Brønsted acid catalyst often helps by protonating the hydroxyl group to give the better leaving group, -OH2+.

In organic synthesis, there are many examples of dehydration reactions:
:2 R-OH → R-O-R + H2O
:R-CH2-CHOH-R → R-CH=CH-R + H2O
:2 RCO2H → (RCO)2O + H2O
:RCONH2 → R-CN + H2O
Enlarge picture
Dienol benzene rearrangement
Some dehydration reactions can be mechanistically complex, for instance the reaction of a sugar with concentrated sulphuric acid (experiment with video) to form carbon involves formation of carbon carbon bonds.[1]
C12H22O11 + 98% Sulfuric acid → 12 C (graphitic foam) + 11 H2O steam + Sulfuric acid/water mixture


The reaction is driven by the strongly exothermic reaction sulfuric acid has with water. (Beware that this reaction produces dangerous sulfuric-acid containing steam, and should only be performed in a fume-hood or well ventilated area.)

Common dehydrating agents; concentrated sulfuric acid, concentrated phosphoric acid, hot aluminium oxide, hot ceramic.

See also

References

1. ^ Margaret Jevnik Gentles, Jane B. Moss, Hershel L. Herzog, and E. B. Hershberg (1958). "The Dienol-Benzene Rearrangement. Some Chemistry of 1,4-Androstadiene-3,17-dione". J. Am. Chem. Soc. 80 (14): 3702 - 3705. DOI:10.1021/ja01547a058. 
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately-well sealed container.
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An elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism [1]. Either the unsaturation of the molecule increases (as in most organic elimination reactions) or the valence of an atom
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ACID (Atomicity, Consistency, Isolation, Durability) is a set of properties that guarantee that database transactions are processed reliably. In the context of databases, a single logical operation on the data is called a transaction.
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Organic synthesis is the construction of organic molecules via chemical processes. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has developed into one of the most important aspects of
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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.
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Ether is the general name for a class of chemical compounds which contain an ether group — an oxygen atom connected to two (substituted) alkyl or aryl groups — of general formula R–O–R'.
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alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond. The simplest alkenes, with only one double bond and no other functional groups, form a homologous series of hydrocarbons with the general formula
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Carboxylic acids are organic acids characterized by the presence of a carboxyl group, which has the formula -C(=O)OH, usually written -COOH or -CO2H. [1] Carboxylic acids are Bronsted acids — they are proton donors.
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acid anhydride is an organic compound which has two acyl groups bound to the same oxygen atom.[1] When the two acyl groups are directly derived from a carboxylic acid (the most common case), the general formula is RC(O)OC(O)R.
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amide is one of two kinds of compounds:
  • the organic functional group characterized by a carbonyl group (C=O) linked to a nitrogen atom (N), or a compound that contains this functional group (pictured to the right); or
  • a particular kind of nitrogen anion.

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A nitrile is any organic compound which has a -C≡N functional group. The -C≡N functional group is called a nitrile group. In the -CN group, the carbon atom and the nitrogen atom are triple bonded together.
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A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule.
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Sulfuric (or sulphuric) acid, H2SO4, is a strong mineral acid. It is soluble in water at all concentrations. It was once known as oil of vitriol, coined by the 8th-century Arabian alchemist Jabir ibn Hayyan (Geber) after his discovery of the chemical.
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Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is a mineral (inorganic) acid having the chemical formula H3PO4.
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Aluminium oxide is an amphoteric oxide of aluminium with the chemical formula Al2O3. It is also commonly referred to as alumina in the mining, ceramic and materials science communities.
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In organic chemistry, a hydration reaction is a chemical reaction in which a hydroxyl group (OH-) and a hydrogen cation (an acidic proton) are added to the two carbon atoms bonded together in the carbon-carbon double bond which makes up an alkene functional group.
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Journal of the American Chemical Society (usually abbreviated as J. Am. Chem. Soc., or JACS), is a peer-reviewed scientific journal, published since 1879 by the American Chemical Society.
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digital object identifier (or DOI) is a permanent identifier given to a document, which is not related to its current location. A typical use of a DOI is to give a scientific paper or article a unique identifying number that can be used by anyone to locate details of the paper, and
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