Dehydrogenation is a chemical reaction that involves the elimination of hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 . It is the reverse process of hydrogenation
Hydrogenation, to treat with hydrogen, also a form of chemical reduction, is a chemical reaction between molecular hydrogen and another compound or element, usually in the presence of a catalyst. The process is commonly employed to reduce or saturate organic compounds. Hydrogenation typically...

. Dehydrogenation reactions may be either large scale industrial processes or smaller scale laboratory procedures.

Classes of the reaction

There are a variety of classes of dehydrogenations:
  • Aromatization — Six-membered alicyclic
    Alicyclic compound
    An alicyclic compound is an organic compound that is both aliphatic and cyclic. They contain one or more all-carbon rings which may be either saturated or unsaturated, but do not have aromatic character...

     rings can be aromatized in the presence of hydrogenation catalysts, the elements sulfur
    Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

     and selenium
    Selenium is a chemical element with atomic number 34, chemical symbol Se, and an atomic mass of 78.96. It is a nonmetal, whose properties are intermediate between those of adjacent chalcogen elements sulfur and tellurium...

    , or quinone
    A quinone is a class of organic compounds that are formally "derived from aromatic compounds [such as benzene or naphthalene] by conversion of an even number of –CH= groups into –C– groups with any necessary rearrangement of double bonds," resulting in "a fully conjugated cyclic dione structure."...

    s (such as DDQ
    2,3-Dichloro-5,6-dicyano-1,4-benzoquinone is the chemical reagent with formula C8Cl2N2O2. This oxidant is useful for the dehydrogenation of alcohols, phenols and steroid ketones in organic chemistry. DDQ decomposes in water, but is stable in aqueous mineral acid.-Preparation:Synthesis of DDQ...

  • Oxidation — The conversion of alcohols to ketones or aldehydes can be effected by metal catalysts such as copper chromite. In the Oppenauer oxidation
    Oppenauer oxidation
    Oppenauer oxidation, named after Rupert Viktor Oppenauer, is a gentle method for selectively oxidizing secondary alcohols to ketones.The reaction is the opposite of Meerwein-Ponndorf-Verley reduction. The alcohol is oxidized with aluminium isopropoxide in excess acetone...

    , hydrogen is transferred from one alcohol to another to bring about the oxidation.
  • Dehydrogenation of amines — amines can be converted to nitriles using a variety of reagents, such as Iodine pentafluoride
    Iodine pentafluoride
    Iodine pentafluoride is an interhalogen compound with chemical formula IF5. It is a fluoride of iodine. It is a colourless or yellow liquid with a density of 3.250 g cm−3. It was first synthesized by Henri Moissan in 1891 by burning solid iodine in fluorine gas...

  • Dehydrogenation of paraffins and olefins — paraffins like n-pentane
    Pentane is an organic compound with the formula C5H12 — that is, an alkane with five carbon atoms. The term may refer to any of three structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, pentane means exclusively the n-pentane isomer; the other two being called...

     and isopentane
    Isopentane, C5H12, also called methylbutane or 2-methylbutane, is a branched-chain alkane with five carbon atoms. Isopentane is an extremely volatile and extremely flammable liquid at room temperature and pressure. The normal boiling point is just a few degrees above room temperature and...

     can be converted to pentene
    Pentene refers to all the alkenes with chemical formula . Each contains one double bond within its molecular structure. There are a total of five different compounds in this class, differing from each other by whether the carbon atoms are attached linearly or in a branched structure, and whether...

     and isoprene
    Isoprene , or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=CCH=CH2. Under standard conditions it is a colorless liquid...

     using chromium
    Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...

     (III) oxide as a catalyst at 500 degree C.

Dehydrogenation converts saturated fats to unsaturated fats. Enzymes that catalyze dehydrogenation are called dehydrogenases. Dehydrogenation processes are used extensively to produce styrene in the fine chemicals
Fine chemicals
Fine chemicals are pure, single chemical substances that are commercially produced with chemical reactions for highly specialized applications. Fine chemicals produced can be categorized into active pharmaceutical ingredients and their intermediates, biocides, and specialty chemicals for technical...

, oleochemicals, petrochemicals, and detergents industries.

Feed stocks

Likely feed stocks to be used in this dehydrogenation process include hydrocarbons, such as:
  • Ethylbenzene
    Ethylbenzene is an organic compound with the formula C6H5CH2CH3. This aromatic hydrocarbon is important in the petrochemical industry as an intermediate in the production of styrene, which in turn is used for making polystyrene, a common plastic material....

  • Methanol
    Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

  • Butane
    Butane is a gas with the formula C4H10 that is an alkane with four carbon atoms. The term may refer to any of two structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, butane refers only to the unbranched n-butane isomer; the other one being called "methylpropane" or...

  • Butene
  • Cyclohexane
    Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is used as a nonpolar solvent for the chemical industry, and also as a raw material for the industrial production of adipic acid and caprolactam, both of which being intermediates used in the production of nylon...

Inorganic compounds, such as hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

 or hydrogen iodide
Hydrogen iodide
Hydrogen iodide is a diatomic molecule. Aqueous solutions of HI are known as iohydroic acid or hydroiodic acid, a strong acid. Gas and aqueous solution are interconvertible...

, are also used.
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