Hydrogenation is a reductive chemical reaction which results in an addition of hydrogen (H₂) usually to saturate organic compounds. Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 In Chemistry, saturation has five different meanings In Physical chemistry, saturation is the point at which a Solution of a substance An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. The process constitutes the addition of hydrogen atoms to the double bonds of a molecule through the use of a catalyst. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Hydrogen also adds to triple bonds if they are present. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Typical substrates include alkenes, alkynes, ketones, nitriles, and imines. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2. A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or A nitrile is any Organic compound which has a - C ≡ N Functional group. An imine is a Functional group or Chemical compound containing a Carbon – Nitrogen Double bond. ^[1] Most hydrogenations involve the direct addition of diatomic hydrogen (H₂) but some involve the alternative sources of hydrogen, not H₂: these processes are called transfer hydrogenations. Transfer hydrogenation is the addition of Hydrogen (H2 dihydrogen in inorganic and organometallic chemistry to a Molecule from a The reverse reaction, removal of hydrogen, is called dehydrogenation. Dehydrogenation is a chemical reaction that involves the elimination of Hydrogen (H2 A reaction involving hydrogen and cleavage of a carbon-oxygen bond or carbon-nitrogen bond is called Hydrogenolysis. A carbon-oxygen bond is a Covalent bond between Carbon and Oxygen and one of the most abundant in Organic chemistry and Biochemistry A carbon-nitrogen bond is a Covalent bond between Carbon and Nitrogen and one of the most abundant in Organic chemistry and Biochemistry Hydrogenolysis is a Chemical reaction whereby a carbon-carbon or carbon- Heteroatom single bond is cleaved or undergoes "lysis" by hydrogen Hydrogenation differs from protonation or hydride addition (e. In chemistry protonation is the addition of a proton ( H[[Cation +]] to an Atom, Molecule, or Ion. Hydride is the name given to the negative Ion of Hydrogen, H− g. use of sodium borohydride): in hydrogenation, the products have the same charge as the reactants. Sodium borohydride, also known as sodium tetrahydroborate, has the Chemical formula Na[[boron B]] H 4

The classical example of a hydrogenation is the addition of hydrogen on unsaturated bonds between carbon atoms, converting alkenes to alkanes. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i A simple example is the hydrogenation of maleic acid to succinic acid depicted on the right. Maleic acid or ( Z)-butenedioic acid or cis -butenedioic acid or malenic acid or maleinic acid or toxilic Succinic acid ( IUPAC Systematic name: butanedioic acid; historically known as spirit of amber) is a Dicarboxylic acid. ^[2] Numerous important applications are found in the petrochemical, pharmaceutical and food industries. Petrochemicals are chemical products made from raw materials of Petroleum or other Hydrocarbon origin

Health concerns associated with the hydrogenation of unsaturated fats to produce saturated fats and trans fats is an important aspect of current consumer awareness. An unsaturated fat is a Fat or Fatty acid in which there are one or more Double bonds in the fatty acid chain Saturated fat is Fat that consists of Triglycerides containing only saturated Fatty acids Explanation Fat that occurs Trans fat is the common name for a type of Unsaturated fat with trans - isomer Fatty acid (s

Contents 1 Process 1.1 Catalysts 1.2 Mechanism of reaction 1.3 Hydrogen sources 1.4 Temperatures 2 Scope 3 In the food industry 3.1 Health implications 4 Hydrogenation of coal 5 History 6 Metal-free hydrogenation 7 See also 8 References 9 Further reading

Process

Hydrogenation has three components:

• the unsaturated substrate,
• the hydrogen (or hydrogen source) and, invariably,
• a catalyst.

The largest scale technological uses of H₂ are the hydrogenation and hydrogenolysis reactions associated with both heavy and fine chemicals industries. Hydrogenolysis is a Chemical reaction whereby a carbon-carbon or carbon- Heteroatom single bond is cleaved or undergoes "lysis" by hydrogen Hydrogenation is the addition of H₂ to unsaturated organic compounds such as alkenes to give alkanes and aldehydes to give alcohols. An organic compound is any member of a large class of Chemical compounds whose Molecules contain Carbon. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i An aldehyde is an organic compound containing a terminal Carbonyl group. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Hydrogenation reactions require metal catalysts, often those composed of platinum or similar precious metals. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Precious Metal is the eighteenth episode in the of the popular American Crime drama, which is set in Las Vegas, Nevada.

The addition of H₂ to an alkene affords an alkane in the protypical reaction:

RCH=CH₂ + H₂ → RCH₂CH₃ (R = alkyl, aryl)

An important characteristic of alkene and alkyne hydrogenations both homogeneous and heterogeneous is that hydrogen addition takes place with syn addition with hydrogen entering from the least hindered side. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i An alkyl is a Univalent radical consisting of Carbon and Hydrogen atoms arranged in a chain In the context of organic molecules aryl refers to any Functional group or Substituent derived from a Simple aromatic ring, may it be Phenyl In Organic chemistry, syn and anti addition are different ways in which two substituents can be added to a Double bond or Triple bond. ^[3]

Catalysts

With rare exception, no reaction below 480 °C occurs between H₂ and organic compounds in the absence of metal catalysts. The catalyst simultaneously binds both the H₂ and the unsaturated substrate and facilitates their union. Platinum group metals, particularly platinum, palladium, rhodium and ruthenium, are highly active catalysts. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Rh redirects here For other uses see Rh (disambiguation Rhodium (ˈroʊdiəm is a Chemical element with the symbol Ruthenium (ruːˈθiːniəm is a Chemical element that has the symbol Ru and Atomic number 44 Highly active catalysts operate at lower temperatures and lower pressures of H₂. Non-precious metal catalysts, especially those based on nickel (such as Raney nickel and Urushibara nickel) have also been developed as economical alternatives but they are often slower or require higher temperatures. Raney nickel (ˈreɪniː ˈnɪkəl is a solid Catalyst composed of fine grains of a Nickel - Aluminium Alloy, used in many industrial processes The trade-off is activity (speed of reaction) vs. cost of the catalyst and cost of the apparatus required for use of high pressures.

Two broad families of catalysts are known - homogeneous and heterogeneous. Homogeneous catalysts dissolve in the solvent that contains the unsaturated substrate. Heterogeneous catalysts are solids that are suspended in the same solvent with the substrate or are treated with gaseous substrate. In the pharmaceutical industry and for special chemical applications, soluble ""homogeneous"" catalyst are sometimes employed, such as the rhodium-based compound known as Wilkinson's catalyst, or the iridium-based Crabtree's catalyst. Homogeneous catalysis is a Chemistry term which describes Catalysis where the Catalyst is in the same phase (ie Rh redirects here For other uses see Rh (disambiguation Rhodium (ˈroʊdiəm is a Chemical element with the symbol Wilkinson's catalyst is the common name for chlorotris(triphenylphosphinerhodium(I, a Chemical compound with the formula RhCl(PPh33 (Ph Iridium (ɪˈrɪdiəm is a Chemical element that has the symbol Ir and Atomic number 77 Crabtree's catalyst is the name given to a complex of Iridium with 15-cyclooctadiene, tris-cyclohexylphosphine and Pyridine.

The activity and selectivity of catalysts can be adjusted by changing the environment around the metal, i. e. the coordination sphere. The primary or first coordination sphere, or simply coordination sphere of a Metal Ion in a Coordination complex is the set of Ligands Different faces of a crystalline heterogeneous catalyst display distinct activities, for example. Miller indices are a notation system in Crystallography for planes and directions in crystal (Bravais lattices In particular a family of Lattice planes Similarly, heterogeneous catalysts are affected by their supports, i. e. the material upon with the heterogeneous catalyst is bound. Homogeneous catalysts are affected by their ligands. In Chemistry, a ligand is either an Atom, Ion, or Molecule (see also Functional group) that bonds to a central metal generally In many cases, highly empirical modifications involve selective "poisons. " Thus, a carefully chosen catalyst can be used to hydrogenate some functional groups without affecting others, such as the hydrogenation of alkenes without touching aromatic rings, or the selective hydrogenation of alkynes to alkenes using Lindlar's catalyst. Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2. A Lindlar catalyst is a Heterogeneous Catalyst that consists of Palladium deposited on Calcium carbonate and treated with various forms For prochiral substrates, the selectivity of the catalyst can be adjusted such that one enantiomeric product is produced. In Chemistry, prochiral molecules can be converted from achiral to chiral in a single step

Mechanism of reaction

Because of its technological relevance, metal-catalyzed “activation” of H₂, has been the subject of considerable study, focusing on the reaction mechanisms of by which metals mediate these reactions. Chemistry, a reaction mechanism is the step by step Sequence of Elementary reactions by which overall Chemical change occurs. ^[4] First of all isotope labeling using deuterium can be used to determine the regiochemistry of the addition:

RCH=CH₂ + D₂ → RCHDCH₂D

Essentially, the metal binds to both components to give an intermediate alkene-metal(H)₂ complex. Isotopic labeling is a technique for tracking the passage of a sample of substance through a system Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth In Chemistry, regioselectivity is the preference of one direction of Chemical bond making or breaking over all other possible directions. The general sequence of reactions is:

• binding of the hydrogen to give a dihydride complex ("oxidative addition"):

L_nM + H₂ → L_nMH₂

• binding of alkene:

L_nM(η²H₂) + CH₂=CHR → L_n-1MH₂(CH₂=CHR) + L

• transfer of one hydrogen atom from the metal to carbon (migratory insertion)

L_n-1MH₂(CH₂=CHR) → L_n-1M(H)(CH₂-CH₂R)

• transfer of the second hydrogen atom from the metal to the alkyl group with simultaneous dissociation of the alkane ("reductive elimination")

L_n-1M(H)(CH₂-CH₂R) → L_n-1M + CH₃-CH₂R

Preceding the oxidative addition of H₂ is the formation of a dihydrogen complex. Dihydrogen complexes are Coordination complexes containing intact H2 as a Ligand.

Hydrogen sources

The obvious source of H₂ is the gas itself, often under pressure. Hydrogen can also be transferred from hydrogen-donor molecules, such as hydrazine,^[5][6] dihydronaphthalene, dihydroanthracene, isopropanol, and formic acid. Hydrazine is a Chemical compound with the formula N2H4 It has an Ammonia -like odor and is derived from the same industrial chemistry Isopropyl alcohol (also isopropanol, iso, isopro, Rubbing alcohol, or the abbreviation IPA) is a common name for Formic acid (systematically called methanoic acid) is the simplest Carboxylic acid. ^[7][8] Transfer hydrogenation can be metal catalysed. Transfer hydrogenation is the addition of Hydrogen (H2 dihydrogen in inorganic and organometallic chemistry to a Molecule from a Hydrogenation does proceed from some hydrogen donors without catalysts, examples being diimide and aluminium isopropoxide. Aluminium isopropoxide is the Chemical compound usually described with the formula Al(O-i-Pr3 where i-Pr is the Isopropyl group (CH(CH32 Some reactions (e. g. reduction of thioketals) do not require the addition of hydrogen if a freshly prepared Raney Nickel catalyst is used; sufficient hydrogen is deposited on the catalyst as it is prepared. A thioketal in Chemistry is the Sulfur analogue of a Ketal with one of the Oxygen replaced by sulfur Raney nickel (ˈreɪniː ˈnɪkəl is a solid Catalyst composed of fine grains of a Nickel - Aluminium Alloy, used in many industrial processes

Temperatures

The reaction is carried out at different temperatures and pressures depending upon the substrate. Hydrogenation is a strongly exothermic reaction. In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but In the hydrogenation of vegetable oils and fatty acids, for example, the heat released is about 25 kcal per mole (105 kJ/mol), sufficient to raise the temperature of the oil by 1. 6-1. 7 °C per iodine number drop. The iodine value (or "iodine adsorption value" or "iodine number" or "iodine index" in Chemistry is the mass of Iodine in grams that

Scope

Alkynes can be selectively converted into alkenes in a so-called semihydrogenation, for instance with the compound Ethyl 2-Butynoate and catalyst palladium on barium sulfate and quinoline (which deactivates the catalyst enhancing chemoselectivity):^[9]

or with 4-(trimethylsilyl)-3-butyn-1-ol:^[10]

The next reaction featuring carvone is an example of homogeneous catalysis i. Alkynes are Hydrocarbons that have at least one Triple bond between two Carbon atoms with the formula CnH2n-2. In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Barium sulfate is a white crystalline solid with the chemical formula BaSO4 Quinoline, also known as 1-azanaphthalene, 1-benzazine, or benzopyridine, is a Heterocyclic Aromatic Organic compound. Chemical reactions are defined usually in small contexts (only up to a small number of neighbouring atoms such generalizations are a matter of utility Carvone is a member of a family of chemicals called terpenoids. Homogeneous catalysis is a Chemistry term which describes Catalysis where the Catalyst is in the same phase (ie e. the Wilkinson's catalyst:^[11]

Hydrogenation is sensitive to steric hindrance explaining the selectivity for reaction with the exocyclic double bond but not the internal double bond. Wilkinson's catalyst is the common name for chlorotris(triphenylphosphinerhodium(I, a Chemical compound with the formula RhCl(PPh33 (Ph See also Intramolecular forces ' Steric effects arise from the fact that each Atom within a Molecule occupies a certain An alicyclic compound is an Organic compound that is both Aliphatic and cyclic

The compound 1-naphthol is completely reduced to a mixture of decalin-ol isomers. beta-Naphtholsvg|thumb|150px|β-Naphthol]] Naphthol, or hydroxynaphthalene or naphthalenol is either of two colorless crystalline solids with the formula C10H7OH Decahydronaphthalene (also known as decalin, or as bicyclodecane) a Bicyclic Organic compound, is an industrial Solvent. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. ^[12]

The compound resorcinol, hydrogenated with Raney nickel in presence of aqeous sodium hydroxide forms an enolate which is alkylated with methyl iodide to 2-methyl-1,3-cyclohexandione:^[13]

An effective catalyst is the Lindlar catalyst for example in the conversion of phenylacetylene to styrene. Resorcinol (or resorcin) is a Chemical compound from the dihydroxy Phenols it is the 13- Isomer of Benzenediol. Raney nickel (ˈreɪniː ˈnɪkəl is a solid Catalyst composed of fine grains of a Nickel - Aluminium Alloy, used in many industrial processes Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature Enols (also known as alkenols) are Alkenes with a Hydroxyl group affixed to one of the carbon atoms composing the Double bond. Iodomethane, commonly called Methyl iodide and commonly abbreviated "MeI" is the Chemical compound with the formula CH3I A Lindlar catalyst is a Heterogeneous Catalyst that consists of Palladium deposited on Calcium carbonate and treated with various forms Phenylacetylene is an Alkyne hydrocarbon containing a Phenyl group Styrene, also known as vinyl benzene as well as many other names (see table is an Organic compound with the Chemical formula C6H5CH=CH2 ^[14]

Hydrogenation is also used in organic reduction of nitro compounds, for instance aromatic nitro compounds in combination with palladium on carbon and formaldehyde:^[15]

or the reduction of imines, for example in a synthesis of m-tolylbenzylamine:^[16]

or the reduction of nitriles for instance in a synthesis of phenethylamine with Raney nickel and ammonia:^[17]

In the food industry

Types of fats in food
Unsaturated fat Monounsaturated fat Polyunsaturated fat Trans fat Omega fatty acids: ω−3 ω−6 ω−9 Saturated fat Interesterified fat
See also
Fatty acid Essential fatty acid

Hydrogenation is widely applied to the processing of vegetable oils and fats. Organic reductions or organic oxidations or organic redox reactions are Redox reactions that take place with Organic compounds In Organic Palladium on carbon, often referred to as Pd/C, is a form of Palladium used for Catalysis. Formaldehyde is a Chemical compound with the formula H2CO It is the simplest Aldehyde —an organic compound containing a terminal Carbonyl An imine is a Functional group or Chemical compound containing a Carbon – Nitrogen Double bond. A nitrile is any Organic compound which has a - C ≡ N Functional group. Phenethylamine, or β -phenylethylamine or 2-phenylethylamine is an Alkaloid and Monoamine. Raney nickel (ˈreɪniː ˈnɪkəl is a solid Catalyst composed of fine grains of a Nickel - Aluminium Alloy, used in many industrial processes Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water Food is any substance usually composed primarily of Carbohydrates Fats water and/or Proteins that can be eaten or drunk by an An unsaturated fat is a Fat or Fatty acid in which there are one or more Double bonds in the fatty acid chain For discussion how dietary fats affect cardiovascular health see Diet and heart disease. In nutrition polyunsaturated fat is an abbreviation of polyunsaturated Fatty acid. Trans fat is the common name for a type of Unsaturated fat with trans - isomer Fatty acid (s n −3 fatty acids (popularly referred to as ω−3 fatty acids or omega-3 fatty acids) are a family of unsaturated Fatty acids that n −6 fatty acids (popularly referred to as ω−6 fatty acids or omega-6 fatty acids) are a family of unsaturated Fatty acids n −9 fatty acids (popularly referred to as ω−9 fatty acids or omega-9 fatty acids) are a family of unsaturated Fatty acids which Saturated fat is Fat that consists of Triglycerides containing only saturated Fatty acids Explanation Fat that occurs Interesterified fats are oils that have been chemically modified (e In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Essential fatty acids, or EFAs are Fatty acids that cannot be constructed within an organism from other components (generally all references are to humans by any known chemical Fats consist of a wide group of compounds that are generally soluble in organic solvents and largely insoluble in water Complete hydrogenation converts unsaturated fatty acids to saturated ones. In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which Saturated fat is Fat that consists of Triglycerides containing only saturated Fatty acids Explanation Fat that occurs In practice the process is not usually carried to completion. Since the original oils usually contain more than one double bond per molecule (that is, they are poly-unsaturated), the result is usually described as partially hydrogenated vegetable oil; that is some, but usually not all, of the double bonds in each molecule have been reduced. This is done by restricting the amount of hydrogen (or reducing agent) allowed to react with the fat.

Hydrogenation results in the conversion of liquid vegetable oils to solid or semi-solid fats, such as those present in margarine. Margarine (ˈmɑrdʒərɨn /ˈmɑrdʒəriːn/ or /ˈmɑrgəriːn/ as a generic term can indicate any of a wide range of Butter substitutes Changing the degree of saturation of the fat changes some important physical properties such as the melting point, which is why liquid oils become semi-solid. Semi-solid fats are preferred for baking because the way the fat mixes with flour produces a more desirable texture in the baked product. Since partially hydrogenated vegetable oils are cheaper than animal source fats, are available in a wide range of consistencies, and have other desirable characteristics (e. g. , increased oxidative stability (longer shelf life)), they are the predominant fats used in most commercial baked goods. Fat blends formulated for this purpose are called shortenings. Shortening is a semisolid Fat used in food preparation especially baked goods and is so called because it promotes a "short" or crumbly texture (as in Shortbread

Health implications

Main article: trans fat

A side effect of incomplete hydrogenation having implications for human health is the isomerization of the remaining unsaturated carbon bonds. Trans fat is the common name for a type of Unsaturated fat with trans - isomer Fatty acid (s In Chemistry isomerisation is the process by which one Molecule is transformed into another molecule which has exactly the same atoms but the atoms are rearranged The cis configuration of these double bonds predominates in the unprocessed fats in most edible fat sources, but incomplete hydrogenation partially converts these molecules to trans isomers, which have been implicated in circulatory diseases including heart disease (see trans fats). Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of Trans-2-butenesvg|right|thumb|Trans-2-butene]] In Chemistry, cis-trans isomerism or geometric isomerism or configuration isomerism is a form of Heart disease is an Umbrella term for a variety for different diseases affecting the Heart. Trans fat is the common name for a type of Unsaturated fat with trans - isomer Fatty acid (s The catalytic hydrogenation process favors the conversion from cis to trans bonds because the trans configuration has lower energy than the natural cis one. At equilibrium, the trans/cis isomer ratio is about 2:1. Food legislation in the US and codes of practice in EU has long required labels declaring the fat content of foods in retail trade, and more recently, have also required declaration of the trans fat content.

In 2006, New York City adopted the US's first major municipal ban on most artificial trans fats in restaurant cooking. The City of New York ^[18]

Hydrogenation of coal

Main article: Bergius process

History

The earliest hydrogenation is that of platinum catalyzed addition of hydrogen to oxygen in the Döbereiner's lamp, a device commercialized as early as 1823. The Bergius Process is a method of production of liquid Hydrocarbons for use as Synthetic fuel by Hydrogenation of high-volatile bituminous coal at high Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Döbereiner's Lamp is a Lighter invented in 1823 by the German chemist Johann Wolfgang Döbereiner, the lighter is based on the The French chemist Paul Sabatier is considered the father of the hydrogenation process. Paul Sabatier ( November 5, 1854 &ndash August 14, 1941) was a French chemist born at Carcassonne. In 1897 he discovered that the introduction of a trace of nickel as a catalyst facilitated the addition of hydrogen to molecules of gaseous carbon compounds in what is now known as the Sabatier process. The Sabatier reaction or Sabatier process involves the reaction of Hydrogen with Carbon dioxide at elevated temperatures and pressures in the presence of For this work Sabatier won half of the 1912 Nobel Prize in Chemistry. The Nobel Prize in Chemistry (Nobelpriset i kemi is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of Chemistry. Wilhelm Normann was awarded a patent in Germany in 1902 and in Britain in 1903 for the hydrogenation of liquid oils using hydrogen gas, which was the beginning of what is now a very large industry world wide. Wilhelm Normann ( January 16, 1870, Petershagen - May 1, 1939, Chemnitz) (sometimes also spelled Norman) was The commercially very important Haber-Bosch process (ammonia hydrogenation) was first described in 1905 and less so Fischer-Tropsch process (carbon monoxide hydrogenation) in 1922. The Haber process, also called the Haber–Bosch process, is the Nitrogen fixation reaction of Nitrogen and Hydrogen, over an iron substrate The Fischer-Tropsch process (or Fischer-Tropsch Synthesis is a catalyzed chemical reaction in which synthesis gas ( Syngas) a mixture of Carbon monoxide Another commercial application is the oxo process (1938), a hydrogen mediated coupling of aldehydes with alkenes. Hydroformylation, also known as oxo synthesis, is an important industrial process for the production of aldehydes from alkenes Wilkinson's catalyst was the first homogeneous catalyst developed in the 1960s and Noyori asymmetric hydrogenation (1987) one of the first applications in asymmetric synthesis. Wilkinson's catalyst is the common name for chlorotris(triphenylphosphinerhodium(I, a Chemical compound with the formula RhCl(PPh33 (Ph Homogeneous catalysis is a Chemistry term which describes Catalysis where the Catalyst is in the same phase (ie The Noyori asymmetric hydrogenation is a Chemical reaction described as an asymmetric reduction of β- keto - Esters Both Asymmetric synthesis, also called chiral synthesis, enantioselective synthesis or stereoselective synthesis, is Organic synthesis which A 2007 review article advocated the use of more hydrogenations in C-C coupling reactions like the oxo process. Hydroformylation, also known as oxo synthesis, is an important industrial process for the production of aldehydes from alkenes ^[19]

Metal-free hydrogenation

For all practical purposes, hydrogenation requires a metal catalyst. Although, there are some metal-free catalytic systems that are investigated in academic research. One such system for reduction of ketones consists of tert-butanol and potassium tert-butoxide and very high temperatures. A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or tert -Butanol, or 2-methyl-2-propanol (colourless liquid or white solid depending on the ambient temperature is the simplest Tertiary alcohol. An alkoxide is the Conjugate base of an Alcohol and therefore consists of an organic group bonded to a negatively charged Oxygen atom ^[20] The reaction depicted below describes the hydrogenation of benzophenone:

A chemical kinetics study^[21] found this reaction is first order in all three reactants suggesting a cyclic 6-membered transition state. Benzophenone is the Organic compound with the formula ( C 6 H 52C O, generally abbreviated Ph 2CO Chemical kinetics, also known as reaction kinetics is the study of rates of chemical processes The reaction rate or rate of reaction for a Reactant or product in a particular reaction is intuitively defined as how fast a reaction takes The transition state of a Chemical reaction is a particular configuration along the Reaction coordinate.

Another system is based on the phosphine-borane compound (1). Phosphine is the common name for phosphorus hydride (PH3 also known by the IUPAC name phosphane and occasionally phosphamine. In chemistry a borane is a chemical compound of Boron and Hydrogen. It reversibly accepts dihydrogen at relatively low temperatures to form the phosphonium borate 2 which is able to reduce a simple hindered imine. In chemistry the phosphonium Cation is a positively charged polyatomic ion with the chemical formula PH4+ resulting from Protonation of Borates in Chemistry are Chemical compounds containing Boron bonded to three Oxygen atoms written as B(OR3 An imine is a Functional group or Chemical compound containing a Carbon – Nitrogen Double bond. ^[22]

See also

• Dehydrogenation
• Transfer hydrogenation
• Hydrogenolysis
• Hydrodesulfurization, Hydrotreater and Oil desulfurization

References

Further reading

• Jang ES, Jung MY, Min DB (2005). Angewandte Chemie is a weekly Peer-reviewed Chemistry journal that covers all disciplines of chemistry A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. "Hydrogenation for Low Trans and High Conjugated Fatty Acids" (PDF). Comprehensive Reviews in Food Science and Food Safety 1.  

• Fred A. Kummerow (2008). Cholesterol Won't Kill You, But Trans Fat Could. Trafford. ISBN 142513808.  

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