organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

, a hydrocarbon is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. The ...

consisting entirely of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

and

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

. Hydrocarbons are examples of

group 14 hydride Group 14 hydrides are chemical compounds composed of hydrogen atoms and group 14 atoms (the elements of group 14 are carbon, silicon, germanium, tin, lead and flerovium). Tetrahydrides The tetrahydride series has the chemical formula XH4, with X ...

s. Hydrocarbons are generally colourless and

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, th ...

, and their odors are usually weak or exemplified by the odors of

gasoline Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic co ...

and lighter fluid. They occur in a diverse range of molecular structures and phases: they can be

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

es (such as

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...

and

propane Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...

liquid A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...

s (such as

hexane Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14. It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...

and

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

), low melting

solid Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...

s (such as

paraffin wax Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal, or oil shale that consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and begins to m ...

and

naphthalene Naphthalene is an organic compound with formula . It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass. As an aromati ...

) or

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

s (such as

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including bo ...

and

polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ...

). In the

fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels m ...

industries, ''hydrocarbon'' refers to the naturally occurring

petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...

and

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

, and to their hydrocarbon derivatives and purified forms. Combustion of hydrocarbons is the main source of the world's energy. Petroleum is the dominant raw-material source for organic

commodity chemicals Commodity chemicals (or bulk commodities or bulk chemicals) are a group of chemicals that are made on a very large scale to satisfy global markets. The average prices of commodity chemicals are regularly published in the chemical trade magazines an ...

such as solvents and polymers. Most anthropogenic (human-generated) emissions of

greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...

es are

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

from the burning of fossil fuels, and methane released from natural gas handling and from agriculture.

Types

As defined by the

International Union of Pure and Applied Chemistry The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...

nomenclature of organic chemistry ''Nomenclature of Organic Chemistry'', commonly referred to by chemists as the ''Blue Book'', is a collection of recommendations on organic chemical nomenclature published at irregular intervals by the International Union of Pure and Applied C ...

, the classifications for hydrocarbons are: #

Saturated Saturation, saturated, unsaturation or unsaturated may refer to: Chemistry * Saturation, a property of organic compounds referring to carbon-carbon bonds ** Saturated and unsaturated compounds **Degree of unsaturation ** Saturated fat or fatty ac ...

hydrocarbons are the simplest of the hydrocarbon types. They are composed entirely of

single bond In chemistry, a single bond is a chemical bond between two atoms involving two valence electrons. That is, the atoms share one pair of electrons where the bond forms. Therefore, a single bond is a type of covalent bond. When shared, each of th ...

s and are saturated with hydrogen. The formula for acyclic saturated hydrocarbons (i.e.,

alkanes In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

) is CH. The most general form (true of both linear and branched species and those with and those without one or more rings) of saturated hydrocarbons is CH, where ''r'' is the number of rings. Those with exactly one ring are the

cycloalkanes In organic chemistry, the cycloalkanes (also called naphthenes, but distinct from naphthalene) are the monocyclic saturated hydrocarbons. In other words, a cycloalkane consists only of hydrogen and carbon atoms arranged in a structure containing ...

. Saturated hydrocarbons are the basis of

petroleum fuels Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...

and are found as either linear or branched species. One or more of the hydrogen atoms can be replaced with other atoms, for example chlorine or another halogen, which is called a substitution reaction. An example would be the conversion of methane to

chloroform Chloroform, or trichloromethane, is an organic compound with chemical formula, formula Carbon, CHydrogen, HChlorine, Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to ...

using a

chlorination reaction In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, ...

. Note that halogenating a hydrocarbon produces something that is not a hydrocarbon. It is a very common and useful process. Hydrocarbons with the same

molecular formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

but different

structural formula The structural formula of a chemical compound is a graphic representation of the molecular structure (determined by structural chemistry methods), showing how the atoms are possibly arranged in the real three-dimensional space. The chemical bondi ...

e are called

structural isomer In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a chemical compound, compound is another compound whose molecule has the same number of atoms of each element, but with logically distinct chemical bond, b ...

s. As given in the example of 3-methylhexane and its higher homologues, branched hydrocarbons can be

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

. Chiral saturated hydrocarbons constitute the side chains of

biomolecule A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large ...

s such as

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to a ...

and

tocopherol Tocopherols (; TCP) are a class of organic chemical compounds (more precisely, various methylated phenols), many of which have vitamin E activity. Because the vitamin activity was first identified in 1936 from a dietary fertility factor in rats, i ...

. #

Unsaturated hydrocarbon 300px, Structure of an ethene molecule, the simplest unsaturated hydrocarbon Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. The term "unsaturated" means more hydrogen atoms may ...

s have one or more double or triple bonds between carbon atoms. Those with one or more double bonds are called

alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

s. Those with one

double bond In chemistry, a double bond is a covalent bond between two atoms involving four bonding electrons as opposed to two in a single bond. Double bonds occur most commonly between two carbon atoms, for example in alkenes. Many double bonds exist betw ...

have the formula CH (assuming non-cyclic structures). Those containing

triple bond A triple bond in chemistry is a chemical bond between two atoms involving six bonding electrons instead of the usual two in a covalent single bond. Triple bonds are stronger than the equivalent single bonds or double bonds, with a bond order o ...

s are called

alkyne \ce \ce Acetylene \ce \ce \ce Propyne \ce \ce \ce \ce 1-Butyne In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...

. Those with one triple bond have the formula CH. #

Aromatic hydrocarbon Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...

s, also known as

arene Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...

s, are hydrocarbons that have at least one

aromatic ring In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to saturat ...

. 10% of total nonmethane organic carbon emission are aromatic hydrocarbons from the exhaust of gasoline-powered vehicles. The term 'aliphatic' refers to non-aromatic hydrocarbons. Saturated aliphatic hydrocarbons are sometimes referred to as 'paraffins'. Aliphatic hydrocarbons containing a double bond between carbon atoms are sometimes referred to as 'olefins'.

Usage

The predominant use of hydrocarbons is as a combustible

fuel A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...

source. Methane is the predominant component of natural gas. The C⁶ through C¹⁰ alkanes, alkenes and isomeric cycloalkanes are the top components of

naphtha Naphtha ( or ) is a flammable liquid hydrocarbon mixture. Mixtures labelled ''naphtha'' have been produced from natural gas condensates, petroleum distillates, and the distillation of coal tar and peat. In different industries and regions ''n ...

jet fuel Jet fuel or aviation turbine fuel (ATF, also abbreviated avtur) is a type of aviation fuel designed for use in aircraft powered by gas-turbine engines. It is colorless to straw-colored in appearance. The most commonly used fuels for commercial a ...

and specialized industrial solvent mixtures. With the progressive addition of carbon units, the simple non-ring structured hydrocarbons have higher

viscosities The viscosity of a fluid is a measure of its drag (physics), resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quant ...

, lubricating indices, boiling points,

solidification Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid o ...

temperatures, and deeper color. At the opposite extreme from methane lie the heavy

tar Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. "a dark brown or black bit ...

s that remain as the ''lowest fraction'' in a crude oil

refining {{Unreferenced, date=December 2009 Refining (also perhaps called by the mathematical term affining) is the process of purification of a (1) substance or a (2) form. The term is usually used of a natural resource that is almost in a usable form, b ...

retort. They are collected and widely utilized as roofing compounds, pavement composition (

bitumen Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

), wood preservatives (the

creosote Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics. Some creosote types were ...

series) and as extremely high viscosity shear-resisting liquids. Some large-scale non-fuel applications of hydrocarbons begins with ethane and propane, which are obtained from petroleum and natural gas. These two gases are converted either to syngas or to

ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene i ...

and

propylene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petrole ...

. These two alkenes are precursors to polymers, including

, polystyrene, acrylates, polypropylene, etc. Another class of special hydrocarbons is BTX, a mixture of

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) at ...

, and the three xylene isomers. Global consumption of benzene in 2021 is estimated at more than 58 million metric tons, which will increase to 60 million tons in 2022. Hydrocarbons are also prevalent in nature. Some eusocial arthropods, such as the Brazilian stingless bee, ''

Schwarziana quadripunctata ''Schwarziana quadripunctata'' is a small, stingless bee found in a stretch of the South American Amazon from Goiás, Brazil, through Paraguay, to Misiones, Argentina.Michener, C.D. (2007). ''The Bees of the World''. Baltimore: Johns Hopkins Univ ...

'', use unique

cuticular hydrocarbon Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

"scents" in order to determine kin from non-kin. This hydrocarbon composition varies between age, sex, nest location, and hierarchal position. There is also potential to harvest hydrocarbons from plants like ''

Euphorbia lathyris ''Euphorbia lathyris'', the caper spurge or paper spurge, is a species of spurge native to southern Europe (Italy, Greece, Spain, Portugal), northwest Africa, and eastward through southwest Asia to western China.''Flora Europaea'Euphorbia lath ...

'' and '' E. tirucalli'' as an alternative and renewable energy source for vehicles that use diesel. Furthermore,

endophytic An endophyte is an endosymbiont, often a bacterium or fungus, that lives within a plant for at least part of its life cycle without causing apparent disease. Endophytes are ubiquitous and have been found in all species of plants studied to date; h ...

bacteria from plants that naturally produce hydrocarbons have been used in hydrocarbon degradation in attempts to deplete hydrocarbon concentration in polluted soils.

Reactions

The noteworthy feature of saturated hydrocarbons is their inertness. Unsaturated hydrocarbons (alkanes, alkenes and aromatic compounds) react more readily, by means of substitution, addition, polymerization. At higher temperatures they undergo dehydrogenation, oxidation and combustion.

Substitution

Of the classes of hydrocarbons, aromatic compounds uniquely (or nearly so) undergo substitution reactions. The chemical process practiced on the largest scale is the reaction of benzene and

ethene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds). Ethylene is ...

to give

ethylbenzene Ethylbenzene is an organic compound with the formula . It is a highly flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the petrochemical industry as an reaction intermediat ...

: : The resulting ethylbenzene is dehydrogenated to

styrene Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...

and then polymerized to manufacture

, a common

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...

material.

Free-radical substitution

Substitution reactions occur also in saturated hydrocarbons (all single carbon–carbon bonds). Such reactions require highly reactive reagents, such as

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

and

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reacti ...

. In the case of chlorination, one of the chlorine atoms replaces a hydrogen atom. The reactions proceed via

free-radical pathway A free-radical reaction is any chemical reaction involving free radicals. This reaction type is abundant in organic reactions. Two pioneering studies into free radical reactions have been the discovery of the triphenylmethyl radical by Moses Gomber ...

s, in which the halogen first dissociates into a two neutral radical atoms ( homolytic fission). :CH + Cl → CHCl + HCl :CHCl + Cl → CHCl + HCl all the way to CCl (

carbon tetrachloride Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVAC ...

) :CH + Cl → CHCl + HCl :CHCl + Cl → CHCl + HCl all the way to CCl (

hexachloroethane Hexachloroethane, also known as perchloroethane is the organochlorine compound with the chemical formula . It is white solid at room temperature with a camphor-like odor. It has been used by the military in smoke compositions, such as base-eject ...

)

Addition

Addition reactions apply to alkenes and alkynes. In this reaction a variety of reagents add "across" the pi-bond(s). Chlorine, hydrogen chloride,

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, and

are illustrative reagents.

Addition polymerization

Alkenes In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, an ...

and some alkynes also undergo

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are ...

by opening of the multiple bonds to produce

polybutylene Polybutylene (polybutene-1, poly(1-butene), PB-1) is a polyolefin or saturated polymer with the chemical formula (CH2CH(Et))n. Not be confused with polybutene, PB-1 is mainly used in piping. Production Polybutylene is produced by polymerisation ...

, and

. The alkyne

acetylene Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...

polymerizes to produce

polyacetylene Polyacetylene (IUPAC name: polyethyne) usually refers to an organic polymer with the repeating unit . The name refers to its conceptual construction from polymerization of acetylene to give a chain with repeating olefin groups. This compound i ...

. Oligomers (chains of a few monomers) may be produced, for example in the

Shell higher olefin process The Shell higher olefin process (SHOP) is a chemical process for the production of linear alpha olefins via ethylene oligomerization and olefin metathesis invented and exploited by Royal Dutch Shell.''Industrial Organic Chemistry'', Klaus Weisserme ...

, where

α-olefin In organic chemistry, alpha-olefins (or α-olefins) are a family of organic compounds which are alkenes (also known as olefins) with a chemical formula , distinguished by having a double bond at the primary or alpha (α) position.''Petrochemical ...

s are extended to make longer α-olefins by adding ethylene repeatedly.

Hydrogenation

Metathesis

Some hydrocarbons undergo ''metathesis'', in which substituents attached by C–C bonds are exchanged between molecules. For a single C–C bond it is

alkane metathesis Alkane metathesis is a class of chemical reaction in which an alkane is rearranged to give a longer or shorter alkane product. It is similar to olefin metathesis, except that olefin metathesis cleaves and recreates a carbon-carbon double bond, but ...

, for a double C–C bond it is

alkene metathesis Olefin metathesis is an organic reaction that entails the redistribution of fragments of alkenes (olefins) by the scission and regeneration of carbon-carbon double bonds. Because of the relative simplicity of olefin metathesis, it often creates ...

(olefin metathesis), and for a triple C–C bond it is

alkyne metathesis Alkyne metathesis is an organic reaction that entails the redistribution of alkyne chemical bonds. The reaction requires metal catalysts. Mechanistic studies show that the conversion proceeds via the intermediacy of metal alkylidyne complexes. T ...

High-temperature reactions

Cracking

=Dehydrogenation

Pyrolysis

Combustion

Combustion of hydrocarbons is currently the main source of the world's energy for

electric power generation Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery (transmission, distribution, etc.) to end users or its storag ...

, heating (such as home heating) and transportation. Often this energy is used directly as heat such as in home heaters, which use either

. The hydrocarbon is burnt and the heat is used to heat water, which is then circulated. A similar principle is used to create

electrical energy Electrical energy is energy related to forces on electrically charged particles and the movement of electrically charged particles (often electrons in wires, but not always). This energy is supplied by the combination of electric current and electr ...

power plants A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many pow ...

. Common properties of hydrocarbons are the facts that they produce steam,

and heat during

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combusti ...

and that

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

is required for combustion to take place. The simplest hydrocarbon,

, burns as follows: :CH + 2 O → 2 HO + CO + energy In inadequate supply of air,

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

gas and

water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

are formed: :2 CH + 3 O → 2 CO + 4 HO Another example is the combustion of

: :CH + 5 O → 4 HO + 3 CO + energy And finally, for any

linear alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whic ...

of n carbon atoms, :CH + O → (''n'' + 1) HO + ''n'' CO + energy. Partial oxidation characterizes the reactions of alkenes and oxygen. This process is the basis of

rancidification Rancidification is the process of complete or incomplete autoxidation or hydrolysis of fats and oils when exposed to air, light, moisture, or bacterial action, producing short-chain aldehydes, ketones and free fatty acids. When these processes oc ...

and paint drying.

Origin

The vast majority of hydrocarbons found on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

occur in

crude oil Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crude ...

, petroleum,

, and natural gas. Petroleum (literally "rock oil") and coal are generally thought to be products of decomposition of organic matter. Coal, in contrast to petroleum, is richer in carbon and poorer in hydrogen. Natural gas is the product of

methanogenesis Methanogenesis or biomethanation is the formation of methane coupled to energy conservation by microbes known as methanogens. Organisms capable of producing methane for energy conservation have been identified only from the domain Archaea, a group ...

. A seemingly limitless variety of compounds comprise petroleum, hence the necessity of refineries. These hydrocarbons consist of saturated hydrocarbons, aromatic hydrocarbons, or combinations of the two. Missing in petroleum are alkenes and alkynes. Their production requires refineries. Petroleum-derived hydrocarbons are mainly consumed for fuel, but they are also the source of virtually all synthetic organic compounds, including plastics and pharmaceuticals. Natural gas is consumed almost exclusively as fuel. Coal is used as a fuel and as a reducing agent in

metallurgy Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys. Metallurgy encompasses both the sc ...

. A small fraction of hydrocarbon found on earth, and all currently-known hydrocarbon found on other planets and moons, is thought to be abiological. Hydrocarbons such as ethylene, isoprene, and monoterpenes are emitted by living vegetation. Some hydrocarbons also are widespread and abundant in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

. Lakes of liquid methane and ethane have been found on

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictiona ...

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

's largest moon, as confirmed by the ''

Cassini–Huygens ''Cassini–Huygens'' ( ), commonly called ''Cassini'', was a space research, space-research mission by NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a space probe to study the planet Saturn and its system, i ...

'' space probe. Hydrocarbons are also abundant in nebulae forming

polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...

compounds.

Environmental impact

Burning hydrocarbons as fuel, which produces

and

, is a major contributor to anthropogenic

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

. Hydrocarbons are introduced into the environment through their extensive use as fuels and chemicals as well as through leaks or accidental spills during exploration, production, refining, or transport of fossil fuels. Anthropogenic hydrocarbon contamination of soil is a serious global issue due to contaminant persistence and the negative impact on human health. Mechanisms involved in phytoremediation

When soil is contaminated by hydrocarbons, it can have a significant impact on its microbiological, chemical, and physical properties. This can serve to prevent, slow down or even accelerate the growth of vegetation depending on the exact changes that occur. Crude oil and natural gas are the two largest sources of hydrocarbon contamination of soil.

Bioremediation

Bioremediation of hydrocarbon from soil or water contaminated is a formidable challenge because of the chemical inertness that characterize hydrocarbons (hence they survived millions of years in the source rock). Nonetheless, many strategies have been devised, bioremediation being prominent. The basic problem with bioremediation is the paucity of enzymes that act on them. Nonetheless the area has received regular attention. Bacteria in the gabbroic layer of the ocean's crust can degrade hydrocarbons; but the extreme environment makes research difficult. Other bacteria such as ''

Lutibacterium anuloederans ''Lutibacterium'' is a genus of Gram-negative staining bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microo ...

'' can also degrade hydrocarbons.

Mycoremediation Mycoremediation (from ancient Greek ''μύκης (mukēs)'', meaning "fungus" and the suffix ''-remedium'', in Latin meaning 'restoring balance') is a form of bioremediation in which fungi-based remediation methods are used to decontaminate the en ...

or breaking down of hydrocarbon by

mycelium Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...

and

mushroom A mushroom or toadstool is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source. ''Toadstool'' generally denotes one poisonous to humans. The standard for the name "mushroom" is t ...

s is possible.

Safety

Hydrocarbons are generally of low toxicity, hence the widespread use of gasoline and related volatile products. Aromatic compounds such as benzene and

are narcotic and chronic toxins, and benzene in particular is known to be

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive substan ...

ic. Certain rare polycyclic aromatic compounds are carcinogenic. Hydrocarbons are highly

flammable A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...

References

External links

The Methane Molecule

Encyclopedia of Hydrocarbons
{{Use dmy dates, date=August 2019

Types

Usage

Reactions

Substitution

Free-radical substitution

Addition

Addition polymerization

Hydrogenation

Metathesis

High-temperature reactions

Cracking

=Dehydrogenation

Pyrolysis

Combustion

Origin

Environmental impact

Bioremediation

Safety

See also

References

External links