Difference between revisions of "Hydrocarbon" - New World Encyclopedia
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| − | [[Image:ShellMartinez-refi.jpg|thumb|right|340px|Hydrocarbons are refined at oil refineries and chemical plants]]In | + | [[Image:ShellMartinez-refi.jpg|thumb|right|340px|Hydrocarbons are refined at [[oil refinery|oil refineries]] and processed at chemical plants]] |
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| + | In chemistry, a '''hydrocarbon''' is any [[chemical compound]] that consists only of the elements '''[[carbon]]''' (C) and '''[[hydrogen]]''' (H). They all contain a carbon backbone, called a carbon skeleton, and have hydrogen atoms attached to that backbone. (Often the term is used as a shortened form of the term [[aliphatic]] hydrocarbon.) Most hydrocarbons are [[combustible]]. | ||
== Examples == | == Examples == | ||
| − | + | The simplest hydrocarbon is [[methane]] ([[natural gas|swamp/marsh gas]]), a hydrocarbon with one carbon atom and four hydrogen atoms: CH<sub>4</sub>. [[Ethane]] is a hydrocarbon (more specifically, an [[alkane]]) consisting of two carbon atoms held together with a single bond, each with three hydrogen atoms bonded: C<sub>2</sub>H<sub>6</sub>. [[Propane]] has three carbon atoms (C<sub>3</sub>H<sub>8</sub>) and [[butane]] has four carbons (C<sub>4</sub>H<sub>10</sub>). | |
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| + | {| align="right" | ||
| + | |- | ||
| + | | [[Image:Kalottenmodell_Benzol.png|thumb|right|180px|A model of an arene called [[Benzene]]]] | ||
| + | |- | ||
| + | | [[Image:Kalottenmodell_Hexan.png|thumb|right|180px|A model of the alkane known as [[Hexane]]]] | ||
| + | |- | ||
| + | | [[Image:Kalottenmodell_Ethin.png|thumb|right|180px|A model of the alkyne called [[Ethyne]]]] | ||
| + | |} | ||
== Three types of hydrocarbons == | == Three types of hydrocarbons == | ||
| − | + | There are essentially three types of hydrocarbons: | |
#[[aromatic hydrocarbon]]s, which have at least one [[aromatic ring]] | #[[aromatic hydrocarbon]]s, which have at least one [[aromatic ring]] | ||
| − | #[[saturated hydrocarbon]]s, also known as [[alkane]]s, which don't have double, triple or aromatic bonds | + | #[[saturated hydrocarbon]]s, also known as [[alkane]]s, which don't have any double, triple or aromatic bonds |
#[[unsaturated hydrocarbon]]s, which have one or more double or triple bonds between carbon atoms, are divided into: | #[[unsaturated hydrocarbon]]s, which have one or more double or triple bonds between carbon atoms, are divided into: | ||
#*[[alkene]]s | #*[[alkene]]s | ||
#*[[alkyne]]s | #*[[alkyne]]s | ||
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== The number of hydrogen atoms == | == The number of hydrogen atoms == | ||
The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations: | The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations: | ||
| − | * | + | *[[Alkane]]s: C<sub>''n''</sub>H<sub>''2n+2''</sub> |
| − | * | + | *[[Alkene]]s: C<sub>''n''</sub>H<sub>''2n''</sub> (assuming only one double bond) |
| − | * | + | *[[Alkyne]]s: C<sub>''n''</sub>H<sub>''2n-2''</sub> (assuming only one triple bond) |
| − | Each of these hydrocarbons must follow the 4-hydrogen rule which states that all carbon atoms must have the maximum number of hydrogen atoms that it can hold (the limit is four). Note, an extra bond removes 2 hydrogen atoms and only saturated hydrocarbons can attain the full four. This is because of the unique positions of the carbon's four electrons. | + | *[[Cyclic hydrocarbon]]s: C<sub>''n''</sub>H<sub>''2n''</sub> |
| + | Each of these hydrocarbons must follow the 4-hydrogen rule which states that all carbon atoms must have the maximum number of hydrogen atoms that it can hold (the limit is four). A carbon atom has a bonding capacity of 4 and therfore must make 4 bonds, whether it be with hydrogen or an ajoining carbon atom. Note, an extra bond removes 2 hydrogen atoms and only saturated hydrocarbons can attain the full four. This is because of the unique positions of the carbon's four electrons. | ||
| − | == Molecular graph == | + | == Molecular graph== |
| − | Usually carbon backbone is represented as molecular [[graph theory|graph]] in which only carbon atoms are represented as [[vertex|vertices]] and bonds as [[edge | + | Usually carbon backbone is represented as molecular [[graph theory|graph]] in which only carbon atoms are represented as [[vertex|vertices]] and bonds as [[edge]]s. [[Molecular graph]]s contain the structure of the hydrocarbon in which missing hydrogen atoms can be added in a unique way. Hydrocarbons are extensively studied in [[mathematical chemistry]]. |
== Petroleum == | == Petroleum == | ||
Liquid geologically-extracted hydrocarbons are referred to as [[petroleum]] (literally "rock oil") or [[mineral oil]], while gaseous geologic hydrocarbons are referred to as [[natural gas]]. All are significant sources of [[fuel]] and raw materials as a [[feedstock]] for the production of [[organic chemistry|organic chemicals]] and are commonly found in the Earth´s subsurface using the tools of [[petroleum geology]]. | Liquid geologically-extracted hydrocarbons are referred to as [[petroleum]] (literally "rock oil") or [[mineral oil]], while gaseous geologic hydrocarbons are referred to as [[natural gas]]. All are significant sources of [[fuel]] and raw materials as a [[feedstock]] for the production of [[organic chemistry|organic chemicals]] and are commonly found in the Earth´s subsurface using the tools of [[petroleum geology]]. | ||
| − | + | The extraction of liquid hydrocarbon [[fuel]] from a number of [[sedimentary basin]]s has been integral to modern [[energy development]]. Hydrocarbons are [[mining|mined]] from [[tar sands]], [[oil shale]] and potentially extracted from sedimentary [[methane hydrate]]s. These reserves require distillation and upgrading to produce [[synthetic crude]] and petroleum. | |
| − | Hydrocarbons are of prime economic importance because they encompass the constituents of the major [[fossil fuel]]s ([[coal]], [[petroleum]], [[natural gas]], etc.) and [[biofuel]]s, as well as [[plastic]]s, [[ | + | [[Oil reserves]] in sedimentary rocks are the principal source of hydrocarbons for the energy, [[transport]] and [[petrochemical]] industries. Hydrocarbons are of prime economic importance because they encompass the constituents of the major [[fossil fuel]]s ([[coal]], [[petroleum]], [[natural gas]], etc.) and [[biofuel]]s, as well as [[plastic]]s, [[paraffin]], [[wax]]es, [[solvent]]s and oils. In urban [[pollution]], these components—along with NOx and [[sunlight]]—all contribute to the formation of [[tropospheric ozone]]. |
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| + | The concentration of hydrocarbon vapours can be harmful if inhaled. | ||
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| + | == Burning hydrocarbons == | ||
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| + | {{See also|:Flue gas emissions from fossil fuel combustion}} | ||
| + | Hydrocarbons are one of [[Earth]]'s most important natural resources. Hydrocarbons are currently the main source of the world’s electric energy and heat sources (such as home heating) because of the energy produced when burnt. Hydrocarbons are all substances with low [[entropy]] (meaning they hold a lot of energy potential), which can be released and harnessed by burning them. Often this energy is used directly as heat such as in home heaters, which use either oil or natural gas. The hydrocarbon is burnt and the heat is used to heat water, which is then circulated in pipes around the building heating every room. A similar principle is used to create electric energy in [[power plants]]. Hydrocarbons (usually [[coal]]) are burnt and the energy released in this way is used to turn water in to [[steam]], which is used to turn a [[turbine]] that generates energy. | ||
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| + | In an ideal reaction the waste would be only water and carbon dioxide but because the coal is not pure or clean there are often many toxic byproducts such as [[Mercury (element)|mercury]] and [[arsenic]]. Also, incomplete [[combustion]] causes the production of carbon monoxide which is toxic because it will bind with [[hemoglobin]] more readily than oxygen, so if it is breathed in, oxygen can not be absorbed, causing suffocation. Incomplete [[combustion]] also has a byproduct of [[carbon]] in the form of [[soot]]. | ||
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| + | Coal reserves will last for decades and possibly beyond [[2100]]. Mostly in response to [[climate change|climate concerns]], [[clean coal]] [[technology]] is currently under [[technology development|development]]. For example, the [[United Kingdom|UK]] and [[China]] have signed an [[agreement]] to develop such technology with carbon dioxide emissions capture and storage in both China and the [[EU]] by [[2020]]. Similar research is being conducted in the [[United States|U.S.]] and other countries. By some, hydrocarbons in the atmosphere are considered to be dangerous air pollutants. | ||
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{{commons|Gallery Hydrocarbons}} | {{commons|Gallery Hydrocarbons}} | ||
== External links == | == External links == | ||
| + | *[http://www.worldofmolecules.com/fuels/methane.htm The Methane Molecule] | ||
*[http://www.gasresources.net/DisposalBioClaims.htm Dismissal of the Claims of a Biological Connection for Natural Petroleum.] | *[http://www.gasresources.net/DisposalBioClaims.htm Dismissal of the Claims of a Biological Connection for Natural Petroleum.] | ||
| − | *[http://www. | + | * [http://www.poten.com/ut_glossary.asp Poten & Partners: Glossary of Hydrocarbon Terms] |
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== See also == | == See also == | ||
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*[[Abiogenic petroleum origin]] | *[[Abiogenic petroleum origin]] | ||
*[[Energy storage]] | *[[Energy storage]] | ||
| − | *[[ | + | *[[Fractional distillation]] |
| − | *[[ | + | *[[Functional group]] |
| + | *[[Alkanes]] | ||
[[Category:Physical sciences]] | [[Category:Physical sciences]] | ||
[[Category:Chemistry]] | [[Category:Chemistry]] | ||
| − | [[Category: | + | [[Category:Environmental Chemistry]] |
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Revision as of 22:51, 29 July 2006
In chemistry, a hydrocarbon is any chemical compound that consists only of the elements carbon (C) and hydrogen (H). They all contain a carbon backbone, called a carbon skeleton, and have hydrogen atoms attached to that backbone. (Often the term is used as a shortened form of the term aliphatic hydrocarbon.) Most hydrocarbons are combustible.
Examples
The simplest hydrocarbon is methane (swamp/marsh gas), a hydrocarbon with one carbon atom and four hydrogen atoms: CH4. Ethane is a hydrocarbon (more specifically, an alkane) consisting of two carbon atoms held together with a single bond, each with three hydrogen atoms bonded: C2H6. Propane has three carbon atoms (C3H8) and butane has four carbons (C4H10).
 A model of an arene called Benzene |
Three types of hydrocarbons
There are essentially three types of hydrocarbons:
- aromatic hydrocarbons, which have at least one aromatic ring
- saturated hydrocarbons, also known as alkanes, which don't have any double, triple or aromatic bonds
- unsaturated hydrocarbons, which have one or more double or triple bonds between carbon atoms, are divided into:
The number of hydrogen atoms
The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations:
- Alkanes: CnH2n+2
- Alkenes: CnH2n (assuming only one double bond)
- Alkynes: CnH2n-2 (assuming only one triple bond)
- Cyclic hydrocarbons: CnH2n
Each of these hydrocarbons must follow the 4-hydrogen rule which states that all carbon atoms must have the maximum number of hydrogen atoms that it can hold (the limit is four). A carbon atom has a bonding capacity of 4 and therfore must make 4 bonds, whether it be with hydrogen or an ajoining carbon atom. Note, an extra bond removes 2 hydrogen atoms and only saturated hydrocarbons can attain the full four. This is because of the unique positions of the carbon's four electrons.
Molecular graph
Usually carbon backbone is represented as molecular graph in which only carbon atoms are represented as vertices and bonds as edges. Molecular graphs contain the structure of the hydrocarbon in which missing hydrogen atoms can be added in a unique way. Hydrocarbons are extensively studied in mathematical chemistry.
Petroleum
Liquid geologically-extracted hydrocarbons are referred to as petroleum (literally "rock oil") or mineral oil, while gaseous geologic hydrocarbons are referred to as natural gas. All are significant sources of fuel and raw materials as a feedstock for the production of organic chemicals and are commonly found in the Earth´s subsurface using the tools of petroleum geology.
The extraction of liquid hydrocarbon fuel from a number of sedimentary basins has been integral to modern energy development. Hydrocarbons are mined from tar sands, oil shale and potentially extracted from sedimentary methane hydrates. These reserves require distillation and upgrading to produce synthetic crude and petroleum.
Oil reserves in sedimentary rocks are the principal source of hydrocarbons for the energy, transport and petrochemical industries. Hydrocarbons are of prime economic importance because they encompass the constituents of the major fossil fuels (coal, petroleum, natural gas, etc.) and biofuels, as well as plastics, paraffin, waxes, solvents and oils. In urban pollution, these components—along with NOx and sunlight—all contribute to the formation of tropospheric ozone.
The concentration of hydrocarbon vapours can be harmful if inhaled.
Burning hydrocarbons
Hydrocarbons are one of Earth's most important natural resources. Hydrocarbons are currently the main source of the world’s electric energy and heat sources (such as home heating) because of the energy produced when burnt. Hydrocarbons are all substances with low entropy (meaning they hold a lot of energy potential), which can be released and harnessed by burning them. Often this energy is used directly as heat such as in home heaters, which use either oil or natural gas. The hydrocarbon is burnt and the heat is used to heat water, which is then circulated in pipes around the building heating every room. A similar principle is used to create electric energy in power plants. Hydrocarbons (usually coal) are burnt and the energy released in this way is used to turn water in to steam, which is used to turn a turbine that generates energy.
In an ideal reaction the waste would be only water and carbon dioxide but because the coal is not pure or clean there are often many toxic byproducts such as mercury and arsenic. Also, incomplete combustion causes the production of carbon monoxide which is toxic because it will bind with hemoglobin more readily than oxygen, so if it is breathed in, oxygen can not be absorbed, causing suffocation. Incomplete combustion also has a byproduct of carbon in the form of soot.
Coal reserves will last for decades and possibly beyond 2100. Mostly in response to climate concerns, clean coal technology is currently under development. For example, the UK and China have signed an agreement to develop such technology with carbon dioxide emissions capture and storage in both China and the EU by 2020. Similar research is being conducted in the U.S. and other countries. By some, hydrocarbons in the atmosphere are considered to be dangerous air pollutants.
External links
- The Methane Molecule
- Dismissal of the Claims of a Biological Connection for Natural Petroleum.
- Poten & Partners: Glossary of Hydrocarbon Terms
See also
- Abiogenic petroleum origin
- Energy storage
- Fractional distillation
- Functional group
- Alkanes
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