Hydrocarbon
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Hydrocarbons are refined at oil refineries and processed at chemical plants |
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.
The simplest hydrocarbon is
methane (
swamp/marsh gas), a hydrocarbon with one carbon atom and four hydrogen atoms: CH
4.
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
2H
6.
Propane has three carbon atoms (C
3H
8) and
butane has four carbons (C
4H
10).
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| A model of the alkane known as Hexane |
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| A model of the alkyne called Ethyne |
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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:#*
alkenes#*
alkynes
The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations:
*
Alkanes: C
nH
2n+2*
Alkenes: C
nH
2n (assuming only one double bond)
*
Alkynes: C
nH
2n-2 (assuming only one triple bond)
*
Cyclic hydrocarbons: C
nH
2nEach 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.
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.
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
plastics,
paraffin,
waxes,
solvents and oils. In urban
pollution, these componentsall contribute to the formation of
tropospheric ozone.
The concentration of hydrocarbon vapours can be harmful if inhaled.
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. Mounting evidence links the use of Hydrocarbons in the form of fossil fuels to environmental pollution and
Global Warming.
*
The Methane Molecule*
Dismissal of the Claims of a Biological Connection for Natural Petroleum.*
Poten & Partners: Glossary of Hydrocarbon Terms*
Abiogenic petroleum origin*
Alkanes*
Energy storage*
Fractional distillation*
Functional group*
Peak Oil*
Petroleum
