In organic chemistry, a hydrocarbon is an organic compound consisting
entirely of hydrogen and carbon,:620 and thus are group 14
hydrides. Hydrocarbons, from which one hydrogen atom has been removed,
are functional groups called hydrocarbyls. Because carbon has 4
electrons in its outermost shell (and because each covalent bond
requires a donation of 1 electron, per atom, to the bond) carbon has
exactly four bonds to make, and is only stable if all 4 of these bonds
Aromatic hydrocarbons (arenes), alkanes, cycloalkanes and alkyne-based
compounds are different types of hydrocarbons.
Most hydrocarbons found on
1 Types of hydrocarbons
1.1 General properties 1.2 Simple hydrocarbons and their variations
2 Usage 3 Poisoning 4 Reactions
4.1 Substitution reactions 4.2 Addition reactions 4.3 Combustion
4.3.1 Petroleum 4.3.2 Bioremediation
5 Safety 6 Environmental impact 7 See also 8 References 9 External links
Types of hydrocarbons The classifications for hydrocarbons, defined by IUPAC nomenclature of organic chemistry are as follows:
Saturated hydrocarbons are the simplest of the hydrocarbon species. They are composed entirely of single bonds and are saturated with hydrogen. The formula for acyclic saturated hydrocarbons (i.e., alkanes) is CnH2n+2.:623 The most general form of saturated hydrocarbons is CnH2n+2(1-r), where r is the number of rings. Those with exactly one ring are the cycloalkanes. Saturated hydrocarbons are the basis of petroleum fuels and are found as either linear or branched species. Substitution reaction is their characteristics property (like chlorination reaction to form chloroform). Hydrocarbons with the same molecular formula but different structural formulae are called structural isomers.:625 As given in the example of 3-methylhexane and its higher homologues, branched hydrocarbons can be chiral.:627 Chiral saturated hydrocarbons constitute the side chains of biomolecules such as chlorophyll and tocopherol. Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms. Those with double bond are called alkenes. Those with one double bond have the formula CnH2n (assuming non-cyclic structures).:628 Those containing triple bonds are called alkyne. Those with one triple bond have the formula CnH2n−2.:631 Aromatic hydrocarbons, also known as arenes, are hydrocarbons that have at least one aromatic ring.
Hydrocarbons can be gases (e.g. methane and propane), liquids (e.g. hexane and benzene), waxes or low melting solids (e.g. paraffin wax and naphthalene) or polymers (e.g. polyethylene, polypropylene and polystyrene). General properties Because of differences in molecular structure, the empirical formula remains different between hydrocarbons; in linear or "straight-run" alkanes, alkenes and alkynes, the amount of bonded hydrogen lessens in alkenes and alkynes due to the "self-bonding" or catenation of carbon preventing entire saturation of the hydrocarbon by the formation of double or triple bonds. This inherent ability of hydrocarbons to bond to themselves is known as catenation, and allows hydrocarbons to form more complex molecules, such as cyclohexane, and in rarer cases, arenes such as benzene. This ability comes from the fact that the bond character between carbon atoms is entirely non-polar, in that the distribution of electrons between the two elements is somewhat even due to the same electronegativity values of the elements (~0.30), and does not result in the formation of an electrophile. Generally, with catenation comes the loss of the total amount of bonded hydrocarbons and an increase in the amount of energy required for bond cleavage due to strain exerted upon the molecule; in molecules such as cyclohexane, this is referred to as ring strain, and occurs due to the "destabilized" spatial electron configuration of the atom. In simple chemistry, as per valence bond theory, the carbon atom must follow the "4-hydrogen rule", which states that the maximum number of atoms available to bond with carbon is equal to the number of electrons that are attracted into the outer shell of carbon. In terms of shells, carbon consists of an incomplete outer shell, which comprises 4 electrons, and thus has 4 electrons available for covalent or dative bonding. Hydrocarbons are hydrophobic like lipids. Some hydrocarbons also are abundant in the solar system. Lakes of liquid methane and ethane have been found on Titan, Saturn's largest moon, confirmed by the Cassini-Huygens Mission. Hydrocarbons are also abundant in nebulae forming polycyclic aromatic hydrocarbon (PAH) compounds. Simple hydrocarbons and their variations
1 Methane — — — —
5 Pentane Pentene Pentyne Cyclopentane Pentadiene (piperylene)
6 Hexane Hexene Hexyne Cyclohexane Hexadiene
7 Heptane Heptene Heptyne Cycloheptane Heptadiene
8 Octane Octene Octyne Cyclooctane Octadiene
9 Nonane Nonene Nonyne Cyclononane Nonadiene
10 Decane Decene Decyne Cyclodecane Decadiene
11 Undecane Undecene Undecyne Cycloundecane Undecadiene
Oil refineries are one way hydrocarbons are processed for use. Crude oil is processed in several stages to form desired hydrocarbons, used as fuel and in other products.
Hydrocarbons are a primary energy source for current civilizations.
The predominant use of hydrocarbons is as a combustible fuel source.
In their solid form, hydrocarbons take the form of asphalt (bitumen).
Mixtures of volatile hydrocarbons are now used in preference to the
chlorofluorocarbons as a propellant for aerosol sprays, due to
chlorofluorocarbons' impact on the ozone layer.
Substitution reaction Addition reaction Combustion
Substitution reactions Substitution reactions only occur in saturated hydrocarbons (single carbon–carbon bonds). In this reaction, an alkane reacts with a chlorine molecule. One of the chlorine atoms displaces a hydrogen atom. This forms hydrochloric acid as well as the hydrocarbon with one chlorine atom.
CH4 + Cl2 → CH3Cl + HCl CH3Cl + Cl2 → CH2Cl2 + HCl
all the way to CCl4 (carbon tetrachloride)
C2H6 + Cl2 → C2H5Cl + HCl C2H4Cl2 + Cl2 → C2H3Cl3 + HCl
all the way to C2Cl6 (hexachloroethane) Addition reactions Addition reactions involve alkenes and alkynes. In this reaction a halogen molecule breaks the double or triple bond in the hydrocarbon and forms a bond. Combustion Main article: Combustion 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. Often this energy is used directly as heat such as in home heaters, which use either petroleum or natural gas. The hydrocarbon is burnt and the heat is used to heat water, which is then circulated. A similar principle is used to create electric energy in power plants. Common properties of hydrocarbons are the facts that they produce steam, carbon dioxide and heat during combustion and that oxygen is required for combustion to take place. The simplest hydrocarbon, methane, burns as follows:
CH4 + 2 O2 → 2 H2O + CO2 + energy
In inadequate supply of air, carbon monoxide gas and water vapour are formed:
2 CH4 + 3 O2 → 2 CO + 4 H2O
Another example is the combustion of propane:
C3H8 + 5 O2 → 4 H2O + 3 CO2 + energy
And finally, for any linear alkane of n carbon atoms,
CnH2n+2 + 3n + 1/2 O2 → (n + 1) H2O + n CO2 + energy.
Burning of hydrocarbons is an example of an exothermic chemical reaction. Hydrocarbons can also be burned with elemental fluorine, resulting in carbon tetrafluoride and hydrogen fluoride products. Petroleum Main article: Petroleum
Natural oil spring in Korňa, Slovakia.
Extracted hydrocarbons in a liquid form are referred to as petroleum
(literally "rock oil") or mineral oil, whereas hydrocarbons in a
gaseous form are referred to as natural gas.
Abiogenic petroleum origin
^ a b c d e f Silberberg, Martin (2004). Chemistry: The Molecular
Nature Of Matter and Change. New York: McGraw-Hill Companies.
^ IUPAC Goldbook hydrocarbyl groups Archived 7 January 2010 at the
^ Clayden, J., Greeves, N., et al. (2001) Organic Chemistry Oxford
ISBN 0-19-850346-6 p. 21
^ McMurry, J. (2000). Organic Chemistry 5th ed. Brooks/Cole: Thomson
Learning. ISBN 0-495-11837-0 pp. 75–81
^ Meierhenrich, Uwe. Amino Acids and the Asymmetry of Life Archived 2
March 2017 at the Wayback Machine.. Springer, 2008.
^ NASA's Cassini Spacecraft Reveals Clues About Saturn Moon Archived 2
September 2014 at the Wayback Machine.. NASA (December 12, 2013)
^ Guzman-Ramirez, L.; Lagadec, E.; Jones, D.; Zijlstra, A. A.;
Gesicki, K. (2014). "PAH formation in O-rich planetary nebulae".
Monthly Notices of the Royal Astronomical Society. 441: 364.
arXiv:1403.1856 . Bibcode:2014MNRAS.441..364G.
^ Nunes, T.M.; Turatti, I.C.C.; Mateus, S.; Nascimento, F.S.; Lopes,
N.P.; Zucchi, R. (2009). "Cuticular Hydrocarbons in the Stingless Bee
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Saturated aliphatic hydrocarbons
Alkanes CnH2n + 2
Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane
Isobutane Isopentane 3-Methylpentane Neopentane Isohexane Isoheptane Isooctane Isononane Isodecane
Cyclopropane Cyclobutane Cyclopentane Cyclohexane Cycloheptane Cyclooctane Cyclononane Cyclodecane
Methylcyclopropane Methylcyclobutane Methylcyclopentane Methylcyclohexane Isopropylcyclohexane
Adamantane Diamondoid Perhydrophenanthrene Sterane Cubane Prismane Dodecahedrane Basketane Churchane Pagodane Twistane
Unsaturated aliphatic hydrocarbons
Ethene Propene Butene Pentene Hexene Heptene Octene Nonene Decene
Isobutene Isopentene Neopentene Isohexene Isoheptene Isooctene Isononene Isodecene
Alkynes CnH2n − 2
Ethyne Propyne Butyne Pentyne Hexyne Heptyne Octyne Nonyne Decyne
Isobutyne Isopentyne Neopentyne Isohexyne Isoheptyne Isooctyne Isononyne Isodecyne
Cyclopropene Cyclobutene Cyclopentene Cyclohexene Cycloheptene Cyclooctene Cyclononene Cyclodecene
Methylcyclopropene Methylcyclobutene Methylcyclopentene Methylcyclohexene Isopropylcyclohexene
Cyclopropyne Cyclobutyne Cyclopentyne Cyclohexyne Cycloheptyne Cycloctyne Cyclononyne Cyclodecyne
Propadiene Butadiene Pentadiene Hexadiene Heptadiene Octadiene Nonadiene Decadiene
Alkatriene Alkadiyne Cumulene Cyclooctatetraene Cyclododecatriene Enyne
Naphthalene Anthracene Naphthacene Pentacene Hexacene Heptacene
Azulene Fluorene Helicenes Circulenes
Toluene Xylene Ethylbenzene Cumene Styrene Mesitylene Pseudocumene Hexamethylbenzene
Benzene Phenanthrene Chrysene Pyrene Corannulene Kekulene
Annulenes Annulynes Alicyclic compounds
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