Alkanes, also known as paraffins, are chemical compounds that consist only of the elements carbon (C) and hydrogen (H) (i. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. In chemistry paraffin is the common name for the Alkane Hydrocarbons with the general formula C n H2 n +2 A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 e. , hydrocarbons), wherein these atoms are linked together exclusively by single bonds (i. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. e. , they are saturated compounds) without any cyclic structure (i. In Chemistry, saturation has five different meanings In Physical chemistry, saturation is the point at which a Solution of a substance e. loops). Alkanes belong to a homologous series of organic compounds in which the members differ by a constant relative atomic mass of 14. In Chemistry, a homologous series is a series of Organic compounds with a similar General formula, possessing similar chemical properties due to the presence

Each carbon atom must have 4 bonds (either C-H or C-C bonds), and each hydrogen atom must be joined to a carbon atom (H-C bonds). A series of linked carbon atoms is known as the carbon skeleton or carbon backbone. In general, the number of carbon atoms is often used to define the size of the alkane (e. g. , C₂-alkane).

An alkyl group is a functional group or side-chain that, like an alkane, consists solely of singly-bonded carbon and hydrogen atoms, for example a methyl or ethyl group. An alkyl is a Univalent radical consisting of Carbon and Hydrogen atoms arranged in a chain In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions In Chemistry, a methyl group is a Hydrophobic Alkyl Functional group named after Methane (4 In Chemistry, an ethyl group is an Alkyl Functional group derived from Ethane ( C 2 H 6

Saturated hydrocarbons can be linear (general formula C_nH_2n+2) wherein the carbon atoms are joined in a snake-like structure, branched (general formula C_nH_2n+2, n>3) wherein the carbon backbone splits off in one or more directions, or cyclic (general formula C_nH_2n, n>2) wherein the carbon backbone is linked so as to form a loop. Polymer chemistry, branching occurs by the replacement of a Substituent, e In Organic chemistry, a cyclic compound is a compound in which a series of carbon atoms are connected to form a loop or ring According to the definition by IUPAC, the former two are alkanes, whereas the third group is called cycloalkanes. The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization Cycloalkanes (also called naphthenes, especially if from Petroleum sources are types of Alkanes which have one or more rings of Carbon Atoms ^[1] In other words, saturated hydrocarbons are divided into alkanes and cycloalkanes, depending on whether or not they have cyclic structures, and, in the technical sense, cycloalkanes are not alkanes. However, cycloalkanes are sometimes called cyclic alkanes, which can be confusing when "real" alkanes are called acyclic alkanes. Saturated hydrocarbons can also combine any of the linear, cyclic (e. g. , polycyclic) and branching structures, and they are still alkanes (no general formula) as long as they are acyclic (i. e. , having no loops).

The simplest possible alkane (the parent molecule) is methane, CH₄. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. There is no limit to the number of carbon atoms that can be linked together, the only limitation being that the molecule is acyclic, is saturated, and is a hydrocarbon. In Chemistry, saturation has five different meanings In Physical chemistry, saturation is the point at which a Solution of a substance In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Saturated oils and waxes are examples of larger alkanes where the number of carbons in the carbon backbone tends to be greater than 10. An oil is a substance that is in a viscous Liquid state ( "oily") at ambient temperatures or slightly warmer and is Wax has traditionally referred to a substance that is secreted by Bees ( Beeswax) and used by them in constructing their

Alkanes are not very reactive and have little biological activity. Pharmacological or biological activity is an expression describing the beneficial or adverse effects of a Drug on living matter. Alkanes can be viewed as a molecular scaffold upon which can be hung the interesting biologically-active/reactive portions (functional groups) of the molecule. Scaffolding is a temporary framework used to support people and material in the construction or repair of buildings and other large structures In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions

Contents 1 Isomerism 2 Nomenclature 2.1 Linear alkanes 2.2 Branched alkanes 2.3 Cyclic alkanes 2.4 Trivial names 3 Occurrence 3.1 Occurrence of alkanes in the Universe 3.2 Occurrence of alkanes on Earth 3.3 Biological occurrence 3.4 Ecological relations 4 Production 4.1 Petroleum refining 4.2 Fischer-Tropsch 4.3 Laboratory preparation 5 Applications 6 Physical properties 6.1 Boiling point 6.2 Melting point 6.3 Conductivity 6.4 Molecular geometry 6.5 Bond lengths and bond angles 6.6 Conformation 6.7 Spectroscopic properties 6.7.1 Infrared spectroscopy 6.7.2 NMR spectroscopy 6.7.3 Mass spectrometry 7 Chemical properties 7.1 Reactions with oxygen 7.2 Reactions with halogens 7.3 Cracking 7.4 Isomerization and reformation 7.5 Other reactions 8 Hazards 9 See also 10 References 11 Further reading

Isomerism

Alkanes with more than three carbon atoms can be arranged in a multiple number of ways, forming different structural isomers. Structural isomerism, or constitutional isomerism, is a form of isomerism in which Molecules with the same Molecular formula have Atoms An isomer is like a chemical anagram, in which the atoms of a chemical compound are arranged or joined together in a different order. An anagram ( Greek anagramma 'letters written anew' passive participle of ana- 'again' + gramma 'letter' is a type of Word play A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. The simplest isomer of an alkane is the one in which the carbon atoms are arranged in a single chain with no branches. This isomer is sometimes called the n-isomer (n for "normal", although it is not necessarily the most common). However the chain of carbon atoms may also be branched at one or more points. The number of possible isomers increases rapidly with the number of carbon atoms (sequence A000602 in OEIS). The On-Line Encyclopedia of Integer Sequences ( OEIS) also cited simply as Sloane's, is an extensive searchable Database of Integer sequences For example:

• C₁: 1 isomer—methane
• C₂: 1 isomer—ethane
• C₃: 1 isomer—propane
• C₄: 2 isomers—n-butane, isobutane
• C₁₂: 355 isomers
• C₃₂: 27,711,253,769 isomers
• C₆₀: 22,158,734,535,770,411,074,184 isomers

In addition to these isomers, the chain of carbon atoms may form one or more loops. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 Isobutane, also known as methylpropane or 2-methylpropane, is an Alkane, Isomeric with Butane. Such compounds are called cycloalkanes. Cycloalkanes (also called naphthenes, especially if from Petroleum sources are types of Alkanes which have one or more rings of Carbon Atoms

Nomenclature

Main article: Organic nomenclature

The IUPAC nomenclature (systematic way of naming compounds) for alkanes is based on identifying hydrocarbon chains. The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Unbranched, saturated hydrocarbon chains are named systematically with a Greek numerical prefix denoting the number of carbons and the suffix "-ane". ^[2]

August Wilhelm von Hofmann suggested systematizing nomenclature by using the whole sequence of vowels a, e, i, o and u to create suffixes -ane, -ene, -ine (or -yne), -one, -une, for the hydrocarbons. August Wilhelm von Hofmann ( April 8, 1818 &ndash May 5, 1892) was a German Chemist. The first three name hydrocarbons with single, double and triple bonds; "-one" represents a ketone; "-ol" represents an alcohol or OH group; "-oxy-" means an ether and refers to oxygen between two carbons, so that methoxy-methane is the IUPAC name for dimethyl ether. 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 Ether is a class of Organic compounds which contain an ether group — an Oxygen Atom connected to two (substituted Alkyl

It is difficult or impossible to find compounds with more than one IUPAC name. This is because shorter chains attached to longer chains are prefixes and the convention includes brackets. Numbers in the name, referring to which carbon a group is attached to, should be as low as possible, so that 1- is implied and usually omitted from names of organic compounds with only one side-group; "1-" is implied in Nitro-octane. Symmetric compounds will have two ways of arriving at the same name.

Linear alkanes

Straight-chain alkanes are sometimes indicated by the prefix n- (for normal) where a non-linear isomer exists. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. Although this is not strictly necessary, the usage is still common in cases where there is an important difference in properties between the straight-chain and branched-chain isomers, e. g. , n-hexane or 2- or 3-methylpentane. Hexane is an Alkane Hydrocarbon with the Chemical formula CH3(CH24CH3 or C6H14

The first four members of the series (in terms of number of carbon atoms) are named as follows:

methane, CH₄

ethane, C₂H₆

propane, C₃H₈

butane, C₄H₁₀

Alkanes with five or more carbon atoms are named by adding the suffix -ane to the appropriate Greek-language prefix numerical multiplier^[3] with elision of any terminal vowel (-a or -o) from the basic numerical term. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 An affix is a Morpheme that is attached to a stem to form a word Compound affixes The affix for a number larger than twelve is constructed is the opposite order to that which the number is written in Hence, pentane, C₅H₁₂; hexane, C₆H₁₄; heptane, C₇H₁₆; octane, C₈H₁₈; etc. Pentane is any or one of the Organic compounds with the formula C5H12 Hexane is an Alkane Hydrocarbon with the Chemical formula CH3(CH24CH3 or C6H14 n -Heptane is the straight-chain Alkane with the Chemical formula H3C(CH25CH3 or C7H16 Octane is a straight-chain Alkane with the Chemical formula CH3(CH26CH3 For a more complete list, see List of alkanes. The following is a list of straight-chain Alkanes and their common names sorted by number of Carbon atoms

Branched alkanes

Simple branched alkanes often have a common name using a prefix to distinguish them from linear alkanes, for example n-pentane, isopentane, and neopentane. Ball-and-stick models and Space-filling models (also known as Calotte models) are 3D or spatial Molecular models which serve to display the structure Isopentane, C5[[hydrogen H12]] also called methylbutane or 2-methylbutane, is a branched-chain Alkane with five Pentane is any or one of the Organic compounds with the formula C5H12 Isopentane, C5[[hydrogen H12]] also called methylbutane or 2-methylbutane, is a branched-chain Alkane with five Neopentane, also called dimethylpropane or 22-dimethylpropane, is a double-branched-chain Alkane with five Carbon atoms

IUPAC naming conventions can be used to produce a systematic name.

The key steps in the naming of more complicated branched alkanes are as follows:^[4]

• Identify the longest continuous chain of carbon atoms
• Name this longest root chain using standard naming rules
• Name each side chain by changing the suffix of the name of the alkane from "-ane" to "-yl"
• Number the root chain so that sum of the numbers assigned to each side group will be as low as possible
• Number and name the side chains before the name of the root chain
• If there are multiple side chains of the same type, use prefixes such as "di-" and "tri-" to indicate it as such, and number each one.

Comparison of nomenclatures for three isomers of C₅H₁₂

Common name	n-pentane	isopentane	neopentane
IUPAC name	pentane	2-methylbutane	2,2-dimethylpropane
Structure

Cyclic alkanes

Main article: Cycloalkane

So-called cyclic alkanes are, in the technical sense, not alkanes, but cycloalkanes. Cycloalkanes (also called naphthenes, especially if from Petroleum sources are types of Alkanes which have one or more rings of Carbon Atoms They are hydrocarbons just like alkanes, but are containing one or more rings.

Simple cycloalkanes have a prefix "cyclo-" to distinguish them from alkanes. Cycloalkanes are named as per their acyclic counterparts with respect to the number of carbon atoms, e. g. , cyclopentane (C₅H₁₀) is a cycloalkane with 5 carbon atoms just like pentane (C₅H₁₂), but they are joined up in a five-membered ring. Cyclopentane is a highly Flammable alicyclic Hydrocarbon with Chemical formula 510 and CAS number 287-92-3 Pentane is any or one of the Organic compounds with the formula C5H12 In a similar manner, propane and cyclopropane, butane and cyclobutane, etc. Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable Cyclopropane is a Cycloalkane Molecule with the molecular formula C3H6 consisting of three Carbon Atoms linked to Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 Cyclobutane, C4H8 with a molecular mass of 56107g/mol is a four Carbon Alkane in which all the Carbon Atoms are arranged

Substituted cycloalkanes are named similar to substituted alkanes — the cycloalkane ring is stated, and the substituents are according to their position on the ring, with the numbering decided by Cahn-Ingold-Prelog rules. ^[3]

Trivial names

The trivial (non-systematic) name for alkanes is "paraffins. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general In chemistry paraffin is the common name for the Alkane Hydrocarbons with the general formula C n H2 n +2 " Together, alkanes are known as the paraffin series. Trivial names for compounds are usually historical artifacts. They were coined before the development of systematic names, and have been retained due to familiar usage in industry. Cycloalkanes are also called naphthenes.

It is almost certain that the term paraffin stems from the petrochemical industry. In chemistry paraffin is the common name for the Alkane Hydrocarbons with the general formula C n H2 n +2 Branched-chain alkanes are called isoparaffins. The use of the term "paraffin" is a general term and often does not distinguish between a pure compounds and mixtures of isomers with the same chemical formula (i. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes e. , like a chemical anagram), e. An anagram ( Greek anagramma 'letters written anew' passive participle of ana- 'again' + gramma 'letter' is a type of Word play g. , pentane and isopentane. Pentane is any or one of the Organic compounds with the formula C5H12 Isopentane, C5[[hydrogen H12]] also called methylbutane or 2-methylbutane, is a branched-chain Alkane with five

Examples

The following trivial names are retained in the IUPAC system:

• isobutane for 2-methylpropane
• isopentane for 2-methylbutane
• neopentane for 2,2-dimethylpropane

Occurrence

Occurrence of alkanes in the Universe

Alkanes form a significant portion of the atmospheres of the outer gas planets such as Jupiter (0. Isobutane, also known as methylpropane or 2-methylpropane, is an Alkane, Isomeric with Butane. Isopentane, C5[[hydrogen H12]] also called methylbutane or 2-methylbutane, is a branched-chain Alkane with five Neopentane, also called dimethylpropane or 22-dimethylpropane, is a double-branched-chain Alkane with five Carbon atoms An atmosphere (from Greek ατμός - atmos, " Vapor " + σφαίρα - sphaira, " Sphere " 1% methane, 0. 0002% ethane), Saturn (0. 2% methane, 0. 0005% ethane), Uranus (1. 99% methane, 0. 00025% ethane) and Neptune (1. Neptune ( English|AmE] ] is the eighth and farthest Planet from the Sun in the Solar System. 5% methane, 1. 5 ppm ethane). Titan (1. TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as 6% methane), a satellite of Saturn, was examined by the Huygens probe, which indicate that Titan's atmosphere periodically rains liquid methane onto the moon's surface. ^[5] Also on Titan, a methane-spewing volcano was spotted and this volcanism is believed to be a significant source of the methane in the atmosphere. There also appear to be Methane/Ethane lakes near the north polar regions of Titan, as discovered by Cassini's radar imaging. Methane and ethane have also been detected in the tail of the comet Hyakutake. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Comet Hyakutake (çʲakɯ̥take formally designated C/1996 B2) is a Comet discovered on January 30 1996 which passed very close to Earth Chemical analysis showed that the abundances of ethane and methane were roughly equal, which is thought to imply that its ices formed in interstellar space, away from the Sun, which would have evaporated these volatile molecules. ^[6] Alkanes have also been detected in meteorites such as carbonaceous chondrites. A meteorite is a natural object originating in Outer space that survives an impact with the Earth 's surface A carbonaceous chondrite or a C-type chondrite is a type of chondritic Meteorite which contains high levels of Water and Organic compounds

Occurrence of alkanes on Earth

Traces of methane gas (about 0. 0001% or 1 ppm) occur in the Earth's atmosphere, produced primarily by organisms such as Archaea, found for example in the gut of cows.

The most important commercial sources for alkanes are natural gas and oil. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Petroleum ( L petroleum, from Greek πετρέλαιον, lit ^[7] Natural gas contains primarily methane and ethane, with some propane and butane: oil is a mixture of liquid alkanes and other hydrocarbons. Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. These hydrocarbons were formed when dead marine animals and plants (zooplankton and phytoplankton) died and sank to the bottom of ancient seas and were covered with sediments in an anoxic environment and converted over many millions of years at high temperatures and high pressure to their current form. Natural gas resulted thereby for example from the following reaction:

C₆H₁₂O₆ → 3CH₄ + 3CO₂

These hydrocarbons collected in porous rocks, located beneath an impermeable cap rock and so are trapped. Unlike methane, which is constantly reformed in large quantities, higher alkanes (alkanes with 9 or more carbon atoms) rarely develop to a considerable extent in nature. These deposits, e. g. , oil fields, have formed over millions of years and once exhausted cannot be readily replaced. An oil field is a region with an abundance of Oil wells extracting Petroleum (crude oil from below ground The depletion of these hydrocarbons is the basis for what is known as the energy crisis. An energy crisis is any great bottleneck (or price Rise) in the supply of energy resources to an economy.

Solid alkanes are known as tars and are formed when more volatile alkanes such as gases and oil evaporate from hydrocarbon deposits. Tar is a viscous black Liquid derived from the Destructive distillation of organic matter Evaporation is the process by which Molecules in a Liquid state (e One of the largest natural deposits of solid alkanes is in the asphalt lake known as the Pitch Lake in Trinidad and Tobago. Asphalt ( is a sticky black and highly viscous liquid or semi-solid that is present in most crude Petroleums and in some natural deposits sometimes termed asphaltum The Pitch Lake is a lake of natural Asphalt located at La Brea in southwest Trinidad. The Republic of Trinidad and Tobago (ˈtrɪnɪdæd ən təˈbeɪgoʊ is an archipelagic state in the southern Caribbean, lying northeast of the South American

Methane is also present in what is called biogas, produced by animals and decaying matter, which is a possible renewable energy source. See also Natural gas, Biofuel Biogas typically refers to a Gas produced by the biological breakdown of Organic matter in the Renewable energy is Energy generated from Natural resources mdashsuch as Sunlight, Wind, Rain, tides and geothermal

Alkanes have a low solubility in water, so the content in the oceans is negligible; however, at high pressures and low temperatures (such as at the bottom of the oceans), methane can co-crystallize with water to form a solid methane hydrate. Methane clathrate, also called methane hydrate or methane ice, is a solid form of water that contains a large amount of Methane within its Crystal Although this cannot be commercially exploited at the present time, the amount of combustible energy of the known methane hydrate fields exceeds the energy content of all the natural gas and oil deposits put together;methane extracted from methane hydrate is considered therefore a candidate for future fuels.

Biological occurrence

Although alkanes occur in nature in various way, they do not rank biologically among the essential materials. Cycloalkanes with 14 to 18 carbon atoms occur in musk, extracted from deer of the family Moschidae. Musk is the name originally given to a substance with a penetrating Odor obtained from a Gland of the male Musk deer, which is situated between its A deer is a Ruminant Mammal belonging to the family Cervidae. Musk deer are Artiodactyls of the genus Moschus, the only genus of family Moschidae. All further information refers to (acyclic) alkanes.

Bacteria and archaea

Certain types of bacteria can metabolise alkanes: they prefer even-numbered carbon chains as they are easier to degrade than odd-numbered chains. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have

On the other hand, certain archaea, the methanogens, produce large quantities of methane by the metabolism of carbon dioxide or other oxidised organic compounds. Methanogens are Archaea that produce Methane as a Metabolic byproduct in Anoxic conditions Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state The energy is released by the oxidation of hydrogen:

CO₂ + 4H₂ → CH₄ + 2H₂O

Methanogens are also the producers of marsh gas in wetlands, and release about two billion tonnes of methane per year—the atmospheric content of this gas is produced nearly exclusively by them. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. A wetland is an area of Land consisting of Soil that is Saturated with Moisture, such as a Swamp, Marsh, or Bog The methane output of cattle and other herbivores, which can release up to 150 litres per day, and of termites, is also due to methanogens. Cattle, colloquially referred to as cows, are domesticated Ungulates a member of the Subfamily Bovinae of the family Herbivory is a form of Predation in which an Organism, known as a herbivore, consumes principally Autotrophs ref name=Campbell>Campbell The termites are a group of Social Insects usually classified at the taxonomic rank of order Isoptera (but see also taxonomy They also produce this simplest of all alkanes in the intestines of humans. In Anatomy, the intestine is the segment of the alimentary canal extending from the Stomach to the Anus and in humans and other mammals consists Methanogenic archaea are, hence, at the end of the carbon cycle, with carbon being released back into the atmosphere after having been fixed by photosynthesis. The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the Biosphere, Pedosphere, Geosphere, Hydrosphere, and Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. It is probable that our current deposits of natural gas were formed in a similar way. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane,

Fungi and plants

Alkanes also play a role, if a minor role, in the biology of the three eukaryotic groups of organisms: fungi, plants and animals. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex A fungus (ˈfʌŋgəs is a eukaryotic Organism that is a member of the kingdom Fungi (ˈfʌndʒaɪ Some specialised yeasts, e. g. , Candida tropicale, Pichia sp. Pichia is a genus of teleomorphic Yeasts in the family Saccharomycetaceae. , Rhodotorula sp. Rhodotorula is a pigmented Yeast, part of the Basidiomycota phylum easily identifiable by distinctive orange/red colonies when grown on SDA (Sabaroud's , can use alkanes as a source of carbon and/or energy. The fungus Amorphotheca resinae prefers the longer-chain alkanes in aviation fuel, and can cause serious problems for aircraft in tropical regions. Aviation fuel is a specialized type of Petroleum -based fuel used to power Aircraft.

In plants, it is the solid long-chain alkanes that are found; they form a firm layer of wax, the cuticle, over areas of the plant exposed to the air. Plant cuticles are a protective waxy covering produced only by the epidermal cells of leaves, young shoots and all other aerial plant organs without Periderm This protects the plant against water loss, while preventing the leaching of important minerals by the rain. It is also a protection against bacteria, fungi, and harmful insects—the latter sink with their legs into the soft waxlike substance and have difficulty moving. The shining layer on fruits such as apples consists of long-chain alkanes. The carbon chains are usually between twenty and thirty carbon atoms in length and are made by the plants from fatty acids. In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which The exact composition of the layer of wax is not only species-dependent, but changes also with the season and such environmental factors as lighting conditions, temperature or humidity.

Animals

Alkanes are found in animal products, although they are less important than unsaturated hydrocarbons. One example is the shark liver oil, which is approximately 14% pristane (2,6,10,14-tetramethylpentadecane, C₁₉H₄₀). Pristane is a natural saturated Terpenoid Alkane obtained primarily from Shark liver oil. Their occurrence is more important in pheromones, chemical messenger materials, on which above all insects are dependent for communication. A pheromone (from Greek φέρω phero "to bear" + ‘ορμόνη " Hormone " is a Chemical that triggers a natural With some kinds, as the support beetle Xylotrechus colonus, primarily pentacosane (C₂₅H₅₂), 3-methylpentaicosane (C₂₆H₅₄) and 9-methylpentaicosane (C₂₆H₅₄), they are transferred by body contact. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i With others like the tsetse fly Glossina morsitans morsitans, the pheromone contains the four alkanes 2-methylheptadecane (C₁₈H₃₈), 17,21-dimethylheptatriacontane (C₃₉H₈₀), 15,19-dimethylheptatriacontane (C₃₉H₈₀) and 15,19,23-trimethylheptatriacontane (C₄₀H₈₂), and acts by smell over longer distances, a useful characteristic for pest control. This page is about the insect For other meanings see Tsetse (disambiguation. Pest control refers to the regulation or management of a Species defined as a pest, usually because it is perceived to be detrimental to a person's Health

Ecological relations

One example, in which both plant and animal alkanes play a role, is the ecological relationship between the sand bee (Andrena nigroaenea) and the early spider orchid (Ophrys sphegodes); the latter is dependent for pollination on the former. Ophrys sphegodes — early spider-orchid — is an early flowering Orchid found on alkaline meadows and waste land Ophrys sphegodes — early spider-orchid — is an early flowering Orchid found on alkaline meadows and waste land Pollination in angiosperms and Gymnosperms is the process that transfers pollen grains, which contain the male Gametes (sperm to where the female Sand bees use pheromones in order to identify a mate; in the case of A. nigroaenea, the females emit a mixture of tricosane (C₂₃H₄₈), pentacosane (C₂₅H₅₂) and heptacosane (C₂₇H₅₆) in the ratio 3:3:1, and males are attracted by specifically this odour. Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i Alkanes, also known as Paraffins are Chemical compounds that consist only of the elements Carbon (C and Hydrogen (H (i The orchid takes advantage of this mating arrangement to get the male bee to collect and disseminate its pollen; parts of its flower not only resemble the appearance of sand bees, but also produce large quantities of the three alkanes in the same ratio as female sand bees. As a result numerous males are lured to the blooms and attempt to copulate with their imaginary partner: although this endeavour is not crowned with success for the bee, it allows the orchid to transfer its pollen, which will be dispersed after the departure of the frustrated male to different blooms.

Production

Petroleum refining

As stated earlier, the most important source of alkanes is natural gas and crude oil. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Petroleum ( L petroleum, from Greek πετρέλαιον, lit ^[7] Alkanes are separated in an oil refinery by fractional distillation and processed into many different products

Fischer-Tropsch

The Fischer-Tropsch process is a method to synthesize liquid hydrocarbons, including alkanes, from carbon monoxide and hydrogen. An oil refinery is an industrial Process plant where Crude oil is processed and refined into more useful Petroleum products, such as Gasoline Fractional distillation is the separation of a mixture into its component parts or fractions such as in separating Chemical compounds by their Boiling point by heating The Fischer-Tropsch process (or Fischer-Tropsch Synthesis is a catalyzed chemical reaction in which synthesis gas ( Syngas) a mixture of Carbon monoxide Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. This method is used to produce substitutes for petroleum distillates.

Laboratory preparation

There is usually little need for alkanes to be synthesized in the laboratory, since they are usually commercially available. Also, alkanes are generally non-reactive chemically or biologically, and do not undergo functional group interconversions cleanly. When alkanes are produced in the laboratory, it is often a side-product of a reaction. For example, the use of n-butyllithium as a strong base gives the conjugate acid, n-butane as a side-product:

C₄H₉Li + H₂O → C₄H₁₀ + LiOH

However, at times it may be desirable to make a portion of a molecule into an alkane like functionality (alkyl group) using the above or similar methods. n -Butyllithium (abbreviated BuLi is the most prominent Organolithium reagent. In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and Lithium hydroxide (LiOH is a corrosive Alkali hydroxide. It is a white Hygroscopic Crystalline material An alkyl is a Univalent radical consisting of Carbon and Hydrogen atoms arranged in a chain For example, an ethyl group is an alkyl group; when this is attached to a hydroxy group, it gives ethanol, which is not an alkane. In Chemistry, an ethyl group is an Alkyl Functional group derived from Ethane ( C 2 H 6 To do so, the best-known methods are hydrogenation of alkenes:

RCH=CH₂ + H₂ → RCH₂CH₃ (R = alkyl)

Alkanes or alkyl groups can also be prepared directly from alkyl halides in the Corey-House-Posner-Whitesides reaction. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 In Organic chemistry, an alkene, olefin, or olefine is an unsaturated Chemical compound containing at least one Carbon An alkyl is a Univalent radical consisting of Carbon and Hydrogen atoms arranged in a chain The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of Chemical compounds consisting of Alkanes such as Methane The Corey-House synthesis (also called the Corey-House-Posner-Whitesides reaction) is an Organic reaction that involves the reaction of a Lithium dialkyl The Barton-McCombie deoxygenation^[8][9] removes hydroxyl groups from alcohols e. The Barton-McCombie deoxygenation is an Organic reaction in which an Hydroxy Functional group in an Organic compound is replaced by a Hydride g.

and the Clemmensen reduction^{[10][11][12][13]} removes carbonyl groups from aldehydes and ketones to form alkanes or alkyl-substituted compounds e. The Clemmensen reduction is a Chemical reaction described as a reduction of Ketones (or Aldehydes to Alkanes using Zinc g. :

Applications

The applications of a certain alkane can be determined quite well according to the number of carbon atoms. The first four alkanes are used mainly for heating and cooking purposes, and in some countries for electricity generation. Methane and ethane are the main components of natural gas; they are normally stored as gases under pressure. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where It is, however, easier to transport them as liquids: This requires both compression and cooling of the gas.

Propane and butane can be liquefied at fairly low pressures, and are well known as liquified petroleum gas (LPG). Propane is a three- Carbon Alkane, normally a gas but compressible to a liquid that is transportable Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 Liquefied petroleum gas (also called LPG, GPL, LP Gas, or Autogas) is a mixture of Hydrocarbon Gases used as a Fuel Propane, for example, is used in the propane gas burner, butane in disposable cigarette lighters. The two alkanes are used as propellants in aerosol sprays. Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles

From pentane to octane the alkanes are reasonably volatile liquids. Pentane is any or one of the Organic compounds with the formula C5H12 Octane is a straight-chain Alkane with the Chemical formula CH3(CH26CH3 They are used as fuels in internal combustion engines, as they vaporise easily on entry into the combustion chamber without forming droplets, which would impair the uniformity of the combustion. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a Branched-chain alkanes are preferred, as they are much less prone to premature ignition, which causes knocking than their straight-chain homologue. Knocking (also called knock, detonation or spark knock, pinking in UK English or pinging in US English in spark-ignition This propensity to premature ignition is measured by the octane rating of the fuel, where 2,2,4-trimethylpentane (isooctane) has an arbitrary value of 100, and heptane has a value of zero. The octane rating is a measure of the resistance of Gasoline and other Fuels to Detonation ( Engine knocking) in spark-ignition 224-Trimethylpentane, also known as isooctane, is an Octane Isomer which defines the 100 point on the Octane rating scale n -Heptane is the straight-chain Alkane with the Chemical formula H3C(CH25CH3 or C7H16 Apart from their use as fuels, the middle alkanes are also good solvents for nonpolar substances. A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution.

Alkanes from nonane to, for instance, hexadecane (an alkane with sixteen carbon atoms) are liquids of higher viscosity, less and less suitable for use in gasoline. Nonane is an Alkane Hydrocarbon with the Chemical formula CH3(CH27CH3 Hexadecane (also called cetane) is an Alkane Hydrocarbon with the Chemical formula C16H34 Viscosity is a measure of the resistance of a Fluid which is being deformed by either Shear stress or Extensional stress. They form instead the major part of diesel and aviation fuel. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum Aviation fuel is a specialized type of Petroleum -based fuel used to power Aircraft. Diesel fuels are characterised by their cetane number, cetane being an old name for hexadecane. Cetane number or CN is a measurement of the Combustion quality of Diesel fuel during compression ignition However, the higher melting points of these alkanes can cause problems at low temperatures and in polar regions, where the fuel becomes too thick to flow correctly.

Alkanes from hexadecane upwards form the most important components of fuel oil and lubricating oil. Fuel oil is a fraction obtained from Petroleum Distillation, either as a distillate or a residue Mineral oil or liquid Petroleum is a By-product in the Distillation of Petroleum to produce Gasoline and other petroleum In latter function, they work at the same time as anti-corrosive agents, as their hydrophobic nature means that water cannot reach the metal surface. Many solid alkanes find use as paraffin wax, for example, in candles. In chemistry paraffin is the common name for the Alkane Hydrocarbons with the general formula C n H2 n +2 A candle is a Light source and sometimes a Heat source consisting of a solid block of Fuel and an embedded wick. This should not be confused however with true wax, which consists primarily of esters. Wax has traditionally referred to a substance that is secreted by Bees ( Beeswax) and used by them in constructing their Esters are a class of Chemical compounds and Functional groups Esters consist of an inorganic or organic Acid in which at least

Alkanes with a chain length of approximately 35 or more carbon atoms are found in bitumen, used, for example, in road surfacing. Bitumen is a mixture of organic Liquids that are highly Viscous, black sticky entirely soluble in Carbon disulfide, and composed primarily However, the higher alkanes have little value and are usually split into lower alkanes by cracking. In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons

Some synthetic polymers such as polyethylene and polypropylene are alkanes with chains containing hundreds of thousands of carbon atoms. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Polyethylene or polythene ( IUPAC name poly(ethene) is a Thermoplastic commodity heavily used in consumer products (notably the Polypropylene or polypropene ( PP) is a Thermoplastic Polymer, made by the Chemical industry and used in a wide variety of applications These materials are used in innumerable applications, and billions of kilograms of these materials are made and used each year.

Physical properties

Boiling point

Alkanes experience inter-molecular van der Waals forces. The Van der Waals equation is an Equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion Stronger inter-molecular van der Waals forces give rise to greater boiling points of alkanes. ^[7]

There are two determinants for the strength of the van der Waals forces:

• the number of electrons surrounding the molecule, which increases with the alkane's molecular weight
• the surface area of the molecule

Under standard conditions, from CH₄ to C₄H₁₀ alkanes are gaseous; from C₅H₁₂ to C₁₇H₃₆ they are liquids; and after C₁₈H₃₈ they are solids. In Physical sciences standard conditions for temperature and pressure are Standard sets of conditions for experimental measurements to allow comparisons to be made As the boiling point of alkanes is primarily determined by weight, it should not be a surprise that the boiling point has almost a linear relationship with the size (molecular weight) of the molecule. The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one As a rule of thumb, the boiling point rises 20 - 30 °C for each carbon added to the chain; this rule applies to other homologous series. ^[7]

A straight-chain alkane will have a boiling point higher than a branched-chain alkane due to the greater surface area in contact, thus the greater van der Waals forces, between adjacent molecules. For example, compare isobutane and n-butane, which boil at -12 and 0 °C, and 2,2-dimethylbutane and 2,3-dimethylbutane which boil at 50 and 58 °C, respectively. Isobutane, also known as methylpropane or 2-methylpropane, is an Alkane, Isomeric with Butane. Butane, also called n -butane, is the unbranched Alkane with four Carbon Atoms CH3CH2CH2CH3 ^[7] For the latter case, two molecules 2,3-dimethylbutane can "lock" into each other better than the cross-shaped 2,2-dimethylbutane, hence the greater van der Waals forces.

On the other hand, cycloalkanes tend to have higher boiling points than their linear counterparts due to the locked conformations of the molecules, which give a plane of intermolecular contact.

Melting point

The melting points of the alkanes follow a similar trend to boiling points for the same reason as outlined above. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. The boiling point of a liquid is the temperature at which the Vapor pressure of the liquid equals the environmental pressure surrounding the liquid That is, (all other things being equal) the larger the molecule the higher the melting point. There is one significant difference between boiling points and melting points. Solids have more ridged and fixed structure than liquids. This rigid structure requires energy to break down. Thus the stronger better put together solid structures will require more energy to break apart. For alkanes, this can be seen from the graph above (i. e. , the blue line). The odd-numbered alkanes have a lower trend in melting points that even numbered alkanes. This is because even numbered alkanes pack well in the solid phase, forming a well-organised structure, which requires more energy to break apart. The odd-number alkanes pack less well and so the "looser" organised solid packing structure requires less energy to break apart. ^[14]

The melting points of branched-chain alkanes can be either higher or lower than those of the corresponding straight-chain alkanes, again depending on the ability of the alkane in question to packing well in the solid phase: This is particularly true for isoalkanes (2-methyl isomers), which often have melting points higher than those of the linear analogues.

Conductivity

Alkanes do not conduct electricity, nor are they substantially polarized by an electric field. Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can For this reason they do not form hydrogen bonds and are insoluble in polar solvents such as water. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen Since the hydrogen bonds between individual water molecules are aligned away from an alkane molecule, the coexistence of an alkane and water leads to an increase in molecular order (a reduction in entropy). In Thermodynamics (a branch of Physics) entropy, symbolized by S, is a measure of the unavailability of a system ’s Energy As there is no significant bonding between water molecules and alkane molecules, the second law of thermodynamics suggests that this reduction in entropy should be minimised by minimising the contact between alkane and water: Alkanes are said to be hydrophobic in that they repel water. The second law of Thermodynamics is an expression of the universal law of increasing Entropy, stating that the entropy of an Isolated system which In Chemistry, hydrophobicity (from the combining form of water in Attic Greek hydro- and for fear phobos) refers to the physical property of

Their solubility in nonpolar solvents is relatively good, a property that is called lipophilicity. Lipophilicity, fat-liking, refers to the ability of a Chemical compound to dissolve in fats oils lipids and non-polar solvents such as Hexane or Different alkanes are, for example, miscible in all proportions among themselves.

The density of the alkanes usually increases with increasing number of carbon atoms, but remains less than that of water. Hence, alkanes form the upper layer in an alkane-water mixture.

Molecular geometry

The molecular structure of the alkanes directly affects their physical and chemical characteristics. It is derived from the electron configuration of carbon, which has four valence electrons. In Atomic physics and Quantum chemistry, electron configuration is the arrangement of Electrons in an Atom, Molecule, or other Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 In chemistry valence electrons are the Electrons contained in the outermost or valence, Electron shell of an Atom. The carbon atoms in alkanes are always sp³ hybridised, that is to say that the valence electrons are said to be in four equivalent orbitals derived from the combination of the 2s orbital and the three 2p orbitals. -->In Chemistry These orbitals, which have identical energies, are arranged spatially in the form of a tetrahedron, the angle of cos⁻¹(−⅓) ≈ 109. 47° between them.

Bond lengths and bond angles

An alkane molecule has only C – H and C – C single bonds. The former result from the overlap of a sp³-orbital of carbon with the 1s-orbital of a hydrogen; the latter by the overlap of two sp³-orbitals on different carbon atoms. The bond lengths amount to 1. In Molecular geometry, bond length or bond distance is the average distance between nuclei of two bonded Atoms in a Molecule. 09×10⁻¹⁰ m for a C – H bond and 1. 54×10⁻¹⁰ m for a C – C bond.

The spatial arrangement of the bonds is similar to that of the four sp³-orbitals—they are tetrahedrally arranged, with an angle of 109. 47° between them. Structural formulae that represent the bonds as being at right angles to one another, while both common and useful, do not correspond with the reality.

Conformation

Main article: Alkane stereochemistry

The structural formula and the bond angles are not usually sufficient to completely describe the geometry of a molecule. Alkane stereochemistry concerns the Stereochemistry of linear Alkanes and the linear alkane Conformers The existence of more than one conformation is due Molecular geometry or molecular structure is the three- Dimensional arrangement of the Atoms that constitute a Molecule. There is a further degree of freedom for each carbon – carbon bond: the torsion angle between the atoms or groups bound to the atoms at each end of the bond. For information on degrees of freedom in other sciences see Degrees of freedom. In Aerospace engineering, the Dihedral is the Angle between the two wings see Dihedral. The spatial arrangement described by the torsion angles of the molecule is known as its conformation.

Ethane forms the simplest case for studying the conformation of alkanes, as there is only one C – C bond. Ball-and-stick models and Space-filling models (also known as Calotte models) are 3D or spatial Molecular models which serve to display the structure ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where If one looks down the axis of the C – C bond, one will see the so-called Newman projection. See also Conformational isomerism The hydrogen atoms on both the front and rear carbon atoms have an angle of 120° between them, resulting from the projection of the base of the tetrahedron onto a flat plane. However, the torsion angle between a given hydrogen atom attached to the front carbon and a given hydrogen atom attached to the rear carbon can vary freely between 0° and 360°. This is a consequence of the free rotation about a carbon – carbon single bond. Despite this apparent freedom, only two limiting conformations are important: eclipsed conformation and staggered conformation. For other possible meanings of the terms "eclipse" and "eclipsed" see eclipse. A staggered conformation is a Chemical conformation that exists in any open chain single Chemical bond connecting two sp3 hybridised atoms as

The two conformations, also known as rotamers, differ in energy: The staggered conformation is 12. Alkane stereochemistry concerns the Stereochemistry of linear Alkanes and the linear alkane Conformers The existence of more than one conformation is due 6 kJ/mol lower in energy (more stable) than the eclipsed conformation (the least stable).

This difference in energy between the two conformations, known as the torsion energy, is low compared to the thermal energy of an ethane molecule at ambient temperature. Alkane stereochemistry concerns the Stereochemistry of linear Alkanes and the linear alkane Conformers The existence of more than one conformation is due There is constant rotation about the C-C bond. The time taken for an ethane molecule to pass from one staggered conformation to the next, equivalent to the rotation of one CH₃-group by 120° relative to the other, is of the order of 10⁻¹¹ seconds.

The case of higher alkanes is more complex but based on similar principles, with the antiperiplanar conformation always being the most favoured around each carbon-carbon bond. For this reason, alkanes are usually shown in a zigzag arrangement in diagrams or in models. The actual structure will always differ somewhat from these idealised forms, as the differences in energy between the conformations are small compared to the thermal energy of the molecules: Alkane molecules have no fixed structural form, whatever the models may suggest.

NAME	Formula	B. P. /oC	M. P. /oC	Density/g cm -3(20oC)
Methane	CH4	-162	-183	gas
Ethane	C2H6	-89	-172	gas
Propane	C3H8	-42	-188	gas
Butane	C4H10	-0. 5	-135	gas
Pentane	C5H12	36	-130	0. 626
Hexane	C6H14	69	-95	0. 659
Heptane	C7H16	98	-91	0. 684
Octane	C8H18	126	-57	0. 703
Nonane	C9H20	151	-54	0. 718
Decane	C10H22	174	-30	0. 730
Undecane	C11H24	196	-26	0. 740
Dodecane	C12H26	216	-10	0. 749
Triacontane	C30H62	343	37	solid

Spectroscopic properties

Virtually all organic compounds contain carbon – carbon and carbon – hydrogen bonds, and so show some of the features of alkanes in their spectra. Alkanes are notable for having no other groups, and therefore for the absence of other characteristic spectroscopic features.

Infrared spectroscopy

The carbon – hydrogen stretching mode gives a strong absorption between 2850 and 2960 nanometres, while the carbon – carbon stretching mode absorbs between 800 and 1300 nm. The carbon – hydrogen bending modes depend on the nature of the group: methyl groups show bands at 1450 nm and 1375 nm, while methylene groups show bands at 1465 nm and 1450 nm. Carbon chains with more than four carbon atoms show a weak absorption at around 725 nm.

NMR spectroscopy

The proton resonances of alkanes are usually found at δ_H = 0. In Nuclear magnetic resonance (NMR the chemical shift describes the dependence of nuclear magnetic energy levels on the electronic environment in a Molecule. 5 – 1. 5. The carbon-13 resonances depend on the number of hydrogen atoms attached to the carbon: δ_C = 8 – 30 (primary, methyl, -CH₃), 15 – 55 (secondary, methylene, -CH₂-), 20 – 60 (tertiary, methyne, C-H) and quaternary. The carbon-13 resonance of quaternary carbon atoms is characteristically weak, due to the lack of Nuclear Overhauser effect and the long relaxation time, and can be missed in weak samples, or sample that have not been run for a sufficiently long time. In magnetic resonance spectroscopy, the transfer of Spin polarization from one spin population to another via cross-relaxation is generally called the Overhauser Relaxation time is a general concept in Physics for the Characteristic time in which a system changes to an Equilibrium condition from a non-equilibrium

Mass spectrometry

Alkanes have a high ionisation energy, and the molecular ion is usually weak. The ionization potential, ionization energy or EI of an Atom or Molecule is the Energy required to remove an Electron The fragmentation pattern can be difficult to interpret, but, in the case of branched chain alkanes, the carbon chain is preferentially cleaved at tertiary or quaternary carbons due to the relative stability of the resulting free radicals. In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell The fragment resulting from the loss of a single methyl group (M−15) is often absent, and other fragment are often spaced by intervals of fourteen mass units, corresponding to sequential loss of CH₂-groups.

Chemical properties

In general, alkanes show a relatively low reactivity, because their C bonds are relatively stable and cannot be easily broken. Unlike most other organic compounds, they possess no functional groups. In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions

They react only very poorly with ionic or other polar substances. The acid dissociation constant (pK_a) values of all alkanes are above 60, hence they are practically inert to acids and bases (see: carbon acids). A carbanion is an Anion in which Carbon has an unshared pair of Electrons and bears a negative charge usually with three substituents for a total of eight This inertness is the source of the term paraffins (with the meaning here of "lacking affinity"). In crude oil the alkane molecules have remained chemically unchanged for millions of years. Petroleum ( L petroleum, from Greek πετρέλαιον, lit

However redox reactions of alkanes, in particular with oxygen and the halogens, are possible as the carbon atoms are in a strongly-reduced condition; in the case of methane, the lowest possible oxidation state for carbon (−4) is reached. Reaction with oxygen leads to combustion without any smoke; with halogens, substitution. In a substitution reaction, a Functional group in a particular Chemical compound is replaced by another group In addition, alkanes have been shown to interact with, and bind to, certain transition metal complexes in (See: carbon-hydrogen bond activation). Carbon-hydrogen bond activation or CH activation may be defined as a reaction that cleaves a Carbon-hydrogen bond.

Free radicals, molecules with unpaired electrons, play a large role in most reactions of alkanes, such as cracking and reformation where long-chain alkanes are converted into shorter-chain alkanes and straight-chain alkanes into branched-chain isomers. In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell

In highly-branched alkanes, the bond angle may differ significantly from the optimal value (109. 5°) in order to allow the different groups sufficient space. This causes a tension in the molecule, known as steric hindrance, and can substantially increase the reactivity. See also Intramolecular forces ' Steric effects arise from the fact that each Atom within a Molecule occupies a certain

Reactions with oxygen

All alkanes react with oxygen in a combustion reaction, although they become increasingly difficult to ignite as the number of carbon atoms increases. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of The general equation for complete combustion is:

C_nH_2n+2 + (1. 5n+0. 5)O₂ → (n+1)H₂O + nCO₂

In the absence of sufficient oxygen, carbon monoxide or even soot can be formed, as shown below:

C_nH_(2n+2) + ½ nO₂ → (n+1)H₂ + nCO

for example methane:

2CH₄ + 3O₂ → 2CO + 4H₂O

CH₄ + O₂ → C + 2H₂O

See the alkane heat of formation table for detailed data. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Soot (ˈsʊt is a general term that refers to the black impure carbon particles resulting from the incomplete combustion of a hydrocarbon Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. These tables include heat of formation data gathered from a variety of sources including the primary and secondary literature as well as the NIST Chemistry WebBook The standard enthalpy change of combustion, Δ_cH^o, for alkanes increases by about 650 kJ/mol per CH₂ group. The standard enthalpy of combustion is the Enthalpy change when one mole of a substance completely reacts with oxygen under standard thermodynamic conditions (although Branched-chain alkanes have lower values of Δ_cH^o than straight-chain alkanes of the same number of carbon atoms, and so can be seen to be somewhat more stable.

Reactions with halogens

Main article: Free radical halogenation

Alkanes react with halogens in a so-called free radical halogenation reaction. In Organic chemistry, free radical halogenation is a type of Halogenation. Abundance Owing to their high Reactivity, the halogens are found in the environment only in compounds or as Ions Halide ions and oxoanions The hydrogen atoms of the alkane are progressively replaced by halogen atoms. Free-radicals are the reactive species that participate in the reaction, which usually leads to a mixture of products. In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell The reaction is highly exothermic, and can lead to an explosion. An exothermic reaction is a Chemical reaction that releases Heat.

These reactions are an important industrial route to halogenated hydrocarbons. There are three steps:

• Initiation the halogen radicals form by homolysis. In Chemistry, homolysis or homolytic fission is Chemical bond dissociation of a neutral Molecule generating two Free radicals That Usually, energy in the form of heat or light is required.
• Chain reaction then takes place—the halogen radical abstracts a hydrogen from the alkane to give an alkyl radical. This reacts further.
• Chain termination where step the radicals recombine.

Experiments have shown that all halogenation produces a mixture of all possible isomers, indicating that all hydrogen atoms are susceptible to reaction. The mixture produced, however, is not a statistical mixture: Secondary and tertiary hydrogen atoms are preferentially replaced due to the greater stability of secondary and tertiary free-radicals. An example can be seen in the monobromination of propane:^[7]

Cracking

Main article: Cracking (chemistry)

Cracking breaks larger molecules into smaller ones. In Petroleum geology and Chemistry, cracking is the process whereby complex organic Molecules such as Kerogens or heavy Hydrocarbons This can be done with a thermal or catalytic method. The thermal cracking process follows a homolytic mechanism with formation of free-radicals. In Chemistry, homolysis or homolytic fission is Chemical bond dissociation of a neutral Molecule generating two Free radicals That In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell The catalytic cracking process involves the presence of acid catalysts (usually solid acids such as silica-alumina and zeolites), which promote a heterolytic (asymmetric) breakage of bonds yielding pairs of ions of opposite charges, usually a carbocation and the very unstable hydride anion. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Silica-alumina is also known as alumino-silicate(s It is an oxide-like combination of Aluminium, Silicon and Oxygen, and it has a major component of Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure In Chemistry, heterolysis or heterolytic fission (from Greek ἑτερος heteros "different" and λυσις lusis "loosening" An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Hydride is the name given to the negative Ion of Hydrogen, H− An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Carbon-localized free-radicals and cations are both highly unstable and undergo processes of chain rearrangement, C-C scission in position beta (i. Beta scission is the initial step in the Chemistry of thermal Cracking of Hydrocarbons and the formation of free radicals. e. , cracking) and intra- and intermolecular hydrogen transfer or hydride transfer. Intramolecular in Chemistry describes a process or characteristic limited within the structure of a single Molecule; a property or phenomenon limited to the extent In Physics, Chemistry, and Biology, intermolecular forces are forces that act between stable Molecules or between functional groups of Hydride is the name given to the negative Ion of Hydrogen, H− In both types of processes, the corresponding reactive intermediates (radicals, ions) are permanently regenerated, and thus they proceed by a self-propagating chain mechanism. A reaction intermediate or an intermediate is a Molecular entity that is formed from the reactants (or preceding intermediates and reacts further to give the directly The chain of reactions is eventually terminated by radical or ion recombination.

Isomerization and reformation

Isomerization and reformation are processes in which straight-chain alkanes are heated in the presence of a platinum catalyst. Platinum (ˈplætɪnəm is a Chemical element with the Atomic symbol Pt and an Atomic number of 78 In isomerization, the alkanes become branched-chain isomers. In reformation, the alkanes become cycloalkanes or aromatic hydrocarbons, giving off hydrogen as a by-product. Cycloalkanes (also called naphthenes, especially if from Petroleum sources are types of Alkanes which have one or more rings of Carbon Atoms Both of these processes raise the octane number of the substance. The octane rating is a measure of the resistance of Gasoline and other Fuels to Detonation ( Engine knocking) in spark-ignition

Other reactions

Alkanes will react with steam in the presence of a nickel catalyst to give hydrogen. Uses A Steam engine uses the expansion of steam in order to drive a Piston or Turbine to perform Mechanical work. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 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 (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Alkanes can by chlorosulfonated and nitrated, although both reactions require special conditions. Nitration is a general Chemical process for the introduction of a nitro group into a Chemical compound. The fermentation of alkanes to carboxylic acids is of some technical importance. Fermentation is the process of deriving energy from the oxidation of organic compounds such as carbohydrates using an endogenous electron acceptor which is Carboxylic acids are Organic acids characterized by the presence of a Carboxyl group, which has the formula -C(=OOH usually written -COOH or -CO2H In the Reed reaction, sulfur dioxide, chlorine and light convert hydrocarbons to sulfonyl chlorides. The Reed reaction is a Chemical reaction that utilizes light to oxidize Hydrocarbons to Sulfonyl chlorides Chlorine (ˈklɔriːn from the Greek word 'χλωρóς' ( khlôros, meaning 'pale green' is the Chemical element with Atomic number 17 and Photochemistry, a sub-discipline of Chemistry, is the study of the interactions between Atoms, small Molecules, and light (or Electromagnetic radiation Sulfonic acid is an unstable Acid with the formula H-S(=O2-OH

Hazards

Methane is explosive when mixed with air (1 – 8% CH₄) and is a strong greenhouse gas: Other lower alkanes can also form explosive mixtures with air. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared The lighter liquid alkanes are highly flammable, although this risk decreases with the length of the carbon chain. Pentane, hexane, heptane, and octane are classed as dangerous for the environment and harmful. The straight-chain isomer of hexane is a neurotoxin. A neurotoxin is a Toxin that acts specifically on nerve cells ( Neurons, usually by interacting with Membrane proteins such as Ion channels

See also

• Alkene
• Alkyne
• Cycloalkane
• Cracking (chemistry)
• Functional group
• List of n-alkanes

References

Further reading

• Virtual Textbook of Organic Chemistry

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