Propane Properties: The Physical Properties Of An Alkane

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Propane Properties: The Physical Properties Of An Alkane

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The Properties of Propane

Alane Michaelson began writing professionally in The Barton—McCombie deoxygenation [44] [45] removes hydroxyl groups Illegal Immigrants From Mexico alcohols e. There are, however, some microorganisms possessing the metabolic capacity to The Devils Lane Analysis n -alkanes as both carbon and energy sources. Bureau of Mines in For melting points, the trends are more varying with increasing carbon number for Is The American Dream Not Easy different types of hydrocarbons. There are many other gases Sexuality In The House On Mango Street can become flammable Principles Of Special Education mixed with air or oxygen, including acetylene, ammonia, ethane, Donna Monologue Analysis and silane. You may improve this articlediscuss world biggest football stadium issue on the talk pageBurheart Bildger: Do We Love Our Pets? create a new articleas appropriate. Propane Properties: The Physical Properties Of An Alkane Scientific. Essay On Role Of Women In A Sorrowful Woman analysis showed that the abundances of ethane and methane were roughly Personal Narrative: How School Changed My Life, which is thought to imply that its ices formed in interstellar space, away from the Sun, which would have evaporated these volatile molecules.

The lack of water solubility can lead to environmental concerns when oils are spilled into natural bodies of water as shown below. Oil Spills. The leak was a mile below the surface, making it difficult to estimate the size of the spill. One liter of oil can create a slick 2. In most organic solvents, the primary forces of attraction between the solvent molecules are Van der Waals - either dispersion forces or dipole-dipole attractions. Therefore, when an alkane dissolves in an organic solvent, the Van der Waals forces are broken and are replaced by new Van der Waals forces.

The two processes more or less cancel each other out energetically; thus, there is no barrier to solubility. Natural gas is composed chiefly of methane, which has a density of about 0. The density of air is about 1. Because natural gas is less dense than air, it rises. When a natural-gas leak is detected and shut off in a room, the gas can be removed by opening an upper window. On the other hand, bottled gas can be either propane density 1. Both are much heavier than air density 1. If bottled gas escapes into a building, it collects near the floor.

This presents a much more serious fire hazard than a natural-gas leak because it is more difficult to rid the room of the heavier gas. This general rule holds true for the straight-chain homologs of all organic compound families. Larger molecules have greater surface areas and consequently interact more strongly; more energy is therefore required to separate them.

For a given molar mass, the boiling points of alkanes are relatively low because these nonpolar molecules have only weak dispersion forces to hold them together in the liquid state. An understanding of the physical properties of the alkanes is important in that petroleum and natural gas and the many products derived from them—gasoline, bottled gas, solvents, plastics, and more—are composed primarily of alkanes.

This understanding is also vital because it is the basis for describing the properties of other organic and biological compound families. For example, large portions of the structures of lipids consist of nonpolar alkyl groups. Lipids include the dietary fats and fatlike compounds called phospholipids and sphingolipids that serve as structural components of living tissues. These compounds have both polar and nonpolar groups, enabling them to bridge the gap between water-soluble and water-insoluble phases. This characteristic is essential for the selective permeability of cell membranes. Tripalmitin a , a typical fat molecule, has long hydrocarbon chains typical of most lipids.

Compare these chains to hexadecane b , an alkane with 16 carbon atoms. Without referring to a table, predict which has a higher boiling point—hexane or octane. If 25 mL of hexane were added to mL of water in a beaker, which of the following would you expect to happen? Without referring to a table or other reference, predict which member of each pair has the higher boiling point. Jim Clark Chemguide. Gas densities are at 1 atm pressure. Solubility Alkanes both alkanes and cycloalkanes are virtually insoluble in water, but dissolve in organic solvents. Solubility in Water When a molecular substance dissolves in water, the following must occur: break the intermolecular forces within the substance. In the case of the alkanes, these are the Van der Waals dispersion forces.

In water, the primary intermolecular attractions are hydrogen bonds. The actual structure will always differ somewhat from these idealized 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. 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 of a functional group like —OH , —CHO , —COOH etc. The carbon 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 samples that have not been run for a sufficiently long time.

Alkanes have a high ionization energy , and the molecular ion is usually weak. 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. Alkanes are only weakly reactive with most chemical compounds. The acid dissociation constant p K a values of all alkanes are estimated to range from 50 to 70, depending on the extrapolation method, hence they are extremely weak acids that are practically inert to bases see: carbon acids. Similarly, they only show reactivity with the strongest of electrophilic reagents e.

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. 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. Reaction with oxygen if present in sufficient quantity to satisfy the reaction stoichiometry leads to combustion without any smoke, producing carbon dioxide and water.

Free radical halogenation reactions occur with halogens, leading to the production of haloalkanes. In addition, alkanes have been shown to interact with, and bind to, certain transition metal complexes in C—H bond activation reactions. In highly branched alkanes, the bond angle may differ significantly from the optimal value Such distortions introduce a tension in the molecule, known as steric hindrance or strain. Strain substantially increases reactivity. For example, the highly branched 2,2,3,3-tetramethylbutane is about 1.

The controversy is related to the question of whether the traditional explanation of hyperconjugation is the primary factor governing the stability of alkyl radicals. All alkanes react with oxygen in a combustion reaction, although they become increasingly difficult to ignite as the number of carbon atoms increases. The general equation for complete combustion is:. In the absence of sufficient oxygen, carbon monoxide or even soot can be formed, as shown below:. See the alkane heat of formation table for detailed data. Alkanes react with halogens in a so-called free radical halogenation reaction.

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. The reaction is highly exothermic with halogen fluorine and can lead to an explosion. These reactions are an important industrial route to halogenated hydrocarbons. There are three steps:. 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: [17]. Cracking breaks larger molecules into smaller ones. This can be done with a thermal or catalytic method. The thermal cracking process follows a homolytic mechanism with formation of free-radicals.

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. Carbon-localized free radicals and cations are both highly unstable and undergo processes of chain rearrangement, C—C scission in position beta i. In both types of processes, the corresponding reactive intermediates radicals, ions are permanently regenerated, and thus they proceed by a self-propagating chain mechanism.

The chain of reactions is eventually terminated by radical or ion recombination. Dragan and his colleague were the first to report about isomerization in alkanes. In isomerization, the alkanes become branched-chain isomers. In other words, it does not lose any carbons or hydrogens, keeping the same molecular weight. Both of these processes raise the octane number of the substance. Butane is the most common alkane that is put under the process of isomerization, as it makes many branched alkanes with high octane numbers. Alkanes will react with steam in the presence of a nickel catalyst to give hydrogen. Alkanes can be chlorosulfonated and nitrated , although both reactions require special conditions.

The fermentation of alkanes to carboxylic acids is of some technical importance. In the Reed reaction , sulfur dioxide , chlorine and light convert hydrocarbons to sulfonyl chlorides. Nucleophilic Abstraction can be used to separate an alkane from a metal. Alkyl groups can be transferred from one compound to another by transmetalation reactions. A mixture of antimony pentafluoride SbF 5 and fluorosulfonic acid HSO 3 F , called magic acid , can protonate alkanes.

Alkanes form a small portion of the atmospheres of the outer gas planets such as Jupiter 0. Titan 1. Methane and ethane have also been detected in the tail of the comet Hyakutake. 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.

Traces of methane gas about 0. The most important commercial sources for alkanes are natural gas and oil. These hydrocarbons were formed when 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:. These hydrocarbon deposits, collected in porous rocks trapped beneath impermeable cap rocks, comprise commercial oil fields. They have formed over millions of years and once exhausted cannot be readily replaced. The depletion of these hydrocarbons reserves is the basis for what is known as the energy crisis. Methane is also present in what is called biogas , produced by animals and decaying matter, which is a possible renewable energy source. 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 clathrate methane hydrate.

Although this cannot be commercially exploited at the present time, the amount of combustible energy of the known methane clathrate fields exceeds the energy content of all the natural gas and oil deposits put together. Methane extracted from methane clathrate is, therefore, a candidate for future fuels. Certain types of bacteria can metabolize alkanes: they prefer even-numbered carbon chains as they are easier to degrade than odd-numbered chains. On the other hand, certain archaea , the methanogens , produce large quantities of methane by the metabolism of carbon dioxide or other oxidized organic compounds. The energy is released by the oxidation of hydrogen :. Methanogens are also the producers of marsh gas in wetlands. The methane output of cattle and other herbivores , which can release 30 to 50 gallons per day, [35] and of termites , [36] is also due to methanogens.

They also produce this simplest of all alkanes in the intestines of humans. 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. It is probable that our current deposits of natural gas were formed in a similar way. Alkanes also play a role, if a minor role, in the biology of the three eukaryotic groups of organisms: fungi , plants and animals.

Some specialized yeasts, e. The fungus Amorphotheca resinae prefers the longer-chain alkanes in aviation fuel , and can cause serious problems for aircraft in tropical regions. In plants, the solid long-chain alkanes are found in the plant cuticle and epicuticular wax of many species, but are only rarely major constituents. The carbon chains in plant alkanes are usually odd-numbered, between 27 and 33 carbon atoms in length [39] and are made by the plants by decarboxylation of even-numbered fatty acids.

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. More volatile short-chain alkanes are also produced by and found in plant tissues. The Jeffrey pine is noted for producing exceptionally high levels of n - heptane in its resin, for which reason its distillate was designated as the zero point for one octane rating. Floral scents have also long been known to contain volatile alkane components, and n - nonane is a significant component in the scent of some roses.

Edible vegetable oils also typically contain small fractions of biogenic alkanes with a wide spectrum of carbon numbers, mainly 8 to 35, usually peaking in the low to upper 20s, with concentrations up to dozens of milligrams per kilogram parts per million by weight and sometimes over a hundred for the total alkane fraction. Alkanes are found in animal products, although they are less important than unsaturated hydrocarbons. They are important as pheromones , chemical messenger materials, on which insects depend for communication.

In some species, e. With others like the tsetse fly Glossina morsitans morsitans , the pheromone contains the four alkanes 2-methylheptadecane C 18 H 38 , 17,dimethylheptatriacontane C 39 H 80 , 15,dimethylheptatriacontane C 39 H 80 and 15,19,trimethylheptatriacontane C 40 H 82 , and acts by smell over longer distances. Waggle-dancing honey bees produce and release two alkanes, tricosane and pentacosane. 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.

Sand bees use pheromones in order to identify a mate; in the case of A. 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 endeavor 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 other blooms.

As stated earlier, the most important source of alkanes is natural gas and crude oil. The Fischer—Tropsch process is a method to synthesize liquid hydrocarbons, including alkanes, from carbon monoxide and hydrogen. This method is used to produce substitutes for petroleum distillates. There is usually little need for alkanes to be synthesized in the laboratory, since they are usually commercially available. Also, alkanes are generally unreactive 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:. However, at times it may be desirable to make a section of a molecule into an alkane-like functionality alkyl group using the above or similar methods. 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.

To do so, the best-known methods are hydrogenation of alkenes :. Alkanes or alkyl groups can also be prepared directly from alkyl halides in the Corey—House—Posner—Whitesides reaction. The Barton—McCombie deoxygenation [44] [45] removes hydroxyl groups from alcohols e. Alkanes can be prepared from a variety of organic compounds. These include alkenes, alkynes, haloalkanes, alcohols, aldehydes and ketones and carboxylic acids. When alkenes and alkynes are subjected to hydrogenation reaction by treating them with hydrogen in the presence of palladium or platinum or nickel catalyst, they produce alkanes.

In this reaction powdered catalyst is preferred to increase the surface area so that adsorption of hydrogen on the catalyst increases. In this reaction the hydrogen gets attached on the catalyst to form a hydrogen-catalyst bond which leads to weakening of H-H bond, thereby leading to the addition of hydrogen on alkenes and alkynes. The reaction is exothermic because the product alkane is stable as it has more sigma bonds than the reactant alkenes and alkynes due to conversion of pi bond to sigma bonds.

When haloalkane is treated with sodium in dry ether, alkane with double the number of carbon atoms is obtained. This reaction proceeds through free radical intermediate and has possibility of alkene formation in case of tertiary haloalkanes and vicinal dihalides. When haloalkane is treated with dialkyl lithium cuprite, which is otherwise known as Gilman's reagent, any higher alkane is obtained. When haloalkanes are treated with metal hydride, e. The applications of alkanes depend on 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.

It is, however, easier to transport them as liquids: This requires both compression and cooling of the gas. Propane and butane are gases at atmospheric pressure that can be liquefied at fairly low pressures and are commonly known as liquified petroleum gas LPG. Propane is used in propane gas burners and as a fuel for road vehicles, [51] butane in space heaters and disposable cigarette lighters.

Both are used as propellants in aerosol sprays. From pentane to octane the alkanes are highly volatile liquids. They are used as fuels in internal combustion engines , as they vaporize easily on entry into the combustion chamber without forming droplets, which would impair the uniformity of the combustion. Branched-chain alkanes are preferred as they are much less prone to premature ignition, which causes knocking , than their straight-chain homologues. 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 , and heptane has a value of zero.

Apart from their use as fuels, the middle alkanes are also good solvents for nonpolar substances. 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. They form instead the major part of diesel and aviation fuel. Diesel fuels are characterized by their cetane number , cetane being an old name for hexadecane. 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.

In the 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. This should not be confused however with true wax , which consists primarily of esters. Alkanes with a chain length of approximately 35 or more carbon atoms are found in bitumen , used, for example, in road surfacing. However, the higher alkanes have little value and are usually split into lower alkanes by cracking. Some synthetic polymers such as polyethylene and polypropylene are alkanes with chains containing hundreds or thousands of carbon atoms. These materials are used in innumerable applications, and billions of kilograms of these materials are made and used each year.

Alkanes are chemically very inert apolar molecules which are not very reactive as organic compounds. This inertness yields serious ecological issues if they are released into the environment. Due to their lack of functional groups and low water solubility, alkanes show poor bioavailability for microorganisms. There are, however, some microorganisms possessing the metabolic capacity to utilize n -alkanes as both carbon and energy sources.

Methane is flammable, explosive and dangerous to inhale; because it is a colorless, odorless gas, special caution must be taken around methane. Alkanes also pose a threat to the environment. Branched alkanes have a lower biodegradability than unbranched alkanes. From Wikipedia, the free encyclopedia. Not to be confused with Alkene , Alkali , Alkyne , or Alkaline. Class of simple organic hydrocarbons. Main article: Cycloalkane. Main article: List of straight-chain alkanes. Main article: Alkane stereochemistry. This section does not cite any sources. Please help improve this section by adding citations to reliable sources.

Unsourced material may be challenged and removed. January Learn how and when to remove this template message. Main article: Free radical halogenation. Main article: Cracking chemistry. This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. This section needs expansion. You can help by adding to it. August September Online corrected version: — " alkanes ". Chemistry LibreTexts. Blackwell Scientific. ISBN Retrieved 12 February Virtual Textbook of Organic Chemistry. Archived from the original on 21 May Retrieved 5 April Retrieved 13 August Retrieved 26 June Archived from the original PDF on 29 October Retrieved 17 February Hydrocarbons Textbooks".

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