Biofuel

Biofuel is any fuel that derives from biomass - recently living organisms or their metabolic byproducts, such as manure from cows. It is a renewable energy, unlike natural resources such as petroleum, coal and nuclear fuels.

Typically biofuel is burned to release its stored chemical energy. Research into more efficient methods of converting biofuels and other fuels into electricity utilizing fuel cells is an area of very active work.

The carbon in biofuels was recently extracted from atmospheric carbon dioxide by growing plants, so burning it does not contribute carbon dioxide to the Earth's atmosphere.

Bioenergy covers about 15% of the world's energy consumption. Sweden and Finland supply 17% and 19% respectively, of their energy needs with bioenergy. Biomass can be used both for centralized production of electricity and district heat, and for local heating.

Oxidisation of biomass does not release more CO2 than that which was absorbed by production of that same biomass. Both agricultural products specifically grown for this use and waste from industry, agriculture, forestry, and households -including straw, lumber, manure, and food leftovers-can be used for the production of bioenergy.

Classes of Biofuels

Solid

There are many forms of solid biomass that are combustible as a fuel such as:

• Wood — see wood fuel
• Dried compressed peat
• straw and other dried plants
• animal waste such as poultry droppings or cattle dung.
• husks or shells from crops such as rice, groundnut and cotton.
• bagasse

Liquid

There are also a number of liquid forms of biomass that can be used as a fuel:

• Bioalcohols — see alcohol as a fuel
• Ethanol produced from sugar cane is being used as automotive fuel in Brazil. Ethanol produced from corn is being used as a gasoline additive (oxygenator ) in the United States.
• Methanol, which is currently produced from natural gas, can also be produced from biomass — although this is not economically viable at present.
• Biologically produced oils can be used in diesel engines:
• Straight vegetable oil (SVO).
• Waste vegetable oil (WVO).
• Biodiesel obtained from transesterification of animal fats and vegetable oil.
• Oils and gases can be produced from various wastes:
• Thermal depolymerization can extract methane and oil similar to petroleum from waste.
• Methane and oils are being extracted from landfill wells and leachate in test sites.

Gaseous

• Methane produced by the nature decay of garbage or agricultural manure can be collected for use as fuel.
• Biogas
• Hydrogen can be produced by cracking any hydrocarbon fuel in a reforme or by the electrolysis of water.
• Gasification

Energy content of Biofuel

fuel type	Specific Energy Density (J/kg)	Volumetric Energy Density (J/l)
wood fuel
dried plants
animal waste
chaff
bagasse
ethanol
methanol
vegetable oil
Biodiesel
Methane
Hydrogen

Dissemination mechanisms

Biofuels have a low specific energy density compared to fossil fuels. This means that biomass energy schemes must work at a local level as their success depends on well-structured and sustainable fuel supply networks from local producers.

Small scale use of biofuels

A widespread use of biofuels is in home cooking and heating. Typical fuels for this are wood, charcoal or dried dung. The biofuel may be burned on an open fireplace or in a special stove. The efficiency of this process may vary widely from 10% for a well made fire up (even less if the fire is not made carefully) to 40% for a custom designed charcoal stove. Inefficient use of fuel may be a minor cause of deforestation (though this is negligible compared to deliberate destruction to clear land for agricultural use) but more importantly it means that more work has to be put into gathering fuel, thus the quality of cooking stoves has a direct influence on the viability of biofuels.

Unfortunately, much cooking with biofuels is done indoors, without efficient ventilation and using those fuels such as dung which cause most airborne polution. This can be a serious health hazard; 1.5 million deaths were attributed to this cause by the World Health Organisation in 2000. There are various responses to this, such as improved stoves, including those with inbuilt flues and switching to alternative fuel sources. Most of these responses have difficulties, for example flues are expensive and easily damage; alternative fuels tend to be more expensive which is difficult to implement since the people who rely on biofuels often do so precisely because they cannot afford alternatives. Organisations such as Intermediate Technology Development Group work to make improved facilities for biofuel use and better alternatives accessible to those who cannot currently get them. This work be done through designing improved ventilation, a switch to different usage of biomass such as through the creation of biogas from solid biomatter or a switch to other alternatives such as micro-hydro power.

Natural gas

Natural gas is a gas produced by the anaerobic decay of organic material. It is usually found in oil fields and natural gas fields, but is also generated in swamps and marshes (where it is called swamp gas or marsh gas), in landfill sites, and during digestion in animals.

Chemical composition and energy content

Chemical composition

The primary component of natural gas is methane (CH₄), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane (C₂H₆), propane (C₃H₈) and butane (C₄H₁₀), as well as other gases, in varying amounts, see also natural gas condensate.

Hydrogen sulfide (H₂S see acid gas) and mercury (Hg) are common contaminants, which must be removed prior to most uses.

Energy content

Combustion of one hundred cubic feet (1 ccf) of commercial quality natural gas typically yields approximately 1 therm (100,000 British thermal units, 30 kWh). One cubic meter yields 38 MJ (10.6 kWh).

Storage and transport

The major difficulty in the use of natural gas is transportation. Natural gas pipelines are economical, but are impractical across oceans. Many existing pipelines in North America are close to reaching their capacity prompting some politicians in colder climates to speak publicly of potential shortages. Liquefied natural gas (LNG) tankers are also used, but have higher cost and safety problems. In many cases, as with oil fields in Saudi Arabia, the natural gas which is recovered in the course of recovering petroleum cannot be profitably sold, and is simply burned at the oil field (known as flaring ). This wasteful practice is now illegal in many countries, especially since it adds greenhouse gas pollution to the atmosphere, and since a profitable method may be found in the future. The gas is instead re-injected back into the ground for possible later recovery, and to assist oil pumping by keeping underground pressures higher.

Natural gas is often stored as Compressed Natural Gas or CNG.

Natural gas crisis

Many politicians and prominent figures in North America have spoken publicly about a possible natural gas crisis . This list includes former Secretary of Energy Spencer Abraham, Chairman of the Federal Reserve Alan Greenspan, Ontario Minister of Energy Dwight Duncan.

The natural gas crisis is typically described by the increasing price of natural gas in the U.S. over the last few years due to the decline in indigenous supply and the increase in demand for electricity generation. The price has become so high that many industrial users, mainly in the petrochemical industry, have closed their plants causing loss of jobs. Alan Greenspan has suggested that a solution to the natural gas crisis is the importation of liquified natural gas, or LNG.

Uses

Power generation

Natural gas is important as a major source for electricity generation through the use of gas turbines and steam turbines. Particularly high efficiencies can be achieved through combining gas turbines with a steam turbine in combined cycle mode. Environmentally, natural gas burns cleaner than other fossil fuels, such as oil and coal, and produces less greenhouse gases. For an equivalent amount of heat, burning natural gas produces about 30% less carbon dioxide than burning petroleum and about 45% less than burning coal. Combined cycle power generation using natural gas is thus the cleanest source of power available using fossil fuels, and this technology is widely used wherever gas can be obtained at a reasonable cost. Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not price-competitive.

Natural gas vehicles

Compressed natural gas (and LPG) is used as a clean alternative to other automobile fuels. As of 2003, the countries with the largest number of natural gas vehicles were Argentina, Brazil, Pakistan, Italy, and India.

Domestic use

Natural gas is supplied to homes where it is used for such purposes as cooking and heating CNG is used in rural homes without connections to piped-in public utility services, or with portable grills.

Fertilizer

Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production.

Sources

Natural gas is commercially produced from oil fields and natural gas fields.

Possible future sources

One experimental idea is to use the methane gas that is naturally produced from landfills to supply power to cities. Tests have shown that methane gas could be a financially sustainable power source.

There are plans in Ontario to capture the methane gasses rising from the manure of cattle caged in a factory farm and to use that gas to provide power to a small town.

There is also the possibility that with the source separation of organic materials from the waste stream that by using an anerobic digester, the methane can be used to produce useable energy. This can be improved by adding other organic material (plants as well as slaughter house waste) to the digester.

Safety

In any form, a strong bad scent (such as ethanethiol) is deliberately added to the otherwise colorless and odorless gas, so that leaks can be detected by the smell before an explosion occurs. In mines, sensors are used and mining apparatus has been specifically developed to avoid ignition sources (e.g. the Davy lamp). Adding scent to natural gas began after the 1937 New London School explosion. The buildup of gas in the school went unnoticed, and killed three hundred students and faculty when it ignited.

Explosions caused by natural gas leaks occur a few times each year. Individual homes and small businesses are most frequently affected when an internal leak builds up gas inside the structure. Frequently, the blast will be enough to significantly damage a building but leave it standing. In these cases, the people inside tend to have minor to moderate injuries. Occasionally, the gas can collect in high enough quantities to cause a deadly explosion, disintegrating one or more buildings in the process. The gas usually dissipates readily outdoors, but can sometimes collect in dangerous quantities if weather conditions are right. Considering the tens of millions of structures that use the fuel, the risks of using natural gas are very low.

Natural gas is non-toxic, though some gas fields yield 'acid gas' or 'sour gas' containing hydrogen sulfide. This untreated gas is toxic.

Extraction of natural gas (or oil) leads to decrease in pressure in the reservoir. This in turn may lead to subsidence at ground level. Subsidence may affect ecosystems, waterways, sewer and water supply systems, foundations etc.

Future of Oil

Future of oil

The Hubbert peak theory, also known as peak oil, is a controversial theory concerning the long-term rate of conventional oil and other fossil fuel production and depletion. It assumes that oil reserves are not replenished, and predicts that future world oil production must inevitably reach a peak and then decline as these reserves are exhausted. Much of the controversy is over whether past production or discovery data can be used to predict a future peak. Based on available production data, proponents have previously (and incorrectly) predicted the peak years to be 1989, 1995, or 1995-2000. A new prediction by Goldman Sachs picks 2007 for oil and some time later for natural gas.

Classification

The oil industry classifies "crude" by the location of its origin (e.g., "West Texas Intermediate, WTI" or "Brent") and often by its relative weight or viscosity ("light", "intermediate" or "heavy"); refiners may also refer to it as "sweet", which means it contains relatively little sulfur, or as "sour", which means it contains substantial amounts of sulfur and requires more refining in order to meet current product specifications.

The world reference barrels are:

• Brent Blend, comprising 15 oils from fields in the Brent and Ninian systems in the East Shetland Basin of the North Sea. The oil is landed at Sullom Voe terminal in the Shetlands. Oil production from Europe, Africa and Middle Eastern oil flowing West tends to be priced off the price of this oil, which forms a benchmark.
• West Texas Intermediate (WTI) for North American oil.
• Dubai used as benchmark for the Asia-Pacific region for Middle East Oil
• Tapis (from Malaysia, used as a reference for light Far East oil)
• Minas (from Indonesia, used as a reference for heavy Far East oil)
• The OPEC Basket consisting of
• Arab Light Saudi Arabia
• Bonny Light Nigeria
• Fateh Dubai
• Isthmus Mexico (non-OPEC)
• Minas Indonesia
• Saharan Blend Algeria
• Tia Juana Light Venezuela

OPEC attempts to keep the price of the Opec Basket between upper and lower limits, by increasing and decreasing production. This makes the measure important for market analysts. The OPEC Basket, including a mix of light and heavy crudes, is heavier than both Brent and WTI.

Pricing

In modern western economies, both the primary source of energy and the primary form of stored and transported energy is hydrocarbon fossil fuels. Because pumping the hydrocarbons out of the ground is currently inexpensive (about one U.S. dollar per barrel in Saudi Arabia in 2004), the price of energy comes from the costs of refining and distribution, and from taxation and profits by the various governments and companies in the custody chain between producer and consumer. The price of crude delivered to a refinery in the U.S. is about $50 a barrel in late 2004.

The price of oil fluctuates quite widely in response to crises or recessions in major economies, because any economic downturn reduces the demand for oil. On the supply side the OPEC cartel uses its influence to stabilise or raise oil prices. During 2004, the OPEC official price range for its crude oil is US $22 to US $28 per barrel.

A recent low point was reached in January 1999, after increased oil production from Iraq coincided with the Asian financial crisis, which reduced demand. The prices then rapidly increased, more than doubling by September 2000, then fell until the end of 2001 before steadily increasing, reaching US $40 to US $50 per barrel by September 2004 (see Oil price increases of 2004). In October 2004, light crude futures on the NYMEX for November delivery exceeded US $53 per barrel and for December delivery exceeded US $55 per barrel.

The New York Mercantile Exchange (NYMEX) trades crude oil (including futures contracts) and provides the basis of US crude oil pricing via WTI (West Texas Intermediate). Other exchanges also trade crude oil futures, eg the International Petroleum Exchange (IPE) in London trades contracts in Brent crude. Wet oil is normally bought and sold via bilateral deals between companies, typically with reference to a marker crude oil grade that is typically quoted via the pricing agency Platts , for example in Europe a particular grade of oil, say Fulmar, might be sold at a price of "Brent plus US$0.25/barrel".

Top petroleum producing countries

(Ordered by amount produced in 2003):

• Saudi Arabia (OPEC)
• United States
• Russia
• Iran (OPEC)
• Mexico
• China
• Norway
• Canada
• United Arab Emirates (U.A.E) (OPEC)
• Venezuela (OPEC)
• United Kingdom (U.K)
• Kuwait (OPEC)
• Nigeria (OPEC)

(Ordered by amount exported in 2003):

• Saudi Arabia (OPEC)
• Russia
• Norway
• Iran (OPEC)
• United Arab Emirates (U.A.E) (OPEC)
• Venezuela (OPEC)
• Kuwait (OPEC)
• Nigeria (OPEC)
• Mexico
• Algeria (OPEC)
• Libya (OPEC)

Note that the USA consumes almost all of its own production.

Source: Energy Statistics from the U.S. Government

Petroleum

Petroleum (from Latin petra – rock and oleum – oil), crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earth's crust. It consists of a complex mixture of various hydrocarbons, largely of the alkane series, but may vary much in appearance, composition, and purity. It is an important "primary energy" source (IEA Key World Energy Statistics).

Origin

Biogenic theory

Most geologists view crude oil, like coal and natural gas, as the product of compression and heating of ancient vegetation over geological timescales. According to this theory, it is formed from the decayed remains of prehistoric marine animals and terrestrial plants. Over many centuries this organic matter, mixed with mud, is buried under thick sedimentary layers of material. The resulting high levels of heat and pressure cause the remains to metamorphose first into a waxy material known as kerogen, and then into liquid and gaseous hydrocarbons in a process known as Catagenesis. These then migrate through adjacent rock layers until they become trapped underground in porous rocks called reservoirs, forming an oil field, from which the liquid can be extracted by drilling and pumping.

Alternative theories (ABIOGENIC ORIGIN OF PETROLEUM)

Thomas Goldwas the most widely known Western proponent of the Russian-Ukrainian theory of a biogenic petroleum origine This theory suggests that large amounts of carbon exist naturally in the planet, some in the form of hydrocarbons. Hydrocarbons are lighter than rocks so they seep upward. Deep microbial life convert them into the various hydrocarbon deposits.

Composition

In refining, the component chemicals of petroleum are separated by distillation Products based on refined crude oil include kerosene, benzene, gasoline, paraffin wa, asphalt, etc. Subtler techniques, such as gas chromatography, HPLC, and GC-MS, can separate some fractions of petroleum into individual compounds.

Strictly speaking, petroleum consists of hydrocarbons: compounds of hydrogen and carbon; and non-hydrocarbon fractions: compounds which might also include nitrogen, sulfur, oxygen, or traces of metals such as vanadium or nickel.

The four lightest alkane — CH₄ (methane), C₂H₆ (ethane), C₃H₈ (propane) and C₄H₁₀ (butane) — are all gases, boiling at -161.6°C, -88.6°C, -42°C, and -0.5°C, respectively (-258.9°, -127.5°, -43.6°, and +31.1° F).

The chains in the C_5-7 range are all light, easily vaporized, clear naphthas. They are used as solvents, dry cleaning fluids, and other quick-drying products. The chains from C₆H₁₄ through C₁₂H₂₆ are blended together and used for gasoline. Kerosene is made up of chains in the C₁₀ to C₁₅ range, followed by diesel fuel/heating oil (C₁₀ to C₂₀) and heavier fuel oils as the ones used in ship engines. These petroleum compounds are all liquid at room temperature.

Lubricating oils and semi-solid greases (including Vaseline®) range from C₁₆ up to C₂₀.

Chains above C₂₀ form solids, starting with paraffin wax, then tar and asphaltic bitumen.

Boiling ranges of petroleum atmospheric pressure distillation fractions in degrees Celsius:

• petrol ether : 40 - 70 °C (used as solvent)
• light petrol: 60 - 100 °C (automobile fuel)
• heavy petrol: 100 - 150 °C (automobile fuel)
• light kerosene : 120 - 150 °C (household solvent and fuel)
• kerosene: 150 - 300 °C (jet engine fuel)
• gas oil : 250 - 350 °C (Diesel fuel/ heating)
• lubrication oil : > 300 °C (engine oil)
• remaining fractions: tar, asphalt, residual fuel

Extraction

Generally the first stage in the extraction of crude oil is to drill a well into the underground reservoir. Historically, in the USA some oil field existed where the oil rose naturally to the surface, but most of these fields have long since been depleted. Often many wells will be drilled into the same reservoir, to ensure that the extraction rate will be economically viable. Also some wells may be used to pump water, steam or various gas mixtures into the reservoir to raise or maintain the reservoir pressure, and so maintain an economic extraction rate.

If the underground pressure in the oil reservoir is sufficient then the oil will be forced to the surface under this pressure. Gaseous fuels or natural gas are usually present, which also supplies needed underground pressure. In this situation it is sufficient to place a complex arrangement of valves on the well head to connect the well to a pipeline network for storage and processing.

Over the lifetime of the well the pressure will fall, and at some point there will be insufficient underground pressure to force the oil to the surface and the remaining oil in the well must be pumped out. see: Energy balance and Net energy gain.

Various techniques aid in recovering oil from depleted or low pressure reservoirs, including Beam Pumps, Electrical Submersible Pumps (ESPs), and Gas Lift. Other techniques include Water Injection and Gas Re-injection, which help to maintain reservoir pressure.

History

The first oil wells were drilled in China in the 4th century or earlier. The oil was burned to evaporate brine and produce salt. By the 10th century, extensive bamboo pipelines connected oil wells with salt springs.

The modern history of oil began in 1853, with the discovery of the process of oil distillation. Crude oil was destilled into kerosene by Ignacy Lukasiewicz, a Polish scientist. The first "rock oil" mine was created in Bobrka, near Krosno in southern Poland in the following year and the first refinery (actually a distillery) was built in Ulaszowice, also by Lukasiewicz.

The American petroleum industry began with Edwin Drake's discovery of oil in 1859, near Titusville Pennsylvania. The industry grew slowly in the 1800s and did not become a real national concern until the early part of the 20th century; the introduction of the internal combustion engine provided a demand that has largely sustained the industry to this day. Early "local" finds like those in Pennsylvania and Ontario were quickly exhausted, leading to "oil booms" in Texas, Oklahoma, and California. Other countries had sizable oil reserves as a part of their colonial holdings, and started to develop them at an industrial level.

While even in 1955 coal was still the world's foremost fuel, oil began to take over. Following the 1973 energy crisis and the 1979 energy crisis there was significant media coverage of oil supply levels. This brought to light the concern that oil is a limited resource that will eventually run out, at least as an economically viable energy source. At the time, the most common and popular predictions were always quite dire, and when they did not come true, many dismissed all such discussion. The future of petroleum as a fuel remains somewhat controversial. USA Today news (2004) reports that there is 40 years of petroleum left in the ground. Some would argue that because the total amount of petroleum is finite, the dire predictions of the 1970s have merely been postponed. Others argue that technology will continue to allow for the production of cheap hydrocarbons and that the earth has vast sources of unconventional petroleum reserves in the form of tar sands, bitumen fields and oil shale that will allow for petroleum use to continue for an extremely long period in the future.

Today about 90% of fuel needs are met by oil. Petroleum's worth as a portable, dense energy source powering the vast majority of vehicles and as the base of many industrial chemicals makes it one of the world's most important commodities. Access to it was a major factor in several military conflicts, including World War II and the Persian Gulf War. About 80% of the world's readily accessible reserves are located in the Middle East. USA territory has less than 3%.

Environmental effects

The presence of oil has significant social and environmental impacts, from accidents and routine activities such as seismic exploration, drilling, and generation of polluting wastes. Oil extraction is costly and sometimes environmentally damaging, although Dr. John Hunt from Woods Hole pointed out in a 1981 paper that over 70% of the reserves in the world are associated with visible macroseepages, and many oil fields are found due to natural leaks. Offshore exploration and extraction of oil disturbs the surrounding marine environment. Extraction may involve dredging, which stirs up the sea bed, killing the sea plants that marine creatures need to survive. Crude oil and refined fuel spills from tanker ship accidents have damaged fragile ecosystems in Alaska, the Galapagos Islands, Spain and many other places. Renewable energy source alternatives do exist, although the degree to which they can replace petroleum and the possible environmental damage they may cause is controversial.

Fossil fuel

Fossil fuels, also known as mineral fuels, are hydrocarbon-containing natural resources such as coal, petroleum and natural gas. The utilization of fossil fuels has fueled industrial development and largely supplanted water driven mills, as well as the burning of wood or peat for heat.

When generating electricity, energy from the combustion of fossil fuels is often used to power a turbine. Older generators used steam generated by the burning of the fuel to turn the turbine, but in newer power plants the gases produced by burning of the fuel turn a gas turbine directly.

The burning of fossil fuels by humans is their major source of emissions of carbon dioxide which is one of the greenhouse gases that is believed to contribute to global warming. A small amount of hydrocarbon-based fuels are biofuels which are derived from atmospheric carbon dioxide and thus do not increase the carbon dioxide in the atmosphere.

Origin

There are two theories on the origin of fossil fuels: the mainstream biogenic theory and the abiogenic theory. The two theories have been intensely debated since the 1860s, shortly after the discovery of widespread petroleum. According to the biogenic theory, fossil fuels are the altered remnants of ancient plant and animal life deposited in sedimentary rocks. The organic molecules associated with these organisms forms a group of chemicals known as kerogens which are then transformed into hydrocarbons by the process of catagenesis. According to the abiogenic theory, hydrocarbon deposits are primordial, being part of the Earth as it formed.

The biogenic theory was favored early because in the late 19th century it was believed that the Earth was extremely hot (possibly molten rock) during its formation. This would have precluded the accretion of hydrocarbons, which would have been oxidized into water and carbon dioxide. When it was later discovered that all fossil fuels contain traces of biological debris, the biogenic theory gained further support because the idea that life (even microbial life) could exist at the depths at which petroleum had been found seemed even less plausible.

Research in the abiogenic theory is in progress. For details on the subject see the article Abiogenic petroleum origin.

A limited resource

The reports from the early 1970s (the 1973 energy crisis) that oil supplies would run out in the 1990s have proven wrong, but oil is still believed to be a finite resource. Even if abiogenic oil is the source, the theory is not of practical use unless significant deposits are discovered. Significant usage of hydroelectricity and nuclear power (outside the United States) and scientific advances have reduced the dependency on fossil fuels, of which household usage has increased nonetheless. Petroleum is also important because it is a source of petrochemicals, for which there are a vast variety of uses.

Sooner or later we will have to find alternatives. However, many people share a viewpoint that the time at which we would run out of fossil fuels is far in the future. Some hope that by then we may have presently unavailable power systems such as solar power satellites or nuclear fusion.

The principle of supply and demand suggests that as hydrocarbon supplies diminish, prices will rise. It has therefore been pointed out that higher prices will lead to increased supplies as previously uneconomic sources become more economical to exploit. Artificial gasolines and other renewable energy sources presently require more expensive production and processing technologies than conventional petroleum reserves, but may then become economically viable. See future energy development.

Hydrocarbon

Organic chemistry

Organic chemistry is the scientific study of the structure, properties, composition, reactions, and synthesis of organic compounds. Organic compounds are composed of carbon and hydrogen, and can possibly contain any of the other elements such as nitrogen, oxygen, phosphorus, and sulfur.

History

Organic chemistry as a science is generally agreed to have started in 1828 with Friedrich Woehler's synthesis of the organic, biologically significant compound urea by accidentally evaporating an aqueous solution of ammonium cyanate NH₄OCN.

Characteristics of organic substances

The reason that there are so many carbon compounds is that carbon has the ability to form many carbon chains of different lengths, and rings of different sizes (catenation). Many carbon compounds are extremely sensitive to heat, and generally decompose below 300°C. They tend to be less soluble in water compared to many inorganic salts. In contrast to such salts, they tend to be much more soluble in organic solvents such as ether or alcohol. Organic compounds are covalently bonded.

Aliphatic compounds

Aliphatic compounds are organic molecules that do not contain aromatic systems. ....

Hydrocarbons - Alkanes- Alkenes - Diene or Alkadienes - Alkynes - Halogenoalkanes

Aromatic compounds

Aromatic compounds are organic molecules that contain one or more aromatic ring system.

Benzene - Toluene - Styrene- Xylene- Aniline - Phenol - Acetophenone - Benzonitrile - Halogenoarenes -Naphthalene- Anthracene- Phenanthrene- Benzopyrene - Coronene- Azulene - Biphenyl

Heterocyclic compounds

Heterocyclic compounds are cyclic organic molecules whose ring(s) contain at least one heteroatom. These heteroaoms can include oxygen, nitrogen, phosphorous, and sulfur.

Pyridine - Pyrrole- Thiophene - Furan

Functional groups

Alcohols - Mercaptans - Ethers - Aldehydes- Ketones- Carboxylic acids - Esters - Carbohydrates -Alicyclic compounds - Amides- Amines - Lipids - Nitriles

Polymers

Polymers are a special kind of molecule. Generally considered "large" molecules, polymers get their reputation regarding size because they are molecules that consist of multiple smaller segments. The

segments could be chemically identical, which would make such a molecule a homopolymer. Or the segments could be vary in chemical structure, which would make that molecule a heteropolymer. Polymers are a subset of "macromolecules" which is just a classification for all molecules that are considered large.

Polymers can be organic or inorganic. Commonly-encountered polymers are usually organic (e.g.,polyethylene, polypropylene, Plexiglass, etc.). But inorganic polymers (e.g., silicone) are also familiar to everyday items.

Organic nomenclature

Organic nomenclature is the system established for naming and grouping organic compounds.

Formally, rules established by the International Union of Pure and Applied Chemistry (known as IUPAC nomenclature) are authoritative for the names of organic compounds, but in practice, a number of simply-applied rules can allow one to use and understand the names of many organic compounds.

For many compounds, naming can begin by determining the name of the parent hydrocarbon and by identifying any functional groups in the molecule that distinguish it from the parent hydrocarbon. The numbering of the parent alkane is used, as modified, if necessary, by application of the Cahn Ingold Prelog priority rules in the case that ambiguity remains after consideration of the structure of the

parent hydrocarbon alone. The name of the parent hydrocarbon is modified by the application of the highest-priority functional group suffix, with the remaining functional groups indicated by numbered prefixes, appearing in the name in alphabetical order from first to last.

In many cases, lack of rigor in applying all such nomenclature rules still yields a name that is intelligible — the aim, of course, being to avoid any ambiguity in terms of what substance is being discussed.

For instance, strict application of CIP priority to the naming of the compound

NH2CH2CH2OH

would render the name as 2-aminoethanol, which is preferred. However, the name 2-hydroxyethanamine unambiguously refers to the same compound.

How the name was constructed:

1. There are two carbons in the main chain; this gives the root name "eth".
2. Since the carbons are singly-bonded, the suffix begins with "an".
3. The two functional groups are an alcohol (OH) and an amine (NH₂). The alcohol has the higher atomic number, and takes priority over the amine. The suffix for an alcohol ends in "ol", so that the suffix is "anol".
4. The amine group is not on the carbon with the OH (the #1 carbon), but one carbon over (the #2 carbon); therefore we indicate its presence with the prefix "2-amino".
5. Putting together the prefix, the root and the suffix, we get "2-aminoethanol".

There is also an older naming system for organic compounds known as common nomenclature , which is often used for simple, well-known compounds, and also for complex compounds whose IUPAC names are too complex for everyday use.

Hydrocarbon

In chemistry, a hydrocarbon is a group of chemical compounds consisting only of carbon (C) and hydrogen (H). They all consist of a carbon backbone and atoms of hydrogen attached to that backbone. (Often the term is used as a shortened form of the term aliphatic hydrocarbon.)

For example, methane (swamp gas/marsh gas) is a hydrocarbon with one carbon atom and four

hydrogen atoms: CH₄. Ethane is a hydrocarbon (more specifically, an alkane) consisting of two carbon atoms held together with a single bond, each with three hydrogen atoms bonded: C₂H₆. Propane has three C atoms (C₃H₈) and so on (C_nH_2·n+2).

There are basically three types of hydrocarbons:

1. aromatic hydrocarbons, which have at least one aromatic ring in addition to whatever bonds they have
2. saturated hydrocarbons, also known as alkanes, which don't have double, triple or aromatic bonds
3. unsaturated hydrocarbons, which have one or more double or triple bonds between carbon atoms, are divided into:

· alkenes

· alkynes

· dienes

The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations:

• Alkanes: C_nH_2n+2
• Alkenes: C_nH_2n (assuming only one double bond)
• Alkenes: C_nH_2n-2 (assuming only one triple bond)

Liquid geologically-extracted hydrocarbons are referred to as petroleum (literally "rock oil") or mineral oil, while gaseous geologic hydrocarbons are referred to as natural gas. All are significant sources of fuel and raw materials as a feedstock for the production of organic chemicals and are commonly found in the subsurface using the tools of petroleum geology.

Hydrocarbons are of prime economic importance because they encompass the constituents of the major fossil fuels (coal,petroleum, natural gas, etc.) and biofuels, as well as plastics, waxes, solvents and oils. In urban pollution, these components--along with NOx and sunlight--all contribute to the formation of tropospheri ozone.

Alkane

An alkane in organic chemi

stry is a type of hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds (they are saturated).

The general formula for acyclic/linear alkanes, also known as aliphatic hydrocarbons is C_nH_2n+2; the simplest possible alkane is methane (CH₄). The next in the series is ethane (C₂H₆) and the series continues with larger and larger molecules. Each C atom is hybridized sp³. The series of alkanes is often

Properties

Arrangements

The atoms in alkanes with more than three carbon atoms can be arranged in multiple ways, forming different isomers. "Normal" alkanes have the most linear, unbranched configuration, and are denoted with an n. The number of isomers increases rapidly with the number of carbon atoms; for acyclic alkanes with n = 1..12 carbon atoms, the number of isomers equals 1, 1, 1, 2, 3, 5, 9, 18, 35, 75, 159, 355 .

The names

of all alkanes end with -ane. The alkanes, and their derivatives, with four or fewer carbons have non-systematic common names, established by long precedence. For a more complete list, see List of alkanes.

methane	CH4
ethane	C2H6
propane	C3H8
n-butane	C4H10
n-pentane	C5H12
n-hexane	C6H14
n-heptane	C7H16
n-octane	C8H18

Branched alkanes have some non-systematic (or "trivial") names in common use, but there is also a systematic way of naming most such compounds, which starts from identifying the longest non-branched parent alkane in the molecule, counting up from one sequentially starting from the carbon involved in the most prominent functional group (or, more formally, attached to the collection of

heteroatoms with highest priority according to some rules), and then numbering the side chains according to this sequence.

Naming Alkanes

Alkanes are named according to IUPAC nomenclature. The suffix of an alkanes name is always -ane. The prefix depends on the number of carbon atoms in the molecule and on any branched chains that may be attached. Refer to IUPAC nomenclature for greater detail.

Reactions

Cracking reactions

"Cracking" breaks larger molecules into smaller ones. This can be done with a thermic or catalytic method. The thermal cracking process follows a homolytic mechanism, that is, bonds break symmetrically and thus pairs of free radicals are formed. 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.e., cracking) and intra-and intermolecular hydrogen transfer or hydride transfer . 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.

Here is an example of cracking with butane CH₃-CH₂-CH₂-CH₃

• 1st possibility (48%): breaking is done on the CH₃-CH₂ bond.

CH₃* / *CH₂-CH₂-CH₃

after a certain number of steps, we will obtain an alkane and an alkene: CH₄ + CH₂=CH-CH₃

• 2nd possibility (38%): breaking is done on the CH₂-CH₂ bond.

CH₃-CH₂* / *CH₂-CH₃

after a certain number of steps, we will obtain an alkane and an alkene from different types: CH₃-CH₃ + CH₂=CH₂

• 3rd possibility (14%): breaking of a C-H bond

after a certain number of steps, we will obtain an alkene and hydrogen gas: CH₂=CH-CH₂-CH₃ + H₂

Halogenation reaction

R + X₂ → RX + HX

These are the steps when methane is chlorinated. This a highly exothermic reaction that can lead to an explosion.

1. Initiation step: splitting of a chlorine molecule to form two chlorine atoms. A chlorine atom has an unpaired electron and acts as a free radical.

Cl₂ → Cl* / *Cl
energy provided by UV.

2. Propagation (two steps): a hydrogen atom is pulled off from methane then the methyl pulls a Cl from Cl₂

CH₄ + Cl* → CH₃* + HCl

CH₃* + Cl₂ → CH₃Cl + Cl*

This results in the desired product plus another Chlorine radical. This radical will then go on to take part in another propagation reaction causing a chain reaction. If there is an excess of Chlorine, other products like CH₂Cl₂ may be formed.

3. Termination step: recombination of two free radicals

• Cl* + Cl* → Cl₂, or
• CH₃* + Cl* → CH₃Cl, or
• CH₃* + CH₃* → C₂H₆.

The last possibilty in the termination step will result in an impurity in the final mixture; notably this results in an organic molecule with a longer carbon chain than the reactants.

Combustion

R + O₂ → CO₂ + H₂O + H₂

Is a very exothermic reaction. If the quantity of O₂ is insufficient, it will form a poison called carbon monoxide (CO). Here is an example with methane:

CH₄ + 2 O₂ → CO₂ + 2 H₂O

with less O₂:

2 CH₄ + 3 O₂ → 2 CO + 4 H₂O

with even less O₂:

CH₄ + O₂ → C + 2 H₂O

Cycloalkane

Cycloalkanes are chemical compounds with a single ring of carbons to which hydrogens are attached according to the formula C_nH_2n. They are named analogously to their normal alkane counterpart of the same carbon count: cyclopropane, cyclobutane, cyclopentane, cyclohexane, etc.

Cycloalkanes are classified into small, normal and bigger cycloalkanes, where cyclopropane and cyclobutane are the small ones, cyclopentane, cyclohexane, cycloheptane are the normal ones, and the rest are the bigger ones.

Nomenclature

he naming of polycyclic alkanes is more complex, with the base name indicating the number of carbons in the ring system, a prefix indicating the number of rings (eg, "bicyclo"), and a numeric prefix before that indicating the number of carbons in each part of each ring, exclusive of vertices. For instance, a bicyclooctane which consists of a six-member ring and a four member ring, which share two adjacent carbon atoms which form a shared edge, is [4.2.0]-bicyclooctane. That part of the six-member ring, exclusive of the shared edge has 4 carbons. That part of the four-member ring, exclusive of the shared edge, has 2 carbons. The edge itself, exclusive of the two vertices that define it, has 0 carbons.

Reactions

The normal and the bigger cycloalkanes are very stable, like alkanes, and their reactions (cf. radicalic chain reactions ) are like alkanes.

The small cycloalkanes - particularly cyclopropane - have a lower stability due to the Baeyer-tension . They react similar to alkenes, though they don't react with the EA (cf. electrophilic addition), but with the SN2 (cf. nucleophilic substitution) reaction mechanism. These reactions are ring opening reactions or cleavage reactions of alkyl cycloalkanes.

Alkene

An alkene is one of the three classes of unsaturated hydrocarbons that contain at least one carbon-carbon double bond and have the general molecular formula of C_nH_2n (the other two being alkynes and arenes).

The simplest alkene is C₂H₄, which has the common name "ethylene" and theIUPAC name "ethene".

Structure of Alkenes

Shape of Alkenes

As predicted by the VSEPR model of electron pair replusion (see covalent bond), the bond angles about each carbon in a double bond are about 120°, although the angle may be larger because of strain introduced by nonbonded interactions created by groups attached to the carbons of the double bond. For example, the C-C-C bond angle in propene (propylene) is 123.9°.

Molecular Geometry Carbon-Carbon Double Bond

Like single covalent bonds, double bonds can be described in terms of overlapping atomic orbitals, except that unlike a single bond (which consist of a single sigma bond), a carbon-carbon double bond consists of one sigma bond and one pi bond.

Each carbon of the double bond uses its three sp² hybrid orbitals to form sigma bonds to three atoms. The unhybridized 2p atomic orbitals, which lie perpendicular to the plane created by the axes of the three sp² hybrid orbitals, combine to form the pi bond.

Because it requires a large amount of energy to break a pi bond (264 kJ/mol in ethylene), rotation about the carbon-carbon double bond is very difficult and therefore severely restricted.

Reactions

Synthesis

1. The most common industrial synthesis path for alkenes is cracking of petroleum.
2. Alkenes can be synthesized from alcohols via an elimination reaction that removes one water molecule:
   H₃C-CH₂-OH + H₂SO₄ → H₃C-CH₂-O-SO₃H + H₂O → H₂C=CH₂ + H₂SO₄
3. Catalytic synthesis of higher α-alkenes can be achieved by a reaction of ethene with triethylaluminium, an organometallic compound in the presence of nickel, cobalt or platinum.

Addition reactions

Catalytic addition of hydrogen

Catalytic hydrogenation of alkenes produce the corresponding alkanes. The reaction is carried out under pressure in the presence of a metallic catalyst. Common industrial catalysts are based on platinum, nickelor palladium, for laboratory syntheses, Raney's nickel is often employed. This is an alloy of nickel and aluminium.

This is the catalytic hydrogenation of ethylene to yield ethane:

CH₂=CH₂ + H₂ → CH₃-CH₃

Electrophilic addition

Most addition reactions to alkenes follow the mechanism of electrophilic addition.

1. Halogenation: Addition of elementary bromine or chlorine to alkenes yield vicinal Dibromo- and dichloroalkenes, respectively. The decoloration of a solution of bromine in water is an analytical test for the presence of alkenes:
   CH₂=CH₂ + Br₂ → BrCH₂-CH₂Br
2. Hydrohalogenation: Addition of hydrohalic acids like HCl or HBr to alkenes yield the corresponding haloalkanes.
   CH₃-CH=CH₂ + HBr → CH₃-CHBr-CH₃
   If the two carbon atoms at the double bond are linked to a different number of hydrogen atoms, the halogen is found preferentially at the carbon with less hydrogen substituents (Markovnikov's rule).
3. Addition of a carbene or carbenoid yields the corresponding cyclopropane

Oxidation

1. In the presence of oxygen, alkenes burn with a bright flame to carbon dioxide and water.
2. Catalytic oxidation with oxygen or the reaction with percarboxylic acids yields epoxides
3. Reaction with ozone leads to the breaking of the double bond, yielding two aldehydes or ketones
   R₁-CH=CH-R₂ + O₃ → R₁-CHO + R₂-CHO + H₂O
   This reaction can be used to determine the position of a double bond in an unknown alkene.

Polymerisation

Polymerization of alkenes is an economically important reaction which yields polymers of high industrial value, such as the plastics polyethylene and polypropylene. Polymerization can either proceed via a free-radical or an ionic mechanism. For detail regarding the reaction mechanisms, see the polymerization article.

Nomenclature of Alkenes

IUPAC Names

To form the root of the IUPAC names for alkenes, simply change the -an- infix of the parent to -en-. For example, CH₃-CH₃ is the alkane ethANe. The name of CH₂=CH₂ is therefore ethENe.

In higher alkenes, where isomers exist that differ in location of the double bond, the following numbering system is used:

1. Number the longest carbon chain the contains the double bond in the direction that gives the carbon atoms of the double bond the lowest possible numbers.
2. Indicate the location of the double bond by the location of its first carbon
3. Name branched or substituted alkenes in a manner similar to alkanes.
4. Number the carbon atoms, locate and name substituent groups, locate the double bond, and name the main chain

CH3CH2CH2CH2CH==CH26 5 4 3 2 1 1-Hexene

CH3 |CH3CH2CH2CH2CH==CH26 5 4 3 2 1 4-Methyl-1-hexene

CH3 | CH3CH2CH2CH2CH==CH26 5 4 3 |2 1 CH2CH3 2-Ethyl-4-methyl-1-hexene

Common Names

Despite the precision and universal acceptance of the IUPAC naming system, some alkenes are known almost exclusively by their common names:

	CH2="CH2"	CH3CH="CH2"	CH3C(CH3)="CH2"
IUPAC name:	Ethene	Propene	2-Methylpropene
Common name:	Ethylene	Propylene	Isobutylene