Uses and Sources of Alkanes - Report Example

Sources and Uses of Alkanes College Affiliation Sources and Uses of Alkanes Introduction Alkanes are saturated hydrocarbons, that is,they contain only carbon-hydrogen and carbon-carbon single bonds. They may occur as unbranched chains, branched chains and rings. If no carbon rings are present, they are referred to as acyclic compounds and cyclic compounds when rings are present. Alkanes are among the least reactive organic compounds. They exhibit properties similar to those of fats and oils therefore are also described as aliphatic. Alkanes contain only C-C single bonds and have a general formula CnH2n+2. Sources of alkanes Natural sources The major source of alkanes is from natural gas and oil wells that are distributed throughout the world. Its composition varies from field to field but is majorly 80% methane and 10% ethane, with the remaining portion consisting of higher alkanes such as propane. Natural gas is usually collected by via pipeline and then separated into its components on the basis of their different boiling points. Petroleum is usually obtained from underground rock formations by drilling oil wells has a complex mixture of organic compounds majorly alkanes. Some natural gas often exists with petroleum which is usually formed through anaerobic decomposition of plant material that was deposited under inland seas several years ago. Methane is usually the principle product of all the anaerobic decomposition of all organic material. (Lister & Renshaw, 2000) Crude oil is separated into groups of compounds according to boiling points by distillation in a refinery. In this process, the liquid is boiled, and gases move up a large column that becomes cooler towards the top. Compounds condense to liquids at different levels in the column depending on their boiling points. (Malone & Dolter, 2010) Coal can also be used as a raw material for the production of alkanes. Alkanes can be obtained through refinement of coal. Coal is one of the earliest fossil fuels. It occurs in varying depths under the upper crust of the earth. It is mined through open pits or deep mining depending on the level of the depths. Coal mainly consists of carbon, arenes like benzene, toluene, xylene, naphthalene and anthracene besides organic compounds of sulphur and nitrogen. A few alkanes have been detected in the waxy constituents of certain plants. For example-nonacosane, C29H60 has been isolated from cabbage leaves and leaves and n-heptane, C7H16 is found to be present in pinus species. Artificial sources of alkanes Alkanes can be prepared in the laboratory from alkyl halides by reduction, directly with zinc and acetic acid or via Gringard reagent formation followed by hydrolytic work up. The coupling reaction of alkyl halides with Gilman reagent also produces alkanes. Selective reduction of aldehydes or ketones either by Clemmensen reduction or Wolff-Kishner reduction yields alkanes. Alkanes are also prepared simply by catalytic hydrogenation of alkenes or alkynes (Nahar & Sarker, 2013) Uses of alkanes Alkanes are used as solvents especially for dissolving tough to clean greases. These alkanes are low boiling liquid alkanes, for example hexane. These greases are usually made up of many different organic compounds. This is possible because alkanes are non-polar therefore are able to dissolve in most organic compounds which are non-polar. Alkanes do not undergo chemical reactions under normal ionic conditions. This property is referred to as chemical inertness. Therefore alkanes can be stored for a long period of time and can be used to protect other materials from chemical reaction. For example, paraffin wax is often used to seal jars after home canning of fruits and vegetables. Propane is often compressed to liquid form and sold as liquefied propane fuel. Propane, butane and isobutene are used to pressurise aerosol cans since they are chemical inert. Most methane is transported by pipeline and ships in liquid form and is used for heating fuel. Some is burned in internal combustion engines to power vehicles. Some is burned as fuel in gas-fired steam power plants to produce electricity. Through cracking, ethane is converted to ethylene which is either used as a petrochemical raw material or polymerised into plastic called polyethylene. The products of cracking process are generally used for producing linear alkyl benzenes which are used as the raw material for manufacturing detergents. Low molecular weight alkanes are refined and liquefied and sold as Liquefied Petroleum Fuel (LPG). For instance, butane is used as a cigarette lighter. Alkanes with 5 to 7 carbons, sometimes referred to as naphtha is mainly used for solvents and raw materials for the chemical industry. Straight-run gasoline are alkanes with 5 to 10 carbons are usually formulated to produce commercial gasoline. Alkanes with 11 to 16 carbons serve as source of kerosene and jet fuel. Solid residue such as asphalt, tar and paraffin wax are used in both domestic and commercial use. (Johnson, 1999) Alkanes are flammable. They burn in oxygen and give off heat making them energy sources. The combustion reaction produces carbon dioxide and water when the compound reacts with oxygen. Alkanes with 20 to 40 carbon atoms are thick liquids and can be used as lubricants and oils. Alkanes with higher numbers of carbon atoms compose substances such as petroleum jelly and candle wax. Petrolatum is a semi-solid hydrocarbon mixture that is useful in both as a skin softener and as a skin protector. Many moisturizing hand lotions and some medicated slaves contain petrolatum. Neither water nor water solutions can penetrate through. (Tro, 2012) Methane is used for home heating and gas stoves and hot water heaters. Propane is the major component of bottled gas used for home heating and cooking in areas where natural gas is not available. Butane is used in disposable lighters and fuel canisters for gas camping stoves and lanterns. Microbes have also develop effective strategies involving specific enzymes and metabolic pathways to use n-alkanes as a carbon source. Alcanivorax dieselolei, a g-proteobacterium is a member of the hydrocarbonoclastic bacteria and cannot assimilate sugars or amino acids as sources of energy and carbon, but can utilise some organic acids and alkanes. (Singh, 2012) Alkanes can undergo halogenation reactions to form halogenated alkanes. Halogenated methane lie into two categories, chlorinated methanes and Freon. Chloromethane is used as an industrial solvent. It was once used as a refrigerant but was stopped due to toxicity concerns. Presently, chloromethane is used in the manufacture of silicone based polymers and as a solvent in the production of silicone-based polymers and as a solvent in the production of certain types of rubber such as butyl rubber. Methyl chloride is also used for synthesis of ammonia and urea. Dichloromethane (methylene chloride) is used as paint stripper and degreaser. Trichloromethane (chloroform) is a colourless dense sweet smelling liquid used in the manufacture of Teflon. It is a good industrial solvent and was an early popular anaesthetic. Tetra chloromethane is a good solvent for fats, oils and greases. Freon were largely used in refrigeration and air-condition which has been currently discontinued (Hill & Holman, 2000). Many of the organic chemicals synthesises in the industry rely on crude oil, vegetable oils of fats as starting material. The cracking of alkanes in crude oil produces large quantities of short chain alkenes. These include ethene and propene and can be converted into alcohols, ketones, acids and other derivatives by appropriate reactions. Ethene is used to speed up the ripening of fruits such as bananas. Alkane serve as the starting point for majority of organic compounds including plastics, drugs, detergents, insecticides, cosmetics, artificial dyes, artificial fibres and pharmaceutical drugs (Shipman, Wilson, & Higgins, 2013) Conclusion Alkanes are important in both domestic and industrial use. However, they contribute highly in environmental degradation. They are highly essential in modern life but their inertness poses serious ecological problems when released to the environment. Alkanes have psychological effects. The danger in inhaling them lies in potential suffocation due to lack of oxygen. The major immediate danger associated with natural gas leak is the potential formation of an explosive air-alkane mixture rather than the formation of a toxic air-alkane mixture. Some additives too alkanes are toxic. Liquid alkanes can damage lung tissue because of physical effects such as dissolving of lipid molecules of cell membranes causing pneumonia like symptoms. Liquid alkanes can also affect the skin for related reasons. Mineral oil in petrolatum can dissolve non-polar skin materials. References Hill, G. C., & Holman, J. S. (2000). Chemistry in context. Walton-on-Thames: Nelson. Johnson, A. W. (1999). Essentails of organic chemistry. Sudbury, Mass: Jones and Bartlett Publishers. Lister, T., & Renshaw, J. (2000). New understanding chemistry for advanced level. Cheltenham: Thomes. Malone, L. J., & Dolter, T. O. (2010). Basic concepts of chemistry. Hoboken, NJ: John Wiley. Nahar, L., & Sarker, S. (2013). Chemistry for pharmacy students: General, organic and natural product chemistry. Hoboken: John Wiley and Sons. Shipman, J. T., Wilson, J. D., & Higgins, C. A. (2013). An introduction to physical science. Boston, MA: Brooks/Cole, Cengage Learning. Singh, S. N. (2012). Microbial degradation of xenobiotics. Heidelberg, New York: Springer-Verlag Berlin Heidelberg. Tro, N. (2012). Chemistry in Focus: A Molecular View of Our World . Belmont: Brooks/Cole Cengage Learning. Read More