Sources of Alkanes

The two most important natural sources of alkanes are petroleum and natural gas. Petroleum is a complex liquid mixture of organic compounds, many of which are alkanes or cycloalkanes. For more details about how petroleum is refined to obtain gasoline, fuel oil, and other useful substances, read A Word about Petroleum, Gasoline, and Octane Number on pages 102-103. 

Natural gas, often found associated with petroleum deposits, consists mainly of methane (about 80%) and ethane (5% to 10%), with lesser amounts of some higher alkanes. Propane is the major constituent of liquefied petroleum gas (LPG), a domestic fuel used mainly in rural areas and mobile homes. Butane is the gas of choice in some areas. Natural gas is becoming an energy source that can compete with and possibly surpass oil. In the United States, there are about a million miles of natural gas pipelines distributing this energy source to all parts of the country. Natural gas is also distributed worldwide via huge tankers. To conserve space, the gas is liquefied ( — 160°C), because 1 cubic meter (m ) of liquefied gas is equivalent to about 600 m of gas at atmospheric pressure. Large tankers can carry more than 100,000 m of liquefied gas. 

Conduct research on the Internet to find more information and answer questions about natural gas. 

Why do the physical properties of natural gas make it safer to use than most other fossil fuels  

How is natural gas produced in nature What keeps it from escaping to the surface of the earth How is it obtained from its natural source  

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British Foreign Minister Ernest Bevin once said that "The Kingdom of Heaven runs on righteousness, but the Kingdom of Earth tuns on alkanes." Well, actually he said "tuns on oil" not "runs on alkanes," but they re essentially the same. By far, the major sources of alkanes are the world s natural gas and petroleum deposits. Laid down eons ago, these deposits are thought to be derived from the decomposition of plant and animal matter, primarily of marine origin. Natural gas consists chiefly of methane but also contains ethane, propane, and butane. Petroleum is a complex mixture of hydrocarbons that must be separated into fractions and then further refined before it can be used. 

Petroleum, a complex mixture of many different hydrocarbons, is the main source of alkanes. Petroleum can be processed into various fractions by boiling a mixture in huge distilling towers. Each fraction contains alkanes with a relatively narrow range of molar masses. Table lists these major fractions of petroleum and some of their uses. As the table shows, these compounds are the principal sources of energy in our society. 

The principal source of alkanes is petroleum and natural gas, which contain only the more volatile alkanes. Therefore, low molecular weight alkanes, e.g. methane and small amounts of ethane, propane and other higher alkanes can be obtained directly from natural gas. Another fossil fuel, coal, is a potential second source of alkanes. Usually alkanes are obtained through refinement or hydrogenation of petroleum and coal. 

The two main natural sources of alkanes are natural gas and petroleum. Alkanes are insoluble in and less dense than water. Their boiling points increase with molecular weight and, for isomers, decrease with chain branching. 

Summary Rules for Naming Alkanes 94 3-4 Physical Properties of Alkanes 95 3-5 Uses and Sources of Alkanes 97 3-6 Reactions of Alkanes 99 3-7 Structure and Conformations of Alkanes 100 3-8 Conformations of Butane 104 3-9 Conformations of Higher Alkanes 106 3-10 Cycloalkanes 107 3-11 Cis-trans Isomerism in Cycloalkanes 109 3-12 Stabilities of Cycloalkanes Ring Strain 109 3-13 Cyclohexane Conformations 113... 

The principal source of alkanes is petroleum, together witl tl accompanying natural gas. Decay and millions of years of geologicarstresses have transformed the complicated organic compounds that once made up living plants or animals into a mixture of alkanes ranging in size from one carbon to 30 or 40 carbons. Formed along with the alkanes, and particularly abundant in California petroleum, are cycloalkanes (Chap. 9), known to the petroleum industry as naphthenes. 

The primary sources of alkanes are natural gas and petroleum. The smaller alkanes (methane through butane) are gases under ambient conditions. Methane is the principal component of natural gas. Higher molecular weight alkanes are obtained largely by refining petroleum. Methane, the simplest alkane, was one major component of the early atmosphere of this planet. Methane is stiU found in Earth s atmosphere, but no longer in appreciable amounts. It is, however, a major component of the atmospheres of Jupiter, Saturn, Uranus, and Neptune. 

The primary source of alkanes is petroleum. Petroleum is a complex mixture of organic compounds, most of which are alkanes and aromatic compounds (cf. Chapter 14). It also contains small amounts of oxygen-, nitrogen-, and sulfur-containing compounds. 

The chief natural sources of alkanes are natural gas (mainly methane) and petroleum. The mixture in petroleum is so complex that the alkanes are not completely separated from one another, but are collected in groups according to boiling range, by fractional distillation. Table 3.2 lists the fractions collected. 

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