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Shale gas, the future hydrocarbon source Shale gas, the future hydrocarbon source Shale is a fine–grained, porous sedimentary rock. Shale gas is naturally formed from being trapped within shale formations.Once it was not a commercial hydrocarbon source but now–a– days there is an increase in demand due to decline in the conventional fuel production.Shale gas is often trapped very deep beneath the surface, in the source rock, i.e., the rock in which it is, like all hydrocarbons, originally formed.

Learning Objectives

After completing the topic, the student will be able to:

  • Define the hydrocarbons and list their types and sources.
  • Discuss the structure, preparation and properties of the saturated hydrocarbon, alkanes.
  • Discuss the structure, preparation and properties of the un-saturated hydrocarbons, alkenes and alkynes.
  • Appraise the geometrical isomerism shown by alkenes.
  • Discuss the the stability and reactivity of cyclic compounds.
  • Define the aromatic hydrocarbons and apply the Huckel's rule.
  • Discuss the structure, preparation and properties of simple aromatic compound, the benzene.
Hydrocarbons Hydrocarbons Hydrocarbons are the simplest organic compounds . Containing only carbon and hydrogen, they can be straight‐chain, branched chain, or cyclic molecules.
Hydrocarbons

Organic compounds that contain only carbon and hydrogen are hydrocarbons, which differ from one another by the number of carbon and hydrogen atoms they contain. The simplest hydrocarbon is methane, CH4, with only one carbon per molecule. Methane is the main component of natural gas.

The hydrocarbon octane, C8H18, has eight carbons per molecule and is a component of gasoline. The hydrocarbon polyethylene contains hundreds of carbon and hydrogen atoms per molecule. Polyethylene is a plastic used to make many items, including milk containers and plastic bags.

Most of the hydrocarbons on earth are found naturally in crude oil. It consists of hydrocarbons of different molecular weights.

Methane
Formation of Methane
Acetylene burned in this torch
Oxy acetylene welding Acetylene burned in this torch produces a flamehot enough to melt iron
Classification of hydrocarbons - Saturated and unsaturated hydrocarbons

The hydrocarbons in which each carbon atom is bonded to four neighboring atoms by four single covalent bonds are known as saturated hydrocarbons. The term saturated means that each carbon has as many atoms bonded to it as possible. Eg: Methane, Ethane, etc.

A hydrocarbon containing a multiple bond, either double or triple is known as an unsaturated hydrocarbon. Because of the multiple bond, two of the carbons are bonded to fewer than four other atoms. These carbons are thus said to be unsaturated. Eg: Ethene, acetylene, etc.

Acetylene, C2H2 is an unsaturated hydrocarbon containing a triple bond. A confined flame of acetylene burning in oxygen (oxy acetylene) is hot enough to melt iron, which makes acetylene a choice fuel for the welding.

In a saturated hydrocarbon, all the carbon atoms are bonded to four other atoms whereas in an unsaturated hydrocarbon, some of the carbon atoms may only be bonded to three or two other atoms. The number of atoms bonded to each of the two middle carbons of n – butane is four, whereas each of the two middle carbons of 2 – butene is bonded to three other atoms i.e., a hydrogen and two carbons.