Hydrocarbon
Definition
In chemistry, a hydrocarbon is any chemical compound that consists 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.)
Examples
For example, methane (swamp/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 (CnH2·n+2).
Thee types of hydrocarbons
There are essentially three types of hydrocarbons:
- aromatic hydrocarbons, which have at least one aromatic ring
- saturated hydrocarbons, also known as alkanes, which don't have double, triple or aromatic bonds
- unsaturated hydrocarbons, which have one or more double or triple bonds between carbon atoms, are divided into:
The number of hydrogen atoms
The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations:
- Alkanes: CnH2n+2
- Alkenes: CnH2n (assuming only one double bond)
- Alkynes: CnH2n-2 (assuming only one triple bond)
Each of these hydrocarbons must follow the 4-hydrogen rule which states that all carbon atoms must have the maximum number of hydrogen atoms as it can hold (the limit is four). Note, an extra bond removes 2 hydrogen atoms and only saturated hydrocarbons can attain the full four. This is because of the unique positions of the carbon's four electrons.
Petroleum
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 Earth´s subsurface using the tools of petroleum geology. Oil reserves in sedimentary rocks are the principal source of hydrocarbons for the energy and chemicals industries.
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 tropospheric ozone.
