Content
The alkanes are a class of hydrocarbons in which a variable number of carbon atoms are joined together by single bonds, like a skeleton, and each carbon atom in turn is attached to hydrogen atoms, which may eventually be replaced by other atoms or chemical groups.
The molecular formula of alkanes is CnH2n + 2, where C represents carbon, H represents hydrogen and n represents the number of carbon atoms. Alkanes are saturated hydrocarbons. To name them, the suffix “-year”.
It can serve you:
- Examples of Alkynes
- Examples of Alkenes
Classification
Within the alkanes, two large groups are usually recognized with an important difference between them: open chain (also called acyclic) and closed chain (or cyclical).
When the open chain compounds do not present any substitution of the hydrogens that accompany each carbon atom, they are called linear alkanes: these are the simplest alkanes. When they do present a substitution, they are called branched alkanes. The most common substituents are hydroxyl and methyl groups, and halogens.
On the other hand, there are compounds with a single cycle in the molecule and others with several; they are called monocyclic and polycyclic, respectively. Cyclic alkanes can be homocyclic or heterocyclic.
- The former are formed with the exclusive intervention of carbon atoms.
- In the latter, other atoms participate, for example, oxygen or sulfur.
Physical properties
In general, the physical properties of alkanes are conditioned by the molecular mass (in turn linked to length). Those with the lowest number of carbons are gaseous at room temperature, those ranging from 5 to 18 carbon atoms are liquids, and above this number are solid (similar to wax).
Being less dense than water, tend to float on it. In general, alkanes are insoluble in water and soluble in organic solvents. They present a high degree of activation energy.
The alkanes are characterized by being chemical compounds of verypoor reactivity, which is why they are also known as "paraffins" (in Latin, parum affinis means "low affinity"). The most important reaction that alkanes can undergo is combustion, generating heat, carbon dioxide and water in the presence of oxygen.
Alkanes are the basis of an important variety of reactions associated with very important industrial processes, being the most traditional fuels. They also appear as end products of biological processes such as methanogenic fermentation carried out by some microorganisms.
Examples of alkanes
We will mention twenty alkanes, including some well-known linear and branched ones, towards the end of the list:
- Chloroform (fancy name of trichloromethane; CHCl3) - the vapors of this substance were used as an anesthetic in the past. It has been discontinued for this purpose because it has been found to damage important organs such as the liver or kidneys. Its use today is primarily as a solvent or coolant.
- Methane (CH4) - this is the simplest alkane of all: it is composed of only one carbon atom and four hydrogen. It is a gas that occurs naturally by the decomposition of different organic substrates, and is the main component of natural gas. In recent times it has been recognized as one of the gases that contributes the most to the so-called greenhouse effect.
- Octane (C8H18) - this is the eight-carbon alkane and is of great importance since it determines the final quality of the naphtha, which is a mixture of various hydrocarbons. This quality is measured by the octane number or octane number of the fuel, which takes as a reference a low-detonating one (index 100) and a highly detonating one (index 0).
- Hexane (C6H14) - is an important solvent, inhalation should be avoided, as it is very toxic.
- Butane (C4H10) - together with propane (C3H8), make up the so-called liquefied petroleum gases (LPG), which are formed in gas bags during the oil extraction process. The replacement of gasoline or diesel with LPG as fuel is increasingly being promoted, since it is a more environmentally friendly hydrocarbon by emitting only carbon dioxide and water in its combustion.
- Icosano - that's what the twenty-carbon alkane is called (the prefix 'ico' means twenty)
- Cyclopropane - formerly used as an anesthetic
- n heptane - This alkane is the one taken as a reference for the zero point of the octane scale of gasoline, which would be the least desirable, since it burns explosively. It is obtained from the resin of certain plants.
- 3-ethyl-2,3-dimethylpentane (C9H20)
- 2-methylbutane
- 3-chloro-4-n-propylheptane
- 3,4,6-trimethyl heptane
- 1-phenyl 1-bromoethane
- 3-ethyl-4-methylhexane
- 5-isopropyl-3-methylnonane
- bicyclopropane
- 1-bromopropane
- 3-methyl-5-n-propyloctane
- 5-n-butyl-4,7-diethyldecane
- 3,3-dimethyl decane
It can serve you:Examples of Hydrocarbons
