The aliphatic adjective is used in the field of chemistry to describe those organic compounds that have an open chain as the structure of their molecules. In this way, it is possible to speak of different compounds of the aliphatic type.
It is called as aliphatic hydrocarbon to the organic compound formed with hydrogen and carbon and which has no aromaticity, a chemical property related to the behavior of electrons that are in the double bonds. These electrons, since they can move freely between the different bonds, both single and double, give a degree of stability to the molecule that would not be possible to achieve if they remained fixed in the bond.
When designing a graphic representation of the molecule taking into account the aromaticity, the double bonds in one of the configurations must be drawn and related to the others through arrows, to express the other opportunities that the electrons have to form new links around the aromatic ring. An example of this behavior can be seen in benzene, whose molecule has more than one resonance state and its double bonds alternated with the simple ones are represented.
There are many concepts related to the term aliphatic; such is the case of alkanes, hydrocarbons containing exclusive way atoms and hydrogen atoms. They are also known as saturated hydrocarbons, since they do not have double or triple bonds, which is why their carbons have a rearrangement of their electrons called hybridization. On the other hand, they do not have functional groups either.
These aliphatic hydrocarbons can be cyclic or acyclic. In the case of cyclic aliphatic hydrocarbons, their aliphatic chain manages to close and forms a ring. A cycloalkane (or cyclic alkane), therefore, is a saturated hydrocarbon composed only of carbon atoms that are attached through single bonds that take on a ring shape. The generic formula for cyclic alkanes is CnH2nl
The acyclic aliphatic hydrocarbons have a linear hydrocarbon grouping. The simplest of these organic compounds are aliphatic alkanes, with a branched or linear chain and without functional groups.
The reactivity of aliphatic alkanes is very small in contrast to that of other organic compounds. All its links are of the sigma type, that is, simple; they are covalent and have a single pair of electrons in an s orbital, and therefore a series of lines can be seen in their structure that represent the covalent bonds by means of which each linked atom shares a pair of electrons with the others.
An example of aliphatic alkane is propane, a gas derived from petroleum that has three carbon atoms. Its chemical formula is C3H8: through industrial processes that allow the gas to liquefy, propane is used as a fuel, often combined with butane.
On the other hand we have the following two concepts:
* alkenes, unsaturated hydrocarbons that have a carbon-carbon bond or more in their molecule. Alkenes can be understood as alkanes that have lost two hydrogen atoms, which produces a bond between two double-type carbons. In a similar way to what happens with alkanes, cyclic alkenes are called cycloalkenes;
* alkynes, aliphatic hydrocarbons that have at least two pi and one sigma bonds that occur between two carbon atoms.
It should be noted that alkenes (such as ethylene) and alkynes (such as acetylene) are also acyclic aliphatic hydrocarbons. Ethylene is found naturally in plants, although it is usually obtained from hydrocarbons. The same occurs with acetylene, collected from oil or natural gas through different industrial procedures.