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In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes:
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compound
Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...
s and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated
Saturation, saturated, unsaturation or unsaturated may refer to:
Chemistry
* Saturation, a property of organic compounds referring to carbon-carbon bonds
**Saturated and unsaturated compounds
**Degree of unsaturation
**Saturated fat or fatty acid ...
, like hexane
Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14.
It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...
, or unsaturated, like hexene
In organic chemistry, hexene is a hydrocarbon with the chemical formula . The prefix "hex" is derived from the fact that there are 6 carbon atoms in the molecule, while the " -ene" suffix denotes that there is an alkene present—two carbon atoms ...
and hexyne The hexynes are a subgroup from the group of alkynes. It consists of several isomeric compounds having the formula C6H10.
The linear and branched members are:
* 1-Hexyne (''n''-butylacetylene)
* 2-Hexyne
2-Hexyne is an organic compound that belong ...
. Open-chain compound
In chemistry, an open-chain compound (also spelled as open chain compound) or acyclic compound (Greek prefix "α", ''without'' and "κύκλος", ''cycle'') is a compound with a linear structure, rather than a cyclic one.
An open-chain compound h ...
s, whether straight or branched, and which contain no rings of any type, are always aliphatic. Cyclic compounds can be aliphatic if they are not aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satu ...
.
Structure
Aliphatic compounds can besaturated
Saturation, saturated, unsaturation or unsaturated may refer to:
Chemistry
* Saturation, a property of organic compounds referring to carbon-carbon bonds
**Saturated and unsaturated compounds
**Degree of unsaturation
**Saturated fat or fatty acid ...
, joined by single bonds (alkane
In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in whi ...
s), or unsaturated, with double bonds (alkene
In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond.
Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, a ...
s) or triple bonds (alkyne
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Acetylene
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Propyne
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1-Butyne
In organic chemistry, an alkyne is an unsaturated hydrocarbon containing at least one carbon—carbon triple bond. The simplest acyclic alkynes with only one triple bond and n ...
s). If other elements ( heteroatoms) are bound to the carbon chain
In chemistry, catenation is the bonding of atoms of the same element into a series, called a ''chain''. A chain or a ring shape may be ''open'' if its ends are not bonded to each other (an open-chain compound), or ''closed'' if they are bonded ...
, the most common being oxygen, nitrogen, sulfur, and chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...
, it is no longer a hydrocarbon, and therefore no longer an aliphatic compound.
The least complex aliphatic compound is methane (CH4).
Properties
Most aliphatic compounds areflammable
A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...
, allowing the use of hydrocarbons as fuel, such as methane in Bunsen burner
A Bunsen burner, named after Robert Bunsen, is a kind of ambient air gas burner used as laboratory equipment; it produces a single open gas flame, and is used for heating, sterilization, and combustion.
The gas can be natural gas (which is main ...
s and as liquefied natural gas (LNG), and ethyne
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure f ...
(acetylene
Acetylene (systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure f ...
) in welding.
Examples of aliphatic compounds
The most important aliphatic compounds are: * n-, iso- and cyclo-alkanes (saturated hydrocarbons) * n-, iso- and cyclo-alkenes and -alkynes (unsaturated hydrocarbons). Important examples of low-molecular aliphatic compounds can be found in the list below (sorted by the number of carbon-atoms):References