Alkane Alkane For saturated hydrocarbons containing one or more rings see Cycloalkane.
An alkane in organic chemistry is a saturated hydrocarbon without cycles that is an acyclic hydrocarbon in which the molecule has the maximum possible number of hydrogen atoms and so has no double bonds.Alkanes are also often known as paraffins or collectively as the paraffin series these terms however are also used to apply only to alkanes whose carbon atoms form a single unbranched chain when this is done branched chain alkanes are called isoparaffins.Alkanes are aliphatic compounds.
The general formula for alkanes is C n H the simplest possible alkane is therefore methane CH The next simplest is ethane C H the series continues indefinitely Each carbon atom in an alkane has sp hybridization.
Isomerism
The atoms in alkanes with more than three carbon atoms can be arranged in multiple ways forming different isomers Normal alkanes have a linear unbranched configuration The number of isomers increases rapidly with the number of carbon atoms for alkanes with to carbon atoms the number of isomers equals and respectively sequence in OEIS.
Nomenclature of alkanes
The names of all alkanes end with ane.
Alkanes with unbranched carbon chains
The first four members of the series in terms of number of carbon atoms are named as follows. methane CH. ethane C H. propane C H. butane C H.Alkanes with five or more carbon atoms are named by adding the suffix ane to the appropriate numerical multiplier with elision of a terminal a from the basic numerical term Hence pentane C H hexane C H heptane C H octane C H etc For a more complete list see List of alkanes.
Straight chain alkanes are sometimes indicated by the prefix n for normal to distinguish them from branched chain alkanes having the same number of carbon atoms Although this is not strictly necessary the usage is still common in cases where there is an important difference in properties between the straight chain and branched chain isomers e g n hexane is a neurotoxin while its branched chain isomers are not.
Alkanes with branched carbon chains
Branched alkanes are named as follows.
 Identify the longest straight chain of carbon atoms.
 Number the atoms in this chain starting from at one end and counting upwards to the other end.
 Examine the groups attached to the chain in order and form their names.
 Form the name by looking at the different attached groups and writing for each group the following.
 The number or numbers of the carbon atom or atoms where it is attached.
 The prefixes di tri tetra etc if the group is attached in etc places or nothing if it is attached in only one place.
 The name of the attached group.
 The formation of the name is finished by writing down the name of the longest straight chain.
To carry out this algorithm we must know how to name the substituent groups This is done by the same method except that instead of the longest chain of carbon atoms the longest chain starting from the attachment point is used also the numbering is done so that the carbon atom next to the attachment point has the number.
For example the compound
is the only carbon alkane possible apart from butane Its formal name is methylpropane.
Pentane however has two branched isomers in addition to its linear normal form.
 dimethylpropane and methylbutane.
Trivial names
The following nonsystematic names are retained in the IUPAC system. isobutane for methylpropane
 isopentane for methylbutane
 neopentane for dimethylpropane
The name isooctane is very widely used in the petrochemical industry to refer to trimethylpentane.
Occurrence
Methane and ethane make up a large proportion of Jupiter's atmosphere
Alkanes occur both on Earth and in the solar system however only the first hundred or so and even then mostly only in traces The light hydrocarbons especially methane and ethane are of great importance for other heavenly bodies they are found for example both in the tail of the comet Hyakutake and in some 