Alkane nomenclature practice

Introduction :
Alkanes are the saturated hydrocarbons consisting elements of carbon (C) and hydrogen (H) in which atoms are linked together by single bonds. Alkanes are the member of a homologous series of organic compounds, where all members differ by a constant relative molecular mass of 14.

Each carbon atom have 4 single bonds (either C-H or C-C bonds), and each hydrogen atoms are joined to a carbon atom. A series of linked carbon atoms is known as the carbon skeleton or carbon backbone...The first member of alkane is methane, CH₄.

Structure and Isomerism of Alkanes:

Saturated hydrocarbons, Alkanes, may occur in linear, branched or cyclic forms. Alkanes having linear structure must have n<3.In this all the carbon  are attached  in a snake-like structure and alkanes having branched structure must have n>3. Alkanes having cyclic structure must have n>2.Alkanes having more than three carbon atoms are arranged in number of ways, so they form different structural isomers.

• First three members i.e. methane, ethane, and propane have one isomer.  
• Butane ,C₄H₁₀ has 2 isomers. they are n-butane, isobutene
• Pentane ,C₅H₁₂  has 3 isomers. They are pentane, isopentane, neopentane 
• Hexane, C₆H₁₄ has five  isomers
• Branched alkanes are chiral, e.g., 3-methylhexane and its higher homologues

Alkane nomenclature practice

• The number of carbon atoms can be indicated by ‘meth’ for one carbon atom, ‘eth’ for two , ‘prop’ for three, ‘but’ for four , ‘pent’ for five and so on…..

• Alkanes or saturated carbon atoms can be named by adding ‘ane’ suffix to the number of carbon atoms’ name. e.g., CH₄ can be named as methane. C₂H₆ can be named as ethane .First three members of alkanes form linear structure, so they have one isomer each.  

    Butane has two isomers. It can be named by using following rules:

• For naming branched chain isomers, firstly number of carbon atoms in series are counted and named according to it.

• Then number of methyl group is counted and also its position is located.

As per the IUPAC convention, we have certain rules to follow:

• First we have to find and then name the longest chain of carbon.
• Next we have to identify the groups which is being attached to the chain, after that we name it.
• Number the C- atoms in a chain that starts from the nearest substituent group.
• Assign the position of each group by a proper number and then we name it.
• Write the name of the listing groups which should be in an alphabetical order.
• di, tri, tetra, are used as prefix to assign several groups of similar kind. Alphabetizing is not taken into account.

E.g.  
1. C₄H₁₀           `->`     common name – n-butane      IUPAC name- butane 

 

2.

 

IUPAC names of the above alkane is 2- methylpropane

3.

IUPAC name of the above alkane is 2-methylbutane

4.

IUPAC name of the above alkane is 2,2-dimethylpropane

Conclusion for the nomenclature of alkane

From the discussion, we conclude that, in alkane each carbon atom have 4 single bonds and each hydrogen atom must be joined to a carbon atom .There is single bond between each carbon atom. They are saturated hydrocarbons.