Alkanes
The alkanes are acyclic hydrocarbons in which all of the carbon to carbon bonds are single covalent bonds (single bonds).
The alkanes are also considered to be saturated hydrocarbons because they will hold no more hydrogens.
The word ‘alkane’ comes from a prefix and a suffix. The prefix “ALK-“ refers to the Aliphatic hydrocarbon and the suffix ”-ANE” refers to the presence of all single bonds.
The characteristic type of reaction for the alkanes is substitution or replacement since it would be necessary to replace a hydrogen to combine the molecule with another substance.
Alkanes have several alternate names:
Paraffin series.
Methane series.
This series gets its name from the very first member of the class, the gas methane.
All of the members of the alkanes have a molecular formula that may be determined by the general molecular formula of the class: CnH2n+2.
The integer “n” is the number of carbons.
In determining the general molecular formula, you simply substitute the number of carbons where the “n” is.
Naming the Alkanes
When naming the alkanes we use the same rules for nomenclature established by the International Union of Pure and Applied Chemists (IUPAC).
Here are the rules:
First, name the longest chain of carbons.
Then, name the carbon side chain(s) from largest to smallest.
Give addresses for all side chains using smallest numbers.
The name is always written from right to left but it is read from left to right.
The carbon chains are always identified by the appropriate prefix for the number of carbons in the chain.
The longest chain would have the suffix”-ANE”.
Carbon sidechains are also called radicals and they are identified by the appropriate prefix followed by the suffix “-YL” which identifies a radical work carbon sidechain.
IUPAC Prefixes & Suffixes
Name the alkane of one carbon.
Name the alkane of two carbons.
Name the following alkane.
So working through this step-by-step:
We count the number of carbons in the chain which is six. Looking at the prefixes this gives us “HEX”. In looking at the bonds we see that they are all single bonds which gives us the prefix “ANE”. We now know we are dealing with hexane.
So working through this step-by-step:
We see a side chain coming off the second carbon. This sidechain consists of one carbon and three hydrogen. Looking at the prefixes we see the prefix ”METH” which means one and the suffix “-YL” which indicates it’s a side chain. We now know this word is methyl.
So working through this step-by-step:
Now that we have named the main chain and the side chain, we have to indicate where the side chain actually appears. The rule of using smallest numbers comes into play . If you start from the right most side it is five; if you start counting from the left hand side it is two. Since we always use the smallest number, we go with the number ”2”.
Naming Alkanes
So working through this step-by-step:
This gives us the name “2-methyl hexane”
