Question

Common name of $C{{H}_{2}}=CH-CH=C{{H}_{2}}$

Answer 1

To write the common name of any organic compound we have to check the number of carbon atoms such as if 2 carbons are present then we name is eth, if 4 then but and so on. We use prefix n when all the carbon are in a continuous chain like structure i.e. unbranched. If there is any double bond then we use it as the suffix and write "ene" and if triple bond is present then "yne".

Complete step by step solution:
-From your chemistry lessons you have learned about how to write the common name of any organic compound.
-Common name is defined as the nomenclature system which is used for naming the simple organic compounds. In case of complex molecules or compounds we use IUPAC nomenclature instead of common name.
-In common names we do not do the numbering of a functional group or the place at which the branch is connected from the parent carbon chain. There are some steps to write the common name of any compounds such as :
(i) Firstly we have to count the number of carbon atoms present in the parent chain and if the carbon chain is continuous or linear chain i.e. unbranched then we prefix n and then we write the number of carbon atoms. For example:

No. of carbon	prefix
1	Form
2	Acet
3	Prop
4.	Butyl

(ii) Then we have to check if there is any double or triple bond in the compound. If there is any double bond present then we will write "ene" in the suffix and if triple bond is present then we will write "yne" in the suffix.
(iii) If a functional group is present in the carbon chain then that functional group is written at the end of the chain.
(iv) We use prefix iso when all carbon except the one carbon forms a continuous chain i.e. is an methyl group is located at the second carbon of the carbon chain whereas prefix neo is used when all but two carbons form the continuous chain. In this the second last carbon of the chain is trisubstituted i.e. has three methyl groups attached with the carbon.
In the question we have to write the common name of $C{{H}_{2}}=CH-CH=C{{H}_{2}}$
Here four carbon are present in the carbon chain and it is continuous therefore we use n as the prefix before "but" and in the suffix we will use "ene" due to the presence of double bond.

Thus the common name of $C{{H}_{2}}=CH-CH=C{{H}_{2}}$ is n-butene.

Note: We use the prefix "sec" which stands for secondary when one carbon is attached with two other carbon and prefix "ter" which stand for tertiary is used when one carbon is attached with three other carbon. The prefix "sec" is used only for a four carbon chain. It is not used in shorter chains and is also ambiguous for chains which have five or more carbon atoms.