Question

Number of carbon atoms in the longest chain is 3. A methyl group is present at carbon number 2. So, IUPAC name is __________.
A.2 – ethyl propane
B.Butane
C.2 – methyl propane
D.2 – methyl butane

Answer 1

We will first Identify the parent chain by counting the longest number of carbon atoms which are continuously bonded in the molecule and Using this number, we will choose the corresponding root name and add "ane". This is the parent chain name for alkane.

Complete answer:
Given in the question is:
The number of carbon atoms in the longest chain is 3
A methyl group is present at carbon number 2.
Since the number of carbon atoms is 3, we will use the root name ‘prop’. Then we identify the substituent groups attached to the parent chain and place them in front of the parent name in alphabetical order. In the question, a methyl group $\left( {C{H_3}} \right)$ is present at carbon number 2.
So, IUPAC Name will be 2 – methyl propane.

Therefore, the correct answer is option (C).

Note: The names of organic molecules are divided into three parts, the first is the root name, which indicates the number of carbon atoms in the longest continuous chain, which includes the highest priority functional group. The second is the suffix name, which indicates the position and identity of the highest priority functional group. And the third is, the prefix name, which indicates the position and identity of substituent groups. And we assign the number to each of the substituent groups to indicate where it is attached. We Start the numbering from whichever end of the parent chain will give rise to the lowest set of numbers and the lowest set is selected on the basis of the lowest number at the first point of difference. If identical substituents are present, then we combine them using di, tri, tetra etc. as prefixes. These prefixes are not included in the alphabetizing.