Question

In $C_{ 6 }H_{ 14 }$, the number of possible structural isomer is:A. 3B. 6C. 4D. 5

Hint: In this question to get the correct answer you have only one way that is to draw all the different structures possible with the chemical formula given in the question. Now try to figure out the answer by counting the number of isomers.

"Structural Isomers" are compounds that consist of the same number and kind of atoms, arranged in different structures.

Here the $C_{ 6 }H_{ 14 }$ compound is given to us. The name of this six-carbon compound is hexane.
Hexane has 5 structural isomers, which means we can arrange carbons in 5 different ways. We can name these compounds as,
n-hexane
2-methyl pentane
3-methyl pentane
2,2-dimethylbutane
2,3-dimethyl butane

Let’s looks at structures of these five compounds -
n-hexane

2-methyl pentane

3-methyl pentane

2,3-dimethyl butane

2,2-dimethylbutane

Therefore, we can conclude that the correct answer to this question is option D.

Additional information: We should know that all alkanes are colorless. The boiling points of the various hexanes are somewhat similar and, as for other alkanes, are generally lower for the more branched forms.

Note: We can also classify these 5 isomers of hexane into two subtypes of structural isomers.
In chain isomers, the carbon atoms are connected in different orders. Example - n-hexane, 2,3-dimethyl butane, and 2-methyl pentane.
In position isomers, the carbon skeleton remains unchanged, but substituents are moved around. Example - (1) 2,3-dimethylbutane and 2,2-dimethylbutane (2) 3-methyl pentane and 2-methyl pentane