Question

The number of structural isomers of $C_5{H}_{10}$ is :-
A. 10
B. 11
C. 12
D. 13

Answer 1

Hint: The given compound does not have any groups and only hydrocarbons. It can form only chain structural isomers and ring structural isomers. Draw all possible isomers and count them.

Complete step by step answer:
Structural isomers have further categories as chain, positional, functional, tautomerism, metamerism and ring-chain. We have been given a formula as $C_5{H}_{10}$ with no other group of elements other than hydrogen and carbon. So only two types of structural isomers are possible. Chain isomerism and ring-chain isomerism. We will draw all possible isomers and count them. As the formula is of the form $C_n{H}_{2n}$ then the structural isomers are either alkenes or ring compounds. They are as follows starting with chain compounds and then ring compounds:

In the above set of diagrams, we formed ten isomers falling in structural isomers categories.
So, the correct answer is “Option A”.

Note: There is no standard way to calculate the number of structural isomers. Although, it will be laborious work to form an expression separately for each example using permutations and combinations of how groups, hydrogen atoms can be arranged with the carbon atoms.