Question

How many isomers are possible in ${{C}_{4}}{{H}_{8}}$ ?
a.) 3
b.) 2
c.) 4
d.) 5

Answer 1

Hint: Isomers are defined as the molecules which have the same molecular formula but different molecular geometries. There are two types of isomers such as conformational isomers and constitutional isomers.

Complete Solution :
Now we know that the alkane having 4 carbon atoms have the general formulae of ${{C}_{4}}{{H}_{10}}$ but the given hydrocarbon has two hydrogen less hence, there must be a double bond or a ring present in the structure.
- In the given formulae ${{C}_{4}}{{H}_{8}}$, five isomers are possible. They are But-1-ene, but-2-ene, 2-methylpropane, cyclobutane and methyl cyclopropane. The structure of all these isomers is mentioned below:

So, the correct answer is “Option D”. i.e. how many isomers are possible in ${{C}_{4}}{{H}_{8}}$ i.e. 5.

Additional information:
We know that there is no superimposable mirror image and there is no plane of symmetry in the molecule then the molecule is known as chiral. And the chiral carbon has four different groups attached to the carbon. This property is known as chirality and the compounds which have the same molecular formula but different compounds are said to be isomers. The compounds which are mirror images but are not identical to each other. They are known as enantiomers.

Note: Structural isomers are defined as compounds which have the same molecular formula but different connectivity of atoms or bonds. The isomers which are different by the orientation of atoms in space are known as stereoisomers and the isomers which differ by their rotation around a single bond are known as conformational isomers.