Question

The total number of acyclic structural isomers of molecular formula $C_4{H}_6$ is

• A. 5
• B. 3
• C. 6
• D. 4

Answer 1

The correct option is D 4

For a compound with molecular formula $C_c{H}_h{X}_x{N}_n{O}_o$

$\text{Degree of unsaturation}=(c+1)-\frac{h}{2}-\frac{x}{2}+\frac{n}{2}$

Molecular formula of the given compound is $C_4{H}_6$
$\text{Degree of unsaturation}=(4+1)-\frac{6}{2}=2$

Since, it is acyclic, it should have 2 double bond or 1 triple bond.
Thus, the number of acyclic isomers are 4