Question

Given below are isomers of $C_4{H}_8$. Which of the following statements is correct?

1. $\underset{\text{But-1-ene}}{\stackrel{1}{C}{H}_2=\stackrel{2}{C}H-\stackrel{3}{C}{H}_2-\stackrel{4}{C}{H}_3}$
2. $\underset{\text{But-2-ene}}{\stackrel{1}{C}{H}_3-\stackrel{2}{C}H=\stackrel{3}{C}H-\stackrel{4}{C}{H}_3}$
3. $\underset{\text{2-Methylprop-1-ene}}{\stackrel{1}{C}{H}_2=\stackrel{2}{C}\left(C{H}_3\right)-\stackrel{3}{C}{H}_3}$

• A. 1 & 2 are positional isomer
• B. 2 & 3 are chain isomer
  
• C. 1 & 3 are chain isomer
• D. All of the above.

Answer 1

The correct option is D All of the above.

1 & 2 are positional isomer of each other.
Both compounds differ only in the position of multiple bond (here double bond) on the same parent chain. The principal chain is also the same for both (a) and (b) of four carbon atoms

Structural isomers which have different carbon skeletons
(parent chain or side chain)
Chain isomerism is also known as skeletal isomerism.
These compounds have same molecular formula , general formula and emperical formula.
2 & 3 are chain isomer of each other.
1 & 3 are chain isomer of each other.