Question

Define or explain position isomerism with an example.

Answer 1

When two or more compounds with the same molecular formula differ in the position of a substituent atom or functional group on the carbon atom, they are called position isomers and this phenomenon is termed as position isomerism.

Example:

(i) C₄H₆ (Butyne) has two isomers.

\[\ce{\underset{but-1-yne}{CH3 - CH2C ≡ C - H}}\]

\[\ce{\underset{but-2-yne}{CH3 - C ≡ C - CH3}}\]

(ii)

\[\begin{array}{cc}
\ce{O}\\
||\\
\ce{\underset{pentan-3-one}{CH3CH2 - C - CH2CH3}}
\end{array}\]

\[\begin{array}{cc}
\ce{O}\phantom{........}\\
||\phantom{........}\\
\ce{\underset{pentan-2-one}{CH3 - C - CH2CH2CH3}}
\end{array}\]