question_answer

Which of the following pairs of compounds are positional isomers? [JEE Main Online Paper (Held On 11 April 2015)]  

A) \[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-CHO\]and\[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{3}}\]

B) \[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  || \\  O \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{3}}\]and\[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{CH}}\,-C{{H}_{2}}-CHO\]

C) \[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  || \\  O \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{3}}\]and\[C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  || \\  O \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{2}}-C{{H}_{3}}\]

D) \[C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  || \\  O \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{2}}-C{{H}_{3}}\]and

Correct Answer: C

Solution :

(a) (b) \[C{{H}_{3}}-C{{H}_{2}}-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{2}}-C{{H}_{3}}\]and \[C{{H}_{3}}-\overset{\begin{smallmatrix}  O \\  || \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}\]are functional isomers (c) are position isomers. (d)