question_answer

A compound A having the molecular formula \[{{C}_{5}}{{H}_{12}}O,\]on oxidation give a compound B with molecular formula\[{{C}_{5}}{{H}_{10}}O.\] Compound B gave a 2, 4-dinitrophenylhydrazine derivative but did not answer haloform test or silver mirror test. The structure of compound A is

A) \[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}C{{H}_{2}}OH\]

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

C) \[C{{H}_{3}}C{{H}_{2}}\underset{\begin{smallmatrix}  | \\  OH \end{smallmatrix}}{\mathop{CH}}\,C{{H}_{2}}C{{H}_{3}}\]

D) \[C{{H}_{3}}C{{H}_{2}}\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\mathop{CH}}\,C{{H}_{2}}OH\]

E) \[C{{H}_{3}}-\underset{\begin{smallmatrix}  | \\  C{{H}_{3}} \end{smallmatrix}}{\overset{\begin{smallmatrix}  C{{H}_{3}} \\  | \end{smallmatrix}}{\mathop{C}}}\,-C{{H}_{2}}-OH\]

Correct Answer: C

Solution :

Since, the compound B gave a 2, 4-dinitrophenylhydrazine derivative but did not answer halogen test or silver mirror test, it must contains a  group, but it is neither a methyl ketone nor an aldehyde. Moreover compound B is obtained by the oxidation of compound A, having molecular formula\[{{C}_{5}}{{H}_{12}}O,\]so the compound A must be a secondary alcohol. \[C{{H}_{3}}-C{{H}_{2}}\underset{\begin{smallmatrix}  \,\,\,\,\,\,\,2{}^\circ \text{ }alcohol \\  (compound\text{ }A) \end{smallmatrix}}{\mathop{\underset{\begin{smallmatrix}  | \\  OH \end{smallmatrix}}{\mathop{CH}}\,}}\,-C{{H}_{2}}-C{{H}_{3}}\xrightarrow[-{{H}_{2}}O]{[O]}\] \[\underset{\begin{smallmatrix}  \,\,\,\,\,\,\,\,\,\,\,ketone \\  (compound\text{ }B) \end{smallmatrix}}{\mathop{C{{H}_{3}}-C{{H}_{2}}-\underset{\begin{smallmatrix}  || \\  O \end{smallmatrix}}{\mathop{C}}\,-C{{H}_{2}}-C{{H}_{3}}}}\,\]