Question
$$n$$ - Propyl alcohol and $$iso$$ - propyl alcohol can be chemically distinguished by which reagent?
A.
$$PC{l_5}$$
B.
$$\frac{{{H_2}}}{{Ni}}$$
C.
$$\frac{{{K_2}C{r_2}{O_7}}}{{{H_2}S{O_4}}}$$
D.
$$\frac{{{O_3}}}{{Zn{\text{ - }}{H_2}O}}$$
Answer :
$$\frac{{{K_2}C{r_2}{O_7}}}{{{H_2}S{O_4}}}$$
Solution :
$$n$$ - Propyl alcohol on oxidation with potassium dichromate gives an aldehyde which on further oxidation gives an acid. Both aldehyde and acid contain the same number of $$C$$ atoms as the original alcohol.
\[C{{H}_{3}}C{{H}_{2}}C{{H}_{2}}OH\xrightarrow[\frac{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{{H}_{2}}S{{O}_{4}}}]{{{25}^{\circ }}C}\] \[C{{H}_{3}}C{{H}_{2}}CHO\xrightarrow{\frac{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{{H}_{2}}S{{O}_{4}}}}\] \[C{{H}_{3}}C{{H}_{2}}COOH\]
Isopropyl alcohol on oxidation gives a ketone with the same number of $$C$$ atoms as the original alcohol.
\[C{{H}_{3}}\underset{\begin{smallmatrix}
| \\
\,\,\,C{{H}_{3}}
\end{smallmatrix}}{\overset{\begin{smallmatrix}
\,\,\,OH \\
|
\end{smallmatrix}}{\mathop{-CH}}}\,\xrightarrow{\frac{{{K}_{2}}C{{r}_{2}}{{O}_{7}}}{{{H}_{2}}S{{O}_{4}}}}C{{H}_{3}}\overset{\begin{smallmatrix}
O \\
\parallel
\end{smallmatrix}}{\mathop{-C-}}\,C{{H}_{3}}\]