Question

Give a test to differentiate ( Bromobenzene) \[Ph-Br\] and Benzyl bromide (\[PhC{{H}_{2}}Br\]).
$$\begin{array}{*{35}{l}}
\left( A \right)\text{ }aq.KOH,\text{ }Na \\
\left( B \right)\text{ }AgN{{O}_{3}} \\
\left( C \right)\text{ }KMn{{O}_{4}} \\
\left( D \right)\text{ }All\text{ }these \\
\end{array}$$

Answer 1

Hint: To differentiate between two compounds, they must react differently with a given reagent and produce a visible change like change in color or odour in order to differentiate one compound from the other. Understand the reagents given in the options as to what is their function and how they react.

Complete step by step answer:
We will now apply the reagent given in the options to the compounds mentioned in the question and see if there is any difference in their behavior towards the reagent.
Reagent 1: \[aq.KOH,\text{ }Na\]
$Ph-C{{H}_{2}}Br{{\xrightarrow{aq.KOH}}_{{}}}Ph-C{{H}_{2}}O{{H}_{{}}}{{\xrightarrow{Na}}_{{}}}Ph-CHO+{{H}_{2}}$
The evolution of Hydrogen gas confirms the above reaction to hold good.
$Ph-Br{{\xrightarrow[Na]{aq.KOH}}_{{}}}N{{o}_{{}}}reaction$
Hence Reagent 1 can be used to differentiate between the two compounds.
Reagent 2: \[AgN{{O}_{3}}\]
$\begin{align}
& Ph-C{{H}_{2}}Br{{\xrightarrow{AgN{{O}_{3}}}}_{{}}}Ph-C{{H}_{2}}N{{O}_{3}}+AgBr \\
& Ph-Br{{\xrightarrow{AgN{{O}_{3}}}}_{{}}}N{{o}_{{}}}\operatorname{Re}action \\
\end{align}$
The formation of Brown precipitate(\[AgBr\]) distinguishes the above two compounds.
Hence Reagent 2 can be used to differentiate between the two compounds.
Reagent 3: \[KMn{{O}_{4}}\]
$\begin{align}
& Ph-C{{H}_{2}}Br{{\xrightarrow{KMn{{O}_{4}}}}_{{}}}Ph-COOH \\
& Ph-Br{{\xrightarrow{KMn{{O}_{4}}}}_{{}}}N{{o}_{{}}}\operatorname{Re}action \\
\end{align}$
The formation of Benzoic acid shows the difference between the compounds.
Hence Reagent 3 can be used to differentiate between the two compounds
Since all the three reagents can be used to differentiate between the two given compounds,

The correct answer is option (D).

Note: Always read the options carefully. At times you will mark just one of the reagents as it gives the correct answer, however in this question marking only one reagent will not be right as all three of them are correct and hence the correct answer becomes all of these. All three reagents show no reaction with bromobenzene since it is less prone to nucleophilic substitution due to resonance stabilisation.