Question

Mixture of 1 g each of chlorobenzene, aniline and benzoic acid is dissolved in 50 mL ethyl acetate and placed in a separating funnel, 5 M NaOH (30 mL) was added in the same funnel. The funnel was shaken vigorously and then kept aside. The ethyl acetate layer in the funnel contains :

• A. benzoic acid
• B. benzoic acid and aniline
• C. benzoic acid and chlorobenzene
• D. chlorobenzene and aniline

Hint:

In liquid-liquid extraction using a separating funnel, the distribution of compounds between the two immiscible layers (aqueous and organic) depends on their solubility and reactivity with the reagents added. Acids react with bases to form water-soluble salts, and vice versa. Non-polar compounds tend to dissolve in organic solvents, while polar or ionic compounds dissolve in water.

Answer 1

The Correct Option is D

This problem involves understanding the behavior of organic compounds in a separation process using a separating funnel with solvents of different polarities. Here’s a step-by-step explanation:

1. Compounds in the Mixture: We have chlorobenzene, aniline, and benzoic acid dissolved in ethyl acetate, an organic solvent.
2. Role of NaOH: 5 M NaOH is a strong base and will primarily react with benzoic acid, a carboxylic acid. The reaction converts benzoic acid to its sodium salt (sodium benzoate), which is soluble in the aqueous phase.
3. Separation Logic:
   • Benzoic acid, once converted to sodium benzoate, will predominantly reside in the aqueous NaOH layer because ionic compounds are more soluble in water than in organic solvents.
   • Aniline and chlorobenzene do not react with NaOH. Aniline is a weak base and doesn't react significantly with other bases, and chlorobenzene is unreactive.
4. Ethyl Acetate Layer: After shaking and allowing the separating funnel to settle, the non-polar organic layer (ethyl acetate) will contain the unreacted compounds, which are chlorobenzene and aniline.
5. Final Decision: Considering the above points, the ethyl acetate layer will contain chlorobenzene and aniline but not benzoic acid.

Thus, the correct answer is chlorobenzene \text{ and } aniline.

Answer 2

Step 1: Understand the chemical properties of the given compounds.
Chlorobenzene is a neutral, non-polar organic compound. It is insoluble in water but soluble in organic solvents like ethyl acetate. It does not react with NaOH.
Aniline is a weak organic base due to the lone pair of electrons on the nitrogen atom. It can react with strong acids to form salts. Its basicity is not strong enough to react with NaOH in a significant way to form a water-soluble salt under these conditions. Aniline is sparingly soluble in water but soluble in organic solvents like ethyl acetate.
Benzoic acid is a weak organic acid containing a carboxyl group (-COOH). It can react with strong bases like NaOH to form a water-soluble sodium benzoate salt.

Step 2: Analyze the reaction with NaOH.
When NaOH (an aqueous base) is added to the ethyl acetate solution containing chlorobenzene, aniline, and benzoic acid, a reaction will occur with the acidic component, benzoic acid: \[ \text{C}_6\text{H}_5\text{COOH} (in \, ethyl \, acetate) + \text{NaOH} (aq) \rightarrow \text{C}_6\text{H}_5\text{COONa} (aq) + \text{H}_2\text{O} \] The product, sodium benzoate, is an ionic salt and is soluble in the aqueous layer (NaOH solution) but insoluble in the organic layer (ethyl acetate). 
Chlorobenzene, being neutral and non-polar, will not react with NaOH and will remain dissolved in the ethyl acetate layer. Aniline, being a weak base, will not react significantly with the strong base NaOH. It will mostly remain in its molecular form. Aniline has some solubility in water (though limited) and is also soluble in ethyl acetate. In a separating funnel, it will be distributed between the aqueous and organic layers based on its partition coefficient. However, since it did not undergo a chemical transformation into a highly water-soluble ionic species, a significant portion of aniline will likely remain in the ethyl acetate layer. 

Step 3: Determine the contents of the ethyl acetate layer after separation.
After shaking the separating funnel and allowing the layers to separate, the aqueous layer (containing NaOH and sodium benzoate) will be at the bottom (due to higher density). The ethyl acetate layer (organic layer) will be at the top.
The compounds that would have preferentially dissolved in the ethyl acetate layer are those that are non-polar or have limited reactivity with NaOH and limited solubility in the aqueous phase under these conditions. These are chlorobenzene and aniline. Benzoic acid would have been converted to its sodium salt and moved into the aqueous layer. Therefore, the ethyl acetate layer will primarily contain chlorobenzene and aniline.