Question

 
The incorrect statement about 'B' is: 

• A. It gives test with Tollens reagent
• B. It gives test with Fehling’s solution
• C. It does not give test with NaOH + I\(_2\) solution
• D. It forms acid and alcohol with concentrated NaOH, followed by acidification

Hint:

Carboxylic acids do not give Fehling’s or Tollens' test since they are already in their most oxidized form.

Answer 1

The Correct Option is B

To determine the incorrect statement about the compound 'B', we need to analyze how it reacts with different reagents: Tollens reagent, Fehling's solution, NaOH + I₂ solution, and concentrated NaOH followed by acidification.

1. Tollens Reagent: This reagent is used to test for the presence of aldehydes. Aldehydes reduce the Tollens reagent (ammoniacal silver nitrate) to metallic silver, indicating a positive result. The statement "It gives test with Tollens reagent" suggests 'B' is an aldehyde.

2. Fehling's Solution: This is another test for carbohydrates and aldehydes but not for ketones. A solution containing Cu²⁺ ions, it forms a brick-red precipitate of copper(I) oxide in the presence of reducing sugars or aldehydes. "It gives test with Fehling’s solution" would only be true if 'B' were an aldehyde; however, since this is the correct answer, it indicates that 'B' does not react this way, so 'B' is likely a ketone or another non-reactive compound for this test.

3. NaOH + I₂ solution: This test is for methyl ketones (iodoform test). If 'B' were a methyl ketone, it would produce a yellow precipitate of iodoform. "It does not give test with NaOH + I₂ solution" suggests 'B' is not a methyl ketone.

4. Concentrated NaOH followed by acidification: This combination can cause an aldol condensation if 'B' is an aldehyde or certain types of ketones, leading to the formation of an acid and alcohol. The statement "It forms acid and alcohol with concentrated NaOH, followed by acidification" is consistent with this reaction condition.

Therefore, the incorrect statement is indeed that 'B' gives a test with Fehling’s solution, implying 'B' is not an aldehyde that would react with Fehling’s reagent.

Answer 2

Step 1: Formation of 'A' 
Benzene reacts with methyl chloride (\(\text{CH}_3\text{Cl}\)) in the presence of anhydrous aluminum chloride (\(\text{AlCl}_3\)) to form toluene (\(\text{C}_6\text{H}_5\text{CH}_3\)): \[ \text{C}_6\text{H}_6 + \text{CH}_3\text{Cl} \xrightarrow{\text{Anhy. AlCl}_3} \text{C}_6\text{H}_5\text{CH}_3 (A) \] Step 2: Oxidation of 'A' to 'B' 
Toluene undergoes oxidation with chromic acid (\(\text{CrO}_3\)) in acetic anhydride at 273-283 K, followed by hydrolysis with \(\text{H}_3\text{O}^+\) to form benzoic acid (\(\text{C}_6\text{H}_5\text{COOH}\)): \[ \text{C}_6\text{H}_5\text{CH}_3 \xrightarrow{\text{CrO}_3, (\text{CH}_3\text{CO}_2\text{O})} \text{C}_6\text{H}_5\text{COOH} (B) \] 
Step 3: Analysis of the Given Statements 
- Tollens' Test: - Tollens' reagent \(\text{Ag(NH}_3\text)_2^+\) is used to test for aldehydes, which oxidize to carboxylic acids and produce a silver mirror. Since benzoic acid is already a carboxylic acid, it does not give a Tollens' test. - Fehling’s Test: 
- Fehling's reagent is used to test for aldehydes that can be oxidized to carboxylic acids. Benzoic acid is already oxidized and does not contain an aldehyde functional group, so it does not give a positive Fehling’s test. (Incorrect statement)
- NaOH + I\(_2\) Test (Iodoform Test):
- The Iodoform test is positive for compounds containing the CH\(_3\)CO group (like methyl ketones, ethanol, etc.). Benzoic acid does not have this functional group, so it does not give a positive test. 
- Reaction with NaOH:
- Benzoic acid \(C_6H_5COOH\) reacts with NaOH to form sodium benzoate (\(\text{C}_6\text{H}_5\text{COO}^-\text{Na}^+\)). Upon acidification, it regenerates benzoic acid. This statement is correct. 
Final Answer: 
The incorrect statement is (2) "It gives test with Fehling’s solution", as benzoic acid does not respond to Fehling's test.