Consider the following sequence of reactions :

11.25 mg of chlorobenzene will produce x × 10⁻¹$\mathrm{x} \times 10^{-1}$ mg of product B. (Consider the reactions result in complete conversion.) [Given molar mass of C, H, O, N and Cl as 12, 1, 16, 14 and 35.5g mol⁻¹$35.5\mathrm{g\,mol}^{-1}$ respectively]

Core Logic

Let's perform a step-by-step diagnostic analysis:

• Molar Mass & Nitrogen Test: Compound 'A' has a nitrogen atom and a molar mass of 121 g mol⁻¹$121 \text{ g mol}^{-1}$. Let's verify Benzamide (C₆H₅CONH₂$\text{C}_6\text{H}_5\text{CONH}_2$):

This matches perfectly.

• Alkaline Hydrolysis: Hydrolysis of benzamide under basic conditions yields benzoic acid upon acidification:

Benzoic acid reactively gives effervescence with NaHCO₃$\text{NaHCO}_3$ due to the liberation of CO₂$\text{CO}_2$ gas.

• Esterification: Reaction of benzoic acid with ethanol in the presence of acid catalyst results in the creation of ethyl benzoate, an ester with a pleasant fruity smell:

Pattern Recognition

"Fruity smell" is an absolute indicator for an ester product. "Effervescence with NaHCO₃$\text{NaHCO}_3$" dictates a carboxylic acid intermediate. Basic hydrolysis converting an organo-nitrogen compound into an acid points directly to an amide or a nitrile—molar mass calculation establishes benzamide over benzonitrile (M = 103$M = 103$).

Chapter Mix

Class 12 Chemistry: Amines Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Core Logic

Let's track sequence (1):

• Nitrobenzene (Ph-NO₂$Ph-NO_2$) is reduced using Sn/HCl$Sn/HCl$ to form Aniline (Ph-NH₂$Ph-NH_2$).
• Aniline undergoing diazotization with NaNO₂/HCl$NaNO_{2}/HCl$ at cold temperatures (0-5circC$0-5^{circ}C$) creates Benzene diazonium chloride (Ph-N₂⁺Cl⁻$Ph-N_{2}^{+}Cl^{-}$).
• The diazonium salt undergoes a coupling reaction with β$\beta$-naphthol in alkaline conditions (NaOH$NaOH$) to synthesize a highly vibrant red-orange azo dye.

Pattern Recognition

The standard sequence for azo dye preparation is: Aromatic Nitro arrow$\rightarrow$ Primary Amine arrow$\rightarrow$ Diazonium Salt arrow$\rightarrow$ Phenol/Naphthol Coupling.

Chapter Mix

Class 12 Chemistry: Amines

Core Logic

Let us resolve each structural step sequentially:

• Step 1: Aniline undergoes diazotization when treated with NaNO₂ + HCl$\text{NaNO}_2 + \text{HCl}$ at 273-278 K$273-278\text{ K}$, forming benzene diazonium chloride [A]$[A]$ (C₆H₅N₂^+Cl^-$\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^-$).
• Step 2: Warming benzene diazonium chloride with potassium iodide (KI$\text{KI}$) substitutes the diazonium group with iodine, producing iodobenzene [B]$[B]$ (C₆H₅I$\text{C}_6\text{H}_5\text{I}$).
• Step 3: Treating iodobenzene with sodium metal in dry ether causes a Fittig coupling reaction, dimerizing two phenyl radicals into biphenyl [C]$[C]$ (C₆H₅-C₆H₅$\text{C}_6\text{H}_5-\text{C}_6\text{H}_5$).

  

  

Pattern Recognition

Shortcut: Aniline arrow NaNO₂/HCl arrow$\rightarrow \text{NaNO}_2/\text{HCl} \rightarrow$ Diazonium salt arrow KI arrow$\rightarrow \text{KI} \rightarrow$ Iodobenzene. The final sodium metal treatment triggers a symmetrical radical dimer homocoupling (Fittig reaction) to yield a biphenyl product.

Evaluation Rubric / Model Answer

Option (C)

Chapter Mix

Class 12 Chemistry: Amines Class 12 Chemistry: Haloalkanes and Haloarenes

Core Logic

When benzene diazonium chloride is treated with ethanol (CH₃CH₂OH$\text{CH}_3\text{CH}_2\text{OH}$), it undergoes a reduction reaction (deamination). Ethanol acts as a reducing agent and gets oxidized to ethanal (CH₃CHO$\text{CH}_3\text{CHO}$), while the diazonium group is replaced by hydrogen to yield pure benzene, not phenetole (ethoxybenzene).

Step 1: Review of Alternative Choices

Reactions (2), (3), and (4) show standard correct transformations: hypophosphorous acid reduction to benzene, potassium iodide substitution to iodobenzene, and cuprous cyanide substitution to benzonitrile.

Pattern Recognition

Shortcut: Remember that H₃PO₂$\text{H}_3\text{PO}_2$ and CH₃CH₂OH$\text{CH}_3\text{CH}_2\text{OH}$ are standard classic reducing agents that reduce ArN₂^+Cl^-$\text{ArN}_2^+\text{Cl}^-$ directly down to ArH$\text{ArH}$ (benzene). They do not undergo nucleophilic ether substitution paths.

Chapter Mix

Class 12 Chemistry: Amines