Aldehydes Ketones And Carboxylic Acids

Goal: Convert benzene (C₆H₆) into benzoic acid (C₆H₅COOH)

Option (A):

1. (i) Br₂/Fe → Bromination: C₆H₆ → C₆H₅Br
2. (ii) Mg/dry ether → Grignard reagent formation: C₆H₅Br → C₆H₅MgBr
3. (iii) CO₂ → Carboxylation: C₆H₅MgBr + CO₂ → C₆H₅COOMgBr
4. (iv) H₃O⁺ → Acid workup: C₆H₅COOMgBr + H₃O⁺ → C₆H₅COOH (benzoic acid)

Option (C):

1. (i) CH₃Cl + Anhyd. AlCl₃ → Friedel–Crafts Alkylation: C₆H₆ → C₆H₅CH₃ (toluene)
2. (ii) KMnO₄ / OH⁻ / Δ → Side-chain oxidation: C₆H₅CH₃ → C₆H₅COO⁻
3. (iii) H₃O⁺ → Acidification: C₆H₅COO⁻ + H₃O⁺ → C₆H₅COOH

Option (D):

1. (i) CH₃COCl + Anhyd. AlCl₃ → Friedel–Crafts Acylation: C₆H₆ → C₆H₅COCH₃ (acetophenone)
2. (ii) Br₂, NaOH → Haloform reaction: C₆H₅COCH₃ → C₆H₅COO⁻
3. (iii) H₃O⁺ → Acidification: C₆H₅COO⁻ + H₃O⁺ → C₆H₅COOH

Final Answer:

Correct option(s): (A), (C), and (D)

Given reaction sequence:

C₆H₁₂O₆ → (i) OH⁻/H₂O, Δ → (ii) H₃O⁺ → H + 1 → CrO₃/H⁺

Step-by-step explanation:

Step 1: C₆H₁₂O₆ → Under basic hydrolysis and heating (OH⁻/H₂O, Δ), glucose undergoes degradation reactions (retro-aldol type cleavages) that break it into smaller fragments such as aldehydes and carboxylic acids.

Step 2: Acidification (H₃O⁺) causes the intermediate products to be protonated, stabilizing them for further reaction.

Step 3: Reaction with CrO₃/H⁺ (oxidation) selectively oxidizes aldehyde groups into carboxylic acids, forming esters when alcohols are also present.

Target Compound G: The expected product is an ester with the structure CH₃CH₂COOCH₂CH₂CH₃ – this matches with the systematic breakdown of glucose followed by esterification and oxidation steps.

Correct option: (C): CH₃CH₂COOCH₂CH₂CH₃

Given compound: CH₃CH=C–CHO–CH₂CH₃

Step 1: Identify the longest carbon chain containing the functional group (–CHO)
The aldehyde group (–CHO) has the highest priority, so numbering starts from the carbon of the –CHO group.

Numbering the chain from the aldehyde end:

1 2 3 4 5 CHO–CH=C–CH₂–CH₃–CH₃

This gives us a five-carbon chain with a double bond between carbon 2 and 3, and a methyl (–CH₃) substituent on carbon 2.

Step 2: Name the compound

• Parent chain: butenal (4 carbons with aldehyde and double bond)
• Substituent: ethyl group at position 2
• Double bond at position 2

So, the correct IUPAC name is: 2-Ethylbut-2-enal

Correct answer: Option (B)