Q.Match the items of Column I with the items of Column II.
Column I:

The key idea is Electrophilic Aromatic Substitution (EAS) — phenol is highly activated, directing incoming groups ortho/para and undergoing specific named reactions.

Reasoning:

1. Methanol is obtained industrially by the destructive distillation of wood (pyrolysis). → (i)-(d)
2. Phenol reacts with $CO_2$ and NaOH under heat/pressure to form salicylic acid — this is Kolbe's reaction. → (ii)-(a)
3. Bromination of phenol (with $Br_2$ water) gives 2,4,6-tribromophenol (white precipitate) — no catalyst needed. → (iii)-(c)
4. Nitration of phenol (dilute $HNO_3$) yields ortho/para-nitrophenol due to the strong activating -OH group. → (iv)-(e) …

Concept & Intuition: Electrophilic Aromatic Substitution (EAS) on Phenol

Phenol (C6H5OH) is unusually reactive in EAS because the -OH group is a strong activating and ortho/para-directing group. The lone pair on oxygen donates electron density into the ring via resonance, making the ortho and para positions electron-rich and thus the primary sites for attack by electrophiles like Br+ (from Br2) or NO2+ (from HNO3). This explains why bromination of phenol is so fast it gives the trisubstituted product (2,4,6-tribromophenol) even without a catalyst, and why nitration yields a mixture of ortho and para nitrophenols.

Kolbe's reaction is a specific EAS variant: under high pressure, CO2 acts as a weak electrophile and attacks the ortho position of the phenoxide ion (formed by NaOH), giving salicylic acid after acidification. Salicylic acid is then acetylated to make aspirin (acetylsalicylic acid).

Methanol, historically called 'wood alcohol', is obtained by the destructive distillation of wood (heating wood in the absence of air). The reaction of any alcohol (R-OH) with sodium metal is a simple acid-base reaction: the O-H bond is weakly acidic, and sodium displaces hydrogen, evolving H2 gas.

Step-by-step matching

1. Methanol -> (d) destructive distillation of wood

   Methanol (CH3OH) was traditionally produced by heating wood in a closed vessel (destructive distillation). This is its classic source, though modern methods use synthesis gas.

2. Phenol (with CO2 and NaOH) -> (a) Kolbe's reaction

   When phenol is treated with NaOH, it forms sodium phenoxide. Under pressure (about 5-7 atm) and at 125 degrees C, CO2 inserts at the ortho position. Acidification yields salicylic acid. This specific carboxylation is called the Kolbe-Schmitt reaction (often just Kolbe's reaction).

3. Bromination of phenol -> (c) 2,4,6-tribromophenol formation

   Phenol reacts instantly with bromine water (Br2/H2O) at room temperature. The -OH group activates the ring so strongly that all three available ortho/para positions get brominated, giving a white precipitate of 2,4,6-tribromophenol. This is a test for phenol.

4. Nitration of phenol -> (e) ortho/para-substitution

   Dilute nitric acid at low temperature (about 0 degrees C) nitrates phenol to give a mixture of ortho-nitrophenol (volatile, steam-distillable) and para-nitrophenol. The -OH group directs the nitro group to these positions. This is a classic example of ortho/para-directing EAS.

5. Salicylic acid -> (f) precursor for aspirin

   Salicylic acid (o-hydroxybenzoic acid) is acetylated using acetic anhydride to form acetylsalicylic acid, the drug aspirin. This is a standard esterification of the phenolic -OH group. …

Method: Reaction Mapping by Functional Group Transformation

This method works by identifying the key reagent, condition, or product in each Column I entry and matching it to the named reaction or characteristic outcome in Column II.

Steps:

1. Identify the defining reaction or property for each item in Column I.
2. Recall the standard name or outcome from your syllabus for that reaction.
3. Match directly — one unique match per pair.

Step-by-step matching:

(i) Methanol

• Produced industrially by destructive distillation of wood.
• Match: (d) destructive distillation of wood

(ii) Phenol (with $CO_2$ and NaOH)

• This is the Kolbe–Schmitt reaction — phenol reacts with $CO_2$ under basic conditions to form salicylic acid.
• Match: (a) Kolbe's reaction

(iii) Bromination of phenol

• Phenol undergoes electrophilic substitution so readily that bromine water gives 2,4,6-tribromophenol (white precipitate).
• Match: (c) 2,4,6-tribromophenol formation

(iv) Nitration of phenol

• The –OH group is strongly activating and ortho/para-directing. Nitration gives a mixture of ortho and para nitrophenols.
• Match: (e) ortho/para-substitution

(v) Salicylic acid

• Reacted with acetic anhydride to form aspirin (acetylsalicylic acid).
• Match: (f) precursor for aspirin …

Here are the most common mistakes students make when matching these items, along with the conceptual fixes to avoid them.

Mistake 1: Confusing Methanol with Phenol in "Destructive Distillation"

• The Error: Students often match Methanol (i) with Kolbe's reaction (a) or precursor for aspirin (f) because they know methanol is an alcohol. They forget the source of methanol.
• The Fix: Recall the industrial preparation.
  • Methanol was historically obtained via the destructive distillation of wood (hence "wood alcohol"). This directly links (i) → (d).
  • Phenol is the starting material for Kolbe's reaction and aspirin, not methanol.

Mistake 2: Forgetting the "Phenol" Requirement for Kolbe's Reaction

• The Error: Students match Salicylic acid (v) with Kolbe's reaction (a). While salicylic acid is the product, the question asks for the reaction that produces it.
• The Fix: Read the column items carefully.
  • Kolbe's reaction is the process of reacting Phenol with $CO_2$ and NaOH under pressure. Therefore, (ii) → (a).
  • Salicylic acid is the result of Kolbe's reaction. It is also the precursor for aspirin (acetylsalicylic acid). Therefore, (v) → (f).

Mistake 3: Ignoring the "Ortho/Para" Rule for Activating Groups

• The Error: Students match Nitration of phenol (iv) with 2,4,6-tribromophenol formation (c) because both involve substitution. They miss the specific directing effect.
• The Fix: Understand the directing power of the $-OH$ group.
  • $-OH$ is a strong activating and ortho/para-directing group.
  • Bromination of phenol (iii) is so fast that it happens three times (even without a catalyst) to give 2,4,6-tribromophenol. Therefore, (iii) → (c).
  • Nitration of phenol (iv) is controlled (using dilute $HNO_3$) to give a mixture of ortho and para nitrophenols. Therefore, (iv) → (e).

Mistake 4: Misidentifying the Gas Evolved in the Sodium Test

• The Error: Students match Alcohols with sodium (vi) with Kolbe's reaction (a) or aspirin (f) because they think of sodium as a catalyst.
• The Fix: Recall the chemical test for alcohols. …