Matching Organic Compounds with Their Chemical Reaction Types

To determine the correct matches between the compounds in Column I and the reactions they can undergo in Column II, we analyze the chemical structure and reactivity of each compound:

1. Compound (A): 3-bromo-2,3-dihydrobenzofuran

• Structure: A bicyclic system comprising a benzene ring fused to a dihydrofuran ring with a bromine substituent at the benzylic position (C-3) and adjacent hydrogens at C-2.
• Reactions:
  • (p) Nucleophilic substitution: The bromine atom is at a benzylic position, making it highly reactive toward nucleophilic substitution reactions ($\text{S}_\text{N}1$ or $\text{S}_\text{N}2$) to form substituted derivatives.
  • (q) Elimination: In the presence of a base (such as alcoholic $\text{KOH}$), it readily undergoes dehydrohalogenation (elimination of $\text{HBr}$) involving the benzylic bromide and the $\beta$-hydrogen at C-2 to generate the fully aromatic benzofuran ring.
  • (t) Dehydrogenation: Catalytic dehydrogenation (loss of $\text{H}_2$) can occur across the saturated positions of the dihydrofuran ring to aromatize the system.
• Matches: (A) $\rightarrow$ p, q, t

2. Compound (B): Benzyl alcohol ($\text{C}_6\text{H}_5\text{CH}_2\text{OH}$)

• Structure: A primary alcohol attached to a phenyl ring.
• Reactions:
  • (p) Nucleophilic substitution: The hydroxyl group ($-\text{OH}$) can be substituted by halides or other nucleophiles upon protonation or conversion into a good leaving group (e.g., using $\text{PCl}_5$, $\text{SOCl}_2$, or concentrated $\text{HX}$).
  • (s) Esterification with acetic anhydride: As a primary alcohol, it readily reacts with acetic anhydride ($(\text{CH}_3\text{CO})_2\text{O}$) in the presence of an acid or base catalyst to form benzyl acetate (an ester).
  • (t) Dehydrogenation: Primary alcohols undergo dehydrogenation over heated catalysts (e.g., $\text{Cu}$ at $573\text{ K}$) by losing $\text{H}_2$ to yield benzaldehyde:
    $\text{C}_6\text{H}_5\text{CH}_2\text{OH} \xrightarrow{\text{Cu}, \Delta} \text{C}_6\text{H}_5\text{CHO} + \text{H}_2$
• Matches: (B) $\rightarrow$ p, s, t

3. Compound (C): Salicylaldehyde (2-hydroxybenzaldehyde)

• Structure: Contains both an aromatic aldehyde group ($-\text{CHO}$) and a phenolic hydroxyl group ($-\text{OH}$).
• Reactions:
  • (r) Nucleophilic addition: The carbonyl carbon of the aldehyde group undergoes characteristic nucleophilic addition reactions (e.g., with $\text{HCN}$, $\text{NaHSO}_3$, or Grignard reagents).
  • (s) Esterification with acetic anhydride: The phenolic $-\text{OH}$ group is acetylated upon reaction with acetic anhydride to produce an ester (specifically, 2-formylphenyl acetate).
• Matches: (C) $\rightarrow$ r, s

4. Compound (D): 4-Bromonitrobenzene ($p$-bromonitrobenzene)

• Structure: An aryl halide with a strong electron-withdrawing nitro group ($-\text{NO}_2$) located para to the bromine atom.
• Reactions:
  • (p) Nucleophilic substitution: Due to the strong $-M$ (mesomeric) and $-I$ (inductive) effects of the para-nitro group, the carbon bearing the halogen is activated toward nucleophilic aromatic substitution ($\text{S}_\text{N}\text{Ar}$) via the Meisenheimer complex intermediate (e.g., substitution of $\text{Br}^-$ by ${}^-\text{OH}$ or ${}^-\text{OMe}$).
• Matches: (D) $\rightarrow$ p

Final Matching:

• (A) $\rightarrow$ p, q, t
• (B) $\rightarrow$ p, s, t
• (C) $\rightarrow$ r, s
• (D) $\rightarrow$ p