Organic Chemistry

Hydroboration-oxidation is a two-stage process:

• Hydroboration stage: Propene reacts with diborane ($\text{B}_2\text{H}_6$, A) to form tripropylborane.
• Oxidation stage: Tripropylborane is oxidised by hydrogen peroxide ($\text{H}_2\text{O}_2$, C) in the presence of aqueous sodium hydroxide (providing $\text{OH}^-$, D and $\text{H}_2\text{O}$, B) to give propan-1-ol.

In the nitrating mixture, conc. $\text{H}_2\text{SO}_4$ acts as a Bronsted acid and protonates conc. $\text{HNO}_3$ (which acts as a base), producing the nitronium ion ($\text{NO}_2^+$):

The nitronium ion ($\text{NO}_2^+$) is the active electrophile that attacks the benzene ring.

Chlorobenzene undergoes two competing effects:

• Inductive effect ($-I$): Chlorine strongly withdraws electrons, overall destabilising the cationic intermediate and causing deactivation (Statements A and B).
• Resonance effect ($+R$): Chlorine donates its lone pair to delocalise positive charge specifically in ortho- and para-attacks, creating a stable octet structure (Statement D).

Statement C is incorrect because chlorine donates electrons through resonance (+R), not accepts them. Thus, (A), (B) and (D) only.

Standard named reactions in organic chemistry:

• Swarts reaction: Heating alkyl chloride/bromide with metallic fluoride (e.g. $\text{AgF}$) yields alkyl fluoride $\rightarrow$ (III)
• Finkelstein reaction: Halogen exchange with $\text{NaI}$ in dry acetone yields alkyl iodide $\rightarrow$ (IV)
• Sandmeyer's reaction: Diazotisation of aniline followed by treatment with cuprous halide $\text{Cu}_2\text{X}_2$ yields aryl halide $\rightarrow$ (I)
• Wurtz reaction: Reaction of alkyl halides with sodium in dry ether produces higher alkanes $\rightarrow$ (II)

Correct match: (A)-(III), (B)-(IV), (C)-(I), (D)-(II).