Govt. Exams
Entrance Exams
The HNO₃/H₂SO₄ mixture generates NO₂⁺ (nitronium ion), which is the electrophile attacking the benzene ring in the rate-determining step. This is a classic electrophilic aromatic substitution.
Peroxides initiate free radical mechanism (Kharasch effect). In free radical addition, HBr adds anti-Markovnikov to propene, giving 1-bromopropane as the major product. The Br radical adds first to the terminal carbon.
Dehydration of 2-methylbutan-2-ol follows Zaitsev's rule, producing the most stable (most substituted) alkene. 2-methylbut-2-ene is a trisubstituted alkene and is the major product.
Phenol is highly activated towards electrophilic aromatic substitution due to the electron-donating -OH group. Bromine can add at all three ortho and para positions with excess bromine, giving 2,4,6-tribromophenol.
Hydroboration-oxidation follows anti-Markovnikov's rule and gives Markovnikov's hydration product after oxidation. 1-methylcyclohexene gives secondary alcohol, while pent-1-ene gives primary and 2-methylbut-2-ene gives tertiary alcohol.
Amides have both N-H (hydrogen bond donor) and C=O (hydrogen bond acceptor), allowing formation of strong intermolecular hydrogen bonds.
PCC (Pyridinium chlorochromate) selectively oxidizes primary alcohols to aldehydes without further oxidation, and doesn't affect C=C.
Clemmensen reduction uses zinc amalgam with concentrated HCl to convert C=O to CH2, unlike Wolff-Kishner which uses hydrazine.
Grignard reagent attacks CO2 to form a salt, which upon hydrolysis gives benzoic acid.
The lone pair on nitrogen of aniline is more nucleophilic than the π electrons of benzene, making N-acylation the dominant pathway.
