Govt Exams
This is a dehydration reaction where the OH group leaves, and a rearrangement occurs via hydride shift to form the more stable tertiary carbocation, leading to 2-methylbut-2-ene (more substituted alkene, Zaitsev's rule).
FeBr3 is a Lewis acid that polarizes Br2, generating Br+ (bromonium ion) which acts as the electrophile in electrophilic aromatic substitution of benzene.
Esterification (Fischer esterification) requires acid catalyst (H2SO4 or HCl) which protonates the carbonyl oxygen, increasing electrophilicity and facilitating nucleophilic attack by alcohol.
RMgX + CO2 → RMgX-O2C- → RCOO- MgX+ → RCOOH (after acidification). This is a classic method for carboxylic acid synthesis.
Formic acid is most acidic (Ka = 1.8×10-4) due to favorable +I effect of hydrogen. Acidity decreases with increasing alkyl chain length due to +I effect: Formic > Acetic > Propionic.
SN1 is a unimolecular reaction with rate = k[R-X]. It is first-order with respect to alkyl halide only, independent of nucleophile concentration.
Cannizzaro reaction occurs with aldehydes lacking α-hydrogens. Acetaldehyde has α-hydrogens, so it undergoes aldol condensation instead of Cannizzaro reaction.
Dehydration follows Zaitsev's rule, producing the most substituted (stable) alkene. 2-methylbut-2-ene is the major product with the double bond at the tertiary position.
Nitration involves formation of NO2+ (nitronium ion) from HNO3 in presence of H2SO4. NO2+ acts as the electrophile in electrophilic aromatic substitution.
Basic hydrolysis of alkyl halides follows SN2 mechanism (bimolecular nucleophilic substitution) with OH- as nucleophile, especially for primary halides.