Govt Exams
Although the enolate has negative charge on both oxygen and carbon (resonance), the carbon is more nucleophilic toward alkyl halides. The SN2 attack occurs at the alkyl halide carbon, not the enolate O.
The Robinson annulation combines a Michael addition followed by an aldol condensation, forming a bicyclic ketone product with a new six-membered ring fused to an existing ring system.
The amino group is a strong electron-donating group (by resonance) that activates the benzene ring and directs incoming electrophiles to ortho/para positions due to resonance stabilization of the intermediate.
DIBAL-H (Diisobutylaluminum hydride) reduces carbonyl compounds to primary alcohols (from aldehydes) or secondary alcohols (from ketones). It's milder than LiAlH4.
Propyne (CH3C≡CH) hydrates to form an unstable enol intermediate. The enol tautomerizes to acetone (CH3COCH3), following Markovnikov's rule with H adding to the carbon with more H atoms.
Esterification follows the nucleophilic acyl substitution mechanism: the OH of the alcohol attacks the carbonyl carbon after protonation, forming a tetrahedral intermediate that collapses to form the ester.
The initially formed secondary carbocation rearranges via methyl shift to form a more stable tertiary carbocation, producing 2-methylbut-2-ene as major product.
Formaldehyde is the only aldehyde without an α-hydrogen, so it undergoes the Cannizzaro reaction where it acts as both oxidizing and reducing agent, forming formate and methanol.
Malonic acid derivatives (with two electron-withdrawing groups) undergo decarboxylation through a cyclic transition state mechanism, facilitated by the stabilization of the resulting carbanion by the remaining electron-withdrawing group.
2-bromobutane (CH3CHBrCH2CH3) has a carbon with four different groups attached, making it chiral. The bromine-bearing carbon is a stereocenter.