Second Trimester
Lesson 12: Reaction Mechanisms in Detail-
Allylic Bromination:
Mechanism: Initiated by NBS and light/heat, forming bromine radicals. These radicals abstract hydrogen from the allylic position, leading to the formation of allylic radicals. Subsequent reaction with bromine yields the allylic bromide.
Allylic Oxidation:
Mechanism: Involves electrophilic attack on the double bond adjacent to the allylic position, forming a resonance-stabilized carbocation. Oxidation of this intermediate produces allylic alcohols or ketones.
Conjugated Dienes:
Diels-Alder Reaction: A cycloaddition between a conjugated diene and a dienophile, typically forming a six-membered ring. The reaction proceeds through a concerted mechanism involving overlap of the diene's HOMO and the dienophile's LUMO.
Oxidative Cleavage of Conjugated Dienes:
Mechanism: Ozonolysis with ozone followed by reductive work-up cleaves the double bonds of conjugated dienes. This process yields carbonyl compounds through the formation and decomposition of ozonide intermediates.