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Reactions at the Allylic Position definitions

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  • Allylic Position
    Carbon atom directly adjacent to a double-bonded carbon, exhibiting unique reactivity due to resonance stabilization.
  • Vinylic Position
    Double-bonded carbon atom in an alkene, distinct from the adjacent allylic carbon.
  • Resonance Stabilization
    Delocalization of electrons across adjacent atoms, increasing the stability of intermediates like carbocations or anions.
  • Allylic Carbocation
    Positively charged intermediate at the allylic position, highly stabilized by resonance, forming rapidly in SN1 and E1 reactions.
  • Hyperconjugation
    Stabilization of carbocations by electron donation from adjacent sigma bonds, less effective than resonance in allylic systems.
  • Allylic Anion
    Negatively charged species at the allylic position, resonance-stabilized and more acidic than alkyl analogs.
  • Conjugate Base
    Species formed after deprotonation, with allylic versions being more stable due to resonance.
  • pKa
    Numerical measure of acidity; lower values for allylic protons indicate higher acidity compared to alkyl protons.
  • E2 Reaction
    Elimination process favoring allylic positions due to increased acidity and resonance stabilization of resulting alkenes.
  • Radical Initiator
    Substance like heat, UV light, or peroxides that generates radicals, enabling allylic halogenation.
  • N-Bromosuccinimide
    Reagent used with radical initiators to selectively brominate allylic positions in alkenes.
  • Vicinal Dihalide
    Compound with two halogen atoms on neighboring carbons, formed by halogen addition to alkenes.
  • Grignard Reagent
    Organomagnesium compound that reacts with allylic anions, leading to alkylation at the allylic position.
  • Zaitsev's Rule
    Guideline stating that elimination reactions favor formation of the more substituted, stable alkene.
  • Allylic Oxidation
    Selective transformation of an allylic alcohol to a carbonyl group using manganese dioxide, preserving the alkene.