Inductive Effect and Groups in Chemistry

Jul 27, 2024

Inductive Effect and Groups in Chemistry

Types of Inductive Groups

  • Minus I Groups (Electron-Withdrawing)
    • Draw electrons from sigma bonds, leading to a positive charge on adjacent atoms.
    • Examples:
      • NO2 (Nitro)
      • SO3H
      • CN (Cyanide)
      • Carbonyl groups (Aldehyde, Ketone)
      • Carboxylic Acid
      • Halogens (Fluoro, Chloro, Bromo, Iodo)
  • Plus I Groups (Electron-Donating)
    • Donate electrons to the sigma bond, leading to negative charge on adjacent atoms.
    • Examples:
      • Alkyl Groups (Primary, Secondary, Tertiary)
      • NH2 (Amino)
      • O- (when negatively charged)

Relative Strength of Minus I Groups

  • Order of Strength:
    1. NF3+
    2. NR3+
    3. SR2+
    4. NH3+
    5. Nitro (NO2)
    6. SO3H
    7. Cyanide (CN)
    8. Aldehyde
    9. Ketone
    10. Carboxylic Acid
    11. Halogens (Fluorine, Chlorine, etc.)
    12. C≡C (Triple bonds)
    13. NH2

Factors Influencing Electronegativity and Inductive Effects

  • Electronegativity is influenced by S character in hybridization.
  • SP Carbon has more S character, hence higher electronegativity compared to SP2 and SP3 Nitrogen.

Plus I Groups and Their Strength

  • Order of Strength in Plus I Groups:
    1. CH2-
    2. NH2-
    3. O-
    4. COO-
    5. Tertiary Alkyl Group
    6. Secondary Alkyl Group
    7. Primary Alkyl Group

Summary of Electron Effects

  • The more electronegative an atom/group, the stronger its electron-withdrawing effect.
  • Alkyl groups enhance electron density due to increased number of carbon atoms.
  • O- can exhibit both -I and +I effects depending on its context and bonding.

Key Takeaways

  • Remember the orders of inductive effects experimentally.
  • Inductive effect depends on the distance of groups: closer groups have stronger effects.
  • Practice writing these orders without looking until you can recall them easily.

Application of Inductive Effect

  • Theory of Inductive effect will be taught first, followed by resonance and hyperconjugation.
  • Applications will tie together the effects of inductive, resonance, and hyperconjugation through examples.