What are Electron Donating Groups (EDG) in Organic Chemistry?

An EDG donates its electrons through two main scientific mechanisms:

1. Positive Inductive Effect (+I Effect): This happens through the physical 'push' of electrons through single sigma bonds. Alkyl groups (like Methyl -CH₃) are famous for this. Because carbon is slightly more electronegative than hydrogen, the methyl group physically shoves its electron cloud towards the main molecule.
2. Positive Mesomeric / Resonance Effect (+M / +R Effect): This is much more powerful. If the attached group has a 'Lone Pair' of free electrons (like an Oxygen or Nitrogen atom), it can physically dump those free electrons directly into the pi-bond system of a Benzene ring, moving the electrons around via resonance.

You must memorize these common Electron Donating Groups:

• Strong EDGs (+M effect): Amino group (-NH₂), Hydroxyl group (-OH), and Alkoxy groups (-OR). They all have free lone pairs to donate.
• Weak EDGs (+I effect): Alkyl groups like Methyl (-CH₃) and Ethyl (-C₂H₅).

In electrophilic aromatic substitution reactions, EDGs are known as Activating Groups. Because they pump massive amounts of negative electron density into the Benzene ring, they make the ring highly attractive to positive electrophiles. Furthermore, because of how resonance works, EDGs are Ortho/Para directors, meaning they force the incoming new chemicals to attach specifically at the ortho or para positions of the benzene ring.