IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

mona840

+ R effect means positive resonance effect

Also known as positive mezomereic effect ( +M)

( +M grps r donating grps)

In this effect the transfer of electrons is away from an atom or substituent group

attached to the conjugate system

Example :-

Luk below at de resonating structure of aniline

Since -NH ₂increases electron density over ortho n para positions of benzene

So electrophile can attack at ortho n para positions

Tat is y + M groups are also known as ortho-para directing and activating grp

Other common xamples of +M grps r -OH & -OCH₃