In organic chemistry, an electron withdrawing group (EWG) (deactivating group) is an atom or functional group that removes electron density from a conjugated π system via resonance or inductive electron withdrawal, thus making the π system more electrophilic. They have the opposite effect on electrophilicity as an electron donating groups (EDGs). When attached to a benzene molecule an electron withdrawing group makes electrophilic aromatic substitution reactions slower and more complex. Depending on their relative strengths, EWGs also determine the positions (relative to themselves) on the benzene ring where substitutions must take place; this property is therefore important in processes of organic synthesis.
Other articles related to "deactivating groups":
... The selectivities observed with EDGs and EWGs were first described in 1892 and have been known as the Crum Brown-Gibson Rule. ...
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