Camment upon the statement : 'Usual order of inductive effects of the alkyl groups is often reversed when attached to a double bond or a benzene ring'. Name the electronic effect and illustrate your answer with suitable examples.

Which of the following groups exerts +m effect when attached with benzene ring?

Identification of +m & -m groups : If the first atom of the group has lone pair or negative charge shows +m effect. +m group increases electron density at ortho and para position of benzene ring. If the group has vacant p- orbital on first atom, also a multipal bonded group in which second atom is more electronegative than the first then it shows -m effect. -m group decreases electron density of ortho and para position of benzene ring. Identify which of following group/s show -m effect when attached with benzene ring.