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Question
The correct order of +M effect of ′N′ containing functional group on benzene ring, amongst the given compounds is
(I) 
(II)
(III)
(IV)
The correct order of +M effect of ′N′ containing functional group on benzene ring, amongst the given compounds is
(I) (II)
(III)
(IV)
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Solution
The correct option is C I>II>III>IV
In (b), due to steric inhibition of resonance the amine group will goes out of the plane. Thus it will restrict the resonance of lone pair of electron of N on benzene ring.
In (c), due to cross conjugation the lone pair of electron on N involves in delocalisation with carbonyl group. This decrease the +M effect of N.
In (d), we have two carbonyl groups so more cross conjuation will exist and it results in least +M effect of N.
In (a), due to absence of SIR and cross conjugate it will show the highest +M effect.
Thus, the +M order is
In (b), due to steric inhibition of resonance the amine group will goes out of the plane. Thus it will restrict the resonance of lone pair of electron of N on benzene ring.
In (c), due to cross conjugation the lone pair of electron on N involves in delocalisation with carbonyl group. This decrease the +M effect of N.
In (d), we have two carbonyl groups so more cross conjuation will exist and it results in least +M effect of N.
In (a), due to absence of SIR and cross conjugate it will show the highest +M effect.
Thus, the +M order is
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