Question

The order of +R power in the given group is:
(a)- $-N{{H}_{2}}>-{{O}^{-}}>-O{{H}^{-}}>-NHCOC{{H}_{3}}$
(b)- $-{{O}^{-}}>-N{{H}_{2}}>-O{{H}^{-}}>-NHCOC{{H}_{3}}$
(c)- $-O{{H}^{-}}>-{{O}^{-}}>-N{{H}_{2}}>-NHCOC{{H}_{3}}$
(d)- $-NHCOC{{H}_{3}}>-{{O}^{-}}>-O{{H}^{-}}>-N{{H}_{2}}$

Answer 1

+R power means the + resonance effect or +mesomeric effect. The resonance or mesomeric effect is a system in which there is a flow of electrons from one part of the end of the compound to the conjugated system, and when the electrons are given to the system then it is the +R or +M effect.

Complete step by step solution: There are many effects that are used to explain the stability or reactivity of the organic compound and these are inductive effect, electromeric effect, resonance or mesomeric effect, and hyperconjugation effect.
+R power means the + resonance effect or +mesomeric effect. The resonance or mesomeric effect is a system in which there is a flow of electrons from one part of the end of the compound to the conjugated system. A Conjugated system means when the system has alternate single and double bonds.
The resonance or mesomeric effect is further of two types, i.e., -R effect and +R effect.
Suppose, if a group is attached to a benzene ring as benzene is a conjugated system. The group takes the electrons from the benzene ring then the resonance that we caused is the –R effect.
Suppose, if a group is attached to a benzene ring as benzene is a conjugated system. The group gives the electrons to the benzene ring then the resonance that we caused is the +R effect. So, as the negative charge on the group or at least one lone pair of electrons on the group then the +R effect increases.
So, the decreasing order of the groups will be:
$-{{O}^{-}}>-N{{H}_{2}}>-O{{H}^{-}}>-NHCOC{{H}_{3}}$

Therefore, the correct answer is an option (b).

Note: Some groups that show the –R effect are nitro group ($-N{{O}_{2}}$), cyano group ($-CN$), carbonyl group ($>C=O$), aldehyde group ($-CHO$), ether group (-COOR), etc.