Question

Arrange the following groups in order of decreasing $ + M$ effect
i. $ - \mathop O\limits_{}^ - $
ii. $ - N{H_2}$
iii. $ - OH$
IV. $ - NHCOC{H_3}$
A. $i > ii > iii > iv$
B. $iv > iii > ii > i$
C. $i > iii > ii > iv$
D. $i > iv > iii > ii$

Answer 1

Hint: There are various effects that operate in the chemical structure of the compounds .The range from inductive effect, resonance effect, mesomeric effect etc. here $ + M$ is the mesomeric effect. These effects can be positive or negative based on the substituent groups which are attached to the main compound.

Complete step by step answer:
Various effects operate in organic compounds, the mesomeric effect is one of the most effective effects.
The mesomeric effect is the property that depends on the substituent group that is attached to the main compound.it is related to the polarity shift that occurs in the molecule due to the presence of the substituent group on the main compound. The interaction of the pi- bonds with the lone pair of the compound or another pi-bond is the action that results in the mesomeric effect.
The mesomeric effect quantifies the electron-withdrawing or electron releasing property of the substituent group based on their interaction with the organic compounds.
The mesomeric effect caused by the electron withdrawing group is represented as negative $( - M)$ and the effect of the electron releasing group is termed positive $( + M)$
The order of the groups are somewhat predefined in the general terms and are represented as

$ - {O^ - } > N{H_2} > NHR > OR > NHCOR > OCOR > Ph > F > Cl > Br > I$

This the order of $( + M)$ effect.

So, the correct answer is Option A .

Note: The inductive effect $(I)$ is the effect regarding the transmission of the inequality in the sharing of the electron during the bonding process through the chain of atoms in the molecule.it may be the reason for a permanent dipole in the compound sue to this effect.
The electron-withdrawing effect is termed negative ( $ - I$ ) and the electron-donating effect is termed as the positive inductive effect ( $ + I$ ).