Question

Decrease $(\, - I\,)$ effect of given is
$I.\, \,CN$
$II.\, \,N{O_2}$
$III.\, \,N{H_2}$
$IV.\, \,F$
$A.\, \,II > I > IV > III$
$B.\, \,II > III > IV > I$
$C.\, \,III > II > IV > I$
$D.\, \,III > II > I > IV$

Answer 1

$-I$ effect is described about the magnitude of positive charge on an atom. When the magnitude of positive charge on an atom decreases, the -I effect also decreases. Order of -I effect is given as follows;

$$^ + N{F_3}\, > {\,^ + }N{R_3}\, > {\,^ + }N{H_3}\, > \, - N{O_2}\, > \, - CN\, > - S{O_3}H\, > \, - CHO\, > \, - CO\, \\\ > \, - COOH\, > \, - COCl\, > \, - F\, > \, - Br\, > \, - I\, > \, - OH\, > \, - OR\, > \,N{H_2}\, > \, - H\, \\\$$

Complete step-by-step answer:
Inductive effect is the phenomenon of the permanent dipole. It arises in a molecule due to the unequal sharing of the bonding electrons in a molecule.
The Inductive effect arises due to the $\sigma$ bonds whereas in the electromeric effect arises in $\pi$ bonds.
The atom with higher electronegativity withdraws electron density and shows the covalent bonds between two atoms of different electronegativity.
The Inductive effect generally considered by the transmitted through the framework of a molecule. The electronegativity of an element is usually a measure of its ability to attract electrons. It is on ring substituent because they are related to the concept of electronegativity.
Salient features of the inductive effect:
1.It arises due to the difference in electronegativity between two atoms forming a sigma bond.
2.It transmitted through the $\sigma$ bonds. No $\pi$ bonds are involved.
3.The magnitude of the inductive effect decreases as it is moving away from the group.
4.It is a permanent effect and can create permanent dipoles in the molecule.
5.It influences the physical and chemical properties of the compounds.
6.It is relatively weaker and overshadowed by resonance effect, hyperconjugation, etc.

Hence the decreasing order of -I effect is given as follows;
$N{O_2}\, > \,CN\, > \,F\, > \,N{H_2}$
Therefore, the correct option will be $A.\,\,II > I > IV > III$

So, the answer is option(A).

Note: The -I effect is the concept of in organic chemistry which refers to the interaction of charge on adjacent atoms. Inductive effects are of two types, the first one the electron withdrawing group (EWG) or electron releasing group (ERG) shows -I effects and the second type is the electron donating groups (EDG) shows +I effect.