Question

Which of the following is the correct order of decreasing $S{N_2}$ respectively?
A.$RC{H_2}X > {R_3}CX > {R_2}CHX$
B.$RC{H_2}X > {R_2}CHX > {R_3}CX$
C.${R_3}CX > {R_2}CHX > RC{H_2}X$
D.${R_2}CHX > {R_3}CX > RC{H_2}X$

Answer 1

Hint:Here in this question, we will be discussing the $S{N_2}$ reactions, their order of eases, what compounds follow the reaction and what happens in the reaction.The reaction regularly happens at an aliphatic sp3 carbon centre with an electronegative, stable leaving group connected to it (frequently signified X), which is much of the time a halide atom.

Complete answer:
As the quantity of $R$ groups on carbon with leaving groups increases, the rate of $S{N_2}$ response diminishes. In \[S{N_2}\] reaction transition state is pentavalent. For bulky alkyl groups it will have sterical hindrance and more small alkyl gathering will support the $S{N_2}$ mechanism.
So, on the above explanation correct order of decreasing $S{N_2}$ reaction:
$RC{H_2}X > {R_2}CHX > {R_3}CX$

Thus, the option is B.

Additional information:
What is meant by R groups?
A shortened form of group in which a carbon or hydrogen ion is joined to the rest of the atom. Mostly utilized all the more loosely, to incorporate different components, for example, halogens, oxygen, or nitrogen.
What is the $S{N_2}$ reaction?
The $S{N_2}$ reaction is a sort of response that is regular in organic chemistry. In this mechanism, one bond is broken and one bond is framed simultaneously, i.e., in one stage $S{N_2}$ is a sort of nucleophilic replacement chemical mechanism, the name alluding to the Hughes-Ingold symbol of the mechanism. Since two responding species are engaged with the slow (rate-deciding)step, this prompts the substitution nucleophilic (bi-sub-atomic) or $S{N_2}$; the other significant kind is $S{N_1}$. The reaction regularly happens at an aliphatic $s{p^3}$ carbon centre with an electronegative, stable leaving group connected to it (frequently signified X), which is much of the time a halide atom.

Note:
You need to remember the ease of decreasing order of compounds that follow the $S{N_2}$ reaction, the leaving groups rules and one should always remember what is a $S{N_2}$ reaction.