In S_N2 reaction, the correct order of reactivity for the following compounds:

CH₃Cl,CH3CH₂Cl, (CH₃)₂CHCl and (CH₃)₃CCl is

CH₃Cl > CH₃CH₂Cl > (CH3)2CHCl > (CH₃)₃CCl

The correct answer is option 1. CH₃Cl > CH₃CH₂Cl > (CH3)2CHCl > (CH₃)₃CCl.

Reactivity order 1° halide > 2° halide > 3° halide.

Reactivity of S_N2 = \(\frac{1}{\text{steric hindrance}}\).

Here is a detailed explanation for the correct order of reactivity in an S_N2 reaction for the given compounds:

1. CH₃Cl (methyl chloride): This compound contains a primary carbon atom bonded to the chlorine. Primary carbon atoms have the least steric hindrance because they are only bonded to one alkyl group. The absence of additional alkyl groups allows the nucleophile to approach the carbon atom more easily, resulting in higher reactivity. Therefore, CH₃Cl is the most reactive compound among the given options.

2. CH₃CH₂Cl (ethyl chloride): This compound has a secondary carbon atom bonded to the chlorine. Secondary carbon atoms have more steric hindrance compared to primary carbon atoms due to the presence of an additional alkyl group. The presence of the ethyl group introduces some hindrance, making the approach of the nucleophile slightly more difficult. As a result, CH₃CH₂Cl is less reactive than CH₃Cl but more reactive than compounds with higher steric hindrance.

3. (CH₃)₂CHCl (isopropyl chloride): This compound contains a secondary carbon atom bonded to the chlorine, similar to ethyl chloride. However, (CH₃)₂CHCl has two methyl groups attached to the secondary carbon, resulting in increased steric hindrance compared to ethyl chloride. The presence of two alkyl groups makes the approach of the nucleophile even more difficult, leading to decreased reactivity compared to both CH₃Cl and CH₃CH₂Cl.

4. (CH₃)₃CCl (tert-butyl chloride): This compound has a tertiary carbon atom bonded to the chlorine. Tertiary carbon atoms have the highest steric hindrance because they are bonded to three alkyl groups. The bulky nature of the three methyl groups significantly obstructs the approach of the nucleophile, resulting in the lowest reactivity among the given options.

Therefore, the correct order of reactivity for the compounds in an S_N2 reaction is:

CH₃Cl > CH₃CH₂Cl > (CH3)2CHCl > (CH₃)₃CCl