Explain the difference in reactivity between CH₃OH₂ and CH₃OH in a nucleophilic substitution reaction. (The pKa of H₃O⁺ is -1.7.)

Nucleophilic substitution reaction is a class of organic reactions where one nucleophile replaces another. It is very similar to the normal displacement reactions which we see in chemistry, where, a more reactive element replaces a less reactive element from its salt solution. The group which takes electron pair and displaced from the carbon is known as “leaving group” and the molecule on which substitution takes place known as “substrate”. The leaving group leaves as a neutral molecule or anion.

The relative reactivity would be-

Tertiary> primary > secondary

If secondary alcohols underwent Sn2 reaction with hydrogen halides, they would be less reactive than primary alcohols, because they are more sterically hindered than primary alcohols at the carbon attached to the OH group.