Question

Which of the following reactions is non-stereospecific but stereoselective?

B){E_1} \\\ C){E_2} \\\ D){E_1}cB $$

Answer 1

Hint : A stereospecific mechanism specifies the stereochemical outcome of a given reactant, whereas a stereoselective reaction selects products from those made available by the same, non-specific mechanism acting on a given reactant of stereoisomeric reactants, each behaves in its own specific way.

Complete Step By Step Answer:
The main difference between stereospecific and stereoselective reactions is that a stereospecific reaction gives one specific product whereas stereoselective reaction gives multiple products.
A ${E_1}$ reaction involves the deprotonation of a hydrogen nearby the carbocation resulting in the formation of an alkene product. In order to accomplish this, a Lewis base is required. It is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism
The one-step mechanism is known as the ${E_2}$ reaction, and the two-step mechanism is known as the ${E_1}$ reaction. The numbers refer not to the number of steps in the mechanism, but rather to the kinetics of the reaction. ${E_2}$ Is bimolecular while ${E_1}$ is unimolecular. Elimination may be considered the reverse of an additional reaction.
It is a two-step process of elimination: ionization and deprotonation. Ionization the carbon-halogen bond breaks to give a carbocation intermediate. Deprotonation of the carbocation.
So, the correct answer is $B){E_1}$ .

Note :
There are competitions between ${E_2}$ and ${S_N}2$ and also between ${E_1}$ and ${S_N}1$ . Substitution generally predominates and elimination occurs only during precise circumstances. Generally, elimination is favored over substitution when steric hindrance around the $\alpha -$ carbon increases, a stronger base is used, temperature increases and when the base is a poor nucleophile. Bases with steric bulk are often poor nucleophiles.