Question

Which of the following reactions is non-stereospecific but stereoselective?
\[A)S{N_1} \\
  B){E_1} \\
  C){E_2} \\
  D){E_1}cB \]

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.