Chapter 18, Problem 19P

Interpretation Introduction

Interpretation:

The stepwise mechanism of the given product formation is to be discussed.

Concept Introduction:

Electrophiles are electron deficient species which has positive or partially positive charge. Lewis acids are electrophiles which accept electron pair.

Nucleophiles are electron rich species which has negative or partially negative charge. Lewis bases are nucleophiles which donate electron pair.

In ${\text{S}}_{\text{N}}\text{2}$ reaction, one bond is broken while another is formed in one step.

Sn2 is a kind of nucleophilic substitution reaction mechanism. Since two reacting species are involved in the slow (rate-determining) step, this leads to the term substitution nucleophilic (bi-molecular) or Sn2.

In $\text{Sn2}$ reaction, the nucleophile attacks on the less sterically hindered carbon. $\text{Sn2}$ reaction gives inversion. The reaction takes place in polar aprotic solvents.

Alkylation of ketones takes place with the help of lithium enolates.

Sodium hydride is used to generate enolate ions.

The $\alpha$ hydrogens can undergo halogen substitution reaction in the presence of acid and base.

When halogen substitution reaction takes place in the presence of acid, it is called acid catalyzed halogenation reaction.

When halogen substitution reaction takes places in the presence of a base, it is called base prompted halogenation reaction.